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Clinical significance and reliability of two common grip strength measures Burns, Aglaia Jane 1998

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THE CLINICAL SIGNIFICANCE AND RELIABILITY OF TWO COMMON GRIP STRENGTH MEASURES  By AGLAIA JANE BURNS B . S c . ( H o n s ) , T h e University of Toronto, 1983 B . H . S c . ( P T ) , M c M a s t e r University, 1988  A T H E S I S S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F T H E REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES S c h o o l of Rehabilitation S c i e n c e s W e a c c e p t this thesis a s conforming to the required standard  T H E UNIVERSITY O F BRITISH C O L U M B I A S e p t e m b e r 1998 © A g l a i a J a n e Burns, 1998  In  presenting  this  thesis in partial  degree at the University of  fulfilment  of  the  requirements  for  an advanced  British Columbia, I agree that the Library shall make it  freely available for reference and study. I further agree that permission for extensive copying of  this thesis for scholarly purposes may be granted by the head of  department  or  by  his  or  her  representatives.  It  is  understood  that  copying  my or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of  ^  U 1^*2-  The University of British Columbia Vancouver, Canada Date  DE-6 (2/88)  Oct • WW  dtU  W  Abstract This study surveyed therapist's use of grip strength measures in clinical practice and determined the test-retest reliability of two common grip strength tests to elucidate what drives clinical decision making with respect to grip strength measurements and to determine an effective measurement strategy to detect clinically important change. Survey responses were obtained from 120 facilities across Canada. Results indicated that the Jamar dynamometer was the instrument most commonly used to measure grip strength (87%), and the Standard Grip Strength Test (SGST) (3 trials at position #2) and the 5-Position Grip Strength Test (5PGST) (1 trial at each of 5 positions) were the most common tests used. A normative database for comparison of test results is not consistently used in clinical practice. From our survey results, there was considerable variation in what clinicians deemed a clinically important change in grip strength measurements. Fourteen healthy males (mean age 25.4 years) were involved in a test-retest reliability study of the S G S T and the 5 P G S T using the Jamar dynamometer. Generalizability coefficients (R) were used to determine test-retest reliability. Generalizability coefficients for the S G S T were greater for the mean of 3 trials (R =.67 for the right hand and R=.70 for the left). Handle position of the 5 P G S T was reliable for the left hand only at position 1(R=.87) and position 2 (R=.83). The greatest source of error was seen between subjects across test occasions. Grip strength fluctuations were between 2.8 to 6.6 kgf (6.4 to 12.8%) in the right hand and 2.8 to 5.9 kgf (5.1-10.8%) in the left over 2 test occasions. It appears that clinicians may be stating a true change in grip strength scores when changes in measurement may be due to error alone. From our study, it is recommended that a standardized test protocol be used consistently for grip strength measurements. The clinician needs to determine normal variability for their patients using the standard error of measurement (SEM) and confidence intervals. True grip strength may best be evaluated by taking multiple measurements over a number of test occasions. The use of a normative database should only be compared to when the same test protocol, sample population and instrument used by the clinician has been used to develop the normative data.  iii  Table of Contents Abstract  ii  Table of Contents  iii  List of Tables  v  List of Figures  vi  List of Abbreviations/Definitions  viii  Acknowledgement  ix  Chapter 1 Introduction and Literature Review Theoretical Constructs Grip Strength M e a s u r e m e n t Tool Factors Affecting Grip Strength Rationale for Investigation Reliability of Grip Strength M e a s u r e s Clinical Significance of Grip Strength M e a s u r e s C o n c l u s i o n and P u r p o s e of R e s e a r c h References  1 3 4 4 6 8 8 11 15 16  Chapter 2 Survey Study Introduction Methods Results Discussion Clinical Significance Limitations of S u r v e y Further R e s e a r c h Conclusion References  21 21 22 24 32 36 39 40 40 42  Chapter 3 Reliability Study  43  Introduction P u r p o s e of the Study Statement of H y p o t h e s e s Methods Statistical A n a l y s i s Results Discussion Clinical Significance Limitations of S u r v e y Further R e s e a r c h Conclusion References  43 45 46 46 51 53 59 67 69 71 71 73  S u m m a r y and C o n c l u s i o n s  76  Chapter 4 W h a t is the normal variation in grip strength m e a s u r e s ? H o w reliable are grip strength m e a s u r e s ? H o w c a n w e interpret the results of grip strength m e a s u r e s ? Recommendations S u g g e s t i o n s for further r e s e a r c h Conclusion References  77 80 81 84 86 86 88  Appendices A : Description of the S G S T , 5 P G S T  90  B: S u r v e y F o r m  91  C : C o v e r Letter for S u r v e y  93  D: R e s e a r c h D e s i g n  94  E : S t a n d a r d i z e d Patient Instructions for G r i p Strength Testing  95  F: R a w D a t a  96  G : Statistical A n a l y s e s / A n o v a T a b l e s  100  V  List of Tables Chapter 3 T a b l e 1:  S a m p l e m e a n s between test o c c a s i o n s and a c r o s s trials for the S t a n d a r d Grip Strength T e s t 53  T a b l e 2:  Generalizability Coefficients (R) for the S t a n d a r d Grip Strength Test 54  T a b l e 3:  Estimate of v a r i a n c e c o m p o n e n t s derived from the 3-way A n o v a for the S t a n d a r d Grip Strength T e s t 55  T a b l e 4:  S u m m a r y of the Correlation Coefficients for the 5-Position G r i p Strength Test  57  T a b l e 5:  Estimate of v a r i a n c e c o m p o n e n t s from a 2-way A n o v a for the 5Position G r i p Strength T e s t 57  T a b l e 6:  M e a n grip strength m e a s u r e m e n t fluctuations (kgf) for the 5-Position Grip Strength T e s t and the S t a n d a r d Grip Strength T e s t (n=14, 2 test o c c a s i o n s ) 58  vi  List of Figures Chapter 2 Figure 1:  Figure 2:  S u r v e y r e s p o n s e s indicating the types of grip strength u s e d  25  S u r v e y r e s p o n s e s of grip strength m e a s u r e m e n t tools u s e d in clinical practice  25  Figure 3:  G r i p strength testing by patient population  26  Figure 4:  S u r v e y r e s p o n s e depicting the intended p u r p o s e of grip strength measurements 26  Figure 5:  S u r v e y r e s p o n s e data depicting the u s e of a normative d a t a b a s e in grip strength m e a s u r e m e n t s 27  Figure 6:  S u r v e y r e s p o n s e s depicting m e a s u r e s u s e d to detect clinically important c h a n g e in grip strength  28  Figure 7:  S u r v e y r e s p o n s e indicating amount of c h a n g e in kgforce to detect clinically significant c h a n g e in grip strength m e a s u r e m e n t s b e t w e e n hands 29  Figure 8:  S u r v e y r e s p o n s e data indicating percentage difference b e t w e e n h a n d s c o n s i d e r e d clinically significant with grip strength measurements 29  Figure 9:  S u r v e y r e s p o n s e s depicting clinically significant p e r c e n t a g e c h a n g e between trials reported in grip strength m e a s u r e s 30  Figure 10:  S u r v e y r e s p o n s e s depicting clinically significant c h a n g e in kgforce between trials in grip strength m e a s u r e m e n t s 30  Figure 11:  S u r v e y r e s p o n s e data indicating percentage difference b e t w e e n grip strength s c o r e s and a normative d a t a b a s e to be c o n s i d e r e d clinically significant 31  Figure 12:  S u r v e y r e s p o n s e data indicating absolute difference between a normative d a t a b a s e and grip strength m e a s u r e m e n t s for clinical significance 31  Chapter 3 Figure 1(a,b):Positioning for grip strength testing with the J a m a r dynamometer Figure 2:  Figure 3:  49  Proportion of high s c o r e s occurring on the first, s e c o n d or third of 3 trials on the S t a n d a r d Grip Strength T e s t  56  Test-retest reliability of 5 handle positions of the J a m a r dynamometer  59  Vlll  List of Abbreviations/Definitions A c c u r a c y : Instrumentation a c c u r a c y refers to the e x a c t n e s s of the m e a s u r e m e n t provided by a n instrument by comparing the reading o n the d e v i c e with a standard m e a s u r e (i.e. hanging known weights o n the d y n a m o m e t e r ) . Correlation Coefficient: Mathematical e x p r e s s i o n of the d e g r e e of relationship b e t w e e n two or more variables. Generalizability Theory: P r o v i d e s a method for a s s e s s i n g the dependability of a m e a s u r e a n d allows for the d e c o m p o s i t i o n of the error v a r i a n c e into unique s o u r c e s of variation. Interrater Reliability: T h e c o n s i s t e n c y a m o n g different tester's ratings of the s a m e object or r e s p o n s e . Intrarater Reliability: T h e c o n s i s t e n c y with which o n e rater a s s i g n s s c o r e s to a single set of r e s p o n s e s o n two or more o c c a s i o n s . Reliability: T h e extent to which m e a s u r e m e n t s a r e repeatable. Test-Retest Reliability: T h e d e g r e e to which the s c o r e s c h a n g e or remain stable on repeated administration. Validity: T h e m e a n i n g f u l n e s s of test s c o r e s a s they a r e u s e d for specific p u r p o s e s . T h e extent to w h i c h a test m e a s u r e s what it is intended to m e a s u r e . S G S T : S t a n d a r d Grip Strength T e s t 5 P G S T : 5-Position Grip Strength T e s t kgf: kilograms of force S E M : S t a n d a r d error of m e a s u r e m e n t Cl: C o n f i d e n c e interval ICC: Intraclass correlation coefficient r: P e a r s o n P r o d u c t M o m e n t correlation R: Generalizability correlation coefficient  ix  Acknowledgement  I w o u l d like to thank my supervisor, Dr. D o n n a M a c l n t y r e , for her k n o w l e d g e , support a n d g u i d a n c e throughout my graduate r e s e a r c h . H e r a d v i c e a n d constructive criticism m a d e the p r o c e s s a very rewarding e x p e r i e n c e . A s well, I w o u l d like to thank my committee m e m b e r s , Dr. J o e l S i n g e r a n d Dr. J a n i c e E n g for their invaluable input a n d direction throughout the d e s i g n a n d implementation of my r e s e a r c h . I would a l s o like to thank my c o l l e a g u e , Mr. P a u l Stratford, for his a s s i s t a n c e a n d help with the data a n a l y s i s . T h e support of the S c h o o l of Rehabilitation S c i e n c e s , University of British C o l u m b i a , faculty a n d c o l l e a g u e s throughout graduate s c h o o l w a s greatly a p p r e c i a t e d . Finally, I would like to thank the B C H e a l t h c a r e S c h o l a r s h i p F u n d for financial support.  1  CHAPTER  1 INTRODUCTION AND LITERATURE REVIEW  T h e n e e d for establishing objective m e a s u r e s in p h y s i c a l a n d o c c u p a t i o n a l therapy a n d determining their reliability a n d clinical significance a s rehabilitation tools w a s the motivating factor behind this investigation. Grip strength testing utilizing a s t a n d a r d J a m a r dynamometer (Asimow Engineering Company, Los A n g e l e s , C A ) w a s selected 1  for investigation d u e to its w i d e s p r e a d u s e a s a m e a s u r e m e n t tool in the clinical rehabilitation setting.  2  T h e ability to d o c u m e n t c h a n g e with valid, reliable a n d objective o u t c o m e m e a s u r e m e n t tools is extremely important in any field of study. In rehabilitation m e d i c i n e , objective m e a s u r e s c a n be u s e d for a variety of p u r p o s e s including establishing b a s e l i n e pathology, documenting c h a n g e , planning a n d evaluation of treatment p r o g r a m s , explaining performance a n d predicting rehabilitation o u t c o m e .  3,4  A  m e a s u r e is objective if it is not d e p e n d e n t on the e x a m i n e r , involves the u s e of 5  instrumentation, a n d is e x p r e s s e d in real n u m b e r s .  3  Objective m e a s u r e s are tests or  p r o c e d u r e s w h o s e results are independent of p e r s o n a l feelings or p r e j u d i c e s .  6  S u b j e c t i v e m e a s u r e s , on the other h a n d , are d e p e n d e n t on the patient a n d to s o m e d e g r e e , o n the j u d g e m e n t of the examiner. A c c o r d i n g to B o h a n n o n , in p h y s i c a l 3  therapy, m a n y , if not most, of the m e a s u r e s u s e d are d e p e n d e n t on the patient a n d no matter h o w objective the test, variability within the patient a n d their level of effort is  2  b o u n d to h a v e a n affect on the o u t c o m e .  3  A s Y o u n g et a l stated, it is a c o m m o n 7  m i s c o n c e p t i o n that all tests that generate n u m b e r s are n e c e s s a r i l y objective; this is particularly true of grip a n d pinch strength m e a s u r e m e n t s .  7  Objective m e a s u r e s h a v e potential a d v a n t a g e s over subjective m e a s u r e s including indices of reliability a n d validity. Reliability is the d e g r e e to w h i c h test s c o r e s are free from errors of m e a s u r e m e n t a n d defines a n instrument's ability to m e a s u r e consistently a n d predictably.  4,8  Validity is defined a s the extent to w h i c h a test m e a s u r e s what it is  intended to m e a s u r e . Reliability is a prerequisite to establishment of validity but validity is often cited a s the most important consideration w h e n testing a m e a s u r e a s it refers to the a p p r o p r i a t e n e s s , m e a n i n g f u l n e s s a n d u s e f u l n e s s of a m e a s u r e .  9  W h e n using  m e a s u r e m e n t tools in rehabilitation, e x p e r i e n c e d p r o f e s s i o n a l s s h o u l d be familiar with the reliability a n d validity for the specific application of the tool a s well a s knowing the populations for w h o m the m e a s u r e w a s d e s i g n e d prior to attempting s t a n d a r d i z e d a s s e s s m e n t s or m a k i n g clinical d e c i s i o n s regarding o u t c o m e s .  10  Theoretical Constructs  G r i p strength testing is c o m m o n l y administered in both clinical a n d evaluative work c a p a c i t y settings. M e a s u r e s of grip strength are frequently u s e d in rehabilitation m e d i c i n e to c o m p a r e an individual's grip strength with e s t a b l i s h e d n o r m s or to c o m p a r e affected a n d non-affected limbs within the s a m e individual. A s indicated by Hamilton, B a l n a v e a n d A d a m s , the o u t c o m e of grip strength testing c a n be a major determinant 11  of w h e t h e r rehabilitation will be offered, what type of rehabilitation will be offered or a s a m e a s u r e of sincerity of effort in m e d i c o - l e g a l i s s u e s .  11  T h e results of grip strength  testing are often c o n s i d e r e d indicators for fitness to return to w o r k .  12  However,  3 m e a s u r e m e n t s of strength are constructs that are in t h e m s e l v e s not directly o b s e r v a b l e . T h e r e are no absolute s t a n d a r d s to determine if current m e a s u r e s of 8  strength are valid indicators of what they are s u p p o s e d to m e a s u r e . T h i s p r e s e n t s a real d i l e m m a in p h y s i c a l therapy a s s o m u c h of our treatment centers on "increasing strength" a n d "determining w e a k n e s s " in order to progress a client in rehabilitation.  O n e of the theoretical constructs of physical therapy is the c o n c e p t of m o v e m e n t dysfunction, or a s Hislop  1 3  stated, pathokinesiology. Strength, within a  pathokinesiological framework, relates to kinematics a n d kinetics. Kinetic v a r i a b l e s with e s t a b l i s h e d m e a s u r e m e n t units s u c h a s force a n d torque are often u s e d in p h y s i c a l therapy to a s s e s s m o v e m e n t dysfunctions. T h e v a l u e behind using t h e s e terms is that they are e s t a b l i s h e d a n d c o m m o n l y a c c e p t e d . A s S m i d t  1 4  indicated, p h y s i c a l  therapists will be u n a b l e to d e v e l o p theories of m o v e m e n t u n l e s s the p h e n o m e n a m e a s u r e d are clearly defined in universally a c c e p t a b l e terms. W h e n evaluating strength, it is imperative that the e x a m i n e r feels confident that the m e a s u r e of strength utilized is valid or meaningful. T h e e x a m i n e r must a l s o feel confident that the m e a s u r e obtained is a true m e a s u r e of maximal strength in order to accurately m a k e d e c i s i o n s regarding rehabilitation.  W h i l e m u s c l e strength is a s s e s s e d frequently by physical therapists, there a p p e a r s to be c o n s i d e r a b l e variability in the m e t h o d s a n d tools u s e d . M a n u a l m u s c l e strength testing is u s e d by most therapists but it h a s not b e e n determined to be r e l i a b l e .  15  Hand  held d y n a m o m e t e r s , hand grip d y n a m o m e t e r s s u c h a s the J a m a r , or isokinetic d y n a m o m e t e r s s u c h a s the K i n - C o r n are other methods of m e a s u r i n g m u s c l e strength. S o m e studies h a v e indicated s c o r e s obtained from m a n u a l m u s c l e testing correlate with  4 hand-held dynamometry.  16  Stratford a n d B a l s o r , in a c o m p a r i s o n of the K i n - C o r n a n d 1 7  a h a n d - h e l d d y n a m o m e t e r for tests of m u s c l e strength of the e l b o w flexors, found that h a n d - h e l d d y n a m o m e t r y is a viable alternative to costlier tools s u c h a s the K i n - C o r n , provided that the a s s e s s o r ' s strength is greater than that of the specific m u s c l e group being m e a s u r e d . H a n d held a n d isokinetic d y n a m o m e t e r s , along with the J a m a r d y n a m o m e t e r , attempt to objectively m e a s u r e m u s c l e strength a n d are u s e d in clinical practice. H o w e v e r , a s m e a s u r e m e n t tools, e a c h h a s its o w n inherent set of limitations that clinicians n e e d to be a w a r e of before using them in clinical practice.  Grip Strength Measurement Tool A n a s s e s s m e n t of grip strength first introduced by B e c h t o l in 1954, a n d 1 8  r e c o m m e n d e d by the A m e r i c a n S o c i e t y of H a n d T h e r a p i s t s is widely reported in the 2  literature. It incorporates the J a m a r hand-held d y n a m o m e t e r ( A s i m o w E n g i n e e r i n g C o . , L o s A n g e l e s , Calif.). W h i l e there are m a n y hand d y n a m o m e t e r s currently on the 1  market, the J a m a r hand-held d y n a m o m e t e r remains o n e of the most popular clinical tools to a s s e s s grip strength in the rehabilitation setting. Kirkpatrick  1 9  s u g g e s t e d the  J a m a r test be u s e d by the A m e r i c a n M e d i c a l A s s o c i a t i o n in the evaluation of all upper extremity impairment ratings. T h e literature indicates that the J a m a r d y n a m o m e t e r is widely u s e d in rehabilitation a n d is d e e m e d the most a c c u r a t e for determining grip strength.  20  Smith a n d B e n g e found in a survey of 195 o c c u p a t i o n a l therapy facilities  o v e r 7 9 % of the clinics c o m m o n l y u s e d the J a m a r d y n a m o m e t e r in their s e t t i n g s .  21  T h e J a m a r d y n a m o m e t e r c o n s i s t s of a handle with 5 equally s p a c e d adjustable settings. T h e d y n a m o m e t e r is presented to the individual by the e x a m i n e r a n d the  5 individual is instructed to grip the handle a s hard a s p o s s i b l e . In utilizing the J a m a r h a n d held d y n a m o m e t e r in grip strength testing, isometric strength is m e a s u r e d a n d the subject is unable to p e r c e i v e the distance the handle h a s m o v e d during g r a s p . During a n isometric contraction, the potential tension that c a n be g e n e r a t e d by m u s c l e is c l o s e l y related to the length of the m u s c l e with the potential strength d e c r e a s i n g w h e n the m u s c l e length is either longer than or shorter than the resting l e n g t h .  22  During grip,  the b i o m e c h a n i c a l a d v a n t a g e of the finger joints a n d t e n d o n s is d e t e r m i n e d by the s h a p e a n d s i z e of the object being g r a s p e d therefore grip force will be affected by muscle length.  1 8 2 2  Utilizing the J a m a r d y n a m o m e t e r , the s e c o n d (4 cm) or third (6 cm)  position usually allows most individuals to apply m a x i m a l force comfortably. A c c o r d i n g to B e c h t o l , grip strength is a function both of the s i z e of the object being gripped a n d 18  the ability of opposition b e t w e e n the thenar m u s c l e s a n d the four f i n g e r s .  18  Generally  b e t w e e n the s e c o n d a n d fourth setting on the d y n a m o m e t e r , the subject r e a c h e s a m e c h a n i c a l a d v a n t a g e d e p e n d i n g on the s i z e of their hand a n d it is at this setting that they are a b l e to demonstrate the greatest static grip s t r e n g t h .  18  Instructions for the J a m a r d y n a m o m e t e r do not provide any specific protocols or n o r m s a n d it is regarded to be an instrument lacking in precision a n d a c c u r a c y for 1  m e a s u r i n g grip strength force a c c o r d i n g to Mr. Rick Seifarth at the National Institute of S t a n d a r d s a n d T e c h n o l o g y (NIST), G a t h e r s b u r g , M a r y l a n d (personal c o m m u n i c a t i o n ) . T h e N I S T (equivalent to the National R e s e a r c h C o u n c i l in C a n a d a ) is r e g a r d e d a s the national s t a n d a r d in the United States against which a n a s s e s s m e n t tool must be tested in order to determine a c c u r a c y within its m e a s u r e m e n t unit.  23  H o w e v e r , in  c o m m u n i c a t i o n with a representative from N I S T , it a p p e a r s there are no s t a n d a r d i z e d  6 testing p r o c e d u r e s relating specifically to the J a m a r d y n a m o m e t e r . C o m p a n i e s that calibrate d y n a m o m e t e r s by hanging known weights from the d y n a m o m e t e r h a n d l e m a y exhibit a c h a i n of traceability back to the N I S T , but there is no gold standard with w h i c h to c o m p a r e the force output of a standard J a m a r d y n a m o m e t e r . N o n e t h e l e s s , the J a m a r d y n a m o m e t e r is widely u s e d a s a m e a s u r e m e n t tool in rehabilitation.  2  F a c t o r s Affecting Grip Strength  M a n y factors influence grip strength itself including a g e , h a n d e d n e s s , fatigue, pain, positioning a n d the client's cooperation. Normative data b a s e s for grip a n d pinch strength relating to various population groups have a p p e a r e d in the l i t e r a t u r e . S t u d i e s h a v e indicated that grip strength i n c r e a s e s with a g e .  24  2 6  M a t h i o w e t z et a l  2 7 , 2 8  2 5  in a  study to determine normative grip a n d pinch strength data for adults indicated that the highest grip s c o r e s o c c u r r e d in the 2 5 to 39 a g e groups. M a l e s p e a k e d in grip strength b e t w e e n the a g e s of 2 0 - 3 9 a n d w o m e n b e t w e e n 4 0 to 4 9 y e a r s of a g e .  2 9  h a s b e e n reported to diminish curvilinearly with a g e in elderly i n d i v i d u a l s . a p p e a r to be stronger than f e m a l e s in all a g e g r o u p s .  27  G r i p strength 30  Males  31  H a n d e d n e s s plays a role in grip strength testing with the dominant h a n d largely thought to p o s s e s s 1 0 % greater grip strength than the non-dominant h a n d ( 1 0 % rule). S t u d i e s h a v e s h o w n that the 1 0 % rule a p p e a r s valid for right h a n d e d p e r s o n s only, with grip strength equivalent to the right in left h a n d e d i n d i v i d u a l s . j u d g e d to be a n unimportant variable in children a g e d 5 to 1 2 .  32,33  2 8  Hand dominance was  H a r k o n e n et a l  3 1  in a  s a m p l e of 2 0 4 F i n n i s h adults a g e d 30 to 50 y e a r s , found no significant difference in strength b e t w e e n the dominant a n d non-dominant h a n d s . T h e type of work that a n individual d o e s h a s a n effect on their grip strength. H e a v y m a n u a l w o r k e r s exhibit the  7 greatest strength a n d the least difference between left a n d right h a n d s while office w o r k e r s h a v e the w e a k e s t grips with the greatest difference b e t w e e n h a n d s .  