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Psychophysiological correlates of low back pain Wilfling, Francis Joseph 1981

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PSYCHOPHYSIOLOGICAL CORRELATES OF LOW BACK PAIN by Francis Joseph Wil f l ing M.A. University of Br i t i sh Columbia, 1973 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTORATE OF PHILOSOPHY in the Department of PSYCHOLOGY We accept this thesis as conforming to the requi standard THE UNIVERSITY OF BRITISH COLUMRIA MARCH, 1981 ^ Francis Joseph Wilfling, 1981 In presenting t h i s thesis in p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make it f r e e l y 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 my Department or by his representatives. It is understood that copying or publication of this thesis f o r f i n a n c i a l gain shall not be allowed without my written permission. Department of The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date ftMtCfJ **3, / A P / " i i Abstract Low Back Pain (LBP) is extremely common and is perhaps the single most s o c i a l l y - c o s t l y medical disorder. Yet, very l i t t l e is known about the etiology of LBP, and current treatments for the disorder are thus correspondingly inef fect ive . The research reported here was designed to test a general psycho-physiological model of the etiology of psychosomatic disorders, applied to LBP and lumbar intervertebral disc degeneration by way of established biomechanical pr inc ip les . The general model was proposed by Sternbach (1966) who hypothesized that, in the event of repeated, excessive environmental s t ress , that body part which is the most psychophysiologically responsive w i l l break down. This process i s promoted by the lack of normal homeostatic res t ra in ts , restraints which are often found lacking in neurotic individuals (Alexander, 1972; Goldstein, 1972). In spec i f ic application of the Sternbach model to the LBP condit ion, i t was hypothesized that electromyographic stress responses of abnormal magnitude and duration are evident in the posterior lumbar and abdominal oblique muscles of LBP subjects. On the basis of well researched bio-mechanical and pathophysiological mechanisms, reviewed in this paper, such muscle response abnormalities would be expected to give r ise to LBP and to hasten degeneration of the lumbar intervertebral d iscs . Asymptomatic subjects with a minimal history of LBP, when compared to normal Control subjects without such a h istory, were in fact not found to exhibit the c r i t i c a l character ist ics of the Sternbach model. The LBP subjects were not more neurotic than members of the general population, and in response to various stressors, neither their posterior lumbar muscles nor i i i their abdominal oblique muscles showed act iv i ty that was of excessive magnitude or duration. Two unexpected f indings, however, provided new information which can be incorporated into established biomechanical processes which, in additive or synergistic fashion, would be expected to contribute to the occurrence of LBP and lumbar intervertebral disc degeneration. F i r s t , i t was found that the LBP subjects showed less act iv i ty in the posterior lumbar muscles than did the Control subjects. This finding is discussed in the context of established biomechanical principles of spinal s t a b i l i z -ation and in terms of pathophysiological processes of intervertebral disc degeneration resulting from shear forces acting on the poorly stabi l ized spine. Second, i t was found that during the occurrence of psychological and physical stressors, LBP subjects did not res t r ic t their respiration rate as much as did Control subjects. This finding is discussed in terms of the hydraulic abdominal "balloon effect" which, i f decreased, could be expected to expose the lumbar spine to destructive forces and trauma, producing LBP and lumbar intervertebral disc degeneration. Possible causes for the apparent psychophysiological anomalies found in LBP subjects and possible corrective procedures to overcome them are discussed, and suggestions for further research are given. iv Table of Contents Page Abstract — ' . "ii List of Tables ... vi List of Figures vii Acknowledgements. v i i i Introduction 1 Medical Aspects of Low Back Pain 5 Introduction 5 Anatomy of the Lumbar Spine 6 Biomechanics of the Lumbar Spine.. 11 Pathology of the Lumbar Spine...... 15 Lumbar Disc Degeneration 17 Muscle Spasm 19 Conservative and Surgical Treatment of Low Back Pain 25 Introduction 25 Initial Treatments of LBP Patients 26 Clinical LBP Examination Procedures. 26 Intermediate LBP Treatment 29 Specialist LBP Treatment 30 Psychological Aspects of Low Back Pain.. . 33 Psychological Treatment of LBP 35 Psychophysiological Considerations Concerning LBP Patients. 39 A Psychophysiological Model of Psychosomatic Etiology... . 41 Biofeedback 44 Hypotheses of the Present Study 47 Method 50 Subjects 50 Materials 51 Procedure. 56 Data Scoring 61 Statistical Analyses, . 64 Results 69 Survey Population and Subject Sample Characteristics 69 Effects of the Experimental Stressors 70 V Comparison of Male and Female Subjects 74 Comparison of LBP and Control Subjects 81 Examination Of Individual Response Stereotypy. 86 Discussion 94 Possible Origins of the Observed Psychophysiological Anomalies of LBP Subjects ...106 Implications of the Present Findings for LBP Therapies and Further Research. 108 Bibl iography 113 Appendices. 126 A. Screening Questionnaire (Low Back Pain Survey)... . . . . . .127 B. Subject Consent Form 129 C. Laboratory Interview Form 13'! D. Eysenck Personality Inventory..... 133 E. McGill Pain Assessment Questionnaire. . . . . . . . . . . . . . . 1 3 7 F. Psychophysiological Baselines and Stressor Effects Data 142 G. Eysenck Personality Inventory Data. 150 H. Individual Response Stereotypy Rank Data.... 152 vi List of Tables Page Table 1 Baseline and Response Values of each Psychophysiological Variable for each Experimental Stressor 71 Table 2 Profile Analyses of Group Differences (Males vs. Females) for all Psychophysiological Variables at each Stressor .76 Table 3 Profile Analyses of Group Differences (LBP vs. Control) for all Psychophysiological Variables at each Stressor 83 Table 4 Hierarchical Grouping Analysis Summary.... 92 vi i List of Figures Page Figure 1 Lateral View of Lumbar Spine 7 Figure 2 Lateral and Superior Views of a Lumbar Vertebra... 8 Figure 3 Lateral and Posterior Views of the Articulation :of Two Lumbar Vertebrae..... 9 Figure 4 Back Muscles seen in a Transverse Section Through L3 Vertebra „ . . . 12 Figure 5 Biomechanics Involving the Back Muscles 14 Figure 6 The Casa Colina "Tension-Anxiety-Pain" Model . . . . . . 38 Figure 7 Profile Analysis Comparing Sexes with Regard to the COUNT ABEMG Response. 78 Figure 8 Profile Analysis Comparing Sexes with Regard to the COUNT SC Response... 80 Figure 9 Profile Analysis Comparing LBP and Control Subjects with Regard to the PONG BKEMG Response... 84 Figure 10 Profile Analysis. Comparing LBP and Comtrol Subjects with Regard to the STAND BKEMG Response.. 85 Figure 11 Mean Rank Response Curves for the LBP Subjects, across Psychophysiological Variables, for all Experimental Stressors 88 Figure 12 Mean Rank Response Curves for the Control Subjects, across Psychophysiological Variables, for all Experimental Stressors 89 Figure 13 Sample of the Hierarchial Grouping Analysis Examination of Individual Response Stereotypy for the STAND Experimental Manipulation 91 Acknowledgements I feel greatly indebted to many friends and professional associates who have given me assistance, advice and emotional support during the too-many years that I have taken to complete this work. Without that help I would certainly have abandoned the project on numerous occasions. Of the many who have helped, I feel several individuals must be thanked individually: Dr. R.D.Hare: who provided advice, faci l i t ies and support and understanding well beyond any! reasonable expectancies I would have of a dissertation chairman. Dr. P.O.Wing: who f irst provided me companionship on our entry to the arena of low back pain research, and who continues as friend and associate to stimulate and support my personal and professional growth. P s y c h o p h y s i o l o g i c a l C o r r e l a t e s o f Low B a c k P a i n INTRODUCTION Low B a c k P a i n ( L B P ) i s one o f t h e mos t f r e q u e n t and c o s t l y h e a l t h p r o b l e m s . I t has been d e s c r i b e d by F i n n e s o n , a s e n i o r a u t h o r i t y on t h e c o n d i t i o n , as " . . . t h e w o r s t p l a g u e o f t h e t w e n t i e t h c e n t u r y " ( N e a l , 1 9 7 8 ) . H u l t ( 1 9 5 4 ) , on t h e b a s i s o f e a r l y S w e d i s h r e s e a r c h , s u g g e s t e d t h a t a b o u t t w o - t h i r d s o f a l l p e o p l e e x p e r i e n c e LBP a t some t i m e i n t h e i r l i v e s and o v e r o n e - t h i r d a r e a t some t i m e i n c a p a c i t a t e d by i t , b u t t h e s e f i g u r e s a r e p r o b a b l y t o o c o n s e r v a t i v e ( e . g . , N a c h e m s o n , 1 9 7 6 ) . Rowe ( 1 9 6 9 ) has shown t h a t LBP i s t h e s e c o n d m o s t common c a u s e o f t i m e l o s s f r o m work ( s e c o n d o n l y t o u p p e r r e s p i r a t o r y i n f e c t i o n s ) . The i n c i d e n c e o f c o m p e n s a b l e t i m e l o s s f r o m work w o u l d a p p e a r t o be a b o u t two p e r c e n t o f w o r k e r s p e r y e a r ( K e l s e y , W h i t e , P a s t i d e s & B i s b e e , 1 9 7 9 ; N a c h e m s o n , 1 9 7 6 ) . T h e r e a r e some e i g h t m i l l i o n A m e r i c a n s w i t h p e r m a n e n t i m p a i r m e n t s o f t h e s p i n e , and o f t h e c h r o n i c h e a l t h c o n d i t i o n s t h e s e a r e t h e mos t common and c o s t l y d u r i n g t h e p r i m e w o r k i n g y e a r s ( K e l s e y e t a l . , 1 9 7 9 ; N a c h e m s o n , 1 9 7 6 ) . In i n d u s t r i a l s e t t i n g s , 13% - 38% o f a l l i n j u r y c l a i m s i n v o l v e t h e l o w b a c k ( D r o u i n , 1 9 7 3 ; K o s i a k , A u r e l i u s & H a r t f i e l , 1 9 6 6 ; S c h e i n , 1 9 6 8 ; S t e r n b a c h , W o l f , M u r p h y & A k e s o n , 1 9 7 3 ; T r o u p , 1 9 6 6 ) , and a t t h e B r i t i s h C o l u m b i a W o r k e r s ' C o m p e n s a t i o n 1 2 Board (BCWCB) over 25,000 new LBP claims are now received each year (Sat terberg, 1978). Over 380,000 compensated working days were l o s t because of LBP in B r i t i s h Columbia in 1977 1 . Estimates of the annual cost of LBP problems have often been attempted and have given r ise to overwhelming, perhaps subject ive ly incomprehensible f igures . Neal (1978) has estimated the loss in product iv i ty due to LBP to be 14 to 15 b i l l i o n do l la rs per year in the U.S.A. Fordyce (1979) has reported that the d i rec t costs of LBP problems at the Washington State WCB amounted to 63 mi l l i on do l la rs in 1977, and Satterberg (1978) estimated that in B r i t i s h Columbia the longest 19% of LBP' claims (over 8 weeks of d i s a b i l i t y ) cost in excess of 15 m i l l i o n do l la rs in time loss and pension awards in 1976. Many other annual cost f i g u r e s , stated in mi l l ions i f not b i l l i o n s o f d o l l a r s , can be found (Drouin, 1973; Hayes, 1 970; Sternbach et al . , 1973; Troup, Roantree & Arch iba ld , 1970). The magnitude of the LBP problem is perhaps best appreciated in set t ings such as a WCB, which are inundated by LBP cases which are t y p i c a l l y the most chronic and d i f f icu l t - to -manage 2 cases . Over one th i rd of a l l admissions to the BCWCB Rehabi l i ta t ion C l i n i c involve the low back (Gunn & Mi lbrandt , 1. F a r i s h , J . R. Surgical Consultant , BCWCB, Personal Communication, 1979. 2. The present author has been employed at the BCWCB for over f i ve years . 3 1 9 7 6 ) , and many BCWCB f r o n t - l i n e p e r s o n n e l e s t i m a t e t h a t they spend up to 80% o f t h e i r w o r k i n g t ime on LBP c l a i m s . Even more d i s t u r b i n g than the c u r r e n t i n c i d e n c e and c o s t f i g u r e s c o n c e r n i n g the LBP p rob lem a re r e c e n t a n a l y s e s i n d i c a t i n g t h a t the i n c i d e n c e o f LBP d i s a b i l i t y i s g rowing more r a p i d l y than the work f o r c e o r o t h e r d i s a b i l i t i e s g e n e r a l l y (B rown, 1977 ; D r o u i n , 1973 ; K e l s e y e t a l . , 1979 ; K o s i a k e t a l . , 1966 ; T u n t u r i & P a t i a l a , 1980 ; W i c k s t r o m , 1 9 7 8 ) . D e s p i t e the magn i tude o f the p rob lem o f L B P , the s t a t u s o f knowledge p e r t a i n i n g to c a u s a t i v e p a t h o l o g i c a l o r g a n i c c o n -d i t i o n s i s ve ry poor ( F a h r n i , 1975 ; MacNab, 1978 ; Nachemson, 1 9 7 6 ) . T h i s c u r r e n t s i t u a t i o n i s p r o b a b l y e x p l i c a b l e by the f a c t s t h a t , f i r s t l y , the low back i s a h i g h l y complex s t r u c t u r e h a v i n g some 140 bony segmen ts , l i g a m e n t s and musc les a l l i n t e r -tw ined w i t h n e u r a l t i s s u e s and o p e r a t i n g i n m u l t i p l e p l a n e s (Casa C o l i n a , 1976) a n d , s e c o n d l y , the methods on wh ich most c u r r e n t o r t h o p a e d i c p r a c t i c e i s based are u n s c i e n t i f i c , m a i n l y e m p i r i c a l , and o f t e n a n c i e n t ( F a h r n i , 1 9 7 5 ) . MacNab (1978) has r e f e r r e d to " . . . o u r r e m a r k a b l e and d i s t u r b i n g i g n o r a n c e . . . " , and Troup e t a l . (1970) have remarked on " . . . t h e l a c k o f s c i e n -t i f i c d a t a " c o n c e r n i n g LBP . There a re dozens of p a t h o l o g i c a l c o n d i t i o n s s u g g e s t e d i n the m e d i c a l l i t e r a t u r e to be causes o f L B P , and the a c c e p t a n c e o f t h e s e e x p l a n a t i o n s o f t e n appears to be i n f l u e n c e d by the s t a t u s o f the a u t h o r , h i s s t a t u s not be ing n e c e s s a r i l y d e t e r m i n e d by the s c i e n t i f i c adequacy o f h i s 4 work or by the successes of the correct ive procedure directed at the pathological condit ion by the author, his students, and his fo l lowers . As MacNab (1978) has noted, " . . .we have stumbled from hunch to hunch". The orthopaedic c l i n i c a l - i m p r e s s i o n / e m p i r i c a l approach appears to be highly error-prone for several reasons: F i r s t l y , there are many types of congenital and degenerative anomalies of the human spine and after the second decade of l i f e , one or more such anomalies can be found in the spines of up to 70% of ind iv idua ls ( M c G i l l , 1968). Methodological ly adequate studies have in fact shown l i t t l e or no d i f ference between symptomatic and asymptomatic groups in the incidence of various forms of spinal pathology (Ful lenlove & Wi l l iams, 1957; LaRocca & MacNab, 1969; S p l i t o f f , 1953). Secondly, there appears to be a high spontaneous recovery rate of LBP l e f t untreated (Nachemson, 1976), and this spontaneous recovery rate is rare ly taken into account in evaluating the e f f i c a c y of act ive treatment moda-l i t i e s . In f a c t , the symptomatic recovery rate from various forms of conservative treatment or spinal surgery rare ly appears to be better than the spontaneous recovery rate (Kark, 1972; Nachemson, 1976). The present s i tua t ion confronting the c l i n i -c a l l y - e m p i r i c a l l y - o r i e n t e d physician then, is that there are many types of pathology to choose from, many of the patients presenting with LBP wi l l exhib i t a given pathology, and many of the patients w i l l show improvement with time, almost 5 i r respec t ive of the treatment applied to that pathology. In many ways the present status of knowledge concerning LBP i s : " 1 s imi la r to the status of knowledge concerning psychotherapy in 1952, when Eysenck showed that the then-popular psychotherapies appeared to be contr ibut ing to symptomatic improvement in two-th i rds of patients t reated, when in fact this apparent e f f i c a c y was i l l u s o r y because the same percentage of untreated patients was recovering from symptoms spontaneously. Medical Aspects of Low Back Pain Introducti on This paper w i l l deal with a psychosomatic model of LBP which by i t s nature is i n t e r d i s c i p l i n a r y , and some level of knowledge of the anatomy and pathology of the human back is thus required by psychologists considering i t . Some understand-ing of current medical approaches to the treatment of LBP is also necessary for an appreciat ion of why other approaches are necessary. This sect ion is thus written to provide necessary general medical information to non-orthopaedists and, as such, the considerat ion of various topics covered wi l l not be exhaust-ive of the l i t e r a t u r e a v a i l a b l e , but rather w i l l cover only the major current trends. The reader wishing a more comprehen-sive review of medical information is referred to some of the exce l lent overviews ava i lab le (Adams, 1962; Brown, 1977; Nachemson, 1976; Rothman & Simeone, 1975). 