34  Positioning of the upper extremity h a s b e e n s h o w n to h a v e a n effect o n grip strength testing with the J a m a r d y n a m o m e t e r a n d remains controversial. A wrist position of 3 5 d e g r e e s of extension a n d 7 d e g r e e s of ulnar d e v i a t i o n 90 d e g r e e s of f l e x i o n  30  35  with the e l b o w at  h a s b e e n s h o w n to p r o d u c e the greatest force during grip  strength testing. S u et a l  2 9  investigated s h o u l d e r a n d e l b o w positions o n grip strength  in 160 m e n a n d w o m e n a n d found that grip strength w a s lowest with the s h o u l d e r in 0 d e g r e e s of flexion a n d the e l b o w at 90 d e g r e e s (standard protocol) a s c o m p a r e d with the greatest grip strength found with the arm o v e r h e a d (shoulder at 180 d e g r e e s of flexion) a n d the e l b o w e x t e n d e d . H a n d circumference in relation to grip strength is a l s o important, particularly w h e n testing all 5 positions on the J a m a r .  3 0  T i m e of testing a n d fatigability are important factors to c o n s i d e r with a n y m u s c l e testing. Activities the individual h a s b e e n doing prior to testing is important to note. W h i l e fatigue m a y be a factor in grip strength m e a s u r e m e n t s , the literature is inconsistent. Mathiowetz et a l within multiple trials but F e s s  3 7  2 5  a n d Lusardi a n d B o h a n n o n  3 6  reported no difference  indicated fatigue m a y be a factor during the S t a n d a r d  Grip Strength T e s t . Mathiowetz  3 8  did not find fatigue to be a clinically significant factor  in the S t a n d a r d Grip Strength T e s t of three grip strength trials with a 15 s e c o n d intertrial rest period. It h a s b e e n s u g g e s t e d that two trials be recorded with a five minute rest b e t w e e n trials , h o w e v e r there d o e s not a p p e a r to be any standardization in a review of 21  the literature. M a r i o n a n d N i e b u h r  39  investigated the effect of w a r m - u p trials prior to  m a x i m a l grip strength testing a n d found that w a r m - u p ( s u b m a x i m a l gripping) h a d the  8 effect of improving m a x i m a l grip force v a l u e s , h o w e v e r their s a m p l e s i z e w a s s m a l l (n=15). Grip strength v a l u e s d o not a p p e a r to vary from morning to a f t e r n o o n . 7  T h e u s e of verbal e n c o u r a g e m e n t , while mentioned in the literature a s part of the testing protocol, h a s not b e e n specifically studied with respect to grip strength testing. M c N a i r et a l  4 0  in a K i n - C o r n study looking at the effect of verbal e n c o u r a g e m e n t o n  m a x i m u m voluntary m u s c l e action of the e l b o w flexors during isometric testing found that p e a k force i n c r e a s e d w h e n verbal e n c o u r a g e m e n t w a s p r e s e n t e d . T h e implications of verbal e n c o u r a g e m e n t m a y be important w h e n motivating subjects to give m a x i m a l effort during grip strength testing.  O t h e r instruments h a v e b e e n c o m p a r e d to the J a m a r d y n a m o m e t e r for a s s e s s i n g grip strength including the Baltimore T h e r a p e u t i c E q u i p m e n t W o r k S i m u l a t o r ( B T E )  4 1 4 2  a n d the Modified S p h y g m o m a n o m e t e r . T o o l s that utilize air c o m p r e s s i o n in a c l o s e d 36  s y s t e m s u c h a s the S p h y g m o m a n o m e t e r a n d the Martin vigorimeter h a v e b e e n criticized a s m e a s u r i n g grip pressure a n d not grip f o r c e .  30  H o w e v e r , in s o m e  populations s u c h a s the elderly or t h o s e that h a v e suffered a painful hand injury, t h e s e t y p e s of d e v i c e s m a y be more appropriate than using a J a m a r hand d y n a m o m e t e r in order to obtain b a s e l i n e grip strength m e a s u r e s .  R A T I O N A L E F O R INVESTIGATION  Reliability of Grip Strength Measures  Reliability refers to a m e a s u r e that is free from errors of m e a s u r e m e n t a n d is 8  r e p e a t a b l e w h e n administered on more than o n e o c c a s i o n .  9  Reliability h a s s e v e r a l  c o m p o n e n t s that are often hard to s e p a r a t e including instrument reliability, intrarater  9 reliability, interrater reliability a n d intrasubject reliability. Intrarater reliability, or the 9  c o n s i s t e n c y with w h i c h o n e rater a s s i g n s s c o r e s to a single set of r e s p o n s e s on two o c c a s i o n s m e a s u r e s error of the r e s e a r c h e r . Intrasubject reliability is a s s o c i a t e d with 9  actual c h a n g e s in subject performance in repeated t r i a l s . M o s t reliability s t u d i e s or 9  test-retest r e s e a r c h reflect a combination of instrument errors, tester errors a n d true subject variability.  9  Instrument reliability for the J a m a r d y n a m o m e t e r is tested through calibration. Distributors of the J a m a r d y n a m o m e t e r calibrate the instrument in their labs a n d s u g g e s t that calibration s h o u l d be d o n e at least o n c e a year. F e s s  4 3  s t r e s s e d the n e e d  for c o m p a r i s o n of calibration with known s t a n d a r d s s u c h a s the National Institute of S t a n d a r d s a n d T e c h n o l o g y (NIST). W h i l e J a m a r d y n a m o m e t e r s h a v e b e e n in u s e s i n c e 1954, F e s s found that no o n e had c h e c k e d t h e m against N I S T criteria for o v e r three d e c a d e s , a s s u m i n g that calibration w a s a c c u r a t e .  23  Fess  4 4 , 2 3  , in a study on the  reliability of 5 3 n e w a n d u s e d J a m a r d y n a m o m e t e r s , found o v e r 5 0 % of the u s e d d y n a m o m e t e r s a n d 2 3 . 8 % of the n e w d y n a m o m e t e r s n e e d e d to be recalibrated a c c o r d i n g to her method a n d r e c o m m e n d a t i o n s for c h e c k i n g J a m a r d y n a m o m e t e r calibration.  45  Fess  4 5  states that the J a m a r d y n a m o m e t e r is a highly reliable  a s s e s s m e n t instrument w h e n it is correctly calibrated. High calibration a c c u r a c y h a s b e e n reported for the J a m a r d y n a m o m e t e r .  4647  Flood-Joy and M a t h i o w e t z  4 8  in a  c o m p a r i s o n study of the m e a s u r e m e n t s of three J a m a r d y n a m o m e t e r s , found that there a p p e a r e d to be significant m e a s u r e m e n t differences a m o n g the d y n a m o m e t e r s .  High inter-rater reliability has b e e n r e p o r t e d  20,44  4 9  for the standard J a m a r  d y n a m o m e t e r . Hamilton, B a l n a v e a n d A d a m s , in a test-retest study of grip strength in 4 9  10 healthy individuals using the J a m a r d y n a m o m e t e r , found that the m e a n s c o r e of three trials w a s the most reliable (ICC=0.96 for the right hand a n d I C C = 0 . 9 5 for the left, w h e r e I C C = intraclass correlation coefficient). M a c D e r m i d et a l , in a interrater 46  reliability study of patients with cumulative trauma disorders found the intraclass correlation coefficient w a s high (ICC> 0.87) for all strength m e a s u r e m e n t s using either a single trial or the m e a n of three repetitions. Mathiowetz et a l  2 0  s h o w e d that using the  m e a n of three trials resulted in greater test-retest reliability c o m p a r e d to a single trial or the best s c o r e of two trials (r=0.88 for the right hand a n d r=0.93 for the left for the m e a n of 3 trials). A l t h o u g h all 5 handle positions on the J a m a r d y n a m o m e t e r exhibited g o o d reliability ( I C O 0 . 8 8 ) , Hamilton, B a l n a v e a n d A d a m s  1 1  found that position 1 w a s  significantly l e s s reliable w h e n c o m p a r e d with the other 4 h a n d l e positions on the J a m a r d y n a m o m e t e r (ICC=0.89 for the right hand at position 1 c o m p a r e d to 0.96 for position 5 w h i c h exhibited the greatest test-retest reliability). Stratford et a l ,  49  while using a  different brand of h a n d d y n a m o m e t e r , c o n c l u d e d that test-retest reliability w a s e n h a n c e d by multiple test s e s s i o n s a s c o m p a r e d to increasing the n u m b e r of repetitions during a single test s e s s i o n (R= 0.96 w h e n taking three m e a s u r e m e n t s per day o v e r two d a y s a s o p p o s e d to R=0.90 w h e n taking the estimate of a single measurement).  A s indicated by B e a r - L e h m a n a n d A b r e u , hand a s s e s s m e n t instrument reliability 5 0  and validity studies are n e e d e d a n d it is imperative that the instruments be calibrated regularly a n d the s a m e instrument be u s e d in pre a n d post-test m e a s u r e m e n t s . T h r o u g h o u t the literature, there are a n u m b e r of procedural differences noted during grip strength testing including handle p o s i t i o n ,  37,51  wrist a n d e l b o w p o s i t i o n , n u m b e r of 29  11 trials  38,  a n d the u s e of normative d a t a b a s e s . " T h e s e factors m a k e it very difficult to 24  28  a d e q u a t e l y c o m p a r e the literature regarding the test-retest reliability of grip strength m e a s u r e s . T h e type of reliability statistics u s e d d e p e n d s on the type of reliability being m e a s u r e d a n d is often e x p r e s s e d a s a n intra-class correlation coefficient or a P e a r s o n product m o m e n t correlation w h e n ratings are quantitative a s in grip strength m e a s u r e m e n t s . It is indicated in statistical theory that any m e a s u r e will h a v e a certain d e g r e e of reliability w h e n applied to certain g r o u p s under certain c o n d i t i o n s . O f 49  importance to clinicians is the ability of the m e a s u r e to reliably detect a clinically important c h a n g e in order for the continued u s e of the m e a s u r e m e n t tool in the clinical setting.  Clinical Significance of Grip Strength Measures  M o s t r e s e a r c h involves testing a hypothesis through the application of appropriate statistical tests to determine if there is a statistically significant difference b e t w e e n the m e a s u r e s of interest. H o w e v e r , a m e a s u r e that is found to exhibit statistical significance may, or m a y not, exhibit clinical significance. T h e clinical s i g n i f i c a n c e of a m e a s u r e refers to the ability of that m e a s u r e to distinguish b e t w e e n important a n d unimportant c h a n g e . F o r e x a m p l e , a 10 d e g r e e difference o n a range of motion test of the k n e e m a y be found to be statistically significant, but, of interest in rehabilitation, is how significant that 10 d e g r e e difference is to the function of the patient or to the therapist's evaluation a n d treatment of that patient. T h e r a p i s t s n e e d to be a b l e to determine w h e n a meaningful c h a n g e has occurred for their patients in order to explain p e r f o r m a n c e a n d predict o u t c o m e s . T h e definition of meaningful c h a n g e m a y differ  from patient population to population for a specific m e a s u r e . In the a b o v e illustration, for a n athlete w h o requires full k n e e range of motion in order to return to competitive sport, 1 0 d e g r e e s of r a n g e of motion m a y be a meaningful c h a n g e w h e r e a s another patient w h o s e activity level is less m a y not notice the difference in range of motion throughout their d a y to d a y activities. With all m e a s u r e s or a s s e s s m e n t tools, it is important that therapists k n o w what the normal variation in the m e a s u r e of interest is, h o w reliable the m e a s u r e is a n d h o w to interpret the results of the m e a s u r e . B a c k e d with this information, therapists c a n m a k e informed clinical d e c i s i o n s regarding the evaluation a n d treatment of their patients.  M i n i m a l reference is given in the literature a s to what constitutes a clinically important c h a n g e with respect to grip strength m e a s u r e s . T h e a b s o l u t e difference in grip strength s c o r e s b e t w e e n dominant a n d non-dominant h a n d is s o m e t i m e s u s e d to determine if a true w e a k n e s s exists. H o w e v e r , the A m e r i c a n M e d i c a l A s s o c i a t i o n ' s G u i d e s to E v a l u a t i o n of P e r m a n e n t Impairment states that little e v i d e n c e exists for a significant difference b e t w e e n the dominant a n d non-dominant h a n d .  53  M o s t grip strength studies reviewed c a n be generally classified a s 1 ) s t u d i e s describing a n instrument or c o m p a r i n g m e a n s to a s s e s s grip strength; 2 ) s t u d i e s describing the effects of positioning, environment a n d rest time on grip strength; 3 ) studies to determine m a x i m u m voluntary effort a n d the validity of p e r f o r m a n c e a n d 4) studies determining clinical norms for grip strength in certain a g e s , o c c u p a t i o n s or disabilities . T h e latter group of studies involves efforts to d e v e l o p s t a n d a r d i z e d d a t a 42  for grip strength in various populations.  13  Schmidt and T o e w s ,  5 4  attempted to provide s t a n d a r d i z e d grip strength n o r m s using  a large s a m p l e of e m p l o y e e applicants at a manufacturing plant. H o w e v e r , it h a s b e e n reported that description of the methodology w a s insufficient for replication of this study and the h a n d l e of the d y n a m o m e t e r w a s slightly modified from c o n v e n t i o n a l d y n a m o m e t e r s , therefore generalization from t h e s e results is limited . Kellor et a l 25  5 5  in  1971 p u b l i s h e d normative data for grip a n d pinch strength b a s e d on a s a m p l e of 2 5 0 individuals partitioned in 3 large a g e groups. N o s t a n d a r d i z e d positioning or instructions w e r e followed a n d test-retest reliability w a s not reported, a g a i n m a k i n g t h e s e n o r m s limited in their u s e f u l n e s s . Mathiowetz et a l  2 5  in 1985 e s t a b l i s h e d clinical  n o r m s for adults a g e d 2 0 to 75+ y e a r s on four tests of hand strength, including grip a n d pinch strength. T h e s e norms are most c o m m o n l y cited in the literature. M a t h i o w e t z et al  2 5  m e a s u r e d 6 2 8 volunteers with those in the 20 to 59 y e a r a g e g r o u p s free from  d i s e a s e or injury that could affect upper extremity strength; inclusion criteria for subjects 6 0 y e a r s a n d a b o v e w e r e outlined. Mathiowetz et a l  2 5  u s e d s t a n d a r d i z e d positioning  and instructions utilizing the J a m a r d y n a m o m e t e r at handle position n u m b e r 2 to m e a s u r e grip strength. T h e test s c o r e s for 3 s u c c e s s i v e trials w e r e r e c o r d e d for e a c h h a n d . W h i l e not explicitly stated in the study, it w a s a s s u m e d that the m e a n of the three trials w a s u s e d in the data a n a l y s i s b a s e d on other studies by M a t h i o w e t z . T h e 20  a v e r a g e p e r f o r m a n c e for m e n a n d w o m e n by a g e g r o u p s with respect to right/left hand and including the m e a n , standard deviation a n d standard error w e r e r e p o r t e d .  25  The  p u r p o s e of t h e s e norms w a s to provide a m e a n s of c o m p a r i n g the s c o r e of individual patients to that of normal subjects of the s a m e a g e a n d s e x . H o w e v e r , the interpretation of the s c o r e s a n d the magnitude of difference required to detect clinically important c h a n g e w e r e not explicitly a d d r e s s e d .  14 C l a s s i c a l m e a s u r e m e n t theory a s s u m e s that every p e r s o n h a s a true v a l u e for the m e a s u r e m e n t of interest (i.e. k n e e flexion) a n d that variations in a p e r s o n ' s s c o r e s are m e a s u r e m e n t errors about the true s c o r e .  8  In contrast, generalizability theory  8  r e c o g n i z e s that differences in s c o r e s m a y be related to any n u m b e r of different facets, or s o u r c e s of variability.  In our e x a m p l e of k n e e flexion, facets of interest to the  r e s e a r c h e r might be the skill of the physical therapist in taking the m e a s u r e m e n t , the patient's level of relaxation or level of comfort with the e x a m i n e r taking the m e a s u r e m e n t , a n d the a c c u r a c y of the goniometer.  In p h y s i c a l therapy, the  generalizability a p p r o a c h in the study of m e a s u r e m e n t s a c k n o w l e d g e s a n d provides a w a y to quantify the m a n y s o u r c e s of variability that clinicians s e e in their patients from d a y to d a y . 8  Reliability studies, using a generalizability theory a p p r o a c h , that report the s t a n d a r d error of m e a s u r e m e n t ( S E M ) a n d c o n f i d e n c e intervals (Cl) give a range of v a l u e s for the reliability of the m e a s u r e within the tested population. T h i s is v a l u a b l e to the clinician a s it provides a range of v a l u e s for a particular m e a s u r e a n d is m o r e c o n d u c i v e to making d e c i s i o n s regarding clinical significance. F o r e x a m p l e , in our a b o v e e x a m p l e of k n e e range of motion, if w e know that a m e a s u r e of range of motion is reliable (high r value) a n d the 9 5 % c o n f i d e n c e interval about the S E M a s s o c i a t e d with that m e a s u r e m e n t lies in the magnitude of 2 to 8 d e g r e e s , a 10 d e g r e e i m p r o v e m e n t c o u l d be interpreted a s a clinically significant c h a n g e in the patient's status. T h i s information c o u l d be very helpful to the treating therapist.  N o n e t h e l e s s , upon review of the  literature, there are no clear guidelines a s to what is d e e m e d clinically significant c h a n g e with respect to grip strength test m e a s u r e s .  15  CONCLUSION AND PURPOSE OF R E S E A R C H  In rehabilitation, grip strength testing is a c o m m o n clinical a s s e s s m e n t that is familiar to m a n y p h y s i c a l a n d o c c u p a t i o n a l therapists. T h e literature reveals that there are a variety of different m e t h o d s for m e a s u r i n g grip strength including variations in m e a s u r e m e n t tools, the n u m b e r of trials performed, positions of the e l b o w a n d wrist during testing, the rest time in b e t w e e n trials, position of the J a m a r d y n a m o m e t e r h a n d l e a n d the units of force u s e d (pounds or kilograms).  21  Grip strength testing  protocols are often inadequately d e s c r i b e d in the literature a n d this apparent lack of s t a n d a r d i z e d terminology a n d protocols m a k e s it very difficult to c o m p a r e a c r o s s studies or to interpret results in the context of clinically important c h a n g e . Prior to determining what constitutes a clinically important c h a n g e , the tool or m e a s u r e being u s e d must d e m o n s t r a t e g o o d reliability,  43 5 6  thus reliability studies are a prerequisite to  the utilization of clinical data. M e a s u r e m e n t s must be reliable if therapists are to be confident that c h a n g e s in strength o v e r t i m e , or differences in patient s c o r e s a n d normative v a l u e s , are d u e to real differences a n d not to m e a s u r e m e n t error.  T h e p u r p o s e of this study w a s to survey therapists to determine what grip strength m e a s u r e m e n t strategies w e r e currently being u s e d to detect clinically important c h a n g e in the rehabilitation setting. A s well, the reliability of two grip strength tests using the J a m a r d y n a m o m e t e r w a s investigated in order to p r o p o s e a m e a s u r e m e n t strategy to detect clinically important c h a n g e . T o our k n o w l e d g e , no o n e h a s attempted to specifically look at grip strength m e a s u r e s in this w a y .  16 REFERENCES  1.  A s i m o w E n g i n e e r i n g C o m p a n y . J a m a r Adjustable H a n d D y n a m o m e t e r . 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Grip Test: T h e u s e of a d y n a m o m e t e r with adjustible h a n d l e s p a c i n g s . Journal of Bone and Joint Surgery (Am.) 1954; 3 6 A : 8 3 2 .  19.  Kirkpatrick J E . Evaluation of grip loss. California  20.  M a t h i o w e t z V , W e b e r K, V o l l a n d G , K a s h m a n N. Reliability a n d validity of hand strength evaluations. Journal of Hand Surgery (Am) 1984; 9 : 2 2 2 - 2 2 6 .  21.  Smith R O , B e n g e M W . P i n c h a n d g r a s p strength: S t a n d a r d i z a t i o n of terminology a n d protocol. American Journal of Occupational Therapy 1 9 8 5 ; 39(8):531-535.  22.  G o l d m a n S , C a h a l a n T D , A n K. T h e injured upper extremity a n d the J a m a r five h a n d l e position test. American Journal of Physical Medicine and Rehabilitation 1 9 9 1 ; 70(6): 3 0 6 - 3 0 8 .  23.  F e s s E E . G u i d e l i n e s for evaluating a s s e s s m e n t instruments. Journal Therapy 1995; 8(2): 144-148.  24.  Kellor M , Frost J , Silberberg N, Iversen I, C u m m i n g s R. H a n d strength a n d dexterity. American Journal of Occupational Therapy 1 9 7 1 ; 2 5 : 7 7 - 8 3 .  25.  M a t h i o w e t z V , K a s h m a n N, V o l l a n d G , W e b e r K, D o w e M , R o g e r s S . G r i p a n d pinch strength: Normative data for adults. Archives of Physical Medicine and Rehabilitation 1985; 6 6 : 6 9 - 7 4 .  26.  T o e w s J V . A grip strength study a m o n g steelworkers. Archives Medicine and Rehabilitation 1964; 4 5 : 4 1 3 - 4 1 7 .  27.  M a t h i o w e t z V , W i e m e r D M , F e d e r m a n S M . Grip a n d pinch strength: n o r m s for 6to 1 9 - y e a r s - o l d s . American Journal of Occupational Therapy 1986; 4 0 ( 1 0 ) : 7 0 5 - 1 1 .  28.  A g e r C L , Olivett B L , J o h n s o n C L . G r a s p a n d pinch strength in children 5 to 12 y e a r s old. American Journal of Occupational Therapy 1984; 38(2): 1 0 7 - 1 1 3 .  Medicine  Therapy  1986;  1956; 8 5 : 3 1 4 - 3 2 0 .  of  of Hand  Physical  18  29.  S u C Y , Lin J H , C h i e n T H , C h e n g K F , S u n g Y T . Grip strength in different positions of e l b o w a n d shoulder. Archives of Physical Medicine & Rehabilitation 1994; 75(7):812-5.  30.  D e s r o s i e r s J , B r a v o G , Hebert R, Dutil E. Normative d a t a for grip strength of elderly m e n a n d w o m e n . American Journal of Occupational Therapy 1 9 9 5 ; 49(7):637-44.  31.  H a r k o n e n R, Piirtomaa M a n d A l a r a n t a H. Grip strength a n d hand position of the d y n a m o m e t e r in 2 0 4 Finnish adults. Journal of Hand Surgery 1993; 18B(1): 1 2 9 132.  32.  P e t e r s e n P, Petrick M , C o n n o r H, C o n k l i n D. Grip strength a n d h a n d d o m i n a n c e : challenging the 1 0 % rule. American Journal of Occupational Therapy 1 9 8 9 ; 43(7):444-7.  33.  C r o s b y C A , W e h b e M A , M a w r B. H a n d strength: normative v a l u e s . Journal Hand Surgery 1994; 19(4):665-70.  34.  J o s t y IC, Tyler M P , S h e w e l l P C , R o b e r t s A H . Grip a n d pinch strength variations in different types of workers. Journal of Hand Surgery (British V o l u m e ) 1997; 22(2): 266-9.  35.  O ' D r i s c o l l S W , Horii E, N e s s R, C a h a l a n T D , R i c h a r d s R R , A n K N . T h e relationship b e t w e e n wrist position, g r a s p s i z e a n d grip strength. Journal Surgery (Am) 1992; 17(1): 169-77.  of  of  Hand  36.  L u s a r d i M M , B o h a n n o n R W . H a n d grip strength: Comparability of m e a s u r e m e n t s obtained with a J a m a r d y n a m o m e t e r a n d a modified s p h y g m o m a n o m e t e r . Journal of Hand Therapy 1 9 9 1 ; 4(3): 117-122.  37.  F e s s E E . T h e effects of J a m a r handle position a n d test protocol o n normal grip strength. Journal of Hand Surgery 1982; 7 A : 3 0 8 .  38.  Mathiowetz, V . Effects of three trials on grip a n d pinch strength m e a s u r e m e n t s . Journal of Hand Therapy 1990; 3(4):195-198.  39.  M a r i o n R, N i e b u h r B R . Effect of warm-up prior to m a x i m a l grip contractions. Journal of Hand Therapy 1992; 5(3):143-146.  40.  M c N a i r P J , D e p l e d g e J , Brettkelly M , S t a n l e y S N . V e r b a l e n c o u r a g e m e n t : effects on m a x i m u m effort voluntary m u s c l e action. British Journal of Sports Medicine 1996; 30(3):243-5.  19 41.  B e a t o n D E , O'Driscoll S W , R i c h a r d s R R . Grip strength testing using the B T E work simulator a n d the J a m a r d y n a m o m e t e r : A comparative study. Journal of Hand Surgery 1 9 9 5 ; 2 0 A ( 2 ) : 2 9 3 - 2 9 8 .  42.  King J W , Berryhill B H . A c o m p a r i s o n of two static grip testing m e t h o d s a n d its clinical applications: A preliminary study. Journal of Hand Therapy 1988; 4 : 2 0 4 208.  43.  F e s s E E . W h y trial-to-trial reliability is not e n o u g h . Journal 1994; 7(1):28.  44.  F e s s E E . Reliability of new a n d u s e d J a m a r d y n a m o m e t e r s under laboratory conditions. C o m m e n t . Journal of Hand Therapy 1990; 1:35.  45.  F e s s E E . A method for c h e c k i n g J a m a r d y n a m o m e t e r calibration. Journal Hand Therapy 1987; (4):28-32.  46.  M a c D e r m i d J C , K r a m e r J F , W o o d b u r y M G , M c F a r l a n e R M , R o t h J H . Interrater reliability of pinch a n d grip strength m e a s u r e m e n t s in clients with cumulative t r a u m a disorders. Journal of Hand Therapy 1994; 7: 10-14.  47.  H a r k o n e n R, Harju R, A l a r a n t a H. A c c u r a c y of the J a m a r d y n a m o m e t e r . of Hand Therapy 1993; 6 : 2 5 9 - 2 6 2 .  48.  F l o o d - J o y , M , M a t h i o w e t z , V . Grip-strength m e a s u r e m e n t : A c o m p a r i s o n of three J a m a r d y n a m o m e t e r s . Occupational Therapy Journal of Research 1987; 7:4: 2 3 5 243.  49.  Stratford P W , N o r m a l G R , M c i n t o s h J M . Generalizability of grip strength m e a s u r e s in patients with tennis elbow. Physical Therapy 1989; 6 9 : 2 7 6 - 2 8 1 .  50.  B e a r - L e h m a n J , A b r e a u B C . Evaluating the h a n d : Issues in reliability a n d validity. Physical Therapy 1989; 69(12): 1 0 2 5 - 1 0 3 3 .  51.  N i e b u h r B R , M a r i o n R. Detecting sincerity of effort w h e n m e a s u r i n g grip strength. American Journal of Physical Medicine and Rehabilitation 1987; 6 6 : 1 6 - 2 4 .  52.  H o p k i n s K D , H o p k i n s B R , G l a s s G V . B a s i c Statistics for the B e h a v i o u r a l S c i e n c e s , 3 e d . Toronto: Allyn a n d B a c o n , 1996.  of Hand  Therapy  of  Journal  r d  53.  A m e r i c a n M e d i c a l A s s o c i a t i o n . Guides to the evaluation of permanent impairment, 4th e d . C h i c a g o , Illinois: A m e r i c a n M e d i c a l A s s o c i a t i o n , 1 9 9 3 .  54.  S c h m i d t R T , T o e w s J V . Grip strength a s m e a s u r e d by the J a m a r d y n a m o m e t e r . Archives of Physical Medicine & Rehabilitation 1970; 5 1 : 3 2 1 - 3 2 7 .  20  55.  Kellor M , Frost J , Silberberg N, Iverson I, C u m m i n g s R. H a n d strength a n d dexterity. American Journal of Occupational Therapy 1 9 7 1 : 2 5 : 7 7 - 8 3 .  56.  F l e i s s J L . T h e D e s i g n a n d A n a l y s i s of Clinical E x p e r i m e n t s , N e w Y o r k : J o h n W i l e y a n d S o n s , 1986.  21  CHAPTER  2_ SURVEY STUDY  INTRODUCTION W h e n reviewing the literature on grip strength testing, it b e c o m e s evident that while grip strength m e a s u r e s are c o m m o n l y u s e d in clinical practice, the protocols a n d terminology for testing are not s t a n d a r d i z e d a n d differ widely from study to study a n d clinic to clinic. Positioning, n u m b e r of repetitions, equipment u s e d , testing protocols, intertrial rest periods, equipment calibration a n d interpretation of m e a s u r e m e n t s c o r e s all exhibit c o n s i d e r a b l e variation. T h i s m a k e s it extremely difficult to c o m p a r e a c r o s s studies a n d to c o m p a r e grip strength m e a s u r e s to normative d a t a b a s e s that m a y not h a v e u s e d the s a m e testing p r o c e d u r e s or instruments. The  purpose  of  this  study  was  to  survey  occupational  therapists  and  physiotherapists w h o e m p l o y grip strength testing during their normal clinical evaluation a n d a s s e s s m e n t s of patients in order to gain s o m e insight into what m e a s u r e s are currently  being u s e d . It w a s h y p o t h e s i z e d that 1) most clinicians e m p l o y i n g  grip  strength tests will u s e the S t a n d a r d Grip Strength T e s t ( S G S T ) a n d the 5-Position Grip Strength T e s t (5PGST) (Appendix A ) utilizing the standard J a m a r d y n a m o m e t e r a s a m e a s u r e m e n t tool; 2) that the main p u r p o s e of testing will be to m e a s u r e grip strength in individuals with h a n d a n d upper extremity dysfunction a n d 3) that there will be a wide  22  v a r i a n c e in what clinicians d e e m a clinically important c h a n g e with respect to a n a l y z i n g grip strength test results.  T h e objectives of the study w e r e a s follows: 1. T o determine w h i c h grip strength tests a n d w h i c h testing instruments  are  c o m m o n l y u s e d in clinical practice. 2. T o determine w h i c h patient populations are being m e a s u r e d a n d what is the p u r p o s e of the testing. 3. T o determine if normative d a t a b a s e s are u s e d for c o m p a r i s o n of test results. 4. T o  investigate  what  parameters  clinicians  use  to  determine  clinically  important c h a n g e in grip strength m e a s u r e s .  METHODS Subjects A self-report m e a s u r e (Appendix B) w a s mailed to 140 sites a c r o s s C a n a d a . Facilities w e r e c h o s e n from a m o n g s t a larger s a m p l e of C a n a d i a n University p h y s i c a l therapy a n d o c c u p a t i o n a l therapy student placement information.  D e c i s i o n to include a  facility in the study w a s b a s e d on a description of the treatment s e r v i c e s the facilities offered; inclusion criteria included hand rehabilitation a n d o r t h o p a e d i c s . A s well, 13 m e m b e r s of the C a n a d i a n S o c i e t y of H a n d T h e r a p i s t s unaffiliated with the sites w e r e sent a s u r v e y questionnaire. In total, 153 facilities (sites a n d therapists c o m b i n e d ) w e r e included in the test s a m p l e . Prior to mailing, the survey w a s pilot tested at 5 different sites in V a n c o u v e r , British C o l u m b i a a n d modifications w e r e m a d e with respect to format a n d content  23  b a s e d on their f e e d b a c k . T h e final survey contained 6 closed-format multiple-choice items with s o m e flexibility of r e s p o n s e available by including a n "other" category. T h e r e w e r e a l s o 2 forced c h o i c e questions with a y e s / n o a n s w e r . A o n e - p a g e format w a s c h o s e n in order to i n c r e a s e c o m p l i a n c e a n d e a s e of filling out of the form. T h e University of British C o l u m b i a Ethics C o m m i t t e e a p p r o v e d this r e s e a r c h (#C97-0223). Testing Procedures A c o v e r letter (Appendix C ) w a s sent with e a c h questionnaire outlining the study a n d providing contact information if there w e r e questions. A s t a m p e d , s e l f - a d d r e s s e d e n v e l o p e w a s provided in the survey p a c k a g e a n d r e s p o n d e n t s w e r e a s k e d to return their c o m p l e t e d s u r v e y s by mail or by fax. Data Collection Q u e s t i o n n a i r e s w e r e c o d e d with a n u m b e r that c o r r e s p o n d e d to the facility or individual on a master mailing list. R e s p o n s e s w e r e treated a s being a n o n y m o u s a n d confidential. A cutoff date for survey return w a s e s t a b l i s h e d o n c e returns a p p e a r e d to diminish a n d no further s u r v e y s w e r e included in the study after this date. Data Analysis S u r v e y r e s p o n s e s w e r e a n a l y z e d for frequency distributions. T h e p e r c e n t a g e of subjects w h o r e s p o n d e d to e a c h category under a relevant survey question w a s c a l c u l a t e d . In the c a s e of multiple-choice questions w h e r e r e s p o n d e n t s c h e c k e d off more than o n e c h o i c e , e a c h c h o i c e w a s treated separately in the data a n a l y s i s to avoid biasing the results. W h e r e there w e r e multiple s u r v e y s c o m p l e t e d per site, o n e s u r v e y w a s randomly s e l e c t e d for inclusion in the data set. H o w e v e r , in a n a l y z i n g the d a t a from question n u m b e r s e v e n ("How large would the difference it clinically  significant'),  have to be for you to call  all data (including multiple s u r v e y s from 1 site) w e r e c o n s i d e r e d  24 b e c a u s e a proportion of the r e s p o n d e n t s to question 7 did not indicate the units of m e a s u r e a n d therefore, t h o s e r e s p o n s e s could not be u s e d . T h e qualitative d a t a a n d written c o m m e n t s g e n e r a t e d by the survey w e r e reviewed a n d reported in the text of the results a n d the d i s c u s s i o n .  RESULTS O n e hundred a n d sixty six s u r v e y s in total w e r e c o m p l e t e d a n d returned including multiple r e s p o n s e s from test sites. T h r e e r e s p o n s e s w e r e not u s e d d u e to late return. O f the 153 facilities contacted (140 sites, 13 h a n d therapists), 120 r e s p o n s e s w e r e obtained resulting in a 7 8 % r e s p o n s e rate overall. B r e a k i n g this d o w n into s u b g r o u p s , 7 8 % of the sites contacted r e s p o n d e d (109/140) a n d 8 5 % (11/13) of the h a n d therapists r e s p o n d e d . S e v e n r e s p o n d e n t s indicated they did not u s e grip strength m e a s u r e s in clinical practice a n d their s u r v e y s w e r e r e m o v e d from further d a t a a n a l y s i s , revising the s a m p l e s i z e from 120 to 113. Ninety four percent of all r e s p o n d e n t s (113 of 120 r e s p o n s e s ) indicated that they u s e d grip strength m e a s u r e s in their clinical practice. O f the tests u s e d , 8 3 % indicated that they u s e d the S t a n d a r d Grip Strength T e s t a n d 4 2 % stated they u s e d the 5-Position Grip Strength T e s t (Figure 1); 3 0 % u s e d both tests. Twenty-five percent of r e s p o n d e n t s u s e d the R a p i d E x c h a n g e G r i p Strength T e s t a n d 1 1 % u s e d other grip strength m e a s u r e s . E i g h t y - s e v e n percent u s e d the J a m a r d y n a m o m e t e r to m e a s u r e grip strength while 1 5 % u s e d a blood p r e s s u r e cuff (Figure 2). Other tools u s e d to m e a s u r e grip strength included the digital J a m a r d y n a m o m e t e r (10%) a n d the Baltimore T h e r a p e u t i c E q u i p m e n t W o r k Simulator ( B T E ) (9%) (Figure 2). R e s p o n d e n t s u s e d grip strength testing for a variety of patient  Survey Response - Type of Grip Strength Test Used 100 0  to c o a  90  • All R e s p o n s e s (n=113)  80  • H a n d T h e r a p i s t s Only (n=11) I  70  • S i t e s Only (n=102)  <o  60  c o  40  o on  50 30 20  L.  CL  10 0 Standard Grip  5 Position Grip  Rapid Exchange  Strength Test  Strength Test  Grip Test  Other  Grip Strength Test Figure 1: S u r v e y r e s p o n s e s indicating the types of grip strength u s e d .  Survey Response - Measurement Instrument Used 0)  co c o  O . CO  0)  Q_ +•> c CJ  o o  100 90 80 70 60 50 40 30 20 10 0  • All R e s p o n s e s (n=113) • H a n d Therapists Only (n=11) • S i t e s Only (n=102)  n Jamar  n Digital Jamar  BTE  Blood Pressure Cuff  Grip Strength Measurement Tool Figure 2: S u r v e y r e s p o n s e s of grip strength m e a s u r e m e n t tools u s e d in clinical practice.  Other  26  Survey Responses - Grip Strength Testing by Patient Population o w  c o a. in  G)  al *J  ca u  o  CL  100 90 80 70 60 50 40 30 20 10 0  • All R e s p o n s e s (n=113) • H a n d T h e r a p i s t s O n l y (n=11) • S i t e s O n l y (n=102)  H a n d Injuries  U p p e r Extremity  Back/Neck  Injuries  Injuries  Other  Patient Population Figure 3: Grip strength testing by patient population.  Survey Responses - Test Purpose • All Responses (n=113) V)  • Hand Therapists Only (n=11)  o  • Sites Only (n=102)  C  Q. V) o  ai •*-> c o o  1_  Q.  Determine Grip  Measure  Measure  Assess  Strength  function  impairment  sincerity of effort  Test Purpose Figure 4: S u r v e y r e s p o n s e depicting the intended purpose of grip strength m e a s u r e m e n t s .  27  Survey Response - Use of a Normative Database O CO  c o Q.  CO CU  Q_ c 0 o o  100 90 80 70 60 50 40 30 20 10  • Yes • No  CL  All R e s p o n s e s (n=111)  H a n d Therapists Only  Sites O n l y (n=102)  (n=9) Use of a Normative Database Figure 5: S u r v e y r e s p o n s e data depicting the u s e of a normative d a t a b a s e in grip strength m e a s u r e m e n t s .  populations including 8 5 % for p e r s o n s with hand injuries, 7 3 % for upper extremity injuries, 3 1 % for back a n d neck injuries a n d 3 2 % for other conditions including arthritis a n d c e r e b r o v a s c u l a r a c c i d e n t s ( C V A ' s ) (Figure 3). W h e n a s k e d what p u r p o s e they u s e d grip strength testing for, the r e s p o n d e n t s indicated that 9 8 % m e a s u r e d grip strength itself, 3 5 % u s e d grip strength testing to m e a s u r e function, 5 8 % to m e a s u r e impairment a n d 4 2 % to m e a s u r e sincerity of effort (Figure 4). Descriptive c o m m e n t s indicated the S t a n d a r d Grip Strength T e s t w a s the best test to determine grip strength a n d the 5-Position Grip Strength T e s t w a s indicated a s the best test for sincerity of effort. Thirty-nine percent of r e s p o n d e n t s stated they u s e d a normative d a t a b a s e with which to c o m p a r e results v e r s u s 6 2 % w h o did not; M a t h i o w e t z et a l ' s norms for grip a n d pinch strength w e r e cited a s the most c o m m o n 1  d a t a b a s e u s e d (Figure 5).  28 Clinically Important Change O n a n u m b e r of m e a s u r e s reported to determine clinically important c h a n g e , 5 8 % of the r e s p o n d e n t s stated they u s e d a p e r c e n t a g e difference b e t w e e n h a n d s , 6 0 % stated they u s e d the absolute difference between h a n d s , 2 7 % u s e d the p e r c e n t a g e difference b e t w e e n h a n d s , 3 9 % u s e d the absolute difference b e t w e e n trials, 1 6 % u s e d the p e r c e n t a g e difference between a normative d a t a b a s e a n d the raw s c o r e a n d 1 9 % stated they u s e d the absolute difference between a normative d a t a b a s e a n d the raw s c o r e (Figure 6 ) . Other m e a s u r e s reported to detect clinically important c h a n g e included using coefficients of variation. T h e actual amount of differrence in grip strength that clinicians v i e w e d a s a clinically important c h a n g e varied a c r o s s clinicians. Of those reporting the u s e of a n a b s o l u t e difference b e t w e e n h a n d s to detect important c h a n g e (n=53), 5 7 % indicated a difference of 5 kgforce w a s significant (Figure 7).  Survey R e s p o n s e - Measures Used to Detect Clinically Important Change El A l l R e s p o n s e s (n=113) H a n d T h e r a p i s t s O n l y (n=11) • S i t e s O n l y (n=102)  % diff btwn hands  Abs diff btwn hands  % diff btwn trials  A b s diff btwn trials  % diff btwn NDB/score  Abs diff btwn NDB/score  Other  Measures Figure 6: S u r v e y r e s p o n s e s depicting m e a s u r e s used to detect clinically important c h a n g e in grip strength m e a s u r e m e n t .  Survey Response - Absolute Difference Between Hands (n=53)  100-,  2 kgforce  5 kgforce  15 kgforce  10 kgforce  20 kgforce  27 kgforce  Kgforce deemed clinically significant Figure 7: S u r v e y r e s p o n s e indicating a m o u n t of c h a n g e in kgforce to detect clinically significant c h a n g e in grip strength measurements between hands.  Survey Response - Percentage Difference Between Hands (n 100-,  rcent pons  0)  0)  W  Q_ o  806040200 c CD O CD CLIO  M a  c CD O L CD Q_ O  C CD O i_ CD Q_ IT)  T—  T—  c CD O \ CD  C CD O \ CD Q_  C CD O CD Q_  O CM  LO CN  O CO  0_  c CD O i_ CD CLIO CO  c CD O L— CD CL O  c CD O L— CD CL LO  c CD O CD CL O LO  C CD O i_ CD CL O 00  Percent Difference Deemed Clinically Significant Figure 8: S u r v e y r e s p o n s e data indicating p e r c e n t a g e difference b e t w e e n h a n d s c o n s i d e r e d clinically significant with grip strength m e a s u r e m e n t s .  30  Survey Response - Percentage Difference Between Trials (n=34) 100-, CD  5 Percent  10 Percent  15 Percent  20 Percent  25 Percent  Percentage Reported Clinically Significant Figure 9: S u r v e y r e s p o n s e s depicting clinically significant p e r c e n t a g e c h a n g e b e t w e e n trials reported in grip strength measures.  Survey Response - Absolute Difference Between Trials for Clinical Significance (n=23)  2kgf  5kgf  10kgf  15KGF  Kgforce Reported Clinically Significant  Figure 10: Survey responses depicting clinically significant change in kgforce between trials in grip strength measurements.  Survey Response - Percentage Difference Between Normative Database (n=17) 100n 0)  « o w  8060-  a> u a> a. 5 Percent  10 15 20 25 30 35 40 60 Percent Percent Percent Percent Percent Percent Percent Percent  Percentage Difference Reported Clinically Significant  Figure 1 1 : S u r v e y r e s p o n s e d a t a indicating p e r c e n t a g e difference b e t w e e n grip strength s c o r e s a n d a normative d a t a b a s e to b e c o n s i d e r e d clinically significant.  Survey Response - Actual Difference Between a Normative Database and Grip Strength Scores (n=9)  2 kgforce  5 kgforce  10 kgforce  15 kgforce  20 kgforce  Kgforce Reported Clinically Significant  Figure 1 2 :  S u r v e y r e s p o n s e data indicating absolute difference b e t w e e n a  normative d a t a b a s e a n d grip strength m e a s u r e m e n t s for clinical significance.  32  M e a s u r e s r a n g e d from 2kgforce (15%) to 27 kgforce (2%). Of t h o s e using a p e r c e n t a g e difference b e t w e e n h a n d s (n=82), the range of v a l u e s w a s b e t w e e n 5 % to 8 0 % . Thirty percent of r e s p o n d e n t s stated that a 1 0 % difference b e t w e e n h a n d s w o u l d be c o n s i d e r e d significant a n d 2 4 % stated a 2 0 % difference w o u l d be significant (Figure 8). W h e n looking at b e t w e e n trial significance (n=34), 5 3 % of r e s p o n d e n t s indicated that a 1 0 % difference b e t w e e n trials w a s an important c h a n g e (Figure 9). T h e a b s o l u t e difference b e t w e e n trials (n=23) w a s reportedly significant at 2 kgforce (52%) a n d at 5 kgforce (43%) (Figure 10). Utilizing a normative d a t a b a s e , 2 9 % (n=17) of r e s p o n d e n t s indicated that a 1 0 % difference b e t w e e n the s c o r e a n d the normative v a l u e w a s significant (Figure 11) while 2 4 % stated that a 2 0 % difference w a s significant. Sixtys e v e n percent (n=9) stated a difference of 5kgforce from the normative v a l u e w a s significant (Figure 12). Clinical significance w a s a l s o indicated by 1) using c a t e g o r i e s s u c h a s excellent, a v e r a g e , below a v e r a g e etc. w h e r e below a v e r a g e a n d p o o r w e r e clinically significant; 2) using consistent improvement o v e r t i m e ; 3) using functional level; 4) using a n y c h a n g e in the patient's status a n d 5) using the patient's self-report of function. It w a s a l s o reported that there w e r e too m a n y variables to be a b l e to determine clinical significance.  DISCUSSION T h e high overall r e s p o n s e to the survey m a y indicate that grip strength m e a s u r e m e n t is a n important a n d c o m m o n clinical practice in p h y s i c a l therapy a n d o c c u p a t i o n a l therapy. M a r c u z z i , Kelly, C h a n g a n d H a n n a h , in a s u r v e y of C a n a d i a n 2  h a n d therapists, found that evaluation of grip a n d pinch strength w a s rated o n e of the  33  m o s t important clinical activities performed by the r e s p o n d e n t s . In our survey, 8 7 % u s e d the J a m a r d y n a m o m e t e r , 8 3 % u s e d the S t a n d a r d Grip Strength T e s t a n d 9 8 % indicated that the main p u r p o s e of grip strength testing w a s to m e a s u r e grip strength. H o w e v e r , while clinician u s e of the grip strength tools a n d m e a s u r e s w a s reportedly very high in our s u r v e y a s noted a b o v e , there w a s e v i d e n c e of a range of r e s p o n s e s indicating that s o m e variability exists in clinical practice a s to e q u i p m e n t u s e d , type of grip strength testing performed, patient populations tested a n d the p u r p o s e of e a c h grip strength test. O f c o n s i d e r a b l e interest w a s the range of interpretation of m e a s u r e m e n t s c o r e s (clinical significance) reported in clinical practice. T h e s e variations in s u r v e y r e s p o n s e s could be attributed to a n u m b e r of factors. With respect to m e a s u r e m e n t tools, the J a m a r d y n a m o m e t e r e m e r g e d a s the most frequently u s e d grip strength m e a s u r i n g tool. E i g h t y - s e v e n percent reported using the J a m a r d y n a m o m e t e r in clinical practice while 3 1 % of all r e s p o n d e n t s indicated using more than o n e m e a s u r e m e n t tool. This c o r r e s p o n d s to S m i t h a n d B e n g e ' s s u r v e y of 195 o c c u p a t i o n a l therapy clinics w h e r e 7 9 % stated that the J a m a r 3  d y n a m o m e t e r w a s the most c o m m o n l y u s e d m e a s u r e m e n t tool with 4 0 % of r e s p o n d e n t s using more than o n e tool. T h e J a m a r d y n a m o m e t e r a p p e a r s widely a c c e p t e d a s a grip strength m e a s u r i n g d e v i c e in the literature  4 , 5  a n d the results of our  s u r v e y support this statement in clinical practice. C o m p a r e d to other instruments, it w a s the m e a s u r e m e n t tool of c h o i c e for grip strength a m o n g s t the h a n d therapists s u r v e y e d in our study. W h e n reviewing the survey d a t a , it w a s evident that the u s e of other m e a s u r e m e n t tools reflected both the patient populations being tested a n d the availability of m e a s u r e m e n t tools in the clinical setting. F o r e x a m p l e , r e s p o n d e n t s in  34 this s u r v e y working with elderly or arthritic populations stated that they u s e d a blood p r e s s u r e cuff to m e a s u r e grip strength. T h e J a m a r d y n a m o m e t e r m a y be too difficult to hold or requires too m u c h force to register a v a l u e for this group of patients. A m e a s u r e m e n t tool h a s to "fit" the abilities of the patients a n d be appropriate for the type of population tested in order to gain meaningful m e a s u r e m e n t s . A s well, the affordability of certain tools often dictates their u s e in the clinical setting. A J a m a r d y n a m o m e t e r is relatively i n e x p e n s i v e c o m p a r e d to more sophisticated a n d costly testing d e v i c e s s u c h a s a B T E . T h e most c o m m o n grip strength tests u s e d w e r e the S t a n d a r d G r i p Strength T e s t (83%) a n d the 5-Position Grip Strength (42%) test a s initially h y p o t h e s i z e d . H o w e v e r , a review of the c o m m e n t s noted in the survey r e s p o n s e s s u g g e s t e d there w a s s o m e c o n f u s i o n a s to the protocol for the S t a n d a r d Grip Strength T e s t . U s i n g o n e trial, the m e a n of three trials, or the highest s c o r e on three trials a s the m e a s u r e of grip strength w e r e noted. T h i s indicates the n e e d for accurately defining test p a r a m e t e r s a n d testing protocols. A survey looking at grip a n d pinch strength terminology a n d protocols s u g g e s t e d that " a significant n u m b e r of r e s p o n d e n t s indicated they h a d no particular r e a s o n for using the specific terminology, equipment or protocols that they u s e d " in grip a n d pinch strength testing.  