6 Anatomy of the Lumbar Spine The lumbar sp ine i s composed o f f i v e bony v e r t e b r a e e x t e n d -ing c a u d a l l y from the 12th t h o r a c i c v e r t e b r a , which i s the lowest v e r t e b r a having an a t tached r i b , to the fused v e r t e b r a e which form the sacrum. The lumbar v e r t e b r a e are numbered in the caudal d i r e c t i o n , and the sp inous p r o c e s s of the 5th lumbar v e r t e b r a ( d e s i g n a t e d as L5) can be f e l t approx imate ly three inches s u p e r -i o r to the upper ex tent o f the nata l c l e f t ( the b u t t o c k s 1 v e r -t i c a l f o l d ) . The lumbar v e r t e b r a e and sacrum form a c u r y e , concave p o s t e r i o r l y , r e f e r r e d to as the lumbar l o r d o s i s . These a s p e c t s of the lumbar s p i n e are demonstrated in F i g u r e 1. A v e r t e b r a c o n s i s t s of a s o l i d , approx imate !y c y l i n d r i c a l , v e r t e b r a l body wi th a number of bony p o s t e r i o r p r o j e c t i o n s (see F i g u r e 2 ) . These rearward p r o j e c t i o n s p r o v i d e t r a n s y e r s e and sp inous attachment p r o c e s s e s f o r l igaments b i n d i n g the s tack of v e r t e b r a e t o g e t h e r and s u p e r i o r and i n f e r i o r a r t i c u l a r p r o -c e s s e s forming j o i n t s between a d j a c e n t v e r t e b r a e . F i g u r e 3 demonstrates the a r t i c u l a t i o n ( i n t e r p o s i t i o n i n g ) of two v e r t e b r a e from the l a t e r a l and p o s t e r i o r v iews . The i n f e r i o r a r t i c u l a r process of one v e r t e b r a and the s u p e r i o r a r t i c u l a r p rocess of the next lower v e r t e b r a form the f a c e t or apophyseal j o i n t , the plane of t h i s j o i n t l y i n g at approx-imate ly 45 degrees to the s a g i t t a l p lane of the body. The a r t i c u l a r p r o c e s s e s are wedge s h a p e d , wi th the i n f e r i o r p r o c e s s e s of the cepha lad v e r t e b r a being medial to the s u p e r i o r p r o c e s s e s FIGURE 1. Lateral View of Lumbar Spine Articular Surface Superior Articular Process Transverse Process Spinous Process Articular Surface Inferior Articular Process Transverse Process Superior Articular Process Articular Surface Inferior Articular Process Spinous Process Vertebral Foramen Pedicle Vertebral Body FIGURE 2. Lateral and Superior Views of a Lumbar Vertebra Inferior'Articular Process Apophyseal Joint Superior Articular Process Inferior Articular Process Apophyseal Joint Superior Articular Process Spinous Process FIGURE 3. Lateral and Posterior Views of the Articulation of Two Lumbar Vertebrae 10 of the caudal vertebra. The dura-clad spinal nerves, or cauda equina, l i e s within the spinal canal formed by the vertebral foramina. The pedicles of each vertebra are arched between the vertebral body and apophyseal j o i n t , creat ing i n f e r i o r and superior notches. The nerve roots , which subserve sensory and motor functions in the lower body, ex i t the spinal canal through the holes or foramina formed by these notches between each two stacked vertebrae. As i l l u s t r a t e d in Figures 1 and 3, the vertebrae are separated by in terver tebra l d i s c s . The disc acts as a cushion and is s t r u c t u r a l l y s imi la r to a f la t tened golf b a l l , haying car t i l ag inous end plates at the d i s c ' s inter face with the vertebral bodies, a gelatinous centre ca l led the nucleus p u l -posus, and a sp i ra l l y -a r ranged f ibrous periphery ca l led the annulus f i b r o s u s , which is composed of very long-chain organic molecules including collagen and mucopolysaccharides (Brown, 1971; Naylor, 1971). Hydraulic act ion allows the healthy disc to d i s t r i b u t e weight evenly on the vertebral endplates while al lowing movement in a l l d i rec t ions (Nachemson, 1975; Parke & S c h i f f , 1971 ). The vertebrae are bound together with numerous short ligaments between the vertebral bodies and between the transverse and spinous processes and by poster ior and anter ior longi tudinal ligaments running the length of the spinal column. The bony segments of the spinal column are also surrounded 11 by numerous muscle groups, which s t a b i l i z e the column and provide motor power for movement in a l l planes. The arrangement of muscles seen on a transverse plane through the L3 level is demonstrated in Figure 4. S u r p r i s i n g l y , the exact functions of various muscles of the back are not well understood, and one of the most prominent invest igators of muscle function is pess imis t ic that , because of the i r complexity, the exact functions of the various muscle groups wi l l ever be d i f f e r e n t -iated (Basmajian, 1974).. It is quite evident from a consider-at ion of basic mechanical p r i n c i p l e s , however, that those muscles ly ing para l l e l to the spine must have major involyements in f lex ion /ex tens ion of the trunk, whereas those muscles with oblique or ientat ions must have major involvements in rotat ion of the trunk and spinal s t a b i l i z a t i o n (Far fan, 1973). Biomechanics of the Lumbar Spine The oblique muscles in various combinations provide the motor forces for rotat ional movements of the trunk, the degree of rotat ion being l imi ted by the o b l i q u e l y - o r i e n t e d , wedge-shaped apophyseal j o i n t s . Flexion and extension of the trunk are brought about by two mechanisms: f i r s t l y , by contract ion of muscles running para l l e l to and poster ior to the spinal column, with possib ly some help from the oblique muscles and; secondly, by a hydraul ic "balloon e f fect" involv ing the abdomen (Bar te l ink , 1957). The balloon e f fec t is created by the t ightening of the oblique abdominal muscles, which causes the soft abdominal 12 1. Multifidus 4. Psoas 2. Sacrospinal is 5. Quandratus Lumborum 3. Iliocostal is 6. Latissimus Dorsi FIGURE 4. Back Muscles seen in a Transverse Section Through L3 Vertebra (After Farfan, 1973) 13 contents to push on the pe lv ic f loor and diaphragm, thereby promoting extension of the trunk, th is being s imi la r in p r i n -c i p l e to the indust r ia l app l ica t ion of low-pressure a i r bags to the l i f t i n g of heavy objects . The abdominal balloon e f fec t is in a l l p robab i l i t y very important to movements of the trunk, because extension brought about only.by the muscle groups poster ior to the spinal column is l imi ted by the very i n e f f e c t i v e mechanics•of a f i r s t - c l a s s ' 1 ever having.a very long lever arm to the load and a very short lever arm to the mode of fo rce . These i n e f f e c t i v e mechanics are i l l u s t r a t e d in Figure 5. The unloading e f fec t on the discs of the balloon e f fect can be read i ly appreciated. Bending of the vertebral column is made possible by the in terver tebra l d iscs which, through the i r contained-1iquid centres , act as d is tens ib le hydraul ic cushions and shock absorb-e r s , al lowing an even d i s t r i b u t i o n of ve r t i ca l loading forces over the vertebral end p la tes . The fulcrum of movement of the f i r s t c lass lever described above i s , as shown in Figure 5, in the poster ior portion of the disc (DePalma & Rothman, 1970; White & Panjabi , 1978). Because of the mechanical i n e f f i c i e n c y of the f i r s t c lass lever described above, force loadings of great magnitude act on the d i s c s . The muscles poster ior to the sp ine , which provide the motor force on the short arm of the lever demonstrated in Figure 5, are of massive s ize and have been calculated by Farfan (1973) to be capable of a d i rec t Contracting Back Muscles Fulcrum of Movement Fantastic Force From Back Muscles Required To Balance Lever Fulcrum of 4/Downforce Lever (Height) of Upper Body First Class Lever * Downforce (Weight) of Load Lifted FIGURE 5. Biomechanics Involving the Back Muscles 15 pul l ing force of 650 pounds. The forces operative on the lumbar discs are maximal at the L4 and L5 leve ls (Nachemson & Morr is , 1964), th is being the instant centre of rotat ion of the body (DePalma & Rothman, 1970) in f l ex ion /ex tens ion . For example, i t has been suggested that a 170-pound man l i f t i n g 200 pounds can place a loading of 2000 pounds on his L5-S1 d i s c , but th is f igure may be somewhat excessive (Farfan, 1973). However, Nachemson and Morris (1964), using a pressure transducer to measure d i r e c t l y in t rad isca l f o r c e s , have reported a loading of 220 kilograms in the th i rd lumbar disc of a man l i f t i n g a 50 kilogram weight. Pathology of the Lumbar Spine There are many condit ions of the lumbar spine which can produce LBP, but local inflammatory reac t ions , neop las ia , d i s -orders of bone metabolism, e t c . , are infrequent ly implicated (Adams, 1962; Brown, 1977). Pain may also be " re fe r red" , the pain seemingly being l o c a l i z e d in the back when, in f a c t , i t or ig inates with pathology in the pelv ic or abdominal v i s c e r a . The pathology most frequently held responsible for LBP (Brown, 1977; H i r s c h , 1966; Nachemson, 1975; Rothman & Simeone, 1975) involves a decrease in the height of the d i s c , possibly with protrusion of the nucleus pulposus into the vertebral foramen through which the nerve roots e x i t , and a subsequent degeneration of other parts of the j o i n t . The e t i o l o g i c a l process respon-s i b l e for degeneration of the interver tebra l discs is not t o t a l l y 16 understood and is a" topic that wi l l be discussed further below. However, once the disc degeneration has occurred, a well docu-mented . chai n of other degenerative changes is i n i t i a t e d . F i r s t -l y , with the decrease in d isc height the fulcrum of the f l e x -ion/extension movements s h i f t s pos te r io r l y (White & Panjabi , 1978), and the wedge-shaped apophyseal jo in ts are driven to-gether so that the i r normal, l i g h t s l i d i n g action is destroyed. A heavily laden grinding action resu l ts which soon destroys the smooth car t i l ag inous surfaces of the jo in ts and resul ts in devel opment' of' i nf l animation and rough, a r t h r i t i c sur faces. Secondly, the vertebral bodies themselves may come in close contact , creat ing l i p s or spurs on the i r anter ior or poster ior margins (MacNab, 1971). It would appear that pain can be produced in the degen-erated jo in t in a number of ways. F i r s t l y , the adult disc i t s e l f does not appear to be supplied with pain f ibres (H i rsch , 1966; Parke & S c h i f f , 1971), but the ligaments containing the disc between the vertebrae and the capsules of the apophyseal jo in ts are r i c h l y innervated and can be sources of pain (Frymoyer & Pope, 1978; H i rsch , 1966; Shealy, 1974). Secondly, muscle spasm, thought to r e f l e c t a s p l i n t i n g ref lex protect ing a sore j o i n t , is often seen in the poster ior lumbar muscles of pat ients with LBP and may be a source of pain (the topic of muscle spasm may be of great importance and wi l l be discussed separately below). T h i r d l y , a protrusion of nuclear disc material and/or 17 the l i p s and spurs formed on the vertebrae can impinge on the cauda equina or nerve roots , and pain and/or motor and sensory losses then resu l t in the peripheral area innervated by the impinged nerve. This is the pathological mechanism which has been i d e n t i f i e d as being responsible for the symptom complex known as s c i a t i c a (Mixter & Barr , 1934). Lumbar Disc Degeneration The temporal sequence of changes occurr ing during the degeneration of a lumbar disc is well known, and occurs to some degree in most people, but the e t i o l o g i c a l agent i n i t i a t i n g the degenerative process is unknown, though " . . . s e v e r a l st im-ulat ing although uncertain' expl anati-ons exi st (DePalma & Rothman, 1970, p.175). It has been suggested that an autoimmune react ion may lead to breakdown of the in t rad isca l material (Bobechko & H i rsch , 1965; Naylor, 1971), but this would s t i l l require an antecedent breach of the membrane which normally i so la tes the d i s c . However, i t is well known that there is a diurnal var ia t ion in disc height associated with a decrease in water content a f ter a day in the erect posi t ion (Brown, 1971; Parke & S c h i f f , 1971), which strongly suggests that weight bearing on the disc causes th is change. With age the water content of the disc and the disc height decreases (Brown, 1971; Brown, 1977; Hendry, 1958; Nachemson, 1975; Wickstrom, 1978; White & Panjabi , 1978), th is change being associated with i n -creased v i s c o s i t y of the nucleus pulposus and derangement of 18 the annulus f ibrosus (Ritchie & Fahrni , 1970). With these changes, the disc loses i t s capacity as a d is tens ib le cushion and shock absorber and the gel of the nucleus pulposus may become extruded through rents in the weakened, deranged annulus (Ritchie & Fahrn i , 1970). This is the most probable mechanism of disc degeneration leading to prot rus ion. Trauma, that is sudden, unusually high weight loading on the sp ine , would appear to be an i n s u f f i c i e n t explanation of d isc herniat ion because only about 20% or less of disc herniat ions are preceded by trauma (Di l lane et a l . , 1 966 ; H i rsch , 1 966; Hul t , 1 954; Rowe, 1 969), and even those cases of trauma are usual ly l i f t s of under 50 pounds ( M c G i l l , 1968). Such l i f t s may well be the " las t straws" * p r e c i p i t a t i n g rending and extrusion of already-degenerated weakened d i s c s . There are numerous addi t ional facts which lead to the inference that prolonged weight loading leads to degeneration of the d i s c . F i r s t l y , a primary factor leading to disc degener-ation is probably the force placed on the discs by the mechanics of man's erect posture, as i t has been demonstrated that quad-rupeds forced to assume this posture develop disc lesions that they would not otherwise develop (Yamada, 1962). Secondly, as noted prev ious ly , the maximal forces in the human spine are operative at the L4-L5, and L5-S1 l e v e l s , and i t is at these two leve ls that 96% of a l l d isc protrusions occur (DePalma & 19 Rothman, 1970). T h i r d l y , Fahrni has pointed out that b io -mechanical considerat ions indicate that the major forces act on the poster ior aspects of the lumbar d i s c s , and i t is there that the vast majority of breaches of the annulus occur. The evidence concerning the associa t ion between heaviness of work and the occurrence of LBP and lumbar disc degeneration is ambiguous. Swedish researchers appear not to have found an associat ion between heavier work and increased back problems (Hul t , 1954; Nachemson, 1975, 1976), whereas other researchers and reviewers have reported such an associat ion (Brown, 1977; Lawrence, 1 969; Troup, 1 966;.White & Panjabi , 1 978). In com-paring back problems in heavy manual workers with the i r incidence in o f f i c e workers, however, the issue of disc loading on disc degeneration is clouded because the posture of s i t t i n g places very h igh, unvarying forces on the lumbar d iscs (Andersson, Murphy, Ortengren & Nachemson, 1979; Andersson, Ortengren, Nachemson & E l fs t rom, 1974; Nachemson & Morr is , 1964). Muscle Spasm Spasm (hyperact iv i ty ) of the back muscles is a very frequent observation in patients complaining of low back pain. Burke (1964) has stated that muscle spasm is always present in acute LBP pa t ien ts , but unfortunately an error seems to have been made in c i t i n g the ear ly electromyographic (EMG) research used 3. Fahrn i , W. H. Medical Rounds presentat ion, B . C . W . C . B . , June 9, 1976. 