3  Ninety-eight percent of r e s p o n d e n t s indicated the p u r p o s e of grip strength testing w a s to determine grip strength. S u r v e y results a l s o s u g g e s t e d that grip strength testing w a s u s e d to m e a s u r e function (35%) a n d impairment (60%). H a n d function is a difficult construct to define a s it c a n pertain to a variety of conditions s u c h a s the ability to perform b a s i c activities of daily living or the ability to perform a c o m p l e x work task. T h e r e is no c l e a r c o n s e n s u s a s to what is meant by the term "function" within p h y s i c a l  35  therapy but R o t h s t e i n attempts to define function a s the interaction of the individual 6  with his or her environment. Grip strength testing itself involves the m e a s u r e m e n t of force during static (isometric) m u s c l e contractions, in which virtually no joint m o v e m e n t t a k e s p l a c e . A s s u g g e s t e d by R o t h s t e i n ' s definition of function, hand function w o u l d 7  6  relate to m o v e m e n t patterns of the hand during a task. W h i l e grip strength m a y be o n e c o m p o n e n t of hand function, there m a y be other s t a n d a r d i z e d tests that are better suited a n d more valid estimators of hand function in e a c h specific patient situation. A c c o r d i n g to the W o r l d Health O r g a n i z a t i o n ' s International C l a s s i f i c a t i o n for Impairment Disability a n d H a n d i c a p , a s quoted in P h y s i c a l Rehabilitation O u t c o m e 8  M e a s u r e s , impairment refers to any loss or abnormality of p s y c h o l o g i c a l , p h y s i o l o g i c a l 9  or a n a t o m i c a l structure or function. In p h y s i c a l therapy, impairment of the 8  m u s c u l o s k e l e t a l s y s t e m directly impacts function , a n d m e a s u r e s of impairment (often 6  e x p r e s s e d a s m u s c l e strength or joint range of motion ), are p r e s u m e d to reflect 9  functional ability. T h u s grip strength is c o n s i d e r e d a m e a s u r e of impairment in p h y s i c a l therapy practice although the A m e r i c a n M e d i c a l A s s o c i a t i o n ' s G u i d e s to the E v a l u a t i o n of P e r m a n e n t Impairment  10  d o e s not p l a c e great e m p h a s i s on grip strength  m e a s u r e m e n t s w h e n a s s e s s i n g impairment. In selecting a m e a s u r e to a s s e s s function or impairment, therapists must c o n s i d e r the p u r p o s e for w h i c h the instrument is being sought, the theoretical constructs surrounding the m e a s u r e , the m e a s u r e m e n t d i m e n s i o n a n d the m o d e of administration required in order to s e l e c t the appropriate test instrument. W h i l e the majority of the survey r e s p o n s e s reported p e r s o n s with h a n d a n d u p p e r extremity injuries a s the patient population most often tested for grip strength (85 a n d 7 3 % respectively), 3 1 % indicated using grip strength m e a s u r e s for p e r s o n s with  36 b a c k a n d n e c k injuries. Forty-two percent of r e s p o n d e n t s indicated they u s e d grip strength m e a s u r e s for sincerity of effort a n d c o m m e n t s indicated that the 5 P o s i t i o n G r i p Strength T e s t a n d the R a p i d E x c h a n g e Grip Strength T e s t w e r e the tests m o s t often u s e d for this p u r p o s e . W h i l e the i s s u e of sincerity of effort is b e y o n d the s c o p e of this study, the p u r p o s e of grip strength tests must be v i e w e d cautiously. T h e c o n c e p t of what is actually being m e a s u r e d must be kept in mind a n d clinicians must be careful not to u s e tests a n d extrapolate results for something other than w h a t the tests are purported to m e a s u r e .  Clinical Significance Clinical significance w a s not clearly defined in the survey d u e to o m i s s i o n but the intent w a s to look at m e a s u r e m e n t v a l u e s that clinicians u s e to d o c u m e n t c h a n g e on w h i c h to b a s e treatment d e c i s i o n s . S u r v e y results indicated that the m e a s u r e s u s e d to d o c u m e n t clinically significant c h a n g e a n d the interpretation of m e a s u r e m e n t s c o r e s exhibited c o n s i d e r a b l e range a n d variation. F o r e x a m p l e , the difference b e t w e e n h a n d s w a s the most c o m m o n index reported to detect clinically important c h a n g e in grip strength ( 5 8 % p e r c e n t a g e difference, 6 0 % absolute difference). Within t h e s e m e a s u r e s , the range of v a l u e s e x t e n d e d from 5 % to 8 0 % a n d 2kgforce to 2 7 kgforce difference. O v e r half of the r e s p o n d e n t s (57%) indicated a 5kgforce w a s significant while 3 0 % indicated a 1 0 % difference. H o w e v e r , Y o u n g et a l , in a study of normal 1 1  individuals using a J a m a r d y n a m o m e t e r to m e a s u r e grip strength, found that m e a n grip strength fluctuated b e t w e e n 5.1 a n d 8.4 kgforce or b e t w e e n 19.2 to 2 3 . 7 % . If this information is applied to the survey r e s p o n s e s , it a p p e a r s that a majority of the  37  therapists are s u g g e s t i n g clinically important c h a n g e w h e n the c h a n g e m a y be d u e to normal subject variability a l o n e (Figures 7-12). T h e difference b e t w e e n trials w a s u s e d less frequently than c o m p a r i s o n s b e t w e e n h a n d s ( 2 7 % for p e r c e n t a g e difference a n d 3 9 % for a b s o l u t e difference). T h e r a n g e of r e s p o n s e s for p e r c e n t a g e difference included 5 % to 2 5 % with 1 0 % difference the most frequent r e s p o n s e (53%). Of the absolute difference, the range e x t e n d e d from 2kgforce to 15kgforce with 5 7 % r e s p o n d e n t s indicating 5kgforce w a s clinically significant b e t w e e n trials. T h e problem f o r e s e e n with using a c o m p a r i s o n b e t w e e n trials is that the e x a m i n e r h a s little information to k n o w that the patient h a s g i v e n m a x i m u m effort on s u c c e s s i v e trials. A difference p e r c e i v e d a s clinically significant m a y in fact be d u e to motivation, subject variability from d a y to d a y , a n d / o r m e a s u r e m e n t error. T h e u s e of a normative d a t a b a s e to c o m p a r e results w a s u s e d by 3 9 % of the r e s p o n d e n t s . R e s p o n s e s ranged from a 1 0 % difference b e t w e e n a grip strength s c o r e a n d the normative d a t a b a s e to a 6 0 % difference with the most frequent r e s p o n s e s being a 1 0 % (29%) a n d 2 0 % (24%) difference. A n a b s o l u t e difference b e t w e e n a normative d a t a b a s e a n d grip strength s c o r e ranged from 2kgforce to 2 0 k g f o r c e with 6 7 % of r e s p o n d e n t s indicating a 5kgforce w a s clinically significant. It is important that the therapist be a w a r e of the methodology u s e d to d e v e l o p the normative d a t a b a s e a n d to u n d e r s t a n d w h e t h e r the therapist's testing methodology, patient d e m o g r a p h i c s a n d instrument are congruent with those r e c o m m e n d e d for the u s e of the d a t a b a s e .  1  O t h e r w i s e , the validity of the m e a s u r e of clinically significant c h a n g e w h e n c o m p a r e d to a normative d a t a b a s e is questionable.  38 H a n d therapists s u r v e y e d exhibited s o m e variation in their r e s p o n s e s to clinically significant c h a n g e with 7 3 % indicating that they u s e d the p e r c e n t a g e difference b e t w e e n h a n d s , 4 5 % the absolute difference between h a n d s a n d 2 7 % the p e r c e n t a g e difference b e t w e e n trials to report clinical significance. A s well, 5 6 % of h a n d therapists reported the u s e of a normative d a t a b a s e c o m p a r e d to 3 9 % of the other r e s p o n d e n t s . It is noted though that the s a m p l e s i z e of hand therapists w a s very s m a l l (n=11) c o m p a r e d to the other r e s p o n d e n t s (n=102). W e m a y h a v e e x p e c t e d m o r e c o n s e n s u s in their r e s p o n s e to the question of clinical significance with respect to grip strength s c o r e s d u e to the fact that hand therapists h a v e had a d v a n c e d training in h a n d therapy a n d a s s e s s m e n t , a n d are d e e m e d experts in this clinical a r e a . H o w e v e r , they a p p e a r e d to mimic the g e n e r a l s a m p l e population. T h e variation regarding clinical significance throughout the survey r e s p o n s e s indicates that there is not a c o n s e n s u s on what is clinically significant. T h e problem lies in the fact that w e do not a c c u r a t e l y k n o w what normal variability is with grip strength m e a s u r e m e n t s . O v e r a l l , the survey a p p e a r e d to represent the a r e a of interest (grip strength testing) for clinicians targeted in our survey (general orthopaedic practice a n d h a n d therapists). A c c o r d i n g to our survey, m e a s u r e m e n t of grip strength is a c o m m o n clinical practice but c o n s i s t e n c y a m o n g therapists with respect to m e a s u r e m e n t strategies is variable. T h i s h a s implications not only w h e n different therapists treat a patient in o n e setting but w h e n a patient is transferred to another clinic w h e r e a different m e t h o d of grip strength interpretation could be u s e d . W h i l e this m a k e s it difficult to c o m p a r e results, it c o u l d a l s o h a v e far reaching effects a s grip strength testing is often u s e d to determine further rehabilitation, return to work i s s u e s or disability in m e d i c a l - l e g a l  39 c a s e s . In t h e s e situations, widely a c c e p t e d reliable a n d valid m e a s u r e m e n t s are imperative to predict a c c u r a t e o u t c o m e s .  Limitations of survey W h i l e overall c o m p l i a n c e in completing a n d returning the s u r v e y w a s excellent, there w e r e m a n y inherent limitations in its d e s i g n . T h e a d v a n t a g e to the s u r v e y method c h o s e n w a s that it w a s efficient, r e s p o n s e s remained a n o n y m o u s , it w a s unlimited in terms of the g e o g r a p h i c distribution of the r e s p o n d e n t s a n d it allowed the s c h e d u l i n g of the completion of the questionnaire at the respondent's c o n v e n i e n c e .  12  The  d i s a d v a n t a g e s w e r e that the depth of r e s p o n s e w a s limited a n d the ability to clarify q u e s t i o n s w a s not p o s s i b l e . A s well, c l o s e d format questionnaires t e n d e d to restrict 12  the range of p o s s i b l e c h o i c e s a n d r e s p o n s e s . T h e p u r p o s e of the survey w a s to gain insight into what grip strength m e a s u r e s w e r e currently being u s e d during the normal clinical evaluation a n d treatment of patients. T h e survey questions in s o m e instances w e r e not clearly defined, leading to ambiguity in r e s p o n s e s a n d problems with data retrieval in spite of the pilot survey. Q u e s t i o n s could h a v e b e e n rephrased in order to more accurately gain the d e s i r e d information.  Instructions for completing the survey n e e d e d to be more explicit.  C h a n g i n g the survey format a n d more clearly defining the q u e s t i o n s would greatly aid in information gathering in the future. T h e s u r v e y did not target a certain patient population or a g e range, resulting in a w i d e variety of r e s p o n s e s which m a y h a v e b e e n beneficial overall to gain a larger view of clinical u s e of grip strength m e a s u r e s . T h e survey s a m p l e targeted for the study m a y h a v e b e e n b i a s e d towards t h o s e clinicians interested in hand rehabilitation, h o w e v e r it  40 c a n be a r g u e d that t h e s e clinicians are the o n e s using the m e a s u r e m e n t tool. O f s u r v e y s that w e r e returned indicating the respondent did not u s e grip strength m e a s u r e s (n=7), it w a s b e c a u s e of the type of population they w e r e treating a n d grip strength m e a s u r e m e n t s w e r e not relevant to their client b a s e .  Further research  T h e information collected from this survey e n a b l e s us to m a k e the following r e c o m m e n d a t i o n s for further r e s e a r c h :  1.  F r o m our r e s e a r c h , the u s e of different grip strength tests w a s determined. H o w e v e r , grip strength testing protocols n e e d to be clearly defined and standardized in order to improve consistent testing b e t w e e n a n d within therapists. T h i s should include positioning, testing protocols, number of trials, intertrial rest periods and equipment calibration. T h e r a p i s t s n e e d to be a w a r e of and u s e t h e s e protocols in grip strength m e a s u r e m e n t . Further r e s e a r c h is required to determine what protocols are being u s e d and what is the most reliable.  2.  T h e current m e t h o d s of determining clinical significance vary. In order to e n s u r e clinical significance with grip strength m e a s u r e s , normal variability must first be e s t a b l i s h e d . T h e n the varied validity of e a c h form of a s s e s s i n g clinical significance n e e d s to be studied.  3.  Normative d a t a b a s e s currently in u s e in clinical practice n e e d to be reviewed. W h e n normative d a t a b a s e s are u s e d for patient c o m p a r i s o n , the u s e of the exact protocols that w e r e reported in obtaining the normative data must be followed. Further r e s e a r c h is n e e d e d to determine if clinicians are using normative d a t a b a s e s properly.  CONCLUSION T h i s survey attempted to obtain information regarding grip strength testing during the normal clinical evaluation and a s s e s s m e n t of patients a n d specifically, to investigate what parameters clinicians u s e to determine clinically important c h a n g e . T o  41 our k n o w l e d g e , no o n e h a s attempted to look at grip strength m e a s u r e m e n t s in this w a y . T h e results of this study indicated that the J a m a r d y n a m o m e t e r is c o m m o n l y u s e d to m e a s u r e grip strength using the S t a n d a r d Grip Strength T e s t a n d the 5-Position Grip Strength T e s t . Grip strength testing is u s e d predominantly for u p p e r extremity injuries. A normative d a t a b a s e for c o m p a r i s o n of test results is not consistently u s e d in clinical practice. O f interest in this study is the c o n s i d e r a b l e variation in what clinicians d e e m a clinically important c h a n g e .  42  REFERENCES  1. M a t h i o w e t z V , K a s h m a n N, V o l l a n d G , W e b e r K, D o w e M , R o g e r s S . G r i p a n d pinch strength:Normative data for adults. A r c h i v e s of P h y s i c a l M e d i c i n e a n d Rehabilitation 1 9 8 5 ; 6 6 : 6 9 - 7 4 . 2. M a r c u z z i A , Kelly L, C h a n g M, H a n n a h , S . A survey of C a n a d i a n h a n d therapists: D e m o g r a p h i c s , roles and educational n e e d s . J o u r n a l of H a n d T h e r a p y 1998; 11:3944. 3. Smith R O , B e n g e M W . P i n c h and grasp strength: Standardization of terminology a n d protocol. A m e r i c a n J o u r n a l of O c c u p a t i o n a l T h e r a p y 1 9 8 5 ; 39(8):531-535. 4.  F e s s E E , M o r a n C A . Clinical A s s e s s m e n t R e c o m m e n d a t i o n s . G a r n e r , North C a r o l i n a : A m e r i c a n S o c i e t y of H a n d Therapists 1 9 8 1 : 6-8.  5. M a t h i o w e t z V , W e b e r K, V o l l a n d G , K a s h m a n N. Reliability a n d validity of h a n d strength evaluations. J o u r n a l of H a n d S u r g e r y (Am) 1984; 9 : 2 2 2 - 2 2 6 . 6.  Rothstein J M . M e a s u r e m e n t in physical therapy. 1985.  N e w Y o r k : Churchill Livingstone;  7.  B o h a n n o n R W . T h e clinical m e a s u r e m e n t of strength. Clinical Rehabilitation 1987; 1:5-16.  8. W o r l d Health O r g a n i z a t i o n ( W H O ) . International classification of impairments, disabilities a n d h a n d i c a p s . A m a n u a l of classification relating to the c o n s e q u e n c e s of d i s e a s e . G e n e v a : World Health Organization 1980. 9. C o l e B, F i n c h F, G o w l a n d C , M a y o N. Physical Rehabilitation Toronto, Ont: C a n a d i a n P h y s i c a l therapy A s s o c i a t i o n 1994.  Outcome  10. A m e r i c a n M e d i c a l A s s o c i a t i o n . Guides to the evaluation of permanent 4th e d . C h i c a g o , Illinois: A m e r i c a n M e d i c a l A s s o c i a t i o n , 1 9 9 3 .  Measures.  impairment,  11. Y o u n g V L , Pin P, K r a e m e r B A , G o u l d R B , Nemergut L, P e l l o w s k i M . Fluctuation in grip a n d pinch strength a m o n g normal subjects. Journal of Hand Surgery 1 9 8 9 ; 1 4 A : 125-9. 12. Domholdt E. P h y s i c a l therapy r e s e a r c h : principles and applications. Toronto: W . B . S a u n d e r s ; 1993.  43  CHAPTER  3_ TEST-RETEST RELIABILITY STUDY  INTRODUCTION  In rehabilitation, a n important function of any m e a s u r e m e n t tool is to provide the therapist with relevant information c o n c e r n i n g patient status a n d p r o g r e s s . T o a c h i e v e this, a m e a s u r e m e n t tool must be able to m e a s u r e accurately, diminish subjective error a n d allow c o n c l u s i o n s that are minimally affected by e x t r a n e o u s factors. Reliability 1  d e f i n e s the tool's ability to m e a s u r e consistently a n d predictably.  1  As Fess  2  indicated,  evaluation instruments that are neither reliable or accurate are not appropriate in our current world of e v e r - i n c r e a s i n g d e m a n d s for professional accountability.  In p h y s i c a l therapy r e s e a r c h , the generalizability a p p r o a c h in the study of m e a s u r e m e n t s a c k n o w l e d g e s a n d provides a w a y to quantify the m a n y s o u r c e s of variability that clinicians s e e in their patients from d a y to d a y . T h i s a p p r o a c h is 3  particularly useful in a test-retest r e s e a r c h d e s i g n . T h e rationale for using a 3  generalizability a p p r o a c h , a s o p p o s e d to c l a s s i c a l m e a s u r e m e n t theory to determine reliability, is the ability to identify the relative magnitude of the s o u r c e s of error in the reliability e q u a t i o n . Generalizability coefficients a s outlined by Stratford, N o r m a n a n d M c i n t o s h a n d the standard error of m e a s u r e m e n t ( S E M ) w e r e u s e d to e v a l u a t e grip 4  strength m e a s u r e m e n t s in this study.  44 Reliability is the c o n s i s t e n c y of a m e a s u r e m e n t a n d c o n s i s t s of true variability (the d e g r e e of heterogeneity in the s a m p l e ) a n d error (the difference b e t w e e n the obtained s c o r e a n d a true s c o r e d u e to uncontrolled factors that cannot be a c c o u n t e d for by the m e a s u r e m e n t protocol u s e d ) . T h e r e are different factors that c a n threaten reliability 5  a n d t h e s e include errors in the m e a s u r e m e n t tool itself (instrument variability), a lack of c o n s i s t e n c y in the patient r e s p o n s e (subject variability) a n d errors m a d e by t h o s e taking the m e a s u r e m e n t s (tester variability). Reliability is quantified in two w a y s , a s either 6  relative reliability or a b s o l u t e reliability. Relative reliability e x a m i n e s the relationship 5  b e t w e e n two or more s e t s of repeated m e a s u r e s a n d is m e a s u r e d with a correlation coefficient, or in this study, a generalizability coefficient.  5  A b s o l u t e reliability, or the  extent to w h i c h a s c o r e varies on repeated m e a s u r e m e n t , is m e a s u r e d statistically by the S t a n d a r d Error of M e a s u r e m e n t ( S E M ) . T h e generalizability coefficients (R) (variance attributed to differences a m o n g subjects divided by the total v a r i a n c e ) g e n e r a t e d in our study are unitless. W h i l e the generalizability coefficient d o e s not quantify the m e a s u r e m e n t error a s s o c i a t e d with a n individual s c o r e , the s t a n d a r d error of m e a s u r e m e n t ( S E M ) d e s c r i b e s reliability in clinically relevant terms a n d quantifies m e a s u r e m e n t error of a n individual's s c o r e . T h e S E M is like the s a m p l e s t a n d a r d deviation of a n individual's theoretical p e r f o r m a n c e s a n d therefore its c o n f i d e n c e interval c a n be interpreted using the normal distribution.  7  F o r a n o b s e r v e d s c o r e , the  S E M quantifies the range in which a true s c o r e might be e x p e c t e d to vary a n d therefore p r o v i d e s information required in order to m a k e clinical d e c i s i o n s  7  A c c o r d i n g to E l i a s z i w et a l , a reliability coefficient is just a point estimate b a s e d 6  on o n e s e l e c t e d s a m p l e a n d to be reliable a test must be able to discriminate a m o n g individuals a n d error must be e x p r e s s e d in the s a m e units a s the m e a s u r e m e n t . In  45 order to e s t a b l i s h the true level of reliability in the population, a s o p p o s e d to the s a m p l e , m e t h o d s of data a n a l y s i s must include tests of statistical s i g n i f i c a n c e applied to the reliability coefficients, the u s e of c o n f i d e n c e intervals a n d the calculation of the s t a n d a r d error of m e a s u r e m e n t ( S E M ) . T h e u s e of generalizability coefficients to 6  m e a s u r e reliability a n d the calculation of the S E M in the s a m e units a s the m e a s u r e m e n t s a s s i s t the r e s e a r c h e r in differentiating true c h a n g e from c h a n g e a s s o c i a t e d with error in test-retest d e s i g n s . It w a s felt this w o u l d be the best a p p r o a c h to a n a l y z e the d a t a from this study b a s e d on the context of the r e s e a r c h q u e s t i o n .  B e a r - L e h m a n et a l h a v e indicated that grip strength testing utilizing the J a m a r 8  d y n a m o m e t e r is a n objective rehabilitation o u t c o m e m e a s u r e for w h i c h the reliability h a s not b e e n thoroughly a s s e s s e d . Grip strength testing, utilizing a s t a n d a r d J a m a r d y n a m o m e t e r ( A s i m o w E n g i n e e r i n g C o m p a n y , L o s A n g e l e s , C A ) , w a s s e l e c t e d for 9  investigation in this study d u e to its w i d e s p r e a d u s e a s a m e a s u r e m e n t tool in the clinical rehabilitation s e t t i n g .  10  T h e A m e r i c a n S o c i e t y of H a n d T h e r a p i s t s  r e c o m m e n d e d s t a n d a r d i z e d positioning for grip strength m e a s u r e m e n t s . literature h a s referred to this s t a n d a r d i z e d testing m e t h o d  11,12  10  Recent  a n d therefore it w a s  c h o s e n a s the method of testing in this study.  Purpose of the Study T h e p u r p o s e of this study w a s to investigate the reliability of grip strength testing in healthy subjects. T h e test-retest reliability of the standard J a m a r d y n a m o m e t e r w a s  46 investigated for two c o m m o n l y administered grip strength tests, the S t a n d a r d G r i p Strength T e s t ( S G S T ) a n d the 5-Position Grip Strength T e s t ( 5 P G S T ) ( A p p e n d i x A ) . Both the right a n d the left hand w e r e investigated. It w a s h y p o t h e s i z e d that 1) there w o u l d be no difference in the grip strength s c o r e s a m o n g 3 trials on the S G S T a n d 2) there w o u l d be no difference in the grip strength s c o r e s b e t w e e n test o c c a s i o n s o n both the S G S T a n d the 5 P G S T .  Statement of Hypotheses  Null H y p o t h e s e s : T h e S G S T is not reliable between trials (R* < 0.80). T h e S G S T a n d 5 P G S T is not reliable b e t w e e n test o c c a s i o n s (R < 0.80). Alternate H y p o t h e s e s : T h e S G S T is reliable between trials (R >0.80). T h e S G S T a n d 5 P G S T is reliable between test o c c a s i o n s (R > 0.80) *R= generalizability coefficient  METHODS Subjects F o u r t e e n healthy m a l e volunteers g a v e informed c o n s e n t for testing. T h e s a m p l e of c o n v e n i e n c e c o n s i s t e d of physical therapy students a n d kinesiologists from the University of British C o l u m b i a . S u b j e c t s w e r e e x c l u d e d from the study for any of the following r e a s o n s : 1) past history of hand injury, 2) lesions involving the c e r v i c a l s p i n e , 3) a s s o c i a t e d neurological or m u s c u l o s k e l e t a l injury affecting grip strength, 4) history of u p p e r extremity surgery a n d 5) if the subject reported they w e r e a m b i d e x t r o u s or left h a n d e d . T h e subjects ranged in a g e from 20 to 34 y e a r s with the a v e r a g e a g e 25.4 ±  47 3.8 y e a r s a n d the m e d i a n a g e 24.5 y e a r s . All subjects w e r e self-reported right h a n d dominant. With the exception of o n e subject, all subjects had either no or minimal e x p e r i e n c e with the testing d e v i c e ( J a m a r dynamometer). T h e subjects reported no s t r e n u o u s hand activity prior to testing w h e n q u e s t i o n e d at the beginning of e a c h test s e s s i o n . T h e r e w e r e no inherent risks involved in this study. T h e subjects w e r e a s s i g n e d a numeric c o d e to e n s u r e confidentiality of the data.  Experimental Design In order to e x a m i n e the reliability b e t w e e n trials a n d test o c c a s i o n s , a repeated m e a s u r e s , within subject d e s i g n w a s u s e d (Appendix D). Eight grip strength trials w e r e performed on 2 test o c c a s i o n s for e a c h h a n d . Re-test o c c a s i o n s w e r e within three d a y s of the initial m e a s u r e m e n t . N o clinically important c h a n g e in the patient status w a s e x p e c t e d to o c c u r b e t w e e n test d a y s .  Experimental Procedures Test Protocol T h e testing took p l a c e at the University of British C o l u m b i a , S c h o o l of Rehabilitation S c i e n c e s a n d at P a c i f i c C o a s t Rehabilitation C e n t r e , a private practice p h y s i c a l therapy clinic in North V a n c o u v e r , B C . T h r e e trials for the S G S T a n d 1 trial at e a c h of 5 positions for the 5 P G S T (a total of 8 grip strength trials) w e r e taken on 2 test o c c a s i o n s within three d a y s of e a c h other (range 1-3 d a y s ; m e a n = 1.5 d a y s ) . O n e e x a m i n e r administered all testing.  48 Instrumentation A s t a n d a r d , adjustable handle, hydraulic J a m a r D y n a m o m e t e r ( A s i m o w E n g i n e e r i n g C o . , L o s A n g e l e s , Calif.) w a s u s e d to m e a s u r e grip strength. T h e d y n a m o m e t e r w a s calibrated by the manufacturer prior to the study a n d w a s u s e d e x c l u s i v e l y for testing until the study had b e e n .completed. T h e adjustable h a n d l e w a s u s e d to test grip strength at grip s p a n intervals (Positions 1-5) of 1.0, 1.5, 2.0, 2.5 a n d 3.0 i n c h e s (2.4 c m to 7.6 cm) for the 5 P G S T . T h e S G S T w a s tested at 1.5 i n c h e s (Position 2). G r i p strength w a s m e a s u r e d in kilograms of force with the resolution of the d y n a m o m e t e r s c a l e read to the nearest 2 kilograms (down from 1 kgforce).  Positioning Differences in test p r o c e d u r e s with respect to positioning, intertrial rest period, h a n d l e position, n u m b e r of trials a n d s c o r e s d o c u m e n t e d h a v e b e e n d o c u m e n t e d in the literature.  13  In this study, the s t a n d a r d i z e d test protocol a s outlined by the A m e r i c a n  S o c i e t y of H a n d T h e r a p i s t s ( A S H T ) w a s utilized to m e a s u r e the static grip strength scores.  10  It w a s felt that a s t a n d a r d i z e d method of testing w o u l d allow greater  c o m p a r i s o n to the existing literature on the reliability of grip strength testing. T h e test p r o c e d u r e involved positioning the subject in sitting with the s h o u l d e r a d d u c t e d a n d neutrally rotated, the e l b o w at 90 d e g r e e s a n d the forearm a n d wrist in neutral (Figure 1a,b). T h e subject's a r m w a s not stabilized, a n d while efforts w e r e m a d e to c o n f o r m to s t a n d a r d positioning, this allowed slight variations in e l b o w a n d wrist positions. T h e J a m a r d y n a m o m e t e r w a s p l a c e d in the palmar gutter of the subject's h a n d . T h e subject could not s e e the d y n a m o m e t e r dial or view the m e a s u r e m e n t s during the study.  49  50  Testing P r o c e d u r e s T h e testing p r o c e d u r e w a s d e s i g n e d to replicate the actual clinical test situation and conditions w e r e a s similar a s p o s s i b l e from d a y to d a y a n d from subject to subject. S t u d y participants received s t a n d a r d i z e d instructions ( A p p e n d i x E ) . T h e ethics committee of the University of British C o l u m b i a a p p r o v e d this r e s e a r c h . S u b j e c t s s i g n e d a c o n s e n t form prior to testing. M a x i m u m time to c o m p l e t e the testing p r o c e d u r e w a s approximately 10 minutes for e a c h testing s e s s i o n for a c o m b i n e d total of 2 0 minutes. S u b j e c t s w e r e randomly a s s i g n e d to either S G S T or 5 P G S T at the beginning of testing with the u s e of a c o m p u t e r i z e d r a n d o m generation table. B e t w e e n - d a y test s e s s i o n s w e r e identical; subjects starting with S G S T on D a y 1 started with S G S T on D a y 2. T h i s w a s d o n e in order to eliminate order bias a n d e x t r a n e o u s factors related to fatigue a n d learning. During the S t a n d a r d Grip Strength T e s t ( S G S T ) , the subject w a s a s k e d to maximally grip the J a m a r d y n a m o m e t e r for 3 s e c o n d s at P o s i t i o n 2 on the adjustable h a n d l e with a 1 5 - s e c o n d rest in b e t w e e n trials a s r e c o m m e n d e d by the A m e r i c a n S o c i e t y of H a n d T h e r a p i s t s .  10  Both left a n d right h a n d s w e r e t e s t e d , starting with the left  h a n d a l w a y s . T h r e e grip strength trials w e r e t a k e n . During the 5-Position G r i p Strength T e s t ( 5 P G S T ) , the subject w a s a s k e d to grip the d y n a m o m e t e r at e a c h of the 5 positions for 3 s e c o n d s with a 1 5 - s e c o n d rest b e t w e e n trials (1 trial at e a c h position). A brief rest of 2 minutes w a s given between S G S T a n d 5 P G S T .  L e n g t h s of trials a n d  rest p e r i o d s w e r e timed with a hand held stopwatch. N o f e e d b a c k regarding  51 p e r f o r m a n c e w a s g i v e n , however, minimal verbal e n c o u r a g e m e n t w a s provided during the testing ( A p p e n d i x E ) . T h i s w a s kept consistent throughout the testing.  Data Collection T e s t d a t a including a test s c o r e for e a c h of 3 trials a n d the m e a n s c o r e of 3 trials on the S G S T a n d a single s c o r e at e a c h of the 5 positions o n the 5 P G S T w e r e collected for e a c h subject. D a t a for both left a n d right h a n d s w e r e r e c o r d e d . D a t a w e r e collected o n two s e p a r a t e o c c a s i o n s within 7 d a y s of e a c h other with the m e a n length of time b e t w e e n test s e s s i o n s 1.5 d a y s (sd=0.759, range = 1 - 3 d a y s ) . S e l f report activity information w a s collected to e n s u r e that the subject h a d not e n g a g e d in a n activity immediately prior to testing that m a y h a v e had a n effect on grip strength. A n effort w a s m a d e to retest the subjects at approximately the s a m e time e a c h d a y .  Data A n a l y s i s T h e d a t a w e r e a n a l y z e d after 10 subjects for test-retest reliability for a n estimate of s a m p l e s i z e to meet statistical requirements. A s test-retest reliability using a P e a r s o n r correlation coefficient h a d b e e n e s t a b l i s h e d after 10 subjects ( r > 8 ) , d a t a collection w a s s t o p p e d after 14 subjects. A power a n a l y s i s for s a m p l e s i z e w a s not d o n e .  Statistical Analysis A n a l y s i s included a correlational a n a l y s i s of relationships e m p l o y i n g a generalizability a p p r o a c h to determine the reliability of the m e a s u r e m e n t tool, the 1 4  J a m a r d y n a m o m e t e r . A n a n a l y s i s of v a r i a n c e ( A N O V A ) w a s u s e d to determine if the m e a n s c o r e s differed significantly. T h e S G S T a n a l y s e s w e r e b a s e d on both a 3-way  a n d 2 - w a y A N O V A with a n interaction term; w h e r e a s , the 5 P G S T a n a l y s e s w e r e b a s e d on a 2-way A N O V A without a n interaction term (an interaction term could not be c a l c u l a t e d b e c a u s e there w a s only o n e trial per s e s s i o n ) . V a r i a n c e c o m p o n e n t s w e r e c a l c u l a t e d ( A p p e n d i x G ) a n d u s e d to construct generalizability coefficients. T h e s t a n d a r d error of m e a s u r e m e n t a n d the c o r r e s p o n d i n g lower 1-sided 9 5 % c o n f i d e n c e limits w e r e a l s o c a l c u l a t e d . S e l e c t e d v a r i a n c e c o m p o n e n t s w e r e u s e d to estimate the intertrial a n d interday standard error of m e a s u r e m e n t a n d their u p p e r 9 5 % c o n f i d e n c e intervals. T h e a n a l y s e s w e r e d o n e in M I N I T A B (Version 11) using the " B a l a n c e d A n o v a " option. Landis and K o c h  1 5  p r o p o s e d a s c a l e to subjectively rate reliability w h e r e 0.00-  0.20 indicates slight reliability, 0.21-0.40 fair, 0.41-0.60 moderate, 0.61-.80 substantial a n d 0.81-1.00 almost perfect reliability. T h e generalizability coefficients in our study w e r e c o m p a r e d using this subjective s c a l e . T h e raw data a n d A N O V A tables c a n be found in A p p e n d i x F a n d G respectively.  53  RESULTS  Table 1: S a m p l e M e a n s B e t w e e n T e s t O c c a s i o n s a n d A c r o s s Trials for the S t a n d a r d Grip Strength T e s t (3 trials at Position 2).  Means  n  Test Occasion 1  42*  57.76  52.05  Test Occasion 2  42  60.12  55.24  Trial 1  28*  59.96  54.00  Trial 2  28  59.04  53.46  Trial 3  28  57.82  53.46  Right kgf  Left kgf  * 14 subjects X 3 trials X 1 test occasion = 42 • 14 subjects X 2 test occasions = 28  T h e s a m p l e m e a n s of all subjects (n=14) for the S t a n d a r d G r i p Strength T e s t are p r e s e n t e d in T a b l e 1. T a b l e 2 represents the reliability study results of the S t a n d a r d Grip Strength T e s t by presenting the right, left a n d right-left hand difference p o o l e d e s t i m a t e s b e t w e e n trials (intertrial) a n d b e t w e e n test o c c a s i o n (interoccasion) for 1 trial a n d t h e a v e r a g e of 3 trials. T h e generalizability coefficients (R) a n d the s t a n d a r d error of m e a s u r e m e n t ( S E M ) are indicated. T h e lower 1-sided 9 5 % c o n f i d e n c e interval is given for the generalizability coefficient a s it is more important to the clinician to k n o w h o w low, or h o w far from perfect (R=1) the reliability is. Similarly, the upper 1-sided 9 5 % c o n f i d e n c e interval is given for the S E M , a s it is important for the clinician to k n o w h o w large a s o p p o s e d to how small a m e a s u r e m e n t could b e d u e to error a l o n e . T h e results w e r e p r e s e n t e d this w a y for the p u r p o s e of exploring the reliability of clinical m e a s u r e m e n t strategies s u c h a s looking at the result of taking a single grip strength  54 m e a s u r e m e n t (trial), taking the m e a n of 3 m e a s u r e m e n t s (trials) or looking at the difference b e t w e e n h a n d s . Table 2: Generalizability coefficients (R) for the S t a n d a r d Grip Strength T e s t . Inter-Trial Pooled Estimate SEM R (kgf) RIGHT HAND Single Trial  .60 (.39)*  4.74 ( 4 . 7 6 )  1.66  .67  4.12  .84 (.66)  2.96 (3.51)  .62 (.40)  4.49 (4.59)  Average of 3 Trials  .94  1.71  .70  3.78  D I F F E R E N C E (R-L) Single Trial  .56 (.24)  3.46 (4.10)  .35 (.31)  4.21 (4.56)  Average of 3 Trials L E F T HAND Single Trial  .85 (.70)*  2.87 (3.40)  .95  Inter-Occasion Pooled Estimate SEM R (kgf) f  .80 2.00 .49 Average of 3 Trials 'Lower 1-sided 95% confidence interval for the generalizability coefficient (R) Upper 1-sided 95% confidence interval for the SEM kgf = kgforce  f  3.18  t  T h e generalizability coefficients for the S t a n d a r d Grip Strength T e s t (Table 2) w e r e high for the inter-trial reliability of a single m e a s u r e m e n t o n the right (R =.85) a n d left (R=.84) but the difference b e t w e e n right a n d left o n a single trial exhibited m o d e r a t e reliability (R=.56). T h e lower 1-sided 9 5 % c o n f i d e n c e intervals indicate a lower b o u n d of 0.70 for the right h a n d , .66 for the left a n d .24 for the right-left difference. T h e a v e r a g e of 3 trials resulted in higher generalizability coefficients than for a single trial in all c a s e s . B a s e d o n the within trial v a l u e s of the S t a n d a r d Error of M e a s u r e m e n t ( S E M ) , there is a 9 5 % c h a n c e that the population v a l u e of the S E M is less than 3.40 kgf o n the  55 right, 3.51 kgf on the left a n d 4.10 kgf between h a n d s . T h e S G S T a p p e a r e d reliable b e t w e e n trials (R>0.80) but not b e t w e e n test o c c a s i o n s . Interoccasion, or test-retest estimates of generalizability coefficients exhibited fair to m o d e r a t e reliability with the left hand marginally higher than the right on a single trial (R=0.62 v e r s u s R=0.60 respectively). Generalizability coefficients w e r e slightly higher for the a v e r a g e of 3 trials. T h e r e w a s a 9 5 % c h a n c e that the population v a l u e of the S E M is less than 4.76 for the right, 4.59 on the left a n d 4.56 for the right-left difference (Table 2).  Estimate of v a r i a n c e c o m p o n e n t s (Table 3, A p p e n d i x G )  indicated that the greatest s o u r c e of variability, or differences a m o n g the grip strength m e a s u r e m e n t s c o r e s , o c c u r r e d in the subject by day interaction. High grip strength s c o r e s o c c u r r e d more often on the first of three grip strength trials in the right h a n d a n d a p p e a r e d variable on the left hand (Figure 2).  Table 3: E s t i m a t e of v a r i a n c e c o m p o n e n t s derived from the three-way A N O V A for the S t a n d a r d Grip Strength Test. Intertrial Source  Right  Subjects Trial Day Subjects  X  Trial  Subjects  X  Day  Trial  Error  X  Day  Interoccasion Left  R-L Diff  Right  Left  R-L Diff  34.27 1.21  33.15 0  9.95 .22  33.93  33.37  1.88 0  0 0  1.67  4.38  0  12.40  4.20 0.66 7.22  6.87  12.54  6.98  6.11  0 8.65  0.55 8.08  .23 12.67  8.24  8.77  11.95  Note: Negative variances are set to zero. Please refer to Appendix G for calculations of the variance components.  9.57  56  High grip strength scores by trial for the Standard Grip Strength Test (3 trials at position 2 on the Jamar dynamometer) 100  Right Hand Test  Right Hand Retest  Left Hand Test  Left Hand Retest  Hand/Test O c c a s i o n Figure 2 : Proportion of high scores occurring on the first, second or third of 3 trials on the Standard Grip Strength Test.  T h e 5-Position Grip Strength T e s t correlation coefficients (Table 4 ) s h o w e d g o o d reliability for J a m a r h a n d l e position 1 (R=0.87) a n d 2 (R=0.83) for the left hand only. T h e 5 P G S T did not a p p e a r to be reliable (R>0.80) b e t w e e n test o c c a s i o n s . V a r i a n c e e s t i m a t e s of the 5-Position Grip Strength T e s t including subject v a r i a n c e , time v a r i a n c e a n d error v a r i a n c e are s h o w n in T a b l e 5. Figure 3 depicts the test-retest reliability differences in the left a n d right h a n d s a c r o s s all handle positions; overall the left hand exhibited greater reliability. T a b l e 6 indicates the test-retest m e a s u r e m e n t fluctuations a n d percent c h a n g e for both the S G S T a n d the 5 P G S T .  It a p p e a r s that the fluctuation  in individual s c o r e s a c r o s s test o c c a s i o n s is of the greatest c o n c e r n in a s s e s s i n g the significance of c h a n g e over time.  57  Table 4: S u m m a r y of Correlation Coefficients for the 5 Position Grip Strength Test. Jamar Handle Position Position 1-Left Position Position Position Position Position Position Position Position Position  Correlation Coefficient (Lower 1-sided 95% Cl) .87 (.69)* .58 .83 .64 .70 .70 .80 .78 .79 .72  1-Right 2-Left 2-Right 3-Left 3-Right 4-Left 4-Right 5-Left 5-Right  S E M (kgf) (Upper 1-sided 95% Cl) 2.79 (4.15)  (.20) (.62) (.29) (.39) (.38) (.55) (.52) (.54) (.41)  5.42 2.71 4.38 5.06 3.62 3.09 3.28 3.29 2.57  (8.05) (4.03) (6.51) (7.52) (5.38) (4.59) (4.87) (4.89) (3.82)  * SAMPLE CALCULATION (variance values from Table 5, Position 1 Left) Type 2,11CC = Subject Variance Subject Variance + Time Variance + Error Variance Type 2,11CC = 50.7 50.7 + 0 + 7.8 Type 2,1 ICC =  .87 (lower 1-sided 95% confidence interval =.69)  Table 5: Estimate of v a r i a n c e c o m p o n e n t s from a 2 - W a y A n o v a for the 5 Position Grip Strength Test. Source  Position  1  Position  2  Position  3  Position  4  Position  5  Right  Left  Right  Left  Right  Left  Right  Left  Right  Left  Subjects  40.95  50.75  34.50  41.33  30.85  60.62  38.73  37.25  16.92  41.85  Time  0*  0  0  .82  .08  0  .15  .05  0  .25  Error  29.46  7.84  19.18  7.354  13.13  25.60  10.74  9.55  6.63  10.82  •Negative variances set to zero.  0  Q>  CD  3  O  0  Q_ £ J ||  OS  3  US  O O  3  "01 00  11  OL CO CD  7?  II  O  CD CQ  ^  CD CO  CD  cn  CO  •<  K>  11  II  CD  O  +  OL CO CO CD CQ  CD  cn  Da  O O -I CD  3  <0  O c  £0  O 3 —*  O  SG  cs X  re mi  CQ  CO  Day  59.9  cn cn IE? ' — - CD ?c C3Q" ' CQ cn CD a co O cn —i O  TU 73  n  r—e  CO  ale  'S  3  scon F mean :ion  3  ea ea  o =R CO CD II  #  T j  on  S  CO H •  CO H  =f  Si.  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CD 0) 3  co  c o c CO  CO  o'  co  3  CD ~*  9: " o q cn  C_ 0) 0)  w 3  &>  Q)  CD  O  TJ I  i.S 3^  CD W »  0)  o' II  (D (0  r-»-  cn co  -vl ro  CD CD &) 3 3 0)  o'  CO  13 CO  -^  CD  H >  13 CQ  CD CO  ccTo  cu  ^%  CL  bo CD  co  3"  CO  I—»-  CO  CO  o o  CD  c o zD c  CT  si 0)  Z2  CD 13 r-K 13 O CD 0)  3  rt> 5"  CD °13'  CO — I  3  0) CL  (/> TJ  0) —1 CL  CD  m -n  00  cn  cn  5' o ^  o ?Hai 3 S O  CD  , 3"  & ® 3 rtCQ T*" CD W  59  Test-Retest Reliability of Jamar Handle Position 1  Position 1- Position 2- Position 3- Position 4- Position 5Left Left Left Left Left  Position 1- Position 2- Position 3- Position 4- Position 5Right Right Right Right Right  Jamar Handle Position Figure 3: Test-retest reliability of 5 handle positions of the Jamar dynamometer.  DISCUSSION  Standard Grip Strength Test T h e generalizability coefficients for the S t a n d a r d Grip Strength T e s t in our study indicated almost perfect reliability (according to the subjective rating s c a l e a s outlined by L a n d i s a n d K o c h ) on a single trial in the right hand (R=.85) a n d the left h a n d 15  60 (R=.84) (Table 2). T h i s m a y lead o n e to s u r m i s e that taking a single grip strength m e a s u r e m e n t w o u l d be reliable in our study population. B o h a n n o n a n d S a u n d e r s  1 6  investigated the u s e of a single trial for measuring isometric e l b o w flexion with a h a n d held d y n a m o m e t e r in healthy subjects a n d found that the first m e a s u r e m e n t did not differ significantly from the m a x i m a l or the m e a n ; reliability of all m e a s u r e s w a s comparable. Bohannon and S a u n d e r s  1 6  w a r n e d about generalizing their findings to the  clinical setting t h o u g h , noting that the e x a m i n e r in their study w a s skilled with the m e a s u r e m e n t tool a n d the m e a s u r e s w e r e d o n e in healthy individuals, w h o m a y not h a v e exhibited a s m u c h subject variability a s a patient population presenting with pathology. M a c D e r m i d et a l  1 2  e x a m i n e d the interrater reliabilities of pinch a n d grip  strength in patients with cumulative trauma disorder a n d found that although the I C C ' s w e r e slightly higher for the m e a n of three trials than for a single trial (0.96 v e r s u s 0.93 for s y m p t o m a t i c patients a n d 0.98 v e r s u s 0.94 for a s y m p t o m a t i c patients), there w a s no significant difference b e t w e e n the reliability coefficients s u g g e s t i n g a c c e p t a b l e s c o r e s c o u l d be obtained by using only o n e repetition. W h i l e the u s e of a single grip strength m e a s u r e m a y be d e s i r a b l e for the b u s y clinician, S t r a t f o r d  17  cautioned that with this a p p r o a c h , the therapist d o e s not k n o w if  "the obtained single v a l u e reflects a stable m e a s u r e m e n t or is part of a trend". A l t h o u g h the generalizability coefficients w e r e high for a single trial in our study, they w e r e higher for the a v e r a g e of 3 trials a s indicated in T a b l e 2 (right hand reliability .85 for a single trial c o m p a r e d to .95 for the a v e r a g e of 3 trials). M a t h i o w e t z et a l  1 8  investigated the effects of three trials on grip strength by looking at the correlations for o n e trial, the m e a n of two trials, the m e a n of three trials a n d the highest s c o r e of three trials. T h e y found that the m e a n of three trials a c h i e v e d the highest correlations a n d a  61 single trial a c h i e v e d the lowest correlations. B a s e d on this, they r e c o m m e n d e d the m e a n of three trials a s a more accurate m e a s u r e of grip strength than o n e trial or the highest s c o r e of three trials.  18  Hamilton, B a l n a v e a n d A d a m s ,  1 1  investigating the test-  retest reliability of grip strength using the J a m a r d y n a m o m e t e r in healthy subjects, l o o k e d at the s a m e four m e t h o d s to determine grip strength (the s c o r e of o n e trial, the m e a n s c o r e of two trials, the m e a n s c o r e of three trials, a n d the highest s c o r e of three trials) a n d c o n c l u d e d that b e c a u s e all four m e t h o d s w e r e not significantly different in reliability, no o n e method could be r e c o m m e n d e d a s more a c c u r a t e . Stratford et a l  1 4  stated that a v e r a g i n g repetitions rather than taking the highest or lowest v a l u e in a test s e s s i o n w a s the best strategy to obtain a representative estimate of grip strength. T h e results of our study indicate that the a v e r a g e of three s c o r e s w a s a more reliable m e a s u r e of grip strength on all m e a s u r e s (right, left, difference b e t w e e n right a n d left a n d b e t w e e n d a y s ) (Table 2). B e t w e e n d a y differences, or test-retest reliability, exhibited fair to m o d e r a t e reliability (right hand R=0.60, left hand R=0.62 for a single trial) a c c o r d i n g to the L a n d i s and K o c h  1 5  s c a l e . Reliability b e t w e e n d a y s w a s slightly higher for the a v e r a g e of three  trials (0.60 for 1 trial v e r s u s 0.67 for the a v e r a g e of 3 trials in the right h a n d , 0.62 v e r s u s 0.70 in the left hand). Stratford et a l , in a study of grip strength m e a s u r e m e n t s in 1 4  patients with tennis elbow, looked at the generalizability coefficients for m e a s u r e m e n t s t a k e n within a test s e s s i o n a n d from o n e s e s s i o n to another. T h e y c o n c l u d e d that the greatest s o u r c e of variation w a s between d a y s .  1 4  O v e r a l l generalizability of results could  best be e n h a n c e d by a v e r a g i n g grip strength m e a s u r e m e n t s recorded from multiple test s e s s i o n s , a s o p p o s e d to multiple test repetitions during a single test s e s s i o n .  1 4  Reliability might be e x p e c t e d to be lower with a longer period b e t w e e n test s e s s i o n s  62 d u e to the possibility of a true c h a n g e in the patient's clinical status during that time. H o w e v e r , with our s a m p l e of normal uninjured individuals a n d a short length of time b e t w e e n test s e s s i o n s (mean of 1.5 d a y s , range = 1 - 3 d a y s ) , the i s s u e of time b e t w e e n testing a n d true c h a n g e in our subjects is probably not relevant. T e s t familiarity w o u l d not be e x p e c t e d to c h a n g e m u c h in s u c h a short time. V a r i a n c e for the trial a n d d a y exhibited s m a l l s y s t e m a t i c differences c o m p a r e d to the v a r i a n c e for the subject/day interaction (Table 3). T h e largest s o u r c e of v a r i a n c e in our s a m p l e (Table 3) w a s the subject/day interaction, therefore, our results a p p e a r to support the r e s e a r c h indicating that the greatest s o u r c e of variation in grip strength m e a s u r e m e n t s is in the subject by d a y interaction. T h e effect of fatigue a n d learning on grip strength m e a s u r e m e n t h a s b e e n cited in the literature  19  a n d the important factors affecting fatigue a n d learning a p p e a r to  be intertrial rest intervals a n d the number of repetitions per test s e s s i o n .  