20 to support th is content ion. DePalma and Rothman (1970), c i t i n g c l i n i c a l s tud ies , have also referred to spasm as " . . . a consistent f i n d i n g " . Nashold and Hrubec (1971) systemat ica l ly documented back muscle spasm by c l i n i c a l means in 72% of a ser ies of over 1000 LBP patients at f i r s t h o s p i t a l i z a t i o n . Muscle spasm as referred to in papers such as those c i ted above, is usual ly c l i n i c a l l y assessed by pa lpat ion , a gross and highly subject ive procedure which no doubt suf fers a high error rate in d i f f e r e n t i a t i n g abnormal a c t i v i t y of jnuscle ly ing under var iable thickness fat pads from the "normal" muscle t ightness resu l t ing from posture and possib ly also the pat ients ' tenseness during examination. It may be the methodological shortcomings of th is c l i n i c a l assessment procedure that account for the varying percentages of LBP patients that have been reported as exhib i t ing spasm. Yet, the back muscles of many LBP patients are " . . . r i g i d and board-1ike" (DePalma & Rothman, 1970) even in a rest posture (Nashold & Hrubec, 1971). This observation hardly leaves open to doubt that profound poster ior back muscle spasm is present in many acute LBP pat ients . Biomechanical ly- and k ines io log ica l1y -or ien ted invest igators have recent ly noted that l i t t l e at tent ion has been paid to abnormal muscle a c t i v i t y in LBP patients (Farfan, 1973; F i d l e r , Jowett & Troup, 1975). This almost inexpl icab le lack of inves-t iga t ion of such an obviously abnormal condit ion is possibly accounted for by the fact that the medical profession tends 21 to view muscle spasm as a "secondary" or protect ive phenomenon. That i s , i t is thought that any jo in t pain provokes a s p l i n t i n g response of the surrounding muscles, thus immobilizing the jo in t and preventing the aggravation of any les ion by further movement (Adams, 1962). Invest igat ive e f fo r t has thus been expended in a search for "primary" causes of LBP. The present author has been able to f ind only a very small number of studies in which quant i ta t ive electromyographic (EMG) measures from the back muscles of LBP patients have been used to study spasm or abnormal a c t i v i t y , e s p e c i a l l y in asymptomatic pat ients . Several studies concerned with th is topic were re-corded in a ser ies of almost incomprehensible English abstracts of Japanese research (Itami & Hasegawa, 1968; Miyazaki & Sakou, 1968; Yamaji & Misu, 1968). Those i n v e s t i g a t o r s , however, appeared to conclude that , as compared to normal sub jec ts , LBP subjects showed higher back muscle tension with various movements and in various s t a t i c postures. In recent research, Jayasinghe, Harding, Anderson and Sweetman (1978) found that with prolonged standing LBP subjects showed increases in pos-t e r i o r back muscle EMG, whereas normal subjects showed EMG decreases. It should be noted that many EMG studies of back patients can be found in the l i t e r a t u r e , but these studies involve the qua l i t a t i ve diagnost ic use of EMG measures for the detect ion of denervation of muscle groups by impingements on the nerve roots at the spinal l e v e l . 22 Addit ional ind i rec t evidence of increased tonus in the back muscles of LBP patients is ava i lab le in the English l i t -erature. It has been a frequent observation that LBP patients show a decreased lumbar lo rdos is (Farfan, 1973; Nashold & Hrubec, 1971; Wing, 1972), and a biomechanical analysis has shown that t ightening of the poster ior back muscles f la t tens the lo rdos is (Far fan, 1973). F id le r et a l.(1 9 7 5) have shown that the ra t io of tonic (slow) muscle volume to phasic [ fast) muscle yolume is higher in the back muscles of pat ients with a history of LBP than i t is in normal subjects . One explanation of th is may be related to the process of hypertrophy resu l t ing from excessive use. It is ev ident , in that everyone has had the experience, that prolonged, great ly increased a c t i v i t y of a muscle group leads to fee l ings of s t i f f n e s s and pain. This pain appears to ar ise from the pull of the muscles on the i r per iosteal at-tachments (Adams, 1962) and from a decrease of blood c i r c u -l a t i o n , leading to an ischemic state with accumulation of meta-bo l ic waste in the tensed muscles (Farfan, 1973). Robard (1975) has suggested that pain is produced af ter prolonged contract ion of a muscle because catabol ic waste products leave the muscle c e l l and increase in e x t r a c e l l u l a r concentration to degrees at which the st imulat ion threshold of adjacent nerve f ib res is reached and surpassed. One would thus expect that the extreme spasm accompanying LBP would in many cases i t s e l f be a source of pain. 23 A reasonable conclusion to draw from the above review of l i t e r a t u r e is that at least some of the pain of LBP is of mus-cular o r ig in and that reduction of back muscle spasm would, in i t s e l f , probably be benef ic ia l symptomatica!ly. Moreover, in view of the biomechanical considerat ions discussed above, spasm would also appear"to have the potential of keeping very high force loadings on the in terver tebra l d i s c s , tending to perpetuate the pain resu l t ing from disc protrusions and the fo rced , grinding contact of degenerated areas of the poster ior j o i n t s . Schlesinger and S t i n c h f i e l d Cl950) haye suggested that i t is probable that lumbar spasm can maintain a v ic ious cycle of pain -» re f lex spasm more pain -vmore spasm -» e t c . , and they have questioned whether spasm is purposeful [ i . e . , as the s p l i n t i n g hypothesis would suggest) or whether, in f a c t , i t may not play a part other than that of secondary s p l i n t i n g . That muscle spasm may be of some primary importance is strongly suggested by the work of a number of invest igators who have brought about profound muscle re laxat ion in LBP pa-t i e n t s , often with s t a r t l i n g r e l i e f of symptoms. Hafner, James and Robertshaw (1966) pharmacological ly brought about total muscle para lys is in the i r patients for 15-20 minutes three times per week and reported dramatic, enduring r e l i e f of LBP symptoms. These invest igators did not provide the i r data for inspec t ion , but they provided a conceptual izat ion of the therapeutic mech-anism underlying the i r r e s u l t s , suggesting that the muscle 24 para lys is removed the forces acting on the spine and thereby allowed the retreat of disc prot rus ions . Schlesinger and St inch-f i e l d (1950) in jected the back muscles of the i r patients with Myanesin, a potent muscle re laxant , and reported prompt pain r e l i e f in the pa t i en ts , the r e l i e f being permanent in some. These invest igators suggested that the permanency of r e l i e f was related to the degree of s t ructura l damage present in the pat ients at the time of i n j e c t i o n . Current medical treatment p r a c t i c e , in the search for more primary pathology, appears to pay heed to lumbar muscle spasm only in passing. Drast ic muscle relaxing procedures such as those described above have not found appl ica t ion in treatment. Rather, Diazepam and s imi la r medications are frequently pre-scr ibed to decrease the spasm, but i t is highly questionable i f such compounds have any e f fect beyond central nervous system depression, possib ly producing an e f fec t in reducing the mo-t ivat ional -emot ional aspects of the pain experience (Chapman & Feather, 1973). Other frequently used treatments such as bedrest and t rac t ion would also quite obviously reduce lumbar muscle a c t i v i t y , at least the postural phasic components. T r a c t i o n , e s p e c i a l l y af ter the i n i t i a l period during which the muscles respond with a " f ight ing react ion" (Schlesinger & S t inch-f i e l d , 1950), would tend to keep the patient immobile. Farfan (1973) has also suggested that the apparent 'occasional successes 4. Medical l e t t e r on Drugs and Therapeut ics, 1973, 15(14), 57-58. 25 of manipulation (ch i ropractors ' treatment) may be due to the fact that forcefu l s t re tching causes the paravertebral muscles to re lax . Various forms of heat, which are central to many physiotherapy procedures, would also appear t o h a v e some muscle relaxing and c i r c u l a t i o n improving'" character i s t i cs . (Adams , 1 962). The e f f e c t i v e n e s s , in terms of muscle re laxa t ion , of the above medical conservative treatments i s , however, a moot point given the mediocre e f f i cacy of these procedures in ameliorat ing LBP. Conservative and Surgical Treatment of Low Back Pain  Introduction Dr. W. J . McCracken, executive medical d i rec tor of the Ontario WCB, in an address to a LBP seminar at McMaster Univer-s i t y , provided a rather curt summary of the present status of LBP treatment (Lee, 1976). The Ontario WCB is planning to l i m i t treatment given in LBP cases, because "Treatments are many, cures are few", despite the prescr ip t ion of enough chemical medication to tox i fy Lake E r i e , despite surgery described as " . . . a dismal f a i l u r e " , despite the e f for ts of physiotherapists who " . . . have heated, cooled, v ib ra ted , rad ia ted , kneaded and soaked hundreds of thousands of backs for mi l l ions of hours", despite the e f fo r ts of brace and corset f i t t e r s who " . . .have squeezed, twisted, fo rced , bent and shoved untold numbers of tortured bodies into c o r s e t s , braces, and irons made of almost every known material with the possible exception of gold and 26 plat inum", and despite the e f fo r ts of chiropractors who " . . . have continued to adjust thousands of spines which somehow have developed a l l degrees and types of mi salignment p r o b l e m s . . . " . I n i t i a l Treatments of LBP Patients As noted prev ious ly , s c i e n t i f i c knowledge concerning LBP is very poor (MacNab, 1978; Nachemson, 1976) and LBP has " . . . n o general ly accepted pathological les ion with a s c i e n t i f i c a l l y appl ied t h e r a p y . . . " (Fahrni , 1 975, p.93). Yet on perusal of many case h i s t o r i e s , there would appear to be quite a common course in the i l l n e s s hi s t o r y , o f most LBP pa t ien ts , with a corresponding course of treatments. As noted above, most LBP is of ins id ious onset or associated with only minor trauma. When the patient presents to the general p r a c t i t i o n e r , he usual ly complains of LBP and r e s t r i c t e d ranges of motion of the lumbar spine. Following a c l i n i c a l examination to be described below, the general p rac t i t ioner then almost invar iab ly prescribes analgesics for pain r e l i e f and•supposed' muscie-relaxants such as Diazepam, for r e l i e f of muscle spasm. However, as noted above, there is no convincing evidence that Diazepam or other s imi la r drugs have any s i g n i f i c a n t e f fect in reducing muscle spasm. At th is point the patient is usual ly also instructed to r e s t r i c t his a c t i v i t y to varying degrees, supposedly to allow any natural regenerative processes to take p lace. C l i n i c a l LBP -Examination Procedures After taking a general h is tory of the pat ient 's past health 27 and the circumstances i n i t i a t i n g the LBP, the physician questions the patient about the l o c a t i o n , degree, qua l i t a t i ve nature, temporal c h a r a c t e r i s t i c s and ameliorating and exacerbating antecedents of his pain. The p a t i e n t . i s • t h e n asked to disrobe and, by pa lpa t ion , the physician attempts to l o c a l i z e the pain in the low back and assesses the presence of muscle spasm. The l o c a l i z a t i o n of pain is also c l a r i f i e d during the deter-mination of the ranges of motion of' the sp ine , which the phy-s i c i a n requests the patient to demonstrate by bending forwards, backwards and sideways. The patient" is also asked to del ineate the areas in his l e g s , i f any, which are perceived to be p a i n f u l . Any sensory 1osses in the lower trunk and extremit ies are as-sessed by pr ick ing the skin in a grid fashion while the patient reports any decrements in sensat ion. Any motor losses in the lower extremit ies are assessed by reports concerning sphincter control and by requests for the patient to perform a c t i v i t i e s and isometric e f fo r ts (the physician supplying resistance) which maximally tax s p e c i f i c muscle groups. A number of ref lexes of the lower body are also e l i c i t e d and quant i ta t ive ly compared b i l a t e r a l l y . F i n a l l y , a number of passive ranges of motion are tested: for example, the s t ra ight leg of the supine patient is elevated by the phys ic ian . During th is manoeuvre, ca l l ed the s t ra ight leg ra is ing t e s t , the s c i a t i c nerve begins to move in i t s sheath af ter 30 degrees of the range of motion is com-p le ted , and an abrupt onset of pain can be expected i f the nerve 28 root is tethered or i r r i t a t e d by a disc pro t rus ion . What the physician hopes to f ind during this examination procedure is a ser ies of pain patterns and l o c a l i z a t i o n s in the back, coupled with pain and sensory, motor, or re f lex losses in the extremit ies which correspond to d iscrete dermatomes supplied by the nerve roots ex i t ing the vertebral foramen of the painful spinal 1evel . Anatomical ly-1ogical consistencies of pos i t ive examination f indings are , however, very often lacking and may lead the physician to a diagnosis having psychological connotat ions. It is also p o s s i b l e , however, that with repeated examinations the chronic patient can be subtly shaped by the interpersonal contexts of the examination so that he w i l l come to exhibi t the reports and behaviours of the " c l a s s i c a l LBP syndrome" ( W i l f l i n g , Klonoff & Kokan, 1973). Apparently, general p rac t i t ioners often do not perform examinations as thorough as the one described above, and many of the i r medical reports contain only comments general ly i n -d icat ing the presence of pain and perhaps some statements con-cerning s t ra ight leg ra is ing and spinal ranges of motion. In the present author's c l i n i c a l experience, the i r psychological diagnoses such as "funct ional overlay" are often reached by exclusion af ter prolonged unsuccessful treatment, and long af ter spontaneous - recovery is probable, and can be t ranslated to mean "I r e a l l y don't know what is wrong. I haven't found an organic explanation of the pa t ien t ' s continuing complaints and my usual treatment methods haven't worked." 29 Intermediate LBP Treatment If a f ter several weeks the patient is s t i l l symptomatic, he is often referred to various physiotherapies. At th is point a convincing organic diagnosis is'most often s t i l l l a c k i n g , as is indicated by the fact that 86% of a l l admissions to the BCWCB Rehabi l i ta t ion C l i n i c carry the vague diagnosis "low back sprain" (Gunn & Mi lbrandt , 1976), "sprain" being a term which is loosely used by most general p rac t i t ioners to indicate that no gross s t ructura l damage is evident (Adams, 1962). The percentage of LBP cases diagnosed "sprain" is s imi la r in Ontario (Brown, 1977). Physiotherapy a c t i v i t i e s appear to be broken into a number of categories as concern goals . F i r s t l y , there are appl icat ions of heat, u l t rasound, and massage, which are oriented towards reducing muscle spasm and pain. Secondly, the goals of increasing ranges of motion and mobi l i ty are fur -thered by the above in tervent ions , and a graded ser ies of ex-erc ises may also be prescr ibed , general ly to "loosen up" the spine. T h i r d l y , strengthening exerc ises , espec ia l l y for the abdominal muscles needed in the "balloon e f fec t" described above, are given. Fourth ly , the patient is often taught postures and ways of l i f t i n g which in future w i l l place minimal forces on the low back and d i s c s . Corsets or lumbar spine supports of various kinds may also be prescribed at this time, or at any other point during the i l l n e s s h i s t o r y , to support the lumbar spine and r e s t r i c t i t s movement. 30 S p e c i a l i s t LBP Treatment If the patient continues to be symptomatic, he is usual ly referred to a s p e c i a l i s t , an Orthopaedic Surgeon or Neurosurgeon and, with c h r o n i c i t y , a lengthy ser ies of s p e c i a l i s t s often becomes involved. The s p e c i a l i s t ' s c l i n i c a l examination corres-ponds to the one already described and, in a d d i t i o n , he may e lec t to use a number of more elegant invest iga t ive procedures. Qual i tat ive•EMG studies may be done, documenting motor ac t iva t ion potent ia ls to ascerta in whether or not the motor nerves are compromised. A sedimentation rate test may also be used to ascerta in whether or not there is an inflammatory process some-where in the body, possib ly the back, and oral anti-inf1ammatory agents may be prescr ibed , or s tero id in jec t ions of the back may be given. F i n a l l y , i f c l i n i c a l signs suggest that a disc protrusion is compromising a nerve root or the cauda equina, a myelogram may be undertaken to aid in the exact l o c a l i z a t i o n of the impingement for surgical purposes, but i t is often ap-parently used as a "search" technique. A myelogram consists of an x-ray taken after radioopaque dye has been injected into the subarachnoid space, disc protrusions being seen by indent-at ions of the dye column. Myelography has approximately an 80% accuracy rate (Raaf, 1959; White, 1969). If a disc protrusion is i d e n t i f i e d , by compatible c l i n i c a l and myelographic s i g n s , most s p e c i a l i s t s w i l l undertake to remove the offending d i s c . This is most frequently accomplished by 31 the surgical procedure of discectomy, whereby the soft t issue over ly ing the poster ior elements of the vertebral column is parted and separated and the vertebral canal is entered between the poster ior elements'of the vertebrae so that the protrusion and nucleus pulposus can be curet ted. Laminectomy, that i s , par t ia l or total removal of the'bony laminae, may be undertaken along with discectomy to f a c i l i t a t e access to the spinal canal and also to provide more space for the cauda equina and nerve roots in the degenerated j o i n t . Possibly because of the d i f -fer ing d e f i n i t i o n s of success used, a wide range of success-rate f igures for 1aminectomy/discectomy has been reported. However, . rates as low as 40% (White, 1969), or even 13% (Kosiak et a l . , 1966), based on indices of patient func t ion , have been reported. White, of the Ontario WCB, defined a "good" resu l t as the pa-t i e n t ' s a b i l i t y to return to his preinjury work with minimal continuing time loss because of LBP. A r e l a t i v e l y new procedure, chemonucleolysis, is presently enjoying much at tent ion and has found l imi ted acceptance in Vancouver. Chemonucleolysis is a procedure by which the nucleus pulposus of an offending disc can be dissolved by in jec t ion of the disc (using x-ray guidance of the needle) with chymo-papain, an enzyme which s e l e c t i v e l y destroys the major water-binding material of the d i s c . The success rates of chemonu-c l e o l y s i s treatment appear to be approximately equal to those of discectomy/1aminectomy (Norby & Lucas, 1973). 