1 9  Patterson and  B a x t e r f o u n d m a x i m u m force occurred on the first, s e c o n d , a n d third trial 3 5 % , 3 1 % 20  a n d 3 4 % of the time respectively w h e n using a 1 minute rest b e t w e e n trials. A s the rest period d e c r e a s e d , m a x i m u m force occurred 6 1 % of the time on the first trial, 2 1 % on the s e c o n d a n d 1 3 % on the third trial w h e n using a 5 - s e c o n d rest b e t w e e n trials. Fess  2 1  20  found that during a 3-trial test high s c o r e s occurred 60 percent of the time on the  first attempt a n d 24 percent of the time on the s e c o n d attempt. In our study of the S t a n d a r d Grip Strength Test, with a 15 s e c o n d rest interval b e t w e e n trials, high s c o r e s on the right hand test occurred 4 4 % of the time on the first attempt, 3 3 % on the s e c o n d attempt a n d 2 2 % on the third attempt (Figure 2). R e t e s t s c o r e s on the right exhibited the highest s c o r e on the first attempt (47%), but in the left h a n d , the results w e r e variable. M a t h i o w e t z  19  found no practice or learning effect o v e r three grip strength trials  63 with a 15 s e c o n d rest in b e t w e e n trials a n d our results a p p e a r e d to c o n c u r with M a t h i o w e t z ' s results. W h e n investigating this further, a review of the s a m p l e m e a n s of all s u b j e c t s (Table 1) indicates the difference between the m e a n s of the first trial to the m e a n s of the third trial is small ( 5 4 k g f - 53.46 kgf = 0.54 kgf) for the left h a n d , s u g g e s t i n g a minimal effect on grip strength s c o r e s d u e to fatigue in the non-dominant h a n d . T h e right h a n d difference w a s greater (2.14 kgf), possibly s u g g e s t i n g s o m e fatigue. Mathiowetz  19  found a d e c r e a s e of 0.41 kgf for the right hand a n d 0.86 kgf for the left  o v e r three repeat m e a s u r e m e n t s of grip strength using the s a m e testing p r o c e d u r e a s in our study. Hamilton et a l  1 1  found an overall difference b e t w e e n the first a n d third  s c o r e s on all 5 handle positions of the J a m a r to be 2.18 kgf for the group a s a w h o l e , leading t h e m to s u g g e s t fatigue w a s evident within trials. F r o m the literature, two factors a p p e a r important w h e n looking at the effects of fatigue on grip strength a n d t h e s e include the length of e a c h trial a n d the length of the intertrial interval. Theoretically, the effects of fatigue could be minimized by increasing the rest time b e t w e e n trials, but this w o u l d substantially i n c r e a s e the time required for grip strength testing a n d m a y not be f e a s i b l e in a b u s y clinical situation. D u n w o o d y , Tittmar a n d M c C l e a n  2 2  indicated that a 15 s e c o n d to 6 minute  variability in intertrial rest periods w a s evident in the literature. D u n w o o d y et a l  2 2  studied the effect of a 120 s e c o n d intertrial interval on fatigue with a 3 s e c o n d trial using the Martin Virgometer. T h e y found that grip strength i n c r e a s e d a c r o s s trials from trial 1 to 4 a n d therefore a fatigue effect w a s not s e e n , but a learning effect w a s s u g g e s t e d . D u n w o o d y et a l  2 2  cautioned that familiarization or practice with the grip strength test  m a y r e d u c e the c h a n c e of a T y p e 1 error of reporting significant results w h i c h m a y  22  64 reflect the subject's "learning" how to u s e the m e a s u r e m e n t tool. M a r i o n a n d N i e b u h r  23  e x a m i n e d the effect of w a r m u p prior to m a x i m a l grip contractions, h y p o t h e s i z i n g that subjects w h o e n g a g e d in mild w a r m up e x e r c i s e s would exhibit higher grip force; w a r m up c o n s i s t e d of o n e s u b m a x i m a l grip. T h e y found a statistically significant i n c r e a s e in grip strength d u e to w a r m up a n d noted that the highest f o r c e s o c c u r at the beginning of a s e r i e s of m a x i m a l efforts , the latter of w h i c h supports the findings of our study. 23  T h e r e m a y be a practice or learning effect evident in our study a s the m e a n s c o r e s for d a y s w e r e slightly better on the s e c o n d d a y of testing (Table 1) throughout the s a m p l e set (eg 2.36 kgf difference higher on the s e c o n d d a y of testing on the right, 3.19 kgf on the left). T h e potential motor learning effect over two s u c c e s s i v e testing d a y s s e e n in our study m a y indicate the n e e d for practice testing prior to taking actual grip strength test s c o r e s . T h e addition of a third test o c c a s i o n would h a v e b e e n appropriate to s e e if a true learning effect w a s evident. B a s e d on our test results, the effect of fatigue w a s minimal in healthy adult m a l e s over three repeat trials using a 15s e c o n d rest interval b e t w e e n trials; there m a y h a v e b e e n a learning effect b e t w e e n test occasions.  5-Position Grip Strength Test Reliability of the 5 Position Grip Strength T e s t ( 5 P G S T ) w a s greater than 0.80 (Table 4) for Position 1, 2 a n d 4 on the left but w a s fair to m o d e r a t e for all other positions (Figure 3). Hamilton et a l  1 1  found high test-retest correlations ( I C C > 0.88) for  the five h a n d l e positions on the J a m a r d y n a m o m e t e r . A l t h o u g h within a c c e p t a b l e limits, the test-retest reliability of position 1 w a s lower than that of other handle positions. T h i s d o e s not c o m p a r e with our findings w h e r e position 1 resulted in the highest reliability on  65  the left h a n d (R=0.87), h o w e v e r it w a s true for the right hand (R=0.58) (Figure 3). During testing in our study, subjects reported that they found position 1 uncomfortable a n d difficult to grip a d e q u a t e l y d u e to the small s i z e therefore w e w o u l d h a v e e x p e c t e d to s e e greater variability at this position. Position 2, w h i c h is most often u s e d in grip strength testing, exhibited g o o d test-retest reliability on the left hand (.83) a n d substantial reliability on the right (.64) with a 9 5 % c h a n c e that the population v a l u e of the I C C is greater than .62 a n d .29 respectively (Table 4). Position 3 a n d 4 on the right (dominant hand) in our subjects exhibited the best reliability (Figure 2) a n d this m a y be e x p l a i n e d by the subject's hand s i z e , which m a y h a v e given t h e m the greatest grip a d v a n t a g e a n d comfort at t h e s e positions, therefore they w e r e more consistent in their m e a s u r e m e n t s . Test-retest reliability a p p e a r e d to i n c r e a s e from P o s i t i o n 1 to 4 on the right h a n d (Figure 3). A t position 2 on the right h a n d , the S E M w a s 4 . 3 8 kgf with a n u p p e r limit of 6.51 kgf ( 9 5 % C l ) d u e to error a l o n e (Table 4).  Right versus Left Hand Difference Generalizability coefficients w e r e a n a l y z e d for the right to left hand difference for the S t a n d a r d Grip Strength T e s t (Table 2). T h e right hand w a s consistently stronger a s d e m o n s t r a t e d by higher trial s c o r e s c o m p a r e d to the left (Table 1, A p p e n d i x F). T h e reliability for the intertrial difference between right a n d left h a n d s w a s .56 with a S E M of 3.46kgf. T h e interoccasion reliability w a s .35 with a S E M of 4 . 2 1 . Reliability w a s improved by taking the a v e r a g e of three trials with the intertrial reliability .80 ( S E M 2.00 kgf) a n d the interoccasion reliability .49 ( S E M 3.18 kgf) (Table 2). Hamilton et a l Mathiowetz  18  1 1  and  found that the test-retest reliability of the right hand w a s lower than that of  the left, a finding substantiated in our study, although to a s m a l l d e g r e e (R=.67 right  66 h a n d v e r s u s R=.70 left hand for the test retest a v e r a g e of three trials). H o w e v e r , Hamilton et a l  1 1  noted that they tested the right hand first a n d s u g g e s t e d a n ordering  effect m a y h a v e o c c u r r e d with the left hand achieving greater reliability a s a result of a learning effect. In our study, the left hand w a s tested first a n d our subjects w e r e all right h a n d dominant w h i c h tends to refute this statement. T h e 1 0 % rule is often referred to in the literature to define the a v e r a g e difference in g r a s p i n g p o w e r b e t w e e n the dominant a n d non-dominant h a n d .  24  H o w e v e r , the origin  of the a c c e p t e d 1 0 % difference remains o b s c u r e a n d the m e a n s of calculating this rule (the instrument u s e d a n d the population from w h i c h the a v e r a g e difference w a s obtained) h a s not b e e n explained in the literature. P e t e r s o n et a l 1 0 % rule dated b a c k to the work of B e c h t o l  26  2 5  indicated that the  in 1954 w h o o b s e r v e d that most patients  p r e s e n t e d with a 5 % to 1 0 % difference b e t w e e n their dominant a n d non-dominant h a n d s o n grip strength m e a s u r e m e n t s , with the dominant hand being stronger.  Lunde  et a l , in a 1972 study of the grip strength of college w o m e n , found a 1 3 % difference in 27  grip strength b e t w e e n the dominant a n d non-dominant h a n d s , h o w e v e r 2 4 % of the 107 grip strength m e a s u r e m e n t s revealed strength readings for the non-dominant h a n d e q u a l to or greater than the dominant h a n d . A study by S c h m i d t a n d T o e w s  2 8  found  2 8 % of m e n tested h a d a grip strength in their non-dominant h a n d that w a s e q u a l to or greater than the grip strength in their dominant h a n d , therefore, they q u e s t i o n e d the application of the 1 0 % rule. P e t e r s o n et a l  2 5  found a 1 0 . 7 4 % difference overall b e t w e e n  h a n d s , however, w h e n they s e p a r a t e d out the data into right h a n d dominant a n d left h a n d dominant individuals, the right h a n d e d subjects exhibited a 1 2 . 7 2 % difference a n d the left h a n d e d subjects exhibited a - 0 . 0 8 % difference. Therefore, they c o n c l u d e d that the 1 0 % rule is only valid for right h a n d e d p e r s o n s ; for left h a n d e d p e r s o n s , grip  67 strength is e q u a l to right.  25  H a r k o n e n et a l  2 9  in a s a m p l e of 2 0 4 healthy F i n n i s h adults,  found no significant difference in strength between the dominant a n d non-dominant hands.  Clinical Significance T a b l e 6 indicates the m e a n grip strength fluctuations in kgforce for the 5Position Grip Strength T e s t a n d the S t a n d a r d Grip Strength Test. Clinically, therapists will test a patient on o n e day, then retest them again at a later date to try a n d determine if a clinically important c h a n g e h a s o c c u r r e d . O u r test-retest reliability study m i m i c k e d this with a small (mean = 1.5 days) n u m b e r of d a y s b e t w e e n test s e s s i o n s . H o w e v e r , the p e r c e n t a g e c h a n g e from d a y to d a y a m o n g healthy individuals w a s s h o w n to range from 5 . 1 % to 1 2 . 8 % with a fluctuation (mean difference of highest to lowest s c o r e s ) of 2.8kgf to 6.64 kgf. Therefore, in our study population, b e t w e e n 2.8kgf a n d 6.64 kgf difference in m e a s u r e m e n t b e t w e e n grip strength trials on a test-retest situation a p p e a r s to be d u e to error alone. A c c o r d i n g to H a r k o n e n et a l , the a c c u r a c y of the J a m a r d y n a m o m e t e r at all 5 30  test positions varied from 1.2 kgf to 1.4 kgf w h e n tested against k n o w n weights. Error in kilograms i n c r e a s e d with heavier weights but the relative p e r c e n t a g e error d e c r e a s e d w h e n the load i n c r e a s e d . T h i s indicates that there m a y be more error in t h o s e individuals that present with low grip strength s c o r e s , whether this is d u e to true w e a k n e s s , m a n u a l disability, gender, job type or poor effort. Therefore, clinicians must be a w a r e that there is a d e g r e e of m e a s u r e m e n t error, particularly with low grip strength s c o r e s , that s h o u l d be factored into their interpretation of test results.  68 G r i p strength testing m e a s u r e m e n t s w e r e more reliable w h e n the a v e r a g e of 3 trials w a s t a k e n c o m p a r e d to a single trial, s u g g e s t i n g a n effective m e a s u r e m e n t strategy w o u l d be to u s e multiple trials. Fatigue did not a p p e a r to be a factor in our study a n d therefore the u s e of a 15 s e c o n d trial interval a p p e a r s to be sufficient. B e c a u s e grip strength m e a s u r e s are relatively simple a n d quick to perform in the clinical setting, taking three trials with a 15 s e c o n d rest b e t w e e n trials s h o u l d not be too time c o n s u m i n g for the b u s y clinician a n d will provide him/her with a reliable estimate of grip strength on that day. O v e r a l l , the u s e of a s t a n d a r d i z e d protocol w o u l d be beneficial for all clinicians in order to accurately c o m p a r e patient results a c r o s s clinics a n d b e t w e e n treating physical therapists. O u r study found that the greatest variability occurred in the subject by d a y interaction. Unfortunately, this is what clinicians must m e a s u r e , a s they try to determine patient c h a n g e over time. In our study, the test-retest standard error of m e a s u r e m e n t ( S E M ) w a s 4.12 kgf for the right hand a n d 3.78 kgf for the left hand for the a v e r a g e of three trials. If w e n o w w a n t e d to u s e this information to g e n e r a l i z e to individuals that m a t c h e d our s a m p l e population (healthy right h a n d e d m a l e s b e t w e e n the a g e s of 2 0 a n d 35) w e could perform the following calculation using, for e x a m p l e , 9 5 % c o n f i d e n c e intervals (Cl) a n d the standard error of m e a s u r e m e n t ( S E M ) : S a m p l e Clinical M e a s u r e m e n t Strategy for a Hypothetical Patient Similar to our S a m p l e P o p u l a t i o n  The  confidence  in a value measured  for  the  value  mean  of 3 trials  + (z-value  for  on  the  CI)(SEM)  same  occasion  =  31  If the hypothetical patient's right hand m e a n s c o r e b a s e d on 3 t r i a l s / o c c a s i o n = 59 kgf 9 5 % c o n f i d e n c e interval z - v a l u e (from statistical tables) = 1.96 S E M (from our study) for right h a n d , a v e r a g e of 3 trials = 4.12 kgf  69 Therefore, from equation a b o v e : 59 kgf + (1.96 x 4.12) = 59 ± 8.08 (50.92 to 67.08)  T h e r e f o r e w e w o u l d be 9 5 % confident that c h a n g e s greater than (or less than) ± 8.08 kgf w o u l d signify c h a n g e s greater than that e x p e c t e d by c h a n c e . F o r the hypothetical patient s c o r e in the e x a m p l e a b o v e , this c h a n g e d u e to c h a n c e lies s o m e w h e r e b e t w e e n 50.92 kgf a n d 6 7 . 0 8 kgf: s c o r e s greater than 6 7 . 0 8 kgf or less than 5 0 . 9 2 m a y represent true c h a n g e in the subject's performance.  Limitations of the Study T h e results of our study did not exhibit a s high test-retest reliability a s h a s b e e n reported in the literature. This m a y be d u e to a n u m b e r of factors. Reliability c a n be threatened by errors in the m e a s u r e m e n t tool itself (instrument variability), errors m a d e by t h o s e taking the m e a s u r e m e n t s (tester variability) a n d a lack of c o n s i s t e n c y in the patient being e x a m i n e d (subject variability).  6  T h e J a m a r d y n a m o m e t e r u s e d in the study w a s calibrated prior to the start of the study but w a s not calibrated after to s e e if there w a s any c h a n g e throughout the testing in its m e a s u r e m e n t a c c u r a c y thus affecting instrument variability. T h e J a m a r w a s only u s e d for subject testing during the time of the study s o there w a s no potential interference by other clinician u s e . O n e e x a m i n e r did all the testing in this study. It w a s not felt that calibration a c c u r a c y would c h a n g e significantly over the c o u r s e of 3 w e e k s of grip strength testing, h o w e v e r it would have b e e n interesting to calibrate the d y n a m o m e t e r in the clinic pre a n d post test. M e a s u r e m e n t s c o r e s w e r e read to the nearest kilogram d o w n a n d while e v e r y effort w a s m a d e to be consistent in the taking of m e a s u r e m e n t , there m a y h a v e b e e n  70  s o m e error a s s o c i a t e d with tester variability. T h e tester w a s very familiar with the J a m a r d y n a m o m e t e r a n d w a s skilled in its u s e , probably minimizing tester error. T h e m e t h o d o l o g y for grip strength testing w a s b a s e d o n a s t a n d a r d i z e d p r o c e d u r e a s outlined in the literature.  11,18  H o w e v e r , the e x a m i n e r w a n t e d to m a k e this  study a s clinically relevant a s p o s s i b l e a n d therefore sterile laboratory conditions w e r e not i m p o s e d on the subjects. W h i l e positioning protocol w a s a d h e r e d to by the e x a m i n e r a n d corrected prior to the start of a grip strength trial, the subjects t e n d e d to slightly modify wrist position to be comfortable in their grip, w h i c h is what is s e e n in the clinical setting. M i n i m a l verbal e n c o u r a g e m e n t w a s given to the subjects throughout testing although it c a n be a r g u e d that a " c o a c h i n g " tone of v o i c e w a s u s e d . T h e subjects in our study started with their left h a n d , a s o p p o s e d to the right h a n d w h i c h m a y h a v e had s o m e effect. W h i l e subjects w e r e largely tested individually, there w e r e a few i n s t a n c e s w h e r e 2 subjects w e r e in the testing a r e a at the s a m e time (one waiting to be t e s t e d , the other being tested) a n d it is not known if the p r e s e n c e of a n o t h e r individual had a n effect on motivation or m a x i m a l effort. H o w e v e r , it c a n be a r g u e d that often there are other individuals present in a clinical setting w h e n a therapist is taking grip strength m e a s u r e m e n t s with their patients. T h e r e a s o n for using a generalizability a p p r o a c h in our a n a l y s i s of the d a t a for the test-retest reliability study w a s to be able to allow for the d e c o m p o s i t i o n of the error v a r i a n c e into unique s o u r c e s of variation, a n d e x p r e s s the relative m a g n i t u d e of t h e s e s o u r c e s of error. O v e r a l l , the c o m p o n e n t of subject variability o v e r test o c c a s i o n s contributed the most to the variability s e e n in our study a s e v i d e n c e d by the v a r i a n c e e s t i m a t e s for the two grip strength tests tested (Tables 3 a n d 5). Clinically, this subject  71 variability is difficult for therapists to control over repeated test o c c a s i o n s , h o w e v e r they n e e d to be a w a r e of this s o u r c e of error w h e n interpreting grip strength m e a s u r e m e n t s . Finally, s a m p l e s i z e w a s small in this study (n=14) resulting in large c o n f i d e n c e intervals, although the s a m p l e s i z e w a s h o m o g e n e o u s w h i c h s h o u l d h a v e lead to s m a l l e r S E M ' s . L a r g e r s a m p l e s permit more a c c u r a t e estimation of true population v a l u e s a n d s a m p l e s i z e m a y h a v e contributed to the variability in our study. 3  Recommendations for Further Research  T h e information from this test-retest reliability study e n a b l e s us to m a k e the following r e c o m m e n d a t i o n s for further r e s e a r c h :  1. R e c o g n i z e d grip strength testing protocols should be followed. P r o t o c o l s s h o u l d be clearly defined a n d s t a n d a r d i z e d in order to improve consistent testing b e t w e e n a n d within therapists in the clinical setting. T h i s s h o u l d include positioning, testing p r o c e d u r e s , n u m b e r of trials, intertrial rest periods a n d e q u i p m e n t calibration. 2. T h e m e a n of 3 m e a s u r e m e n t s c o r e s a p p e a r s to be the most reliable b a s e d on the results of our study. Further r e s e a r c h on this m e a s u r e m e n t strategy is r e c o m m e n d e d in various patient groups. 3. T h e grip strength difference between the dominant a n d non-dominant h a n d n e e d s to be more fully investigated before making c o m p a r i s o n s b e t w e e n h a n d s with grip strength testing. 4.  R e s e a r c h n e e d s to be d o n e on patient populations a s o p p o s e d to healthy individuals in order to determine what the true v a r i a n c e in patient grip strength s c o r e s is. It is a s s u m e d that a p e r s o n with a pathology will mimic healthy individuals but present with lower m e a s u r e m e n t s c o r e s ( p e r s . c o m m , P a u l Stratford). T h i s m a y not a l w a y s be the c a s e .  72  CONCLUSION T h i s study attempted to investigate the reliability of grip strength testing in healthy subjects using two c o m m o n l y administered grip strength tests. T h e results of our study indicate that the S t a n d a r d Grip Strength T e s t w a s reliable (R >0.80) b e t w e e n trials for the right hand (R=.85) a n d the left (R=.84) for a single trial a n d for the m e a n of 3 trials (R=.95 right, R=.94 left). T h e S t a n d a r d Grip Strength T e s t exhibited substantial reliability (R=0.61 to 0.80) b e t w e e n d a y s . T h e 5-Position Grip Strength T e s t w a s reliable b e t w e e n d a y s at position 1, 2 a n d 4 on the left h a n d (R >0.80) a n d h a d substantial reliability (R=0.61-0.80) at other positions a n d with the right h a n d . T h e r e w a s m o r e subject variability b e t w e e n d a y s on all tests. T h e s e findings h a v e implications for clinical practice a n d for the d e v e l o p m e n t of a m e a s u r e m e n t strategy to aid in the detection of clinically important c h a n g e .  73  REFERENCES 1. F e s s E E . 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Statistical m e t h o d o l o g y for the concurrent a s s e s s m e n t of interrater and intrarater reliability: U s i n g goniometric m e a s u r e m e n t s a s a n e x a m p l e . P h y s i c a l T h e r a p y 1994; 74:8: 7 7 7 - 7 8 8 .  7.  B i r m i n g h a m T B , K r a m e r J F , S p e e c h l e y M , C h e s w o r t h B, M a c D e r m i d J . Test-retest reliability of the coefficient of variation a s a m e a s u r e of sincerity of effort during isometric testing. P h y s i o t h e r a p y C a n a d a 1997; 4 9 : 3 : 1 8 4 - 1 9 0 .  8. B e a r - L e h m a n J , A b r e a u B C . Evaluating the h a n d : Issues in reliability a n d validity. P h y s i c a l T h e r a p y 1989; 69(12): 1 0 2 5 - 1 0 3 3 . 9. A s i m o w E n g i n e e r i n g C o m p a n y . J a m a r Adjustable H a n d D y n a m o m e t e r . Angeles: A s i m o w Engineering.  Los  10. F e s s E E , M o r a n C A . Clinical A s s e s s m e n t R e c o m m e n d a t i o n s . G a r n e r , North C a r o l i n a : A m e r i c a n S o c i e t y of H a n d Therapists 1 9 8 1 : 6-8. 11. Hamilton A , B a l n a v e R, A d a m s R. Grip strength testing reliability. T h e r a p y 1994; 7(3): 163-170.  J o u r n a l of H a n d  12. M a c D e r m i d J C , K r a m e r J F , W o o d b u r y M G , M c F a r l a n e R M , R o t h J H . Interrater reliability of pinch a n d grip strength m e a s u r e m e n t s in clients with cumulative trauma disorders. J o u r n a l of H a n d T h e r a p y 1994; 7: 10-14. 13. S m i t h R O , B e n g e M W . P i n c h and grasp strength: Standardization of terminology a n d protocol. A m e r i c a n J o u r n a l of O c c u p a t i o n a l T h e r a p y 1985; 39(8):531-535. 14. Stratford P W , N o r m a l G R , M c i n t o s h J M . Generalizability of grip strength m e a s u r e s in patients with tennis elbow. P h y s i c a l T h e r a p y 1989; 6 9 : 2 7 6 - 2 8 1 .  74 15. L a n d i s J R , K o c h G G . T h e m e a s u r e m e n t of o b s e r v e r a g r e e m e n t for categorical d a t a . 1977 Biometrics 3 3 : 1 5 9 - 1 7 4 16. B o h a n n o n R W , S a u n d e r s N. H a n d - h e l d dynamometry: A single trial m a y be a d e q u a t e for m e a s u r i n g m u s c l e strength in healthy individuals. P h y s i o t h e r a p y C a n a d a 1990; 4 2 : 1 : 6 - 9 . 17. Stratford P W . S u m m a r i z i n g the results of multiple strength trials; truth or c o n s e q u e n c e . P h y s i o t h e r a p y C a n a d a 1992; 4 4 : 1 : 14-18. 18. M a t h i o w e t z V , W e b e r K, V o l l a n d G , K a s h m a n N. Reliability a n d validity of h a n d strength evaluations. J o u r n a l of H a n d S u r g e r y (Am) 1984; 9:222-226. 19. Mathiowetz, V . Effects of three trials on grip and pinch strength m e a s u r e m e n t s . J o u r n a l of H a n d T h e r a p y 1990; 3(4): 195-198. 2 0 . P a t t e r s o n R P , Baxter T. A multiple m u s c l e strength testing protocol. A r c h i v e s of P h y s i c a l M e d i c i n e and Rehabilitation 1988; 6 9 : 3 6 6 - 3 6 8 . 2 1 . F e s s E E . T h e effects of J a m a r handle position and test protocol o n normal grip strength. J o u r n a l of H a n d S u r g e r y 1982; 7 A : 3 0 8 . 2 2 . D u n w o o d y L, Tittmar H G , M c C l e a n W S . Grip strength a n d intertrial rest. a n d Motor Skills 1996; 8 3 : 2 7 5 - 2 7 8 .  Perceptual  2 3 . M a r i o n R, Niebuhr B R . Effect of warm-up prior to m a x i m a l grip contractions. J o u r n a l of H a n d T h e r a p y 1992; 5(3):143-146. 24. T o e w s J V . A grip strength study a m o n g steelworkers. A r c h i v e s of P h y s i c a l M e d i c i n e a n d Rehabilitation 1964; 4 5 : 4 1 3 - 4 1 7 . 2 5 . P e t e r s e n P, Petrick M, C o n n o r H, C o n k l i n D. Grip strength a n d h a n d d o m i n a n c e : challenging the 1 0 % rule. A m e r i c a n J o u r n a l of O c c u p a t i o n a l T h e r a p y 1 9 8 9 ; 43(7):444-7. 26. B e c h t o l C O . Grip Test: T h e use of a d y n a m o m e t e r with adjustible h a n d l e s p a c i n g s . J o u r n a l of B o n e a n d Joint S u r g e r y (Am.) 1954; 3 6 A : 8 3 2 . 