32 Another surgical procedure, spinal f u s i o n , is used when x-rays indicate vertebral i n s t a b i l i t y , that i s , when one ver-tebra is seen to move in the saggital plane in re la t ionsh ip to the vertebrae above and below i t . Spinal fusion immobi1izes the vertebra by attaching (fusing) i t to another vertebra with various conf igurat ions of screws and/or bone-implant br idges, often af ter 1 aminectomy/discectomy procedures have been under-taken at the same sess ion . Fusion was also apparently used as a l a s t - d i t c h resort with chronic low back pain patients in past years.(Adams, 1962), but in B r i t i s h Columbia the use of spinal fusions has dec l ined , probably because of research undertaken l o c a l l y CKokan, Wing & ' W i l f l i n g , 1975). The success rate of spinal fusion has been var iously reported, with f igures as low as 22% having been reported for a small group of patients with ambiguous" ind icat ions for surgery (White, 1969). A recurrent f inding in many studies is that the p robab i l i t y of a successful outcome drops p rec ip i tous ly with mult iple sur-geries in thesame pat ient . White (1966) has rather strongly commented on th is f a c t , noting that "...damage to the i r (mul-t ip ly -opera ted patients 1) productive capacity is in proportion to at least the square of the number of procedures" (p.874). 5. Morton K. S . , . Professor and Head, D iv is ion of Orthopaedics Faculty of Medicine, Univers i ty of B r i t i s h Columbia, personal communication, 1974. 33 Psychological Aspects of Low Back Pain The probable importance of "emotional" factors in the e t io logy of some cases of low back pain was suggested as ear ly as 1911 (Chabot, 1911), and by World War II many s imi la r c l i n i c a l judgments, phrased in terms of many d i f fe rent personal i ty the-o r i e s , began to appear frequently in the l i t e r a t u r e . A l s o , many formal and informal studies documented voca t iona l , s o c i a l , m a r i t a l , and personal maladjustments in LBP patients (Tunturi & P a t i a l a , 1980; White & Panjabi , 1978; W i l f l i n g , 1973). The f i r s t object ive documentation of the personal i ty charac-t e r i s t i c s of LBP patients was undertaken by Hanvik (1951) in a 1949 d isse r ta t ion at the Univers i ty of Minnesota. Hanvik showed that LBP pat ients without i d e n t i f i e d spinal pathology had much higher "neurotic t r i ad" ( e . g . , hypochondriasis, depression, and hyster ia) e levat ions on the Minnesota Mult iphasic Personal i ty Inventory (MMPI) than did LBP patients with i d e n t i f i e d spinal pathology. After a slow s tar t in the ear ly 1970s there has been a rapid accelerat ion in the number of methodological ly adequate psychological studies of LBP pat ients . W i l f l i n g , et a l . (1973), showed MMPI neurotic t r iad elevat ions to be higher in LBP pat ients who were more d isab led , more chronic and had had more back operat ions. Publ icat ions of s imi la r f indings have become commonplace in the las t several years. Beals and Hickman (1972) showed that abnormally-elevated MMPI neurotic t r iads character ized i n d u s t r i a l l y - i n j u r e d LBP 34 patients but not i n d u s t r i a l l y - i n j u r e d peripheral trauma pat ients . These invest igators showed, furthermore, that the psychologist was more accurate than the orthopaedist in predict ing the outcome of LBP treatment. This superior accuracy was thought to suggest that psychological factors are heavi ly involved in some primary way in the LBP problem. Wiltse and Rocchio (1975) s i m i l a r l y showed the superior prognost icat ion ab i1 i ty of the psychologist as compared to the or thopaedist . Those authors demonstrated that there was l i t t l e cor re la t ion between the organic and MMPI examination f indings of LBP pat ients and that the hypochondriasis and hyster ia scales of the MMPI could predict 36% of the outcome variance of chemo-nuc leo lys is and laminectomy treatments. Only 10% of patients with T-scores over 85 on these two MMPI scales showed l as t ing r e l i e f of symptoms af ter treatment, whereas 90% of patients with T-scores under 55 showed such r e l i e f . In a second study, Kokan, Wing and W i l f l i n g (1975) showed, by the use of mul t ivar ia te analyses, that independent c o n t r i -butions to LBP d i s a b i l i t y are made by both psychological and orthopaedic factors and that the contr ibut ions of those two types of factors are roughly equal in importance in the pro-duction of LBP d i s a b i l i t y . Of the 100 subjects in th is study (also reported in W i l f l i n g , 1973), subjects who were represen-ta t ive of the BCWCB population having undergone spinal f u s i o n , f u l l y 46% showed one or more abnormal elevat ions on the MMPI neurot ic t r i a d . 35 The Kokan et a l . (1975) study is important to the thesis to be presented here in that , even though there was an indepen-dent neurotic ism factor i d e n t i f i e d in the study, parts of the variance of measures of neuroticism (such as. MMPI neurotic t r i ad scores) were found to load on factors r e f l e c t i n g organic d e f i c i t s . This f inding strongly suggests that there is an i n t e r r e l a t i o n s h i p between the psychological and organic path-ologies in LBP, possib ly related to some in tegra t ing , e t i o -l o g i c a l , psychosomatic process. Unfortunately, studies to date have followed the Cartesian dualism model, and invest igators have not attempted to combine the psychological and organic c h a r a c t e r i s t i c s of LBP patients into an integrated psychosomatic model. The present study represents a step in that d i r e c t i o n . Psychological Treatment of LBP The i d e n t i f i c a t i o n of psychological contr ibutors to LBP d i s a b i l i t y has in recent years led to the development of a number of psycho log ica l ly -or ien ted LBP treatment programs. A program developed by Fordyce and his co-workers (Fordyce, Fowler, Lehmann & DeLateur, 1968) is based on operant theory and is concerned only with behaviours ind ica t ive of pain or d i s a b i l i t y . This in -pat ient treatment program thus focuses on changing the"pat ient 1 s socia l and other reinforcement con-t ingencies to promote increases in a c t i v i t y and socia l "well" behaviours and decreases in drug taking and medical a t tent ion-seeking. Fordyce does not concern himself with the intrapersonal 36 experience of pain or i t s reduct ion, and his patients are ind iv idua ls with chronic LBP! h i s t o r i e s . The importance of learned behaviours in these chronic patients is probably greater than in acute patients with a very short d isab i l i t y - re in fo rcement h is to ry . Fordyce (1974) has, in f a c t , warned that his program is inappropriate for acute pa t ients . Fordyce has published l i t t l e treatment outcome data, but those which he has published (Bonica & Fordyce, 1974), as well as informal ly communicated data and statements concerning the demand for his s e r v i c e s , a l l suggest therapeutic e f fec t iveness . The Fordyce program has been widely adopted, Z and some very high success rates have been reported ( e . g . , Anderson, Cole^ G u l l i c k s o n , Hudgens & Roberts, 1977; Seres & Newman, 1976). A conceptual ly d i f f e r e n t , psycho log ica l ly -or ien ted LBP treatment program has been developed at Casa Colina Hospital in Pomona, C a l i f o r n i a ( G o t t l i e b , 1975; Hockersmith, 1975; K o l l e r , 1975; S t r i t e , 1975). The conceptual or theoret ica l bases of the Casa Colina Program have not been well enunciated, but the central notion appears to be that LBP patients suf fer from excessive psychological and physio logica l tensions, which are further exacerbated by the various addit ional l i f e stresses that become associated with d i s a b i l i t y . The Casa Colina model 6. Fordyce, W. E. Personal communication, 1974 7. See-abstracts of the Second World Congress on Pain , held in Montreal , Canada, August 27 to September 1, 1978. 37 is i l l u s t r a t e d here in Figure 6. In an intensive four to six week in -pat ient program, the Casa Colina patients are indoctr inated with the notion that they can exert s e l f - c o n t r o l on the i r pain experience. Ind iv idua l , group and family psychotherapy sessions and sexual , f i n a n c i a l , and vocational counsel l ing sessions are undertaken as indicated to reduce l i f e s t r e s s . F i n a l l y , an intensive tension-reduct ion program, involv ing biofeedback and autogenic t ra in ing is under-taken. With biofeedback the patients are taught, in two one-hour sessions per day, to reduce . f inger t ip galvanic skin res-ponse (GSR) a c t i v i t y , and af ter they have become p r o f i c i e n t in that task, they are taught to reduce forearm EMG a c t i v i t y . g It is thought by at least one of the Casa Colina personnel that tension reduction through biofeedback techniques is the most important treatment component leading to the Casa Colina program e f fec t iveness . While i t is d i f f i c u l t to argue with the e f f i c a c y of th is program, which returns over 80% of chronic LBP patients to func t iona l ly working status regardless of i n i t i a l organic or psychological diagnoses, the program unfortunately includes so many loosely conceptual ized, confounded procedures that i t is impossible to understand why the program works. For example, i t is controversia l whether or not GSR and per iphera l -muscle EMG biofeedback can be used to bring about generalized 8. Hockersmith, V. W. Personal communication, 1976. 38. RUN AROUND (DOCTORS, THERAPISTS) INS. CARRIER POSTURE (UNNATURAL) SHORTENED MUSCLE (CONTRACTURE) IMMOBILITY CRUTCH SHORTENED MUSCLES (TIGHT) I PAIN DECONDITIONED WT. GAIN INCREASE MEDS WITHDRAWAL LACK OF BODY AWARENESS LACK OF SOCIAL CONTACT PROBLEM i AGITATION i ANGER DRAIN CNS ENERGY FIGURE 6. The Casa Colina "Tension-Anxiety-Pain" Model. 39 tension ( is that anxiety?) reduction (Alexander, 1975; Stoyva, 1979). Psychophysio logica l ,Considerat ions Concerning LBP Patients There have been v i r t u a l l y no systematic psychophysiological studies of LBP pa t ien ts , but some of the i r probable psycho-physio logica l c h a r a c t e r i s t i c s can be deduced given other known personal i ty c h a r a c t e r i s t i c s and the known psychophysiological corre la tes of those c h a r a c t e r i s t i c s . One ear ly psychophysiological study of LBP, reported by Holmes and Wolff in 1952, appears to stand forgotten or unin-tegrated in current thought. Holmes and Wolff monitored the muscle a c t i v i t y in the backs and other locat ions in LBP patients and normal subjects , and found the former to give much greater EMG responses than the l a t t e r when confronted by soc ia l s t r e s s -o r s . Unfortunately, Holmes and Wolff provided no data or s ta -t i s t i c a l analysis in the i r repor t , and thus i t is d i f f i c u l t to t e l l whether muscle groups other than the back also showed excessive responses in"LBP pat ients . Also confusing is the fact that Holmes and Wolff ca l l ed the excessive EMG a c t i v i t i e s in LBP patients a response to socia l stress but appear to have des-cr ibed the EMG in tonic terms. These invest igators then con-ceptual ized the i d e n t i f i e d excessive EMG responses in LBP patients in the " f l i g h t or f ight" terminology of the day and suggested that th is increased muscle a c t i v i t y gave r ise to LBP by biomechanical mechanisms. Over the years others (Dorpat 40 & Holmes, 1962; Kraus, 1970; Sarno, 1978) have suggested a s imi la r mechanism for the production of LBP, but the basis of these suggestions is unclear . The Holmes and Wolff study c i ted above seems to be one of a number of invest igat ions around 1950 in which associat ions between increased EMG a c t i v i t y and musculoskeletal symptoms were es tab l ished . For example, Sainsbury and Gibson (1954), and Malmo and Shagass (1949), conducted EMG studies of patients with neck, head, and arm pains and found the EMG a c t i v i t y in the symptomatic areas to be higher than in other areas monitored. S i m i l a r , more recent research studies are reported by Roessler and Engel (1974), Levenson (1979), and Stoyva (1979). One psychophysiological mechanism which would lead one to expect increased phasic and perhaps tonic muscle a c t i v i t y in LBP patients follows from the l i t e r a t u r e c i ted above, which indicates that many LBP patients exhib i t neurotic character-i s t i c s . Recent psychophysiological research has quite cons is -tent ly been in support of work by Malmo, who showed in the ear ly 1950s that in various funct ions , inc luding EMG a c t i v i t y , neurotic ind iv idua ls respond to a var iety of s t ressors with responses of larger magnitude and of longer duration than do normal sub-jec ts (Alexander, 1972; Go lds te in , 1972). Less consistent has been support of the notion" that neurotic ind iv idua ls exhib i t higher tonic leve ls of EMG and other physio logica l a c t i v i t i e s (Alexander, 1972; Go lds te in , 1972), but the common lay notion 41 that neurotics are muscularly "uptight" has found some support in the app l ica t ion of EMG biofeedback re laxat ion techniques (Raskin, Johnson & Rondestvedt, 1973; Stoyva, 1979) and even in the app l ica t ion of verbal re laxat ion- induct ion procedures or ig inated by Jacobson (1934, 1938). The greatest d i f f i c u l t y in evaluating the l i t e r a t u r e dealing with the EMG response c h a r a c t e r i s t i c s of neurotic ind iv idua ls is that usual ly only a small number of muscles is monitored in any given study. If no d i f ferences are found between normals and neuro t ics , then the negative studies can always.be dismissed by c i t i n g the p r i n c i p l e of indiv idual response stereotypy. This p r ine ip le wi11 be described below. A Psychophysiological Model of Psychosomatic Et iology Sternbach (1966) has integrated a number of we l l -es tab l ished psychophysiological concepts a t t r ibutab le to the work of other researchers to provide an e t i o l o g i c a l model of psychosomatic d isorders . Though very p laus ib le in l i g h t of antecedent re-search, the Sternbach model has generated l i t t l e i n v e s t i g a t i o n , possib ly because the biofeedback boom started at about the same time as the model was proposed, which provided invest igators an area of more easi ly-performed .but more s u p e r f i c i a l psycho-somatic s tud ies . Stoyva (1979) has recent ly proposed a return to more comprehensive research test ing such a model, and has reviewed the few such studies that have been reported. Sternbach used the concept of response stereotypy, developed 42 by John Lacey, to explain organ s p e c i f i c i t y in the psychosomatic process. Lacey showed that , within one i n d i v i d u a l , the responses of various autonomical ly- innervated organs a l ign themselves into a ranked o r d e r , o r h ierarchy, as regards the i r degrees of response, across a wide spectrum of d i f fe rent s t r e s s o r s . This ranked physio logica l response hierarchy is quite stable within some ind iv idua ls over t ime, and those ind iv idua ls are said to show indiv idual response stereotypy. Di f ferent i n d i v i d -uals show d i f f e ren t i d i o s y n c r a t i c response s te reotyp ies , that i s , d i f fe ren t autonomic functions w i l l hold d i f fe rent ranked posi t ions in the response hierarchies of these d i f fe rent i n -d iv idua ls across s t r e s s o r s . Sternbach has hypothesized that the organs of the most responsive funct ion of an indiv idual ' s response stereotypy would be the f i r s t to break down i f a long ser ies of s t ressors was encountered and the i n d i v i d u a l ' s homeo-static.mechanism was d i s i n h i b i t e d . Such d i s i n h i b i t i o n is shown in the excessive (magnitude and duration) physio logica l res-ponsiveness of neurotic ind iv idua ls demonstrated by Malmo, and may resu l t from prolonged periods of l i f e s t r e s s . Poten-t i a l l y , the Sternbach model would appear to be appl icable to the e t io logy of musculoskeletal disorders as well as autonomic disorders in that indiv idual response stereotypy has been demon-strated in the skeleta l musculature by Goldstein and her co-workers (Goldste in , Gr inker , Heath, Oken & Shipman, 1964). Goldstein et al . showed that separate h ierarchies may ex is t 43 within'-'O'ne'Individual- as regards his autonomically innervated organs and his skeleta l muscle groups. The Sternbach model appears to be a very promising basis for invest igat ions concerning the et io logy of LBP. The l i t - * erature reviewed in e a r l i e r sect ions of the present paper strong-ly suggests-the hypothesis that abnormal, excessiye lumbar muscle a c t i v i t y is responsible for both pain and disc degeneration in LBP condi t ions . It may be that LBP patients are ind iv idua ls who have a musculoskeletal response stereotypy character ized by maximally responsive lumbar muscle groups. The many s o c i a l , m a r i t a l , v o c a t i o n a l , and other pre-morbid maladjustments of LBP patients would make i t probable that they would encounter frequent s t ressors in da i ly l i v i n g , leading to frequent act -iva t ion of the lumbar muscle groups. The known associat ions between LBP, neurotic features , and physio logica l overrespon-siveness further suggest that the lumbar muscle responses of LBP pat ients .are of an excessive magnitude and of excessive durat ion. Thus frequent, large magnitude, long duration back muscle ac t iva t ion would, on a chronic b a s i s , lead to repeated force loadings on the lumbar d i s c s , causing the i r untimely or accelerated degeneration. Overact iv i ty of the lumbar muscles as described above would pre-date the onset of LBP symptoms and i f only on a chronic b a s i s , would lead to degeneration of the d i s c s . It is well known from the work of Rahe and others ( e . g . , Graham, 1972) 44 that periods of high stress occur in the six months preceding the onset of i l l n e s s , stress which from the view of the present model would be expected to accelerate the degenerative process and perhaps even lead to the i n i t i a t i o n of pain of skeleta l and/or intramuscular o r i g i n . With the onset of overt d i s a b i l i t y , even greater s t ressors such as concerns about pa in , surgery, prognosis , f inances , interpersonal r e l a t i o n s h i p s , vocational fu ture , and the l i ke confront the i n d i v i d u a l , as indicated by the Casa Colina model shown in Figure 6, leading by the mechanisms described to even more lumbar muscle a c t i v i t y . Perhaps at some point in th is e t i o l o g i c a l sequence, addi t ional muscle spasm might also be created by the s p l i n t i n g re f lex described above. It would of course be extremely cost ly to conduct a pro-spective study concerning the Sternbach model in the et io logy of LBP. However, the v a l i d i t y of a Sternbach model of LBP would require phasic lumbar muscle hyperact iv i ty to be present in asymptomatic LBP patients ear ly in the i r i l l n e s s h i s t o r i e s , and study of such a group would be the f i r s t step in test ing the model. The impl icat ions of iden t i f y ing such an e t i o l o g i c a l process for LBP w i l l be more f u l l y discussed below, but the potent ia l of biofeedback for r e c t i f y i n g any muscle a c t i v i t y abnormalit ies should b r i e f l y be considered. Biofeedback I f •abnormal i t ies of lumbar muscle a c t i v i t y are i d e n t i f i e d 45 in LBP p a t i e n t s , symptomatic or asymptomatic, another psycho-physio logica l procedure, biofeedback, may be the most d i rec t and rapid means of removing the abnormal i t ies , thereby ar rest ing the degenerative process and a l l e v i a t i n g current pain. Biofeedback is a c l i n i c a l procedure through which an i n -div idual can learn to change the rate of a c t i v i t y in various of his physio logica l functions i f he is given information via external sensory channels concerning the a c t i v i t y level of the function to be changed. This feedback is usual ly supplied by an e lec t ron ic apparatus having a transducer to convert the relevant b io log ica l f luc tuat ions to minute e l e c t r i c a l f l u c -tua t ions , an ampl i f ier to increase the power of the e l e c t r i c f l u c t u a t i o n s , and some type of output transducer such as an audio speaker or a panel meter to relay the ampli f ied f l u c -tuations to the subject by auditory or visual means. The theoret ica l framework on which biofeedback is based developed in the ear ly 1960s, when i t was recognized that bodily functions are amenable to change by operant or reward cond i t ion -ing rather than only by c l a s s i c a l condit ioning methods. Kimmel (1974) has provided a good h i s t o r i c a l account of the animal and human research leading to th is change in theoret ica l per-spect ive and of the rapid ly p r o l i f e r a t i n g subsequent c l i n i c a l appl icat ions of biofeedback techniques. Blanchard and Young (1974) have reviewed the biofeedback l i t e r a t u r e in a conservative manner and have concluded that 46 of a l l the physio logica l functions reported to have been mod-i f i e d by biofeedback, only with EMG a c t i v i t y is there strong evidence that biofeedback is e f f e c t i v e . Those authors consider the ef fect iveness of EMG biofeedback associated with treatment of such disorders as tension headaches to be "soundly confirmed". In a review of biofeedback l i t e r a t u r e concerned with pain re-duct ion , Roberts (1974) describes EMG biofeedback as the most promising of the biofeedback types. Electromyographic feedback has been applied most frequently in the reduction of tension headaches and spasmodic t o r t i c o l l i s . This l i t e r a t u r e has been reviewed.by Blanchard and Young (1974), Roberts (1974), M i l l e r (1974), Jessup, Neufeld & Mersky (1979), and others. These appl ica t ions of EMG biofeedback appear to be more than vaguely al igned with the use of EMG biofeedback to reduce -1umbar muscle tension in that they are frequently appl ied to spinal muscles, but in the cerv ica l region. More c l o s e l y re lated to the reduction of lumbar muscle tension is an appl ica t ion of EMG biofeedback reported by Jacobs and Fenton (1969), who used i t to treat the cerv ica l muscle spasms of neck- injured pat ients . Jacobs and Fenton found that neck-injured patients showed much higher EMG leve ls in the cerv ica l spine area.than did normal subjects and, that when simply instructed to do so , the neck-injured patients could not relax those muscles as well as could the normal subjects . These i n v e s t i -gators demonstrated that with only ten , 15-second biofeedback 47 t r i a l s the neck- injured patients could bring the i r cerv ica l EMG leve ls down to equal those of normal subjects . Inexpl icably , Jacobs and Fenton did not report what e f f e c t , i f any, th is EMG reduction had on the pain experienced by the neck-injured pa-t i e n t s , nor did they follow up on what EMG reduct ion, . i f any, remained even af ter a few hours. The rate at which many subjects can master biofeedback t ra in ing is very rapid and makes'the potential use of such t ra in ing for research manipulations and for c l i n i c a l therapy very a t t r a c t i v e . Many EMG biofeedback tasks can be mastered in under t h i r t y minutes (Goldste in , 1972), and in the present author 's experience (Hanna, W i l f l i n g & McNe i l l , 1976), the technique can be taught to a subject with a few minutes of coaching. Hypotheses of the Present Study The present study was designed to invest igate whether or not the e t io logy of LBP conforms to the psychosomatic model proposed by Sternbach (1966). Repeated overact ivat ion of the lumbar muscles by stress would, by way of the biomechanical p r i n c i p l e s discussed in e a r l i e r parts of th is paper, be expected to lead to acce lerat ion of lumbar spine degeneration. If the Sternbach model is va l id with respect to the et io logy of LBP, one would expect the fol lowing hypotheses to be supported in an asymptomatic sample of ind iv idua ls with a minimal h istory of LBP: 48 1) LBP subjects w i l l show a greater EMG response of the poster ior lumbar muscles to stress of a psychological or physical nature than do subjects with no history of LBP. 2) The LBP subjects w i l l show a s p e c i f i c indiv idual response stereotypy to s t r e s s , such that when the respon-siveness of a number of physio logica l functions is compared, the poster ior lumbar muscles wi l l be the most responsive. Subjects without a h istory of LBP wi l l not show a s imi la r ind iv idual response stereotypy pat tern , though indiv idual response stereotypy patterns dominated by physio logica l functions other than the back muscles may be present. 3) Subjects with LBP wi l l be more neurotic than subjects without a LBP h is to ry . This should be psychometrical 1 y demonstrable, espec ia l l y with an instrument having a demonstrated associat ion between elevated neuroticism scores and increased physio logica l responsiveness to s t r e s s . The Eysenck Personal i ty Inventory would appear to be such an instrument (Eysenck & Eysenck, 1968). 4) Associated with the neuroticism wi l l be a lack of homeo-s t a t i c c o n t r o l , which w i l l lead to a longer period unt i l the physio logica l responses return to baseline leve ls in the LBP subjects as compared to the Control subjects . Biomechanical discussions e a r l i e r in this paper explored the probable great importance of a hydraul ic "balloon ef fect" of the abdominal contents in unloading forces bearing on the 49 interver tebra l d i s c s . This hydraul ic e f fect is brought about by the abdominal oblique muscles (Bar te l ink , 1957), and i t was thus decided to include the abdominal oblique muscles in the study of indiv idual response stereotypy. However, procedures were also added to study a c t i v i t y of the abdominal oblique muscles in physical s i tuat ions such as keeping the body erect or f l exed . In both the psychological stress and postural s i t -uat ions, hypoact iv i ty of the abdominal oblique muscles would adversely load the d i s c s . The hypothesis was thus adopted that: 5) Hypoactivi ty of the abdominal obiique.muscies w i l l be seen in both the pyschological stress and postural manipulations of LBP subject . 50 METHOD Subjects Subjects , the majority of them being teachers, were chosen from students attending the 1977 summer session at the Univer-s i t y of B r i t i s h Columbia. Faculty members in the Department of Psychology and the Faculty of Education were approached by the experimenter, who asked permission for br ie f access to their c l a s s e s . At the c l a s s e s , the experimenter provided the students with short explanations about LBP and about the methods.and the measures of his research. It was also explained that , on a chance b a s i s , one out of every eight subjects would receive $50 for pa r t i c ipa t ion in the research. The students were then requested to f i l l out a short screening questionnaire concerning demographic and LBP history informat ion, regardless of whether or not they wished to par t ic ipa te as subjects in the study proper. Those wishing to volunteer as subjects could do so by f i l l i n g in their names and telephone numbers at the end of the quest ionnaire . Subjects were chosen for the experimental group on the basis that they reported having experienced l im i ta t ion in the i r da i ly funct ioning and/or having v i s i t e d a physician at least once in the past year because of LBP. Individuals who reported a gross pathological condit ion or substant ial trauma accounting for t h e i r . L B P , as well as those who had undergone low back surgery, were excluded from the study. Ten females and ten 51 males were thus chosen for the experimental group. They were then sex- and age-matched to within four years with volunteers for a control group who reported never having experienced LBP. Materi als As described above, students were screened for p a r t i c i -pation in the study by use of a short screening quest ionnaire , included here in Appendix A. On presenting at the laboratory , the subjects completed a standard consent form (Appendix B). A short interview with regard to recent unusual or s t ress fu l events, any medication taken, and menstrual cycle information was then conducted by the experimenter with the information being recorded on a data sheet, included here in Appendix C. Subjects then completed the Eysenck Personal i ty Inventory (Eysenck & Eysenck, 1972) and the McGill Pain Assessment Ques-t ionnaire (Melzack, 1975), samples of which are included in Appendices D and E respec t i ve ly . A Beckman Type R eight channel dynograph with r e c t i l i n e a r recording pens was used to record forearm electromyographic (EMG) a c t i v i t y , b i l a t e r a l poster ior low back muscle EMG ac-t i v i t y , abdominal oblique muscle EMG a c t i v i t y , skin conductance (SC), heart rate (HR), respi ra tory rate (RR), and peripheral vasomotor (VM) a c t i v i t y at a chart speed of f ive mi l l imeters per second. A marker channel was manually t r iggered by the experimenter to mark s i g n i f i c a n t experimental events. A l l e lectrodes used in monitoring EMG, HR, and SC were of the Beckman 52 s i l v e r s i l v e r - c h l o r i d e b ipotent ia l va r ie ty , each with a contact area .78 centimeter in diameter. The electrodes were attached to the subjects by using Beckman st icky c o l l a r s . Hewlett Packard Redux paste was used to clean the EMG and HR monitoring s i tes as well as to provide a contact medium in the corresponding e lect rodes . A 0.5% NaCl paste was used as the contact medium in the SC e lect rodes . Forearm EMG a c t i v i t y was recorded in raw form with a Beckman Type 9852 coupler; three couplers of the same type, modified to function as accumulating devices (as described below), were used for monitoring the low back and abdominal muscle s i t e s . Skin conductance was recorded by a Beckman Type 9844 coupler , which imposed a constant half vo l t across the electrodes and subjects , and provided a d i rec t chart recording in micromhos. Heart rate was recorded by a Beckman Type 9857 cardiotachometer coupler , which provided a d i rec t recording in beats per minute, on a beat-by-beat bas is . Respiratory rate was recorded by fol lowing chest excursions d i r e c t l y with a pneumatic chest bellows attached to a pressure transducer, which provided e l e c t r i c a l s ignals to a Beckman Type 9825 coupler . D ig i ta l VM a c t i v i t y was monitored by a ref lectance photoplethysmograph incorporat ing a l igh t -emi t t ing diode and photot rans is tor , the signal being passed through a Beckman Type 9874 coupler u t i l i z i n g a .03-second time constant. D i f f i c u l t y was encountered on i n i t i a l attempts to monitor low back and abdominal EMG a c t i v i t y with conventional Beckman 53 equipment. The EMG signals derived from the back and abdominal muscles in the experimental paradigm were found to be quant i ta -t i v e l y so smal l , in the order of several microvo l ts , that raw EMG traces or traces from an integrat ing coupler , such as the Beckman Type 9852, would not display them with f i d e l i t y . An accumulating type of EMG coupler , operating over several-second in terva ls was thus required. Sa t is fac tory recording character-i s t i c s were f i n a l l y obtained from a Beckman Type 9852 integrat ing EMG coupler , modified by an e lec t ron ics design technician so as to function as an accumulative device in accordance with the fol1owi ng p r i n c i p l e s : The raw EMG signal is a ser ies of biphasic spike waveforms, the potent ia ls of which may b e ' d i r e c t i y recorded by the dynograph. An integrat ing coupler r e c t i f i e s the biphasic waveforms and charges a condensor with the resul tant energy, the instantaneous potent ia l across the condensor being re f lec ted by the dynograph t r a c i n g . The energy in the condensor is continuously "bled off" through a r e s i s t o r , resu l t ing in a time constant of trace decay. To convert an integrat ing coupler to an accumulating coupler , the bleeder r e s i s t o r is removed and a timing c i r c u i t is added which, at regular i n t e r v a l s , shorts out or instantaneously "dumps" the storage condensor. However, a problem ar ises with regard to the p r i n c i p l e that e l e c t r i c a l energy is progressive ly harder to in t ro jec t into a condensor with increases in the charge that the condensor is already s t o r i n g . This problem can 54 be