27. L u n d e B K , B r e w e r W D , G a r c i a P A . Grip strength of college w o m e n . A r c h i v e s of P h y s i c a l M e d i c i n e and Rehabilitation 1972; 4 9 1 - 4 9 3 . 28. S c h m i d t R T , T o e w s J V . Grip strength a s m e a s u r e d by J a m a r d y n a m o m e t e r . A r c h i v e s of P h y s i c a l M e d i c i n e 1970; 5 1 : 3 2 1 - 3 2 7 . 2 9 . H a r k o n e n R, Piirtomaa M a n d A l a r a n t a H. Grip strength a n d h a n d position of the d y n a m o m e t e r in 204 Finnish adults. J o u r n a l of H a n d S u r g e r y 1 9 9 3 ; 18B(1): 129132.  75  3 0 . H a r k o n e n R, Harju R, A l a r a n t a H. A c c u r a c y of the J a m a r d y n a m o m e t e r . H a n d T h e r a p y 1993; 6 : 2 5 9 - 2 6 2 .  J o u r n a l of  3 1 . H o p k i n s K D , H o p k i n s B R , G l a s s G V . B a s i c Statistics for the B e h a v i o u r a l S c i e n c e s , 3 e d . Toronto: Allyn and B a c o n , 1996. r d  76  CHAPTER  SUMMARY AND CONCLUSIONS  In clinical practice, therapists n e e d to know if their treatment strategies are effective in order to plan a n d progress c a r e for their patients. O f v a l u e to the therapist, is the ability to monitor c h a n g e in their patients with a valid a n d reliable m e a s u r e m e n t tool. Grip strength a s s e s s m e n t s are c o m m o n l y u s e d in clinical practice d u e to the 1  objectivity of the m e a s u r e m e n t d e v i c e s , the relative e a s e a n d c o s t - e f f e c t i v e n e s s of test administration a n d the availability of normative d a t a . T h e J a m a r d y n a m o m e t e r w a s 2  c h o s e n for a s s e s s m e n t in our study d u e to its w i d e s p r e a d u s e a s a grip strength m e a s u r e m e n t tool in rehabilitation. T h e p u r p o s e of our study w a s twofold: 1) to s u r v e y 3  therapist's u s e of grip strength m e a s u r e s in clinical practice a n d 2) to determine the reliability of grip strength testing in healthy subjects. Of interest w a s the investigation of what drives clinical d e c i s i o n making with respect to grip strength m e a s u r e s .  M e a s u r e s of strength must be sensitive e n o u g h to distinguish b e t w e e n s u b n o r m a l a n d normal m u s c l e strength a n d be p r e c i s e e n o u g h to d o c u m e n t both i n c r e a s e s a n d d e c r e a s e s in strength.  4  With all m e a s u r e s or a s s e s s m e n t tools, it is  important that the u s e r k n o w what the normal h o w reliable  the m e a s u r e is a n d how to interpret  variation the  in the m e a s u r e of interest is, results  of the m e a s u r e . T o be  a b l e to m e a s u r e or detect c h a n g e in a patient's status effectively, the m e a s u r e m e n t tool s h o u l d be highly sensitive to clinically important c h a n g e . T h e following d i s c u s s i o n  attempts to incorporate the results of our survey study, the test-retest reliability study a n d a review of the existing literature on grip strength testing in order to provide s o m e direction to practicing therapists regarding the normal variation, the reliability a n d the interpretation of grip strength m e a s u r e m e n t s with respect to clinically important c h a n g e .  What is the normal variation in grip strength measures?  Y o u n g et a l studied the variations in grip strength a m o n g 95 healthy m e n a n d 5  w o m e n using all 5 positions of the J a m a r d y n a m o m e t e r . Grip strength w a s m e a s u r e d in the morning a n d afternoon, 2 d a y s a w e e k for 3 w e e k s for a total of 12 testing periods. O v e r the c o u r s e of this testing, they found that m e a n grip strength fluctuated b e t w e e n 5.1 kgf a n d 8.4 kgf, or between 1 9 . 2 % a n d 2 3 . 7 % w h e n c o m p a r e d to the group m e a n s . Specifically for m e n in their study (n=34, 30 being right h a n d e d , a g e range 18 to 67 y e a r s ) , the dominant hand exhibited an 8.4 kgf grip strength difference a n d the non-dominant hand 8.1 kgf difference ( 1 9 . 2 % a n d 1 9 . 4 % c h a n g e respectively) o v e r all 5 h a n d l e positions of the J a m a r d y n a m o m e t e r . In our study of 14 healthy right h a n d dominant m a l e s (mean a g e 25.4 years), the dominant hand exhibited a 4.7 kgf (8%) grip strength difference with the m e a n of 3 trials at position 2 on the S t a n d a r d Grip Strength T e s t a n d a n overall 4.2 kgf (8.2%) difference over all 5 positions on the J a m a r ( C h a p t e r 3, T a b l e 6). W h i l e our v a l u e s a p p e a r lower than that found by Y o u n g et a l , 5  the differences in s a m p l e s i z e , the n u m b e r of test o c c a s i o n s (2 in our study, 12 in Y o u n g et al's) a n d the large a g e range of the subjects probably a c c o u n t e d for the larger fluctuation in grip strength m e a s u r e s s e e n in Y o u n g et al's study. In our study, the s t a n d a r d error of m e a s u r e m e n t for the test-retest m e a n of 3 trials on the S t a n d a r d Grip  78  Strength T e s t w a s 4.12 kgf for the right hand a n d 3.78 kgf for the left h a n d . A s well, the S E M of the difference b e t w e e n right a n d left h a n d s w a s 3.18 kgf for the a v e r a g e of 3 trials.  A s the subjects in our study w e r e healthy individuals, a n d the time b e t w e e n  testing w a s short e n o u g h (mean=1.5 days) that no a p p r e c i a b l e c h a n g e in the subject's status s h o u l d h a v e o c c u r r e d , fluctuation in grip strength m e a s u r e m e n t s w a s thought to be d u e to error a l o n e in our study subjects. T h e results of our survey study indicated that r e s p o n d e n t s felt that a 5 kgforce difference or 1 0 % difference between trials w a s clinically significant to b a s e treatment d e c i s i o n s o n . H o w e v e r , b a s e d on the results of our reliability study in healthy individuals, it w o u l d a p p e a r that approximately 4.74 kgf for the right h a n d a n d 4 . 4 9 kgf for the left could be d u e to error a l o n e a n d m a y be a m e a s u r e of normal variability in our s a m p l e . M e a n grip strength fluctuations in our healthy s a m p l e population exhibited 4.6 kgf to 6.6 kgf fluctuations b e t w e e n trials on the S G S T in the right h a n d a n d 4.2 kgf to 5.9 kgf in the left ( C h a p t e r 3, T a b l e 6). Grip strength fluctuations w e r e less w h e n the m e a n of 3 trials w a s c o n s i d e r e d (right = 4.7 kgf, left = 4.8 kgf). P e r c e n t difference b e t w e e n trials on the S G S T varied from 7 . 7 % to 11.5 % o n the right hand a n d 7 . 9 % to 1 0 . 8 % on the left h a n d . Therefore, clinicians m a y be stating there is a true c h a n g e b a s e d o n their u s e of 5kgf or 1 0 % difference between trials for clinical s i g n i f i c a n c e w h e n o n e h a s not really occurred a n d the c h a n g e s e e n is d u e to normal subject variability from d a y to day. S u r v e y r e s p o n d e n t s a l s o indicated that a 5kgf or 1 0 - 2 0 % difference b e t w e e n h a n d s w o u l d be clinically significant. B a s e d on our study results of the S G S T , the S E M for the difference b e t w e e n right a n d left h a n d s w a s 4.21 kgf for a single trial a n d 3.18 for the a v e r a g e of 3 trials. P e t e r s o n et a l u s e d a formula in their study to determine the 6  79 percent difference b e t w e e n h a n d s . T h e y took the s c o r e of the n o n d o m i n a n t h a n d a n d divided it by the s c o r e of the dominant hand a n d this v a l u e w a s subtracted from 1. F o r e x a m p l e , for a right h a n d e d subject in their study, with a right hand s c o r e of 80 kg force a n d a left hand s c o r e of 7 2 kg force, the calculation would be 1 - (72/80) = .10 (10%). P e t e r s o n et a l u s e d the stronger of 2 grip strength trials, at either position 2 or 3 on the 7  J a m a r d y n a m o m e t e r (depending on patient preference a n d comfort). T h e s u b j e c t s in our study w e r e all right hand dominant a n d w e u s e d position 2 on the J a m a r for the S t a n d a r d Grip Strength Test. U s i n g P e t e r s o n et a l ' s formula with d a t a from our 6  reliability study to obtain the percent difference b e t w e e n h a n d s with a single subject (LW) (see A p p e n d i x F), taking the highest of 3 trials a s per P e t e r s o n et a l , the 6  calculation w o u l d be 1 - (52kgf/66kgf) = 2 1 % for test o c c a s i o n #1 a n d 1-(58kgf/72kgf) = 1 9 % for the retest o c c a s i o n . H o w e v e r , if w e take the m e a n of all subjects trials (3 trials times 14 subjects) on the first test o c c a s i o n , the percent difference b e t w e e n h a n d s is 1 0 % a n d the test-retest percent difference is 8%. Therefore, the 1 0 % rule , w h i c h is 6  v a g u e l y d e s c r i b e d in the literature a s the a v e r a g e difference in g r a s p i n g p o w e r b e t w e e n the d o m i n a n t a n d non-dominant h a n d , did not a p p e a r to apply to the individual subjects in our study, but more closely m a t c h e d the group norms of our right h a n d e d subjects. H o w e v e r , in clinical practice, the therapist is usually c o n c e r n e d with a n individual patient a n d it w o u l d a p p e a r that normal variability b e t w e e n the dominant a n d n o n d o m i n a n t h a n d s m a y not c o n c u r with the 1 0 % rule in single subjects. In our test-retest reliability study, w e found the greatest s o u r c e of error w a s d u e to subject variation b e t w e e n test o c c a s i o n s . F a c t o r s that affect subject variability include the patient's level of attention and/or motivation, the environmental stimuli surrounding the test site, the patient's familiarity with the testing p r o c e d u r e , a n d the  80 positioning of the patient s u c h a s the p l a c e m e n t of the d y n a m o m e t e r in the patient's hand.  4  In our study of healthy individuals, a range of m e a s u r e m e n t fluctuations of 3 to  7 kgf (5-13%) w a s noted over 2 test o c c a s i o n s for all positions on the J a m a r d y n a m o m e t e r . Individuals that present with true pathology m a y present with a greater variation a c r o s s test o c c a s i o n s d u e to other factors not present in our study s u c h a s pain, medication u s e , fear a n d a p p r e h e n s i o n or actual a n a t o m i c a l c h a n g e s in g r a s p i n g ability. A s clinicians u s e test-retest o c c a s i o n s to b a s e their treatment d e c i s i o n s o n , being a w a r e of a n d attempting to minimize controllable factors that m a y affect subject variability (environment, patient positioning, time of day) s h o u l d be t a k e n during grip strength testing a n d uncontrollable factors (pain level) s h o u l d be d o c u m e n t e d .  How reliable are grip strength measures?  T h e literature indicates that grip strength m e a s u r e m e n t s for the s t a n d a r d J a m a r d y n a m o m e t e r exhibit high (r >0.80) inter-rater r e l i a b i l i t y reliability. " 7  11  789  a n d high test-retest  In our study, the reliability of the S t a n d a r d Grip Strength T e s t w a s less  than 0.80 but greater than 0.35 for the test-retest reliability of the right h a n d , the left h a n d a n d the difference b e t w e e n the right a n d left h a n d s on a single trial a n d the m e a n of 3 trials. In the 5 Position Grip Strength Test, left hand test-retest reliability r a n g e d from R=0.70 to R=0.87, with Position 1,2 a n d 4 exhibiting the greatest reliability. In the right h a n d , test-retest reliability ranged from R=0.58 to R=0.78 with P o s i t i o n 4 , 5 a n d 3 ( in order of d e c r e a s i n g magnitude) exhibiting the greatest reliability. W h i l e our study w a s limited d u e to the s m a l l s a m p l e s i z e (n=14), it a p p e a r e d that the a v e r a g e of 3 trials  81 ( S G S T ) yielded the greatest test-retest reliability (R=.67 right a n d R=.70 left) a n d the difference b e t w e e n h a n d s the least test-retest reliability (R=.49). O v e r a l l , grip strength m e a s u r e m e n t s using the standard J a m a r d y n a m o m e t e r exhibited substantial reliability a s a m e a s u r e m e n t tool.  How can we interpret the results of grip strength measures?  A valid m e a s u r e m e n t tool should be able to detect a n d quantify a clinically important difference. With the a s s e s s m e n t of grip strength, the therapist is often 1  interested in determining if a w e a k n e s s exists. If a w e a k n e s s is identified, the therapist w a n t s to determine whether a c h a n g e in strength h a s o c c u r r e d o v e r t i m e .  12  A  c o m p a r i s o n of the contralateral hand is often u s e d to establish grip strength w e a k n e s s a n d the c o m p a r i s o n of the subject's current m e a s u r e m e n t s c o r e with that of a previous m e a s u r e m e n t determines if a c h a n g e in strength h a s o c c u r r e d o v e r t i m e .  12  Many  clinicians b a s e their m e a s u r e m e n t interpretation on the difference b e t w e e n the "normal" a n d "injured" hand in grip strength testing, with the "normal" h a n d a s s u m i n g the criterion m e a s u r e for c o m p a r i s o n . T h e A m e r i c a n M e d i c a l A s s o c i a t i o n ' s G u i d e s to Impairment  13  indicate that there is little e v i d e n c e for a significant difference in grip strength b e t w e e n the dominant a n d non-dominant h a n d , but a 1 0 % difference b e t w e e n the d o m i n a n t a n d n o n d o m i n a n t hand is often referred to by clinicians with respect to grip strength m e a s u r e s . H o w e v e r , it a p p e a r s that clinicians must be careful w h e n using the 1 0 % rule to apply to their patient populations for 2 r e a s o n s . O n e , the studies reporting differences w e r e d o n e on normal subjects a n d therefore the differences a m o n g t h o s e  82  that truly d o exhibit a difference between their dominant a n d n o n d o m i n a n t h a n d s are u n k n o w n a n d s e c o n d l y , the 1 0 % rule a p p e a r s to apply only to right h a n d e d individuals  6  a n d s h o u l d not be g e n e r a l i z e d to left h a n d e d or ambidextrous individuals. O u r results did not a p p e a r to support the 1 0 % rule for individual subjects. N e v e r t h e l e s s , the A m e r i c a n M e d i c a l A s s o c i a t i o n ( A M A ) b a s e their impairments of grip strength on a calculation: (Normal Strength - A b n o r m a l Strength)/Normal Strength for a P e r c e n t a g e Strength L o s s Index.  13  F o r e x a m p l e , if a patient's involved  right h a n d m e a s u r e s 20kgf a n d that of his left h a n d , w h i c h is normal, is 4 5 kgf, the equation w o u l d be (45kgf-20kgf)/45kgf = 5 6 % Strength L o s s Index. T h i s 5 6 % strength loss is c o n s i d e r e d to be a 2 0 % impairment of the upper extremity a c c o r d i n g to their table of u p p e r extremity impairment for loss of strength. A c c o r d i n g to the A M A strength loss tables, if a right h a n d e d patient presented with grip strength m e a s u r e s of 55kgf in the left h a n d a n d 50 kgf in the injured right h a n d , the calculation would work out to a 9 % strength loss a n d the patient would probably be a w a r d e d a 1 0 % impairment l o s s . H o w e v e r , the 5 kgf difference could be d u e to error a l o n e b a s e d on the results of our study o n the normal variability in normal individuals. T h i s h a s s e r i o u s implications w h e n looking at m e d i c o l e g a l i s s u e s a n d the reliance of grip strength m e a s u r e s to a w a r d impairment a n d disability ratings. T h e clinical significance of a m e a s u r e refers to the ability of that m e a s u r e to distinguish b e t w e e n important a n d unimportant c h a n g e . T h e therapist must feel confident that their m e a s u r e m e n t s reflect a true m e a s u r e m e n t of their patient's abilities. A m e a s u r e m e n t strategy to more accurately determine clinically important c h a n g e in a patient's status with respect to grip strength m e a s u r e s requires the calculation of the s t a n d a r d error of m e a s u r e m e n t ( S E M ) a n d a c o r r e s p o n d i n g c o n f i d e n c e interval (Cl) for  83 that patient. F o r a n o b s e r v e d s c o r e , the S E M quantifies the range in w h i c h the true s c o r e might be e x p e c t e d to vary a n d this provides information that n e e d s to be c o n s i d e r e d in clinical d e c i s i o n m a k i n g . A true c h a n g e in a patient's grip strength s c o r e w o u l d be c a l c u l a t e d by the measured  score  ± (z-value  for  CI)(SEM).  U s i n g this type  of statistical calculation for e a c h patient would lead to a n improved clinical d e c i s i o n making process. T h e interpretation of impairment m e a s u r e s s u c h a s grip strength often involve clinical a s s u m p t i o n s on the part of the therapist which include: •  grip strength m e a s u r e m e n t s are "hard" or objective d a t a  •  impairment m e a s u r e s are related to the patient's s y m p t o m s , pathology or functional limitations  •  a c h a n g e in grip strength will correlate with c h a n g e s in functional status  •  treating impairments or grip strength w e a k n e s s will improve f u n c t i o n .  14  W h i l e t h e s e a s s u m p t i o n s n e e d to be further investigated, the therapist must be a w a r e that there are m a n y factors that m a y affect grip strength m e a s u r e s ; e v e n in our healthy, motivated s a m p l e population w e noted a variation in test s c o r e s a c r o s s d a y s . A s well, grip strength m e a s u r e s m a y not perform equally well at all levels of injury; for e x a m p l e , they m a y not be a s sensitive to c h a n g e with t h o s e individuals presenting with very low or very high grip strength s c o r e s . Finally, the correlation of c h a n g e s in grip strength s c o r e s a n d functional status n e e d s to be a d d r e s s e d in order to more a c c u r a t e l y distinguish b e t w e e n important a n d unimportant c h a n g e , or u s e l e s s or useful therapy to i n c r e a s e in grip strength. T h e therapist must be able to take all t h e s e factors into a c c o u n t w h e n attempting to interpret the results of grip strength m e a s u r e s .  84  Recommendations for Grip Strength Measurements  A s B o h a n n o n indicated, m a n y of the m e a s u r e s u s e d in rehabilitation are 4  d e p e n d e n t on the patient a n d no matter how objective the test, variability within the patient a n d their level of effort is bound to h a v e a n effect on the o u t c o m e .  4  Ideally,  e a c h patient s h o u l d be treated individually w h e n interpreting what is "normal" for that individual. C o m p a r e d to other strength m e a s u r e s (i.e. the Kin C o m isokinetic d y n a m o m e t e r ) , grip strength testing is relatively quick, e c o n o m i c a l a n d e a s y to perform in the clinic. H o w e v e r , the b u s y clinician is a l w a y s f a c e d with the d i l e m m a of a v e r a g i n g s c o r e s o v e r multiple test s e s s i o n s to obtain a greater estimate of variability in a patient's s c o r e s a s o p p o s e d to s a v i n g time by taking a single m e a s u r e m e n t . A s well, b u s y clinicians m a y feel they d o not have the time or the mathematical expertise to c a l c u l a t e the S E M a n d c o n f i d e n c e intervals for their m e a s u r e m e n t s c o r e s . H o w e v e r , a n e a s y method to more accurately m e a s u r e a patient's s c o r e would be to take the a v e r a g e of multiple m e a s u r e m e n t s over a n u m b e r of patient visits (i.e. 3 m e a s u r e m e n t s , o v e r 2 d a y s = a n a v e r a g e of 6 m e a s u r e m e n t s ) . T h e trade off of cost (in time) v e r s u s quality of the d e c i s i o n is that therapists taking into a c c o u n t normal variability a c r o s s test o c c a s i o n s in their patients would h a v e to s e e a greater c h a n g e in a patient's grip strength m e a s u r e in order for that m e a s u r e to be d e e m e d clinically significant. In order to improve the ability to detect clinically important c h a n g e , clinicians s h o u l d be a w a r e of the normal variability in m e a s u r e m e n t w h e n e m p l o y i n g grip strength testing in the clinical setting. T h e following r e c o m m e n d a t i o n s are b a s e d o n a review of the literature on grip strength m e a s u r e m e n t s , the results of our s u r v e y study of  85  clinicians a n d our test-retest reliability study of 2 c o m m o n grip strength tests.  1. Test Knowledge: W h i l e important in any testing but not directly e x a m i n e d in this study, before using any clinical test procedure, therapists s h o u l d be a w a r e of the p u r p o s e of the test, the theoretical b a s i s for the test a n d the test setting in w h i c h the test h a s b e e n d e v e l o p e d a n d u s e d . A n understanding of available m e a s u r e m e n t tools a n d their properties is imperative to obtaining valid, reliable m e a s u r e m e n t s a n d in turn, m a k i n g effective clinical d e c i s i o n s . 15  2. Standardized Positioning: It is r e c o m m e n d e d that s t a n d a r d i z e d positioning a s per the A m e r i c a n S o c i e t y of H a n d Therapists (patient in sitting with the s h o u l d e r a d d u c t e d a n d neutrally rotated, e l b o w at 90 d e g r e e s a n d the forearm a n d wrist in neutral, a r m not stabilized) be u s e d consistently for testing. T e s t position s h o u l d be d o c u m e n t e d in the charting p r o c e d u r e s to allow more a c c u r a t e replication of m e a s u r e m e n t s by another tester. 3. Standardized Test Protocol: A s t a n d a r d i z e d test protocol s h o u l d be a d h e r e d to by the clinician. A 15 s e c o n d intertrial rest a p p e a r s sufficient to minimize fatigue b e t w e e n trials. C o n s i s t e n t protocol s h o u l d be followed (i.e. s t a n d a r d p r o c e d u r e s for test administration a n d s c o r i n g , starting with the s a m e hand e a c h time for testing, using the s a m e c o m m a n d s , testing in the s a m e room, d o c u m e n t i n g activity prior to testing that m a y affect grip strength) to minimize subject variation b e t w e e n test occasions as much as possible. 4.  Measurement Strategy: T h e m e a n of 3 trials w a s more reliable in our study a n d is r e c o m m e n d e d a s a m e a s u r e m e n t strategy a s o p p o s e d to taking o n e trial.  5. Establishing Normal Variability: T i m e m a y be a factor in the clinical setting, but ideally therapists should establish a b a s e l i n e of grip strength m e a s u r e m e n t s for e a c h individual patient w h e n attempting to m e a s u r e c h a n g e o v e r time. F r o m the literature, it a p p e a r s that determination of true grip strength is best m a d e with m e a s u r e m e n t s taken over a number of test o c c a s i o n s . F r o m our study, the greatest s o u r c e of variation w a s d u e to subject variability over test o c c a s i o n s . A v e r a g i n g s c o r e s o v e r a period of a few d a y s to determine a b a s e l i n e m a y be helpful in detecting true c h a n g e from c h a n g e a s s o c i a t e d with error (i.e. 3 m e a s u r e s per d a y a v e r a g e d over 2 d a y s (6 m e a s u r e s in total)). W h i l e grip strength testing exhibits substantial reliability, therapists must be cautious w h e n b a s i n g their clinical d e c i s i o n s o n just o n e m e a s u r e of grip strength. 6. Measurement error: T h e S t a n d a r d Error of M e a s u r e m e n t ( S E M ) is important to calculate with test-retest grip strength m e a s u r e m e n t s a s it g i v e s a n estimate of error in the s a m e units a s the m e a s u r e m e n t . C o n f i d e n c e intervals for the S E M s h o u l d a l s o be c a l c u l a t e d . T h e e x a m p l e a s outlined by Stratford a n d G o l d s m i t h m a y be helpful for clinicians in understanding a n d calculating the S E M a n d its c o r r e s p o n d i n g c o n f i d e n c e interval. 16  86  7.  Use of a Normative Database: A normative d a t a b a s e s h o u l d only be c o m p a r e d to w h e n the s a m e test protocol, s a m p l e population a n d instrument u s e d by the clinician h a s b e e n u s e d to d e v e l o p the normative data.  8. Calibration: W h i l e not a f o c u s in this paper, calibration is important to improve instrument a c c u r a c y a n d therefore the c o n f i d e n c e of m e a s u r e m e n t s c o r e s . It is r e c o m m e n d e d that hand d y n a m o m e t e r s be calibrated on a regular b a s i s (calibration r e c o m m e n d e d o n c e a y e a r by the manufacturer) or d e v e l o p a method of calibrating the d y n a m o m e t e r with known weights a s per the method outlined by F e s s . 