overcome to a large extent, however, by using a large conden-sor which, with maximal expected EMG inputs , w i l l become charged to only a small f rac t ion of i t s capacitance. Equipment for th is study was al tered in accordance with these p r i n c i p l e s . The modified EMG couplers were tested by supplying them with inputs from a Hewlett Packard 3351A transmission test set with attenuator. Test inputs comprised various combinations of amplitudes from f ive to 25 microvolts in f ive microvolt s teps , frequencies of 50, 100, 200, 300, and 400 her tz , and waveforms of sp iked, s inusoidal and square v a r i e t i e s . These tests i n -dicated good l i n e a r i t y between the energy content of the various waveforms imposed on the couplers and the height of the resul tant dynograph t races . In the i r f ina l form, traces from the accumulating couplers took the shape of sawtooth waveforms, with ascending curves r e f l e c t i n g a buildup of stored energy, terminated by abrupt v e r t i c a l drops of the traces back to constant baseline l e v e l s , corresponding to the shortings out , or "dumpings", of the storage condensor. The dumping interval was f i n e l y adjustable and highly stable with reference to the chart speed, and was chosen as two seconds. E l e c t r i c a l noise inherent in the dynograph con-t r ibuted considerably to growth of the accumulators' sawtooth t r a c e s , because of i t s summation over a considerable time per iod . Testing of the dynograph and modified couplers over periods of hours, however, showed the inherent noise in the 55 three channels to be constant af ter a ten minute warm-up period of the equipment, though the noise leve ls of the three channels were quite d i f f e r e n t . Precautions were thus taken to warm up the equipment for at least one-half hour before running a subject and, in a d d i t i o n , reference traces without input from the subject were obtained at the beginning and end of each dynograph chart . The EMG a c t i v i t i e s of the subjects were scored as height d i f -ferences above the sawtooth height resu l t ing from inherent e l e c t r i c a l noise alone, a scoring task which was great ly sim-p l i f i e d by the fortunate s t a b i l i t i e s of both the baselines of the sawtooth waveforms as well as the inherent instrument noise . A l l psychophysiological recording took place with the subjects inside a soundproof, e l e c t r i c a l l y shielded room. Subjects were seated on a common chrome and vinyl o f f i c e c h a i r , with a seat 16 inches above the f l o o r , unpadded arms seven and three-quarter inches above the seat , and a s l i g h t l y angled back extending 15 inches above the seat . A l l ins t ruct ions and st imul i presented to the subjects during the experimental session were tape recorded and reproduced by a Sony TC355 tapedeck through a loudspeaker. One of the experimental tasks required the subjects to play "Pong", a hand-eye co-ord inat ion game s imi la r to tenn is , played on a small TV se t . A Ridgewood Gamatic 7600 unit was used, set to slow speed, "autoserve", and a 40° de f lec t ion angle. The Pong 56 display was a 12-inch black and white TV set placed four and a half feet in front of the subjects . The s ize of the Pong bat or paddle was changed from large to small by the experimenter at the midpoint of the six-minute task, and he was also res-ponsible for reset t ing the game to zero score whenever the f ina l score of 15 was reached. In the course of the experiment the subjects.were requested to immerse the i r hands in ice water, a procedure widely known as the Cold Pressor Test . The apparatus for this test was a one-gal lon insulated beverage conta iner , as is often used on p i c n i c s , which had a four - inch hole cut in i t s top. Standardized quant i t ies of water and crushed ice placed in th is apparatus led to an equi l ibr ium temperature of four degrees centigrade af ter ten minutes, which would be maintained for several hours. Procedure A subject chosen for the study was telephoned and given an appointment t ime, at his convenience, for a two-hour session in the psychophysiology laboratory . On presenting at the lab-oratory , the subject was asked to pick randomly one of a group of mani l la envelopes which assigned a subject number, and which also contained e i ther a f i f t y do l la r b i l l or a thank you note. The envelope was opened at the end of the experimental sess ion . The subject was then asked to sign the consent form before the previously described interview form was completed by the ex-perimenter. It was not found to be necessary to re ject any 57 subject because of current LBP symptoms or recent substant ia l intake of medication. The subject then completed the Eysenck Personal i ty Inventory and the McGill Pain Assessment Question-na i re . A control subject , who of course would not have ex-perienced LBP, was asked to complete the l a t t e r questionnaire "as i f " he had had LBP, drawing on his understanding and ob-. servations of the LBP experience as he had heard i t described or seen i t manifested in others. Following completion of the above "paper work", the subject was given a b r ie f or ienta t ion tour of the psychophysiology laboratory for the purpose of a l l ay ing any unnecessary appre-hensions concerning the e l e c t r i c a l equipment or procedures. He was then requested to go to a nearby washroom to wash his hands thoroughly to f a c i l i t a t e the recording of SC. The subject was also to ld that he would not have further access to such a f a c i l i t y for about one and one-half hours once the physio-log ica l transducers were attached. On returning to the laboratory , the subject was taken into the experimental chamber, and the electrodes and transducers were attached. Because HR and EMG monitoring s i tes were located under the garments, a female laboratory ass is tant hooked up a l l female sub jec ts , while the male experimenter hooked up a l l male subjects . Routine test ing of the in tere lectrode re-sistances was not undertaken with the experimental subjects because of a lack of su i tab le equipment. However, pract ice 58 pr ior to the research showed that the cleansing technique used cons is ten t ly resul ted in in tere lect rode resistances of under 5,000 ohms, as measured by the ava i lab le ohmmeter (which rapid ly polar ized the e lec t rodes) . Lumbar EMG electrodes were attached b i l a t e r a l l y , three centimeters from the midline of the body, on the transyerse plane between the L4 and L5 spinous processes. A second pair of electrodes was placed f ive centimeters superior to the previous e lect rodes . V e r t i c a l l y i n - l i n e pairs of electrodes were then connected to the dynograph input cab les , resu l t ing in the two erector spinae muscles being i n d i v i d u a l l y monitored. Electrodes to monitor the abdominal obiique muscies were attached para l l e l to the sag i t ta l plane of the body, one- th i rd and two-th i rds of the distance between the anter ior superior i l i a c spine and the lowest r i b . The forearm EMG electrodes were attached to the nondominant forearm in the manner described by Lippold (1 967). The HR signal was derived from "chest . leads", with a reference and an act ive electrode placed on the anter ior midline of the chest , and a second act ive electrode placed under the l e f t a x i l l a . The SC electrodes were fastened to the volar surfaces of the middle phalanges of the f i r s t and second f ingers of the sub jec t 's nondominant hand. The photoplethysmo-graph used to monitor VM a c t i v i t y was taped to the middle pha-lange of the r ing f inger of the same hand. A pneumatic bellows was fastened around the sub jec t 's lower chest to monitor chest 59 e x c u r s i o n s as a measure of RR. A f t e r be ing s e a t e d , each s u b j e c t was asked to keep both f e e t on the f l o o r and not to s h i f t around more than necessary f o r the d u r a t i o n of the exper imenta l s e s s i o n . The r o t a r y r h e o -s t a t c o n t r o l f o r the TV Pong game was taped on the arm of the c h a i r c o r r e s p o n d i n g to the s u b j e c t ' s dominant hand, and each s u b j e c t was g iven a s h o r t p r a c t i c e s e s s i o n to f a m i l i a r i z e him or her with the game and the f u n c t i o n i n g of the a s s o c i a t e d equipment . The Cold P r e s s o r Test apparatus was p laced imme-d i a t e l y below the Pong c o n t r o l r h e o s t a t , and b r i e f i n s t r u c t i o n s ' were g iven to the s u b j e c t c o n c e r n i n g how to immerse h is hand in i t . F i n a l l y , i n s t r u c t i o n s were g iven (and demonstrated by the exper imenter ) wi th regard to the exper imenta l tasks i n v o l v i n g forward f l e x i o n of the upper body and the i n c r e a s e of in t raabdomina l p r e s s u r e ( V a l s a l v a manoeuvre) . The exper imenter s t a r t e d the tape r e c o r d e r and undertook f i n a l c a l i b r a t i o n of the dynograph a f t e r l e a v i n g the s u b j e c t in the exper imenta l room with i n s t r u c t i o n s to r e l a x . With s t a r t i n g of the tape r e c o r d e r , a l l f u r t h e r i n s t r u c t i o n s and s t i m u l i p resen ted to the s u b j e c t were thus a u t o m a t i c a l l y t imed and kept s t a n d a r d . A 100 d b . , 500 her t z t o n e , r i s i n g from zero to maximum loudness in i t s .2 second d u r a t i o n (TONE), was de-l i v e r e d to the s u b j e c t a f t e r an i n i t i a l 15 minutes of s i l e n c e . To a l low the s u b j e c t to r e t u r n to p r e s t i m u l u s p s y c h o p h y s i o l o g i c a l a c t i v i t y l e v e l s , three and o n e - h a l f minutes of s i l e n c e f o l l o w e d 60 b e f o r e i n s t r u c t i o n s f o r a c o g n i t i v e i n t e r f e r e n c e t a s k (COUNT) w e r e p r e s e n t e d . The s u b j e c t was t o l d t o remember t h r e e w o r d s ( a p p l e s , l o y a l t y and t u r q u o i s e ) , and was t h e n a s k e d t o c o u n t b a c k w a r d s by t h r e e s as r a p i d l y as p o s s i b l e , s t a r t i n g f r o m 5 1 8 . A f t e r 30 s e c o n d s o f c o u n t i n g , t h e s u b j e c t was a s k e d t o r e c a l l t h e t h r e e w o r d s . A n o t h e r p e r i o d o f s i l e n c e o f t h r e e and a h a l f m i n u t e s d u r a t i o n f o l l o w e d b e f o r e i n s t r u c t i o n s f o r t h e Pong game (PONG) w e r e g i v e n . The PONG t a s k c o n t i n u e d f o r a t o t a l o f s i x m i n u t e s , w i t h t h e e x p e r i m e n t e r s w i t c h i n g t h e m a c h i n e f r o m l a r g e t o s m a l l p a d d l e s i z e a t h a l f t i m e , c u e d by t h e t a p e d comment t o t h e s u b j e c t " L e t ' s make i t a l i t t l e h a r d e r n o w " . D u r i n g t h e PONG t a s k t h e e x p e r i m e n t e r m o n i t o r e d t h e TV p l a y i n g s c r e e n t h r o u g h a p e e p h o l e i n t h e e x p e r i m e n t a l c h a m b e r , r e s e t t h e PONG m a s t e r c o n t r o l when e a c h game o f 15 p o i n t s was c o m -p l e t e d , and m a r k e d t h a t o c c u r r e n c e on t h e d y n o g r a p h c h a r t . F i v e m i n u t e s o f s i l e n c e e l a p s e d a f t e r t h e PONG t a s k b e f o r e , t h e s u b j e c t r e c e i v e d r e c o r d e d i n s t r u c t i o n s t o p l a c e h i s hand i n t o t h e i c e w a t e r (COLD P R E S S O R ) . A f t e r t h r e e m i n u t e s o f i m m e r s i o n he was i n s t r u c t e d t o r emove and d r y h i s h a n d . S i x more m i n u t e s o f s i l e n c e e l a p s e d b e f o r e i n s t r u c t i o n s w e r e p r e -s e n t e d , i n s t r u c t i n g t h e s u b j e c t t o g e t up c a r e f u l l y and s t a n d c o m f o r t a b l y w i t h h i s h a n d s a t h i s s i d e s ( S T A N D ) . T h r e e and o n e - h a l f m i n u t e s l a t e r t h e s u b j e c t was i n s t r u c t e d t o p e r f o r m t h e V a l s a l v a m a n e o u v r e ( V A L S A L V A ) f o r 15 s e c o n d s ( " T a k e a deep b r e a t h , h o l d i t , b u t r e a l l y b l o w h a r d - a c t l i k e y o u a r e t r y i n g 61 to blow out but c a n ' t " ) . Another three and one-hal f 'minutes • followed before the subjectwas instructed to f lex his upper body about 45° at the hips (FLEX) and to hold that posi t ion u n t i l o c c u r r e n c e o f a further taped ins t ruc t ion to straighten up 15 seconds l a t e r . A further three minutes of s i lence then elapsed before the announcement was made that the experiment was over. The experimenter obtained a short record of the EMG accumulator coupler traces without input from' the subject before switching the dynograph to standby mode and entering the experimental chamber. A l l e lectrodes and transducers were removed from the sub-j e c t , he was debriefed and shown his dynograph record i f i n -te res ted , and he was then asked to open the manil la envelope he had chosen on f i r s t entering the laboratory . A subject who found a f i f t y do l l a r b i l l in his envelope was congratulated . and asked to sign a rece ip t . Data Scoring A l l psychometric tests were scored in the conventional manners suggested by their authors. The Eysenck Personal i ty Inventory was scored, with the aid of templates, to y i e l d Neuroticism (N), Extraversion (E) , Psychoticism (P) and Lie (L) scores. The McGill Pain Assessment Questionnaire was scored with regard to adject ives used to describe pa in , the Number of Words Chosen, Sensory, A f f e c t i v e , Eva luat ive , and Miscellaneous values being determined. 62 The dynograph r e c o r d i n g s were handsco red by a r e s e a r c h a s s i s t a n t hav ing some ten y e a r s o f e x p e r i e n c e in such wo rk , and she was kept b l i n d w i t h r e g a r d to the e x p e r i m e n t a l c o n d i t i o n s o f the s u b j e c t s . A r e s c o r i n g o f a random 15 p e r c e n t o f t hese r e c o r d s by the e x p e r i m e n t e r showed a l m o s t p e r f e c t agreement . For pu rposes o f s c o r i n g , a l l p s y c h o p h y s i o l o g i c a l r e c o r d i n g s were c o n s i d e r e d i n i n t e r v a l s o f 30 s e c o n d s . T r a c e s f rom the t h r e e a c c u m u l a t i n g EMG c o u p l e r s , wh ich showed r e s e t s e v e r y two s e c o n d s , were s c o r e d f o r the t o t a l h e i g h t o f the 15 waveforms a t t r i b u t a b l e to s u b j e c t a c t i v i t y . The b a s e l i n e h e i g h t s o f t h e s e waveforms a t t r i b u t a b l e to e l e c t r i c a l n o i s e i n h e r e n t i n the equ ipment ( d i s c u s s e d i n M a t e r i a l s s e c t i o n ) were i g n o r e d and the s u b j e e t - r e l a t e d i n c r e m e n t s i n the waveform h e i g h t s were s c o r e d to the n e a r e s t o n e - q u a r t e r m i l l i m e t e r . D i f f i c u l t i e s w i t h e l e c t r i c a l g a i n l e d , a f t e r s c o r i n g and p r e l i m i n a r y a n a l y s i s , to o m i s s i o n o f d a t a f rom one o f the two c h a n n e l s o f i n f o r m a t i o n f rom the back m u s c l e s . I n s e n s i t i v i t y o f t h i s channe l f r e q u e n t l y d i d not a l l o w changes i n EMG a c t i v i t y to be d i s c e r n i b l e . A l s o , the raw EMG t r a c e r e l a t e d to f o rea rm a c t i v i t y was found not to be s c o r e a b l e because o f a c o n s t a n t equ ipment m a l f u n c t i o n . S k i n c o n d u c t a n c e and HR, t h e i r r e s p e c t i v e v a l u e s i n micromhos and b e a t s per minu te b e i n g d i r e c t l y a v a i l a b l e f rom the dynograph c h a r t s , were s c o r e d w i t h i n each 3 0 - s e c o n d i n t e r v a l f o r n u m e r i c a l mean, maximum, and minimum v a l u e s . R e s p i r a t o r y r a t e was s c o r e d to the n e a r e s t o n e - h a l f c y c l e per m inu te w i t h i n each 3 0 - s e c o n d 63 i n t e r v a l , by inspect ion of the roughly s inusoidal t r a c i n g s , d i r e c t l y r e f l e c t i n g chest movements, seen on the dynograph char ts . Vasomotor a c t i v i t y was scored to the nearest mi l l imeter of trace height of each of the sawtooth-l ike waveforms displayed on the dynograph record. Scores within each scoring interval were then averaged. A great deal of missing VM data was en-countered with the COLD PRESSOR experimental manipulation and the traces became unusable af ter the subjects stood up. Thus, no VM data is ava i lab le for the COLD PRESSOR, STAND, VALSALVA and FLEX experimental manipulations. The dynograph charts were scored for the fol lowing time per iods: the las t two minutes before TONE, and for minutes zero to one and two to three fol lowing i t ; during the cogni t ive inter ference task (COUNT) and for minutes zero to one and two to three af ter i t ; during the PONG task (twelve 30-second in terva ls ) and for minutes one to two and three to four a f ter i t ; during the COLD PRESSOR (six 30-second in terva ls ) and minutes one to two, three to four , and f ive to six af ter i t ; a f ter STANDing up, minutes zero to one and two to three were scored; during the VALSALVA manoeuvre only one ten-second interval was ava i lab le for s c o r i n g , and minutes zero to one and two to three af ter i t were scored, and, during FLEXing the upper body forward, three f ive-second scoring in terva ls were scored, with minute two to three fol lowing i t . In order to make the data scored during VALSALVA and FLEX compatible for s t a t i s t i c a l analysis 64 purposes with a l l the other experimental data, which were derived from 30-second i n t e r v a l s , the 10-second VALSALVA values were mul t ip l ied by three and the three f ive-second FLEX values were summed and mul t ip l ied by two. S t a t i s t i c a l Analyses Two sets of analyses were carr ied out using the s t a t i s t i c s described below, the f i r s t comparing males and females, the second comparing the LBP experimental group to the control group. Psychometric as well as " inc iden ta l " data were compared across groups using mult ip le t - t e s t s . The acceptable level of s ign i f i cance was set as p < .01 because of the numerous comparisons being made. In th is manner the groups were compared with respect to the Neurot icism, Ext ravers ion , Psychoticism and Lie scores of the Eysenck Personal i ty Inventory and the Number of Words Chosen, Sensory, A f f e c t i v e , Eva luat ive , and Miscellaneous indices of the McGill Pain Assessment Question-na i re . Other comparisons involved the height and weight of the subjects and total scores obtained during the PONG game. Some subjects withdrew the i r hands from the COLD PRESSOR before being instructed to do so af ter three minutes of immersion, because they found the pain i n t o l e r a b l e . Between-group com-parisons of the number of subjects showing such lowered pain tolerance were made using Chi Square. A l l other analyses were conducted on the Univers i ty of B r i t i s h Columbia Computer using programs ava i lab le in the 65 Michigan Interact ive Data Analysis System (MIDAS) package (Fox and Guire , 1976). Several major hypotheses of the present study related to d i f ferences in the shapes of psychophysiological s t ressor res-ponse curves. Certain c h a r a c t e r i s t i c s of such data require that considerable caution be exercised with regard to the s t a -t i s t i c a l procedures used in the i r a n a l y s i s . That i s , i t is highly un l ike ly that a ser ies of data points sampled on a psychophysiological response curve are independent of one another because of the la tencies and cont inu i t i es brought about by the arousal and homeostatic mechanisms inherent in physio logica l a c t i v i t y . Because of t h i s , the values of data points close together in time wi l l tend to be more highly corre lated than the values of data points more remote from each other in time. Therefore a covariance matrix of a ser ies of data points taken across psychophysiological response curves wi l l not exhib i t equal values in a l l of f -d iagonal c e l l s . Such a covariance matrix does not exhib i t compound' symmetry and thus s t a t i s t i c a l procedures which re ly on th is assumption, as for example, re-peated-measures analysis of variance (Winer, 1971), should be avoided in analyses of psychophysiological response curve data. P r o f i l e a n a l y s i s , described by Morrison (1976), has no require-ments regarding compound symmetry and i t is thus well suited to the analysis of psychophysiological data such as those of the present study. 66 With p r o f i l e a n a l y s i s , which is ava i lab le in the MIDAS package, the curves of two groups of subjects to be compared are s t a t i s t i c a l l y examined in three independent ways (see H a r r i s , 1975): F i r s t l y , with regard to the para l le l i sm hypothesis, the para l l e l i sm of the two curves is tested with Ho'tel l ing's T 2 and F = ( N ] + N 2 - p ) / • (p - 1) (N ] + N 2 - 2) T 2 , with (p - 1) and (N-j + N 2 - p) degrees of freedom, where p equals the number of data points monitored in each curve and N-| and N 2 equal the number of subjects in the f i r s t and second groups r e s p e c t i v e l y ; Secondly, with regard to the leve ls hypothesis, the separation of the two curves is tested with a univar iate t , comparing the sampled data points of the two groups, with (N-j + N 2 - 2) degrees of freedom (notation as above), and; T h i r d l y , with regard to the f la tness hypothesis, whether or not the two curves d i f f e r s i g n i f i c a n t l y from stra ight l ines is tested with H o t e l l i n g ' s T 2 and F = (N1 + N 2 - p)T 2 / (p - 1) (N-, + N 2 - 2) , with (p - 1) and (N-, + N 2 - p) degrees of freedom (notation as above). As a f i r s t step in test ing the experimental hypothesis concerning indiv idual response stereotypy in LBP pa t ien ts , the magnitudes of a l l psychophysiological responses were adjusted to r e f l e c t p re -s t ressor baseline a c t i v i t y l e v e l s , as suggested by Wilder (1962) in his descr ip t ion of the Law of I n i t i a l Values (LIV). The LIV notes that the magnitude of a phys io log ica l response to st imulat ion is a function of the 67 prestimulus level of physio logica l a c t i v i t y . That i s , the higher the prestimulus level of physio logica l a c t i v i t y the smaller w i l l be the increase of the physio logica l a c t i v i t y resu l t ing from a given st imulus. Following on suggestions made by Sternbach (1966), the psychophysiological response magnitudes in the present study were corrected for the e f fects of the LIV by a covariance procedure (Winer, 1971) ava i lab le in the MIDAS package. The LIV-corrected responses of indiv idual subjects were then converted to both rank and standard score values across the for ty sub jec ts , at each of the experimental s t ressors (TONE, COUNT, PONG, COLD PRESSOR, STAND, FLEX, VALSALVA). Using these two d i f fe ren t types of va lues, ranks and standard scores , two d i f fe ren t tests of the indiv idual response stereotypy hypothesis were undertaken. F i r s t l y , the rank values (across for ty subjects) for each subject for each of the f ive psychophysiological var iables (abdominal oblique EMG or ABEMG, back EMG or BKEMG, HR, SC, RR; VM was omitted because of previously described missing data) were averaged across the seven experimental s t ressors y i e l d i n g an average rank of response for each subject for each psycho-phys io log ica l measure. These averaged ranks of subjects in the LBP and control groups were then compared for each of the f ive psychophysiological var iables by use of Mann-Whitney U t e s t s . 68 Secondly, the standardized response scores were used to construct p r o f i l e s for each indiv idual subject , across the f i ve psychophysiological v a r i a b l e s , at each experimental s t ressor or raanipulation. The p r o f i l e s of the for ty subjects at each experimental manipulation were then examined for opt imal , na tura l ly -occur ing subgroup p r o f i l e s with a h ie rarch ica l group-ing analysis (Ward, 1963) procedure ava i lab le in the MIDAS package. Subgroup memberships,' in terms of LBP or control group o r i g i n , were then establ ished and examined for a predominance of LBP subjects . This method of examining psychophysiological data for the presence of ind iv idual response stereotypy has also been described by Sternbach (1966). 69 RESULTS Survey Population and Subject Sample Charac te r is t ics Three hundred and f i f t een summer school students, mostly teachers from Faculty of Education courses, were asked to complete the screening quest ionnaire . Only two dec l ined , and of the remaining 313 students, 111 indicated the i r wi11ingness to serve as subjects . Of the 313 ind iv idua ls completing the quest ionnaire , 202 or 65% reported having experienced LBP. The reported incidence of LBP in the population surveyed was higher among females, with 71% of the 182 females as compared to 55% of the 131 males p report ing LBP (X = 9.13, df = l ,p<.01). Eighty-seven i n d i -v i d u a l s , or 28% of the surveyed populat ion, reported that they had r e s t r i c t e d the i r a c t i v i t i e s and/or had consulted a physician because of LBP. Of those having had LBP, more females reported symptoms of such greater s e v e r i t y , with 36% of the females as compared to 20% of males having taken such action (X '= 7.08, df = l ,p<.01). Four of the 313 ind iv idua ls surveyed had under-gone low back surgery. The 111 ind iv idua ls volunteering to be subjects comprised 49 men and 62 women of whom 65% and 72%, r e s p e c t i v e l y , reported LBP symptoms and 20% and 42%, r e s p e c t i v e l y , reported a c t i v i t y r e s t r i c t i o n and/or physician contact . These volunteers were t y p i c a l l y in the i r early t h i r t i e s , the men having a mean age of 32.1 years (SD = 7.21), the women a mean age of 30.5 years . 70 (SD = 7.07). The men and women volunteers did not d i f f e r s i g -n i f i c a n t l y in age (t = 0.29, df = 38). The for ty subjects were ten pairs (one subject with a LBP h i s t o r y , another subject without such a h istory) of males and ten pairs of females, the subjects of each pair being age-matched to within four years . Mean ages of the study samples were 31.7 (SD = 4.62) and 30.9 (SD = 5.91) years for males and females r e s p e c t i v e l y , an i n s i g n i f i c a n t age di f ference (t = 0.29, df = 38). While a l l Control subjects reported that they had never experienced LBP, a l l experimental subjects reported experiencing LBP during the past year , on mult iple occasions for 17 of them. The mean duration of the l as t LBP episode was reported to be about 14 days. Seventeen of the subjects had l imi ted the i r non-occupational a c t i v i t i e s because of LBP, though only f ive subjects had missed short periods of time from work (maximum 7 days) because of i t . A l l experimental subjects had consulted a physician because of thei r LBP, with the exception of one subject who worked in a hospital set t ing and f e l t that such an act ion would be' f u t i l e . At some time in the past f ive subjects had seen a s p e c i a l i s t , 12 had had x - r a y s , 10 had taken medica-t i o n s , and nine had received conservative treatment (physio-therapy or ch i roprac t ic ) for LBP. Ef fects of Experimental Stressors Table 1 provides a summary showing the baseline a c t i v i t y 71 TABLE 1. Baseline and Response Values of Each Psychophysiological Variable for Each Experimental Stressor 1. ABEMG BKEMG HR SC RR VM TONE 40.49 46.40 19.53 22.60 76.53 86.05* 6.41 9.39* 7.29 7.64 15.59 11.14* COUNT 41.26 65.46* 18.80 25.27 74.68 103.66* 6.46 12.43* 7.56 8.07 14.67 8.49* PONG 37.23 68.35 21.96 32.00 74.15 92.15* . 6.90 12.05* 7.43 10.95* 14.29 8.79* COLD PRESSOR 28.05 40.20* 21.99 24.38 76.85 88.58* 7.42 9.26* 7.25 7.97 MD STAND 26.26 1-106.23* 16.47 83.22* 71.90 102.95* - 6.59 9.63* 7.49 8.66 MD VALSALV/ 62.44 102.67* 21.10 31 .50 72.18 97.92* 6.42 10.57* MD MD FLEX 52.08 17.23* 27.15 81.20* 86.97 95.24* 7.05 8.70* 7.52 8.04* MD Upper number in each cell indicates pre-stressor baseline value: lower number indicates maximum response value: see text concerning method of choosing these values. * Indicates that the flatness hypothesis of profile analysis across baseline, response, and recovery portions of the psychophysiological response curve was rejected at the p<.05 level. MD = Missing Data 72 value of each psychophysiological var iable pr ior to each of the seven experimental s t r e s s o r s , the maximum response value of each psychophysiological var iable fol lowing the occurrence of each s t r e s s o r , and an ind ica t ion of whether or not a s t a t i s -t i c a l l y s i g n i f i c a n t s t ressor response, or change in psycho-physio logica l a c t i v i t y , occurred in each instance. Appendix F provides more detai led information concerning the number of data sampling points and s t a t i s t i c a l test values with regard to the e f fec ts of each of the seven.experimental s t ressors on each of the six psychophysiological measures. The baseline and response values presented in T a b l e ! are provided with the main purpose of allowing inspect ion of the subject arousal l eve ls in the course of the experiment. These va lues, which r e f l e c t a c t i v i t y during 30-second i n t e r v a l s , are the most extreme values shown in a number of 30-second in terva ls sampled during both the basel ine and response portions of the psycho-physio logica l a c t i v i t y curves. The actual s t a t i s t i c a l tests of the ef fect iveness of each of the experimental s t ressors in e l i c i t i n g s i g n i f i c a n t psychophysiological responses consisted of 42 p r o f i l e analyses which examined departures from l i n e a r i t y of curves plotted across base l ine , d u r i n g - s t r e s s o r , and recovery- to -base l ine data po ints . As reference to Table 1 and Appendix F i n d i c a t e s , the TONE manipulation led to s i g n i f i c a n t increases in HR and SC, as well as s i g n i f i c a n t VM vasocons t r i c t ion . The TONE was not 73 accompanied by s i g n i f i c a n t changes in ABEMG, BKEMG, or RR, though a l l showed mean increases . - The COUNT manipulation produced s i g n i f i c a n t increases in ABEMG, HR and SC, as well as s i g n i f i c a n t VM v a s o c o n s t r i c t i o n . Some mean increases in BKEMG a c t i v i t y and RR resul ted from the COUNT task, but again these changes were not s t a t i s t i c a l l y s i g n i f i c a n t . The PONG manipulation was e f f e c -t ive in e l i c i t i n g s i g n i f i c a n t increases in HR, SC and RR, and a s i g n i f i c a n t degree of VM vasoconst r ic t ion . While the ABEMG and BKEMG measures showed substant ia l mean increases in a c t i v i t y during the PONG game, these increases were-not s i g n i f i c a n t . The COLD PRESSOR manipulation produced s i g n i f i c a n t increases in ABEMG, HR and SC and non-s ign i f i can t increases in BKEMG and RR. The change from a s i t t i n g to a standing pos i t ion ( i . e . , the STAND manipulation) resulted in s i g n i f i c a n t increases in the ABEMG and BKEMG measures, as well as in HR and SC, whereas a s i g n i f i c a n t change in RR did not occur. The VALSALVA mani-pulat ion produced s i g n i f i c a n t increases in ABEMG, HR and SC, whereas the mean increase shown in BKEMG was not s i g n i f i c a n t . Because the VALSALVA manoeuvre involves holding the breath, the RR var iable was not evaluated. The FLEX manipulation pro-duced highly s i g n i f i c a n t increases in BKEMG, HR, SC and RR and a highly s i g n i f i c a n t decrease in ABEMG a c t i v i t y . This l a t t e r decrease may be re lated to biomechanical considerat ions involv ing the "balloon e f fect" discussed prev ious ly , or may have resulted from the abdominal skin and fat bunching up over 74 the underlying muscle in the f lexed p o s i t i o n . Comparison of Male and Female Subjects An i n i t i a l set of analyses, was undertaken to examine the d i f ferences between males and females on the ent i re host of study var iables including demographic, psychometric, psycho-physio logica l -basel ine , and psychophysiological -response char-a c t e r i s t i c s . As would be expected, the males were s i g n i f i c a n t l y t a l l e r (t = 4.53, df = 36, p<.01 ) and heavier (t = 5.37, df = 36, p<.01) than were the females. The sexes did not d i f f e r with regard to the i r descr ipt ions of LBP on the Sensory, A f f e c t i v e , Mot iva t iona l , Miscel laneous, or Number-of-Words-Chosen indices of the McGill Pain Assessment Questionnaire. The males and females also did not d i f f e r psycho-met r ica l ly with regard to the Ext ravers ion , Neuroticism, Psycho-t ic ism or Lie scores of the Eysenck Personal i ty Inventory. The mean scores for both sexes on these personal i ty measures were very s imi la r to the normal population values published by the Eysencks (1972). The Eysenck Personal i ty Inventory scores for subjects from the present study and for the Eysencks' normal population are ava i lab le for inspect ion in Appendix G. As compared to the men, the females of the present study had s i g n i f i c a n t l y higher total scores for the six-minute PONG game (females, I = 90.9; males, X = 71.4; t = 3.34, df = 38, p<.01). A l s o , the females demonstrated a s i g n i f i c a n t l y lower pain tolerance than did the males in that more of them withdrew 75 the i r hands from the ice water before the scheduled three minutes of immersion were over (14 of 20 females withdrew, 4 of 20 males withdrew; X 2 = 10.10, df = 1 , p<C.01 ). The psychophysiological responsiveness di f ferences between male and female subjects were examined by 42 p r o f i l e analyses, performed for each of the psychophysiological v a r i a b l e s , at each of the seven experimental manipulations. Each one of these 42 p r o f i l e analyses provided s t a t i s t i c a l tests of the p a r a l l e l -ism, l eve ls and f la tness hypotheses as described in the Method s e c t i o n . A summary of s ign i f i cance leve ls for the para l le l i sm and leve ls tests from the 42 p r o f i l e analyses comparing males and females is presented in Table 2. In review, s ign i f i cance of the s t a t i s t i c a l test of the leve ls hypothesis indicates that the curves of the two groups are widely separated, while s i g n i -f icance of the s t a t i s t i c a l test of the para l le l i sm hypothesis indicates that convergent or divergent trends ex is t between the curves. If there are s t a t i s t i c a l l y s i g n i f i c a n t convergent or divergent trends between the two curves, the part of the curve where these trends occur can often be determined by visual inspect ion of the plotted curves. forming part of the MIDAS p r o f i l e analysis computer pr in tout . Sample curves from the p r o f i l e analyses w i l l be presented for inspect ion below. Sex d i f ferences in basel ine psychophysiological a c t i v i t y l e v e l s , which were then maintained across the responses ( i . e . , s i g n i f i c a n c e shown by the leve ls hypothesis test with a lack . - 76 ' TABLE 2. Profile Analyses of Group Differences (Males vs. Females) for all Psychophysiological Variables at each Stressor 1. ABEMG BKEMG HR SC RR VM .02* .12 .88 .00* .66 .45 TONE .23 .53 .68 .22 .71 .41 .01 * .21 .54 .00* .17 .73 COUNT .10 .11 .78 .00* .1.4 .35 .03* .25 .62 . .00* .22 .70 PONG .29 .21 .75 .01* .59 .13 COLD .45 .05 .78 .00* .57 PRESSOR MD .22 .06 .37 .14 .84 .27 .32 .62 .00* .16 STAND MD .67 .50 . .66 .00* .21 .31 .24 .41 .00* VALSALVA MD MD .13 .31 .60 .00* .30 .91 .60 .00* .22 FLEX MD .66 .04* .39 .02* .17 Upper numbers in cells are significance levels concerning the levels hypothesis (separation of curves): lower numbers are significance levels concerning the parallelism (of curves) hypothesis. * p<.05 MD = Missing Data 77 of s i g n i f i c a n c e shown by the para l le l i sm hypothesis t e s t ) , were evident in the abdominal muscles (ABEMG) in the ear ly phases of the experimental session (TONE, F = 5.39, df = 1,36, p<.05; COUNT, F = 6.03, df = 1,36, p<.02; PONG, F = 4.85, df = 1,36, p < . 