1 7  Suggestions for Further Research Further r e s e a r c h is n e e d e d to look at the subject variation in grip strength m e a s u r e m e n t s a m o n g patient-specific population groups. T h i s is important to determine the impact of treatment a p p r o a c h e s on individuals a n d o n patient specific g r o u p s a s a w h o l e . A s well, the validity, or the extent to w h i c h grip strength tests m e a s u r e what they are intended to m e a s u r e , s h o u l d be e x p l o r e d . T h e a p p r o p r i a t e n e s s , m e a n i n g f u l n e s s a n d u s e f u l n e s s of grip strength m e a s u r e s requires further investigation before w e c a n accurately u s e t h e s e tests to infer a patient's functional status.  Conclusion T h e most important a s p e c t of a m e a s u r e m e n t tool for the clinician is the ability to reliably detect clinically important c h a n g e . F r o m the literature, a n d a s u r v e y of clinicians, it a p p e a r s that the J a m a r d y n a m o m e t e r is a widely u s e d a n d a c c e p t e d clinical m e a s u r e m e n t tool in rehabilitation. M o s t clinicians are familiar with the S t a n d a r d G r i p Strength T e s t a n d the 5 Position Grip Strength T e s t a n d most u s e grip  87  strength m e a s u r e m e n t s to determine grip strength in hand a n d upper extremity injured populations. Test-retest reliability of two c o m m o n grip strength tests ( S G S T ,  5PGST)  w a s substantial in our study of healthy m a l e s . H o w e v e r , m e a s u r e s reported to detect clinically important c h a n g e w e r e varied, a n d it a p p e a r e d from our study, that clinicians m a y report a c h a n g e in a patient's status w h e n the c h a n g e m a y be d u e to m e a s u r e m e n t error alone.  A s well, the reliability a n d variability in patient specific  populations is not k n o w n a s m a n y of the reliability studies h a v e b e e n d o n e on healthy subjects. In c o n c l u s i o n , knowing the range in which the true s c o r e for a n individual's o b s e r v e d test c a n be e x p e c t e d to vary aids in interpreting the grip strength m e a s u r e m e n t s c o r e s . T h e u s e of the standard error of m e a s u r e m e n t a n d c o n f i d e n c e intervals greatly aid the therapist's clinical d e c i s i o n making in determining if a true c h a n g e h a s o c c u r r e d . Further r e s e a r c h is required to e x a m i n e the i s s u e s of validity with r e s p e c t to grip strength m e a s u r e s .  88  REFERENCES 1. C o l e B, F i n c h F, G o w l a n d C , M a y o N. Physical Rehabilitation Toronto, Ont: C a n a d i a n P h y s i c a l therapy A s s o c i a t i o n 1994.  Outcome  Measures.  2. S m i t h R O , B e n g e M W . P i n c h a n d grasp strength: S t a n d a r d i z a t i o n of terminology a n d protocol. American Journal of Occupational Therapy]985; 39(8):531-535. 3. F e s s E E , M o r a n C A . Clinical Assessment Recommendations. C a r o l i n a : A m e r i c a n S o c i e t y of H a n d T h e r a p i s t s 1 9 8 1 : 6-8. 4.  B o h a n n o n R W . T h e clinical m e a s u r e m e n t of strength. Clinical 1:5-16.  G a r n e r , North  Rehabilitation  1987;  5. Y o u n g V L , P i n P, K r a e m e r B A , G o u l d R B , Nemergut L, P e l l o w s k i M . Fluctuation in grip a n d pinch strength a m o n g normal subjects. Journal of Hand Surgery ( A m e r i c a n v o l u m e ) 1989; 14:1:125-129. 6. P e t e r s e n P , Petrick M , C o n n o r H, C o n k l i n D. Grip strength a n d hand d o m i n a n c e : c h a l l e n g i n g the 1 0 % rule. American Journal of Occupational Therapy 1 9 8 9 ; 43(7):444-7. 7. M a t h i o w e t z V , W e b e r K, V o l l a n d G , K a s h m a n N. Reliability a n d validity of h a n d strength evaluations. Journal of Hand Surgery (Am) 1984; 9 : 2 2 2 - 2 2 6 . 8. B e a r - L e h m a n J , A b r e a u B C . Evaluating the h a n d : Issues in reliability a n d validity. Physical Therapy 1989; 69(12): 1 0 2 5 - 1 0 3 3 . 9. Hamilton A , B a l n a v e R, A d a m s R. Grip strength testing reliability. Journal Therapy 1994; 7(3): 163-70.  of  Hand  10. M a c D e r m i d J C , K r a m e r J F , W o o d b u r y M G , M c F a r l a n e R M , Roth J H . Interrater reliability of pinch a n d grip strength m e a s u r e m e n t s in clients with cumulative t r a u m a d i s o r d e r s . Journal of Hand Therapy 1994; 7: 10-14. 11. Stratford P W , Normal G R , M c i n t o s h J M . Generalizability of grip strength m e a s u r e s in patients with tennis elbow. Physical Therapy 1989; 6 9 : 2 7 6 - 2 8 1 . 12. Stratford P W . S u m m a r i z i n g the results of multiple strength trials: Truth or c o n s e q u e n c e . Physiotherapy Canada 1992; 4 4 : 1 : 1 4 - 1 8 . 13. A m e r i c a n M e d i c a l A s s o c i a t i o n . Guides to the evaluation of permanent 4th e d . C h i c a g o , Illinois:, A m e r i c a n M e d i c a l A s s o c i a t i o n 1 9 9 3 .  impairment,  89 14. Binkley J , Stratford P. M e a s u r e m e n t of o u t c o m e in orthopaedic p h y s i c a l therapy practice; A step-by-step a p p r o a c h for clinicians. Sentinel A s s o c i a t e s , 1997. 15. A m e r i c a n P h y s i c a l T h e r a p y A s s o c i a t i o n ' s T a s k F o r c e on S t a n d a r d s for M e a s u r e m e n t in P h y s i c a l T h e r a p y . S t a n d a r d s for tests a n d m e a s u r e m e n t s in p h y s i c a l therapy practice. Physical Therapy 1 9 9 1 ; 71(8): 5 8 9 - 6 2 2 . 16. Stratford P W , G o l d s m i t h C H . U s e of the standard error a s a reliability index of interest: A n applied e x a m p l e using e l b o w flexor strength data. Physical Therapy 1997; 7 7 : 7 : 7 4 5 - 7 5 0 . 17. F e s s E E . A method for c h e c k i n g J a m a r d y n a m o m e t e r calibration. Journal Therapy 1987; (4):28-32.  of Hand  90  Appendix A  GRIP STRENGTH TEST DESCRIPTION Standard Grip Strength Test T h e s t a n d a r d grip strength test, while not a l w a y s referred to by this n a m e in the literature, in our study c o n s i s t s of 3 grip strength trials at H a n d l e P o s i t i o n #2 o n the J a m a r d y n a m o m e t e r . T h e subject is positioned a c c o r d i n g to the A m e r i c a n S o c i e t y of H a n d T h e r a p i s t s , in sitting with the s h o u l d e r a d d u c t e d a n d neutrally rotated, the e l b o w at 90 d e g r e e s a n d the forearm a n d wrist in neutral. T h e subject's a r m is not stabilized. T i m e b e t w e e n trials w a s 15 s e c o n d s . T h e left hand w a s tested first, a n d h a n d s w e r e alternated for testing (left, then right). T h e subjects w e r e e n c o u r a g e d to give m a x i m a l effort by stating this verbally at the start of the testing a n d by giving minimal verbal e n c o u r a g e m e n t during the testing.  5-Position Grip Strength Test T h e 5-Position Grip Strength T e s t involved similar subject positioning a s indicated in the S t a n d a r d Grip Strength T e s t a b o v e . O n e grip strength m e a s u r e m e n t w a s t a k e n at e a c h of the 5 handle positions on the J a m a r d y n a m o m e t e r , starting with the s m a l l e s t position (handle position #1) a n d progressing to the largest (handle position #5). T h e left hand w a s tested first, then the right at e a c h position. A 15 s e c o n d rest b e t w e e n trials w a s implemented.  91  Appendix B Survey - Grip Strength Measures Please fill out this survey and return it by fax to Jane Burns at (604) 986-8492, or mail it in the self addressed, stamped envelope provided. Thank you for your time. 1.  Are you currently using grip strength measurements in your clinical practice? • Yes • No If No, why not?  2.  What standard | | | |  3.  What instrument(s) do you use to measure grip strength? | | Jamar Dynamometer | | Digital Jamar Dynamometer | | Tekdyne Dynamometer • BTE [ | Blood pressure cuff , [TJ Other (please specify)  4.  What patient populations are you using grip strength testing with? | | Hand injuries | | Upper extremity injuries | | Back/neck injuries | | Other conditions/uses  5.  For what purpose(s) do you use the grip strength tests referred to in Question #2?  grip strength tests do you currently use in your clinic? | Standard Grip Strength Test | 5 Position Grip Strength Test | Rapid Exchange Grip Strength Test | Other (please specify)  Which test is best for each purpose? | | | | 6.  | | | |  Determine grip strength Measure function (i.e. ADL) Measure impairment (i.e. % loss) Assess sincerity of effort  Which of the following measures do you use to determine clinically important differences on which to base your treatment decisions (you may check more than one). | | Percentage difference between hands | | Absolute difference between hands | | Percentage difference between trials | | Absolute difference between trials | | Percentage difference between normative database and raw score | | Absolute difference between normative database and raw score | | Other (please specify):  92  7.  How large would the difference have to be for you to call it clinically significant? (Indicate the differences for the measures that you checked in the question above only). | | | | | | |  8.  | | | | | | |  Percentage difference between hands Absolute difference between hands Percentage difference between trials Absolute difference between trials Percentage difference between normative database/raw score Absolute difference between normative database/raw score Other (please specify):  Do you use a normative database to compare results to? • Yes • No If yes, which one?  % kg/lbs force % kg/lbs force % kg/lbs force  94  Appendix D  R E S E A R C H DESIGN  Testing Protocol - Day 1  -»  Testing Protocol - Day 2  S T A N D A R D GRIP STRENGTH TEST 3 Trials at Position #2  S T A N D A R D GRIP STRENGTH TEST 3 Trials at Position #2  (15 s e c o n d rest b e t w e e n trials)  (15 s e c o n d rest b e t w e e n trials)  2 MINUTE REST  2 MINUTE REST  5 POSITION GRIP STRENGTH TEST 1 trial at e a c h of 5 positions  5 POSITION GRIP STRENGTH TEST 1 trial at e a c h of 5 positions  (15 s e c o n d rest b e t w e e n trials)  (15 s e c o n d rest b e t w e e n trials)  •Randomly assigned to S G S T or 5PGST at beginning of study •Test dates within 1 week of each other •Start with left hand first in all tests •Repeated measures, within subject design  95  Appendix E Standardized Subject Instructions 1. T h e subject will be a s k e d to sign the c o n s e n t forms a n d the study will be e x p l a i n e d to t h e m . O r d e r of testing (Standard Grip Strength Test, 5-Position G r i p Strength Test) will be determined by a computerized r a n d o m n u m b e r table at the start of testing. 2. T h e J a m a r d y n a m o m e t e r will be s h o w n to the subject. Instructions to the subject will be "We are doing a study to test grip strength. I want you to squeeze this handle as hard as you can until I say stop. I want you to try as hard as you can and give maximal effort. Do you have any questions ?" 3. Both h a n d s will be tested, starting with the left h a n d . 4. T h e test p r o c e d u r e involves positioning the subject in sitting with the s h o u l d e r a d d u c t e d a n d neutrally rotated, the e l b o w at 90 d e g r e e s a n d the forearm a n d wrist in neutral. T h e subject's arm will not be stabilized. T h e J a m a r d y n a m o m e t e r is p l a c e d in the p a l m a r gutter of the subject's h a n d . T h e subject cannot s e e the d y n a m o m e t e r dial or view the m e a s u r e m e n t s during the study (data collection will be s c r e e n e d from the subject's view). 5. T h e test will begin by placing the d y n a m o m e t e r in the subject's h a n d . P r o p e r p l a c e m e n t must be maintained in order to give the subject m a x i m a l ability to grip the d y n a m o m e t e r . Instructions to the subject will be "Are you ready ? Squeeze as hard as you can.. Squeeze..Squeeze...Squeeze and Stop". T h e next hand will then be tested in the s a m e manner. T h e s e q u e n c e of testing is a s follows, k e e p i n g in mind that the order will be d e p e n d e n t on randomization at the start of the testing s e s s i o n : Standard Grip Strength Test  Jamar Handle Position: Position #2 Start: Left hand first Procedure: 3 trials on each hand (alternating) Length of Grip: 3 seconds Rest between Trials: 15 seconds Score: Each of 3 trials and the mean of 3 trials 5 Position Grip Strength Test  Jamar Handle Position: Start at Position #1 and progress to Position #5 Start: Left hand Procedure: One trial at each of the 5 handle positions(alternating hands) Length of Grip: 3 seconds Rest Between Trials: 15 seconds Score: 1 trial at each of 5 positions 6. R e s t b e t w e e n tests will be 2 minutes a s timed by a h a n d held s t o p w a t c h . T h e s a m e p r o c e d u r e will be repeated on the retest day, within o n e w e e k of the initial testing. T h e subject will start with the s a m e test a s on d a y 1.  96  Appendix F SURVEY RESULTS RESPONSES SURVEY  QUESTION  CLINICIAN USE Using Grip Strength Measures Not Using Grip Strength Measures  N=120 # All % All Sites Sites 113 7  n=11 n=109 #Hand % Hand # Sites % Sites Only Only Only Only 94 6  11 0  100 0  102 7  94 6  120  TESTS USED Standard Grip Strength Test 5 Position Grip Strength Test Rapid Exchange Grip Strength Test Other INSTRUMENT USED Jamar Digital Jamar Tekdyne BTE Blood Pressure Cuff Other PATIENT POPULATION TESTED Hand Injuries Upper Extremity Injuries Back/Neck Injuries Other PURPOSE OF TEST Determine Grip Strength Measure Function Measure Impairment A s s e s s Sincerity of Effort  n=102  n=11  n=113 94 47 28  83 42 25  10 7 6  91 64 55  84 40 22  82 39 22  12 181  11  1  9  11  11  98 11 0 10 17 24 160  87 10 0 9 15 21  9 0 0 1 0 3  82 0 0 9 0 27  89 11 0 9 17 21  87 11 0 9 17 21  96 83 35 36 250  85 73 31 32  10 7 2 1  91 64 18 9  86 76 33 35  84 75 32 34  111 40 66 48 265  98 35 58 42  10 3 5 8  91 27 45 73  101 37 61 40  99 36 60 39  # All Sites MEASURES TO DETERMINE CIC % diff between hands Absolute diff between hands % diff between trials Absolute diff between trials % diff between NDB/score Absolute diff between NDB/score Other USE OF NORMATIVE DATABASE Yes No No Response  % All Sites  # Hand % Hand # Sites % Sites Only Only Only Only  65 68 31 44 18 21 10 257  58 60 27 39 16 19 9  8 5 3 3 2 2 3  73 45 27 27 18 18 27  57 63 28 41 16 19 7  56 62 27 40 16 19 7  43 69 1  39 62  5 4 2  56 44  38 65  37 64  73  ~0  m  >  o c_  O r I -  cn 0.697  In _^ o  00 -4 CT)ro  cn  CO  cn  CO  —\  O  z o O  cn  cn CD  cn ro  cn --J  cn  cn  o  4^  cn  cn  cn  cn  cn  cn  cn  cn  CO  o  cn  cn  o  00  00  4*. 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Ol  100  Appendix G STATISTICAL RESULTS FOR THE STANDARD GRIP STRENGTH TEST A n a l y s i s of Variance (Balanced Designs)  A n a l y s i s of Variance for RIGHT Source SUBJECTS TRIAL DAY SUBJECTS*TRIAL SUBJECTS*DAY TRIAL*DAY Error Total  DF 13 2 1 26 13 2 26 83  3242 64 116 171 596 0 224 4416  SS 536 667 679 000 155 857 810 702  249 32 116 6 45 0 8  MS 426 333 679 577 858 429 647  F  P  0 76 5 30 0 05  0 755 0 000 0 952  * * *  * No exact F-test can be calculated. Variance Error component term 34 .2729 SUBJECTS * 1.2134 * TRIAL 1.8819 * DAY 7 SUBJECTS*TRIAL -1.0348 12 .4038 7 SUBJECTS*DAY 7 -0.5870 TRIAL*DAY 8.6465 Error  Source 1 2 3 4 5 6 7  Expected Mean Square (using unrestricted model) (7) +3(5) + 2(4) +6(1) (7) + 14 (6) +2(4) + 28 (2) (7) + 14 (6) + 3(5) + 42 (3) (7) + 2(4) (7) + 3(5) (7) + 14(6) (7)  * No exact F-Test can be calculated.  Means DAY 1 2 TRIAL 1 2 3  N 42 42  RIGHT 57.762 60.119 N 28 28 28  RIGHT 59.964 59.036 57.821  Analysis of Variance (Balanced Designs) - Standard Grip Strength Test  A n a l y s i s of Variance for L E F T Source SUBJECTS TRIAL DAY SUBJECTS*TRIAL SUBJECTS*DAY TRIAL*DAY Error Total  DF 13 2 1 26 13 2 26 83  2989 5 213 244 386 31 210 4081  SS 619 357 762 310 571 595 071 286  229 2 213 9 29 15 8  MS 971 679 762 397 736 798 080  F  P  1 16 3 68 1 96  0 352 0 002 0 162  * * *  * No exact F-test can be calculated. Variance Error component term 33.1529 SUBJECTS * -0 . 5156 * TRIAL 4.1978 * DAY 0 . 6584 7 SUBJECTS*TRIAL 7 7 .2189 SUBJECTS*DAY 7 0.5513 TRIAL*DAY 8.0797 Error  Source 1 2 3 4 5 6 7  Expected Mean Square (using unrestricted model) (7) + 3(5) + 2(4) +6 (1) (7) + 14 (6) +2(4) +28(2) (7) + 14 (6) + 3(5) + 42 (3) (7) + 2(4) (7) + 3(5) (7) + 14(6) (7)  * No exact F-Test can be calculated.  Means DAY 1 2 TRIAL 1 2 3  N 42 42  LEFT 52.048 55.238 N 28 28 28  LEFT 54.000 53.464 53.464  Analysis of Variance (Balanced Designs) - Standard Grip Strength Test  A n a l y s i s of Variance for RIGHT Source SUBJECTS DAY SUBJECTS*DAY Error Total  DF 13 1 13 56 83  3242 116 596 461 4416  SS 54 68 15 33 70  Source 1 2 3 4  Variance Error component term SUBJECTS 33 . 928 3 1. 686 3 DAY 12 . 540 4 SUBJECTS*DAY Error 8 .238  Means DAY 1 2  N 42 42  249 116 45 8  MS 43 68 86 24  F 5 44 2 54 5 57  P 0 002 0 135 0 000  Expected Mean Square (using unrestricted (4) + 3 (3) +6 (1) (4) + 3 (3) + 42 (2) (4) + 3(3) (4)  RIGHT 57.762 60.119  Analysis of Variance (Balanced Designs) - Standard Grip Strength Test  A n a l y s i s of Variance for L E F T Source SUBJECTS DAY SUBJECTS*DAY Error Total  DF 13 1 13 56 83  Source 1 2 3 4  2989 213 386 491 4081  SS 62 76 57 33 29  Variance Error component term 33 .372 3 SUBJECTS 4 .382 3 DAY 6.987 4 SUBJECTS *DAY 8 . 774 Error  Means DAY 1 2  N 42 42  LEFT 52.048 55.238  MS . 229 97 213 76 29 74 8 77  F 7 73 7 19 3 39  ,P 0 000 0 019 0 001  Expected Mean Square (using unrestricted (4) +3(3) +6 (1) (4) +3(3) + 42 (2) (4) + 3(3) (4)  Analysis of Variance- Standard Grip Strength Test  A n a l y s i s of Variance for RLDIFF Source SUBJECTS DAY SUBJECTS*DAY Error Total  1140 14 393 669 2217  SS 06 58 58 33 56  87 14 30 11  MS 70 58 28 95  F 2 90 0 48 2 53  P 0 033 0 500 0 008  Variance Error Expected Mean Square component term (using unrestricted model) SUBJECTS 9.5702 3 (4) + 3(3) + 6(1) DAY -0.3736 3 (4) + 3(3) + 42 (2) SUBJECTS*DAY 6.1078 4 (4) +3(3) 11.9524 (4) Error  Source 1 2 3 4  DF 13 1 13 56 83  104  STATISTICAL RESULTS OF THE 5 POSITION GRIP STRENGTH TEST Variance Components Estimation - 5PGST Position 1 Left ANOVA  Source Corrected Model Intercept SUBJECT  Type III S u m of Squares  Mean Square  df 14  101.898  41195.571  1  41195.571  1421.429  13  109.341  1426.571  TIME  5.143  1  5.143  Error  101.857  13  7.835  Total  42724.000  28  1528.429  27  Corrected Total  Dependent Variable: G 1 L  Variance Estimates Component Var(fclUb!JtlJI)  Estimate  50.753  Var(TIME)  -.192  Var(Error)  7.835  Dependent Variable: G 1 L Method: A N O V A (Type III S u m of Squares) a  - F o r the A N O V A and M I N Q U E methods, negative variance component estimates may occur. S o m e possible reasons for their occurrence are: (a) the specified model is not the correct model, or (b) the true value of the variance equals zero.  a  Variance Components Estimation - 5PGST Position 1 Right ANOVA  Source (Corrected Model Intercept SUBJECT TIME Error Total Corrected Total  Type III Sum of Squares 1454.714  14  103.908  47726.286 1447.714  1 13  47726.286 111.363  7.000  1  383.000 49564.000  13 28  7.000 29.462  1837.714  27  Dependent Variable: G1R  Variance Estimates Component Var(t!Llb!JbCI) Var(TIME) Var(Error)  Estimate  40.55-1 -1.604 29.462  Dependent Variable: G1R Method: ANOVA (Type III Sum of Squares) a  Mean Square  df  For the ANOVA and MINQUE methods, negative variance component estimates may occur. Some possible reasons for their occurrence are: (a) the specified model is not the correct model, or (b) the true value of the variance equals zero.  a  Variance Components Estimation - 5PGST Position 2 Left ANOVA  Source corrected Model Intercept SUBJECT  Type III S u m of Squares  Mean Square  df 14  84.934  82840.321  1  82840.321  1170.179  13  90.014  1189.071  TIME  18.893  1  18.893  Error  95.607  13  7.354  Total  84125.000  28  1284.679  27  Corrected Total  Dependent Variable: G 2 L  Variance Estimates Component Var(SUb!Jb(J I)  Estimate  41.330  Var(TIME)  .824  Var(Error)  7.354  Dependent Variable: G 2 L Method: A N O V A (Type III S u m of Squares)  Variance Components Estimation - 5PGST Position 2 Right ANOVA  Source Corrected Model Intercept SUBJECT TIME Error Total Corrected Total  Type III Sum of Squares 1158.000  14  82.714  100320.6 1146.429 11.571 249.429 101728.0  1 13 1 13 28  100320.6 88.187 11.571 19.187  1407.429  27  Dependent Variable: G2R Variance Estimates Component Var(yUb!Jb(JI) Var(TIME) Var(Error)  Estimate 34.500 -.544 19.187  Dependent Variable: G2R Method: ANOVA (Type III Sum of Squares) - For the ANOVA and MINQUE methods, negative variance component estimates may occur. Some possible reasons for their occurrence are: (a) the specified model is not the correct model, or (b) the true value of the variance equals zero. a  Mean Square  df  a  Variance Components Estimation - 5PGST Position 3 Left ANOVA  Source corrected Model Intercept SUBJECT  Type III S u m of Squares  Mean Square  df  1914.000  14  136.714  79929.143  1  79929.143  1908.857  13  146.835  5.143  1  5.143 25.604  TIME Error  332.857  13  Total  82176.000  28  2246.857  27  Corrected Total  Dependent Variable: G 3 L Variance Estimates Component  Estimate  Var(SUBJE(J I)  60.615  Var(TIME)  -1.462  Var(Error)  25.604  Dependent Variable: G 3 L Method: A N O V A (Type III S u m of Squares) a  For the A N O V A and M I N Q U E methods, negative variance component estimates may occur. S o m e possible reasons for their occurrence are: (a) the specified model is not the correct model, or (b) the true value of the variance equals zero.  s  Variance Components Estimation - 5PGST Position 3 Right ANOVA  Source corrected Model Intercept  Type III S u m of Squares  Mean Square  df 14  70.510  93960.143  1  93960.143  972.857  13  74.835  987.143  SUBJECT TIME  14.286  1  14.286  Error  170.714  13  13.132  Total  95118.000  28  1157.857  27  Corrected Total  Dependent Variable: G 3 R  Variance Estimates Component  Var(SUBJhCI)  Estimate  30.852  Var(TIME)  8.242E-02  Var(Error)  13.132  Dependent Variable: G 3 R Method: A N O V A (Type III S u m of Squares)  Variance Components Estimation - 5PGST Position 4 Left ANOVA  Source corrected Model Intercept SUBJECT  Type III S u m of Squares  Mean Square  df 14  78.791  66543.750  1  66543.750  1092.750  13  84.058  10.321  1  10.321 9.552  1103.071  TIME Error  124.179  13  Total  67771.000  28  1227.250  27  Corrected Total  Dependent Variable: G 4 L  Variance Estimates Component  Var(SUBJbCI)  Estimate  37.253  Var(TIME)  5.495E-02  Var(Error)  9.552  Dependent Variable: G 4 L Method: A N O V A (Type III S u m of Squares)  Variance Components Estimation - 5PGST Position 4 Right ANOVA  Source Corrected Model Intercept SUBJECT TIME Error Total Corrected Total  Type III Sum of Squares 1159.357 74366.036 1146.464 12.893 139.607 75665.000 1298.964  Dependent Variable: G4R Variance Estimates Component Var(SUUJbCI) Var(TIME) Var(Error)  Estimate 38.725 .154 10.739  Dependent Variable: G4R Method: ANOVA (Type III Sum of Squares)  Mean Square  df 14  82.811  1 74366.036 13 88.190 1 12.893 13 10.739 28 27  Variance Components Estimation - 5PGST Position 5 Left ANOVA  Source Corrected Model Intercept SUBJECT  T y p e III S u m of Squares  Mean Square  df 14  88.786  47726.286  1  47726.286  1228.714  13  94.516  1243.000  TIME  14.286  1  14.286  Error  140.714  13  10.824  Total  49110.000  28  1383.714  27  Corrected Total  Dependent Variable: G 5 L  Variance Estimates Component Var(yUbiJbul)  Estimate  41.846  Var(TIME)  .247  Var(Error)  10.824  Dependent Variable: G 5 L Method: A N O V A (Type III S u m of Squares)  Variance Components Estimation - 5PGST Position 5 Right ANOVA  Source corrected Model Intercept SUBJECT TIME Error Total Corrected Total  Type III Sum of Squares  14  530.500  27  616.679  Dependent Variable: G5R Variance Estimates Estimate  15.523 -.165 6.629  Dependent Variable: G5R Method: ANOVA (Type III Sum of Squares) - For the ANOVA and MINQUE methods, negative variance component estimates may occur. Some possible reasons for their occurrence are: (a) the specified model is not the correct model, or (b) the true value of the variance equals zero. a  37.893  1 56430.321 13 40.475 1 4.321 13 6.629 28  56430.321 526.179 4.321 86.179 57047.000  Component Var(SUb!JbCI) Var(TIME) Var(Error)  Mean Square  df  a  

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