0 5 ) . Examination of the computer-printed response curves, an example of which is reproduced in Figure 7, demonstrated that the females cons is ten t ly showed the greater ABEMG a c t i v i t i e s . In addit ion to t h e . p r o f i l e analyses, three 2 x 2 analyses of variance (male/female versus LBP/control) were car r ied out using the ABEMG maximum response data for the TONE, COUNT and PONG manipulat ions, to determine i f subjects of d i f -ferent sex with and without LBP responded d i f f e r e n t i a l l y to these s t r e s s o r s . The in teract ion terms from the COUNT and PONG analyses of variance did not approach s t a t i s t i c a l s ign i f i cance (p =..32 and p = .53 r e s p e c t i v e l y ) . However, the in teract ion term from the TONE analysis reached s t a t i s t i c a l s ign i f i cance (F = 4.88, df = 1,34, p<.05). Inspection of the means data for the TONE st ressor indicated that the female LBP subjects showed a much greater ABEMG response than did the female control subjects or the males. S i g n i f i c a n t sex d i f ferences also occurred with regard to the SC v a r i a b l e . Wide separations between para l l e l male and female response curves were found in two experimental manipu-la t ions (TONE, F = 12.79, df = 1,38, p<.002; COLD PRESSOR, F = 10.87, df = 1,20, p<.005), with the females showing the higher 78 Baseline During After 30-Second Time Blocks(see text for specifics) FIGURE 7. Profile Analysis Comparing Sexes with Regard to the COUNT ABEMG Response. 79 SC values. In the other f ive experimental manipulations s i g n i -f i can t non-paral1 el isms of the curves were in evidence (COUNT, T 2 = 35.03, F = 5.07, df = 6,33, p<.001; PONG, T 2 =42 .00 , F = 2.81, df = 11,28, p<.02; STAND, T 2 = 25.12, F = 4.49, df = 5,34, p<.005; VALSALVA, T 2 = 25.50, F = 3 . 6 9 , df = 6,33, p< .01; FLEX, T 2 = 14.26, F = 3.28, df = 4,35, p < . 0 5 ) , making the s i g n i f i c a n t leve ls (or separation of curves) tests (COUNT, F = 33.18, df = 1 ,38, p< .0001 ; PONG, F = 28.49,. df = 1,38, p<.0001 ; STAND, F = 18.78, df = 1,38, p<.0002 ; VALSALVA, F = 23.61, df = 1,38, p<.0001; FLEX, F = 22.16, df = 1,38, p<.0001) d i f f i c u l t to in te rpre t . However, inspect ion of the computer-printed response curves, a sample.of which is reproduced in Figure 8, strongly suggests that the women showed higher i n i t i a l SC values and much larger responses than did the men. Three 2 x 2 analyses of variance (males/females versus • LBP/controls) of the maximum SC response data from several of the experimental manipulations showed non-s ign i f i can t in teract ion e f fects (TONE, F = 0.88, df = 1,36; COUNT, F = 0.01, df = 1,36; PONG, F = 0.01, df = 1,36). These analyses suggest that the sex di f ferences in SC a c t i v i t y were unaffected by the LBP or control group memberships of the subjects . The analyses concerning sex d i f ferences also showed one non-paral1 el ism of a BKEMG response curve, in the FLEX mani-pulat ion (T 2 = 11.64, F = 2 . 6 7 , df = 4,34, p<.05), though the sexes did not d i f f e r in overal l a c t i v i t y or separation of the 80 30-Second Time B1ocks(see text for specifics) FIGURE 8. Profile Analysis Comparing Sexes with Regard to the COUNT SC Response. 81 curves (F = 0 . 0 1 , df = 1,37). Inspection of the computer-printed BKEMG response curves for the FLEX manipulation suggests that th is observation resulted from the males giving a much larger response from a lower baseline level as compared to the females. Comparison of LBP and Control Subjects A second set of analyses was undertaken to examine the data for d i f ferences between the LBP and Control groups with regard to a l l demographic, psychometric, psychophysio logica l -base l ine , and psychophysiological -response c h a r a c t e r i s t i c s . The LBP and Control groups did .not d i f f e r to a s t a t i s -t i c a l ly s i gni f i cant degree with regard to any of the non-psychophysiological measures such as height , weight, PONG, or COLD PRESSOR performances, or in descr ipt ions of the LBP experience on the various McGill Pain Assessment Questionnaire measures.. The Control sub jec ts , as mentioned prev ious ly , had been instructed to complete the McGill Pain Assessment Questionnaire in a manner "as i f " they had had LBP. It should be s p e c i f i c a l l y noted, because i t bears on one of central hypotheses of the present' study, that the LBP and Control sub-jec ts were psychometr ical ly s imi la r with regard to neuroticism as measured by the Eysenck Personal i ty Inventory (t = 0.57, df =38 ) . Indeed, both the LBP and Control subjects were psycho-met r ica l ly very s imi la r (with regard to a l l the Eysenck Person-a l i t y Inventory measures) to a normal population surveyed by the Eysencks (1972). The Eysenck normal population psychometric 82 values , as well as mean values for the LBP and Control groups of the present study, are presented in Appendix G. Again, p r o f i l e analyses were performed to compare the LBP and Control groups with regard to the separation and para-l l e l i s m of each of the six psychophysiological response curves at each of the seven experimental s t ressors or manipulat ions, y i e l d i n g a total of 42 such analyses. Table 3 summarizes the s i g n i f i c a n c e values of s t a t i s t i c a l tests of the para l le l i sm and leve ls hypotheses from these^analyses. As can be seen from Table 3, consistent d i f ferences between the LBP and Control groups.emerged:with regard to the BKEMG measure, these di f ferences being in the nature of wide sepa-rat ions between paral 1 el curves. These di f ferences reached s t a t i s t i c a l s ign i f i cance in the cases of the PONG (F = 5.84, df = 1,37, p<.05), STAND (F = 5 . 7 9 , df = 1,36, p<.05) and VAL-SALVA (F = 5.68, df = 1 ,37, p<.05) manipulat ions, and approached s t a t i s t i c a l s ign i f i cance for the TONE (F = 3.29, df = 1,37, p<.08), COUNT (F = 4.02, df = 1,37, p<.06), COLD PRESSOR (F = 2.21, df = 1 ,20, p<. 16), and FLEX (F = 3.29, df = 1,37, p< .08) manipulat ions. Inspection of the computer-printed response curves indicated that in a l l cases these d i f ferences resulted from lower EMG a c t i v i t y leve ls character iz ing the LBP group and higher EMG a c t i v i t y leve ls character iz ing the control group. Two such curves are reproduced in Figures 9 and 10. In addit ion to the p r o f i l e analyses, seven 2 x 2 analyses of variance 83 TABLE 3. Profile Analyses of Group Differences (LBP vs. Control) for all Psychophysiological Variables at each Stressor 1. ABEMG BKEMB HR SC RR VM TONE .99 .07 .72 .48 .50 .34 .60 .48 .78 .11 .46 .36 COUNT .83 .05 .42 .50 .39 .63 .66 .40 .93 .04* .54 .42 PONG .71 .02 * .28 ' .44 .99 .75 .80 .18 .48 .82 .23 .53 COLD PRESSOR .30 .15 .94 .60 .91 MD .44 .74 .38 .58 .62 STAND .46 .74 .02* .41 .30 .66 .37 .80 .59 .93 MD . VALSALVA .48 .59 .02* .53 .47 .51 .36 .37 MD MD FLEX .45 .92 .07 .58 .29 .10 .20 .94 .84 .65 MD Upper numbers in cells are significance levels concerning the levels hypothesis (separation of curves): lower numbers are significance levels concerning the parallelism (of curves) hypothesis. * p<.05 MD = Missing Data Before During After 30-Second Time B1ocks(see text for specifics) FIGURE 9. Profile Analysis Comparing LBP and Control Subjects with Regard to the PONG BKEMG Response. 85-FIGURE 10. P r o f i l e Analysis Comparing LBP and Control Subjects with Regard to the STAND BKEMG Response. 86 (LBP/Control versus male/female) were carr ied out using the maximum BKEMG response data from a l l the experimental manipula-t i o n s . The in terac t ion terms from these seven analyses did not approach s t a t i s t i c a l s i g n i f i c a n c e . This would strongly suggest that , i r respec t ive of the sex of the sub jec ts , the low back muscles of LBP subjects show less a c t i v i t y than do those muscles in Control subjects . One non-para l l e l i sm, of the SC response curves of the COUNT experimental manipulat ion, was also evident in the com-parisons of the LBP and Control subjects . While these curves were not para l l e l (T 2 = 16.62, F = 2.41, df = 6,33, p<.05) the 1evels hypothesis test suggests that the curves overal l were not widely separated (F = 0.45). Inspection of the computer-printed curves does not make the reason for the s i g n i f i c a n t observation obvious - the two curves appear para l l e l and close together. Examination of Individual Response Stereotypy As described in the S t a t i s t i c a l Analysis sect ion of th is paper, analyses test ing the indiv idual response stereotypy hypothesis proceeded by two routes. F i r s t l y , the basel ine-corrected values for the ABEMG, BKEMG, HR, SC and RR psychophy-s i o l o g i c a l response parameters were ranked across the 40 subjects at each of the seven experimental manipulat ions. These data are deta i led in Appendix H ( larger rank values indicate larger responses). The ranks for each of these psychophysiological 87 var iables were then averaged across the experimental mani-pulat ions for each subject , and these averaged ranks were then re-ranked. The averaged-rank ranks are also contained in Appendix H , and graphic representations of these values for the LBP and Control groups are presented in Figures 11 and 12. When the re-ranked' rank values were-examined'with Mann-Whitney U t e s t s , there was no evidence of a tendency for the ABEMG, HR or SC responses of the LBP and Control groups to d i f f e r (Z = 0.41; Z = 0.19; Z = 0.68 r e s p e c t i v e l y ) . The ranks of the BKEMG responses of the LBP group did show a tendency to be smaller than those of the Control group (LBP, mean rank =17 .53; CONTROL, mean rank =22 .35 ) , but th is tendency was not s i g n i f i c a n t by the Mann-Whitney U test (Z = 1.32). The RR measure showed a s t a t i s t i c a l l y s i g n i f i c a n t tendency for the ranks of the responses of LBP subjects to be higher than the ranks of the Control subjects (LBP, mean rank = 25.83; CONTROL, mean rank = 15.18; Mann-Whitney U t e s t , Z = 2.88, p<05) . This suggests that the LBP subjects tended to breathe. faster than the Control subjects a f ter the occurrence of various s t r e s s o r s . Secondly, evidence-of indiv idual . response stereotypy was sought using h ie rarch ica l grouping a n a l y s i s . B a s e l i n e - , covar-iance-adjusted response values for each psychophysiological measure (ABEMG, BKEMG, HR, SC, RR), at each of the seven exper-imental manipulat ions, were standardized across subjects . These standardized scores were then used to construct p r o f i l e s of *~t 1 1 1 1 1 - * ABEMG BKEMG HR SC RR Psychophysiological Variable * 20.5 = mean rank across LBP and Control subjects i FIGURE 11 . Mean Rank Response Curves for the LBP Subjects, across Psychophysiological Variables,.for all Experimental Stressors. 89 24.5 4 22.5 J c CC (13 OJ 20.5M 18.5 16.5 H COLD PRESSOR VALSALVA FLEX COUNT T I 1 1 ABEMG BKEMG HR SC Psychophysiological Variable * 20.5 = mean rank across LBP and Control subjects FIGURE 12. Mean Rank Response Curves for the Control Subjects, across Psychophysiological Variables, for all Experimental Stressors. RR 90 response magnitudes, across the f ive psychophysiological measures, for each subject at each experimental manipulation. The p r o f i l e s of the 40 subjects at each experimental manipulation were then submitted to a h ierarch ica l grouping a n a l y s i s , a total of seven analyses thus being undertaken . (one analysis for TONE, a second analys is for COUNT, and so f o r t h ) . The na tura l l y -occur r ing h ierarch ica l subgroupings, perhaps more than one set for each of the seven experimental manipulat ions, were then examined with regard to subject membership (LBP versus Control subjects) and with regard to whetheror not"the"psychophysiological res-ponse p r o f i l e s were dominated by extreme values of e i ther of the EMG measures. An exampl e'.from these h ierarch ica l grouping analyses is presented in F i g u r e l 3 , wherein the mean psycho-physio logica l response p r o f i l e s of four na tura l l y -occur r ing subgroups of the 40 subjects , at the STAND experimental mani-p u l a t i o n , are presented. Table 4 provides a summary showing the na tura l l y -occur r ing subgroupings of subjects at each of the experimental manipulat ions, the psychophysiological response extreme by which each of the mean response p r o f i l e s within the subgroupings was character ized , and.the overal l number of subjects and the number of LBP subjects contr ibut ing to each p r o f i l e . By way of example, with reference to Table 4 one can determine that , for the STAND a n a l y s i s , there were 11 subjects contr ibut ing to a mean prof i 1 e character!'zed by a very strong abdominal muscle response, f ive of these subjects having a 91 FIGURE 13. Sample of the Hierarchial Grouping Analysis Examination of Individual Response Stereotypy for the STAND Experimental Manipulation (see Table 4). 92 TABLE 4. Hierarchical Grouping Analysis Summary.* STRESSOR NO.OF GROUPS ABEMG BKEMG RR IRS OF OTHER FUNCTIONS HIGH1 LOW HIGH[ LOW HIGH ] LOW TONE 5 I 1 1/2 | 1 • « 1/1 1 8/19 7/13:1/1 COUNT 6 5 2/3 | 2/3 | 1 0/1 | 0/1 | i 1 3/9 1 4/12 1/3:7/10:5/9 7/10:5/9 PONG 6 4 3/4 | i 0/1 1 1 0/1 1 7/12 | 4/11 7/12 | 9/20 2/5:1/1 1/1 COLD PRESSOR 7 3 1/3 j 1/3 1 1 0/1 | 0/2 1 1 1 6/12 3/8 1 7/11:3/6:0/1 13/25 STAND 6 4** 2/5 1 5/111 1/3 j 1/3 j 4/5 14/12 I 4/12 3/5:3/6 7/10 VALSALVA 5 4 2/5 111/21 .11/21 1 0/3 | 0/3 j 2/2 1 2/2 1 3/7 5/12 FLEX •4* 7 4 0/1 1 0/1 • 1 0/1 1 1 1 I 1/3 1 1/4 i8/19 1/7:1/2:7/12:7/11 8/13 Fraction-like numbers in above Table denote the number of LBP subjects by the numerator and the total number of subjects by the denominator in each subgroup. ** See Figure 11 for graphic representation of this subgrouping. 93 history of LBP. It is also th is subgroup of 11 subjects who compose one of the curves plotted in Figure 13. Examination of Table 4.again provides no support for the hypothesis that EMG-dominated indiv idual response stereotypies character ize LBP subjec ts , but that a RR-based stereotypy does. Again, i t appears that LBP subjects tended to breathe faster a f ter the occurrence of s t ressors than did the Control subjects . 94 DISCUSSION The population of summer school students surveyed seems to be quite representat ive of the general population in the inc idence;of reported LBP complaints. The LBP l i t e r a t u r e gen-e r a l l y shows the incidence of LBP to be the same across sexes (Brown, 1977; Frymoyer & Pope, 1978), though some studies have indicated a greater incidence of back complaints in women (Di l lane et a l . , 1966).. The number of ind iv idua ls in the present study report ing l i m i t a t i o n by the i r LBP is perhaps somewhat lower than that suggested by the maxim usual ly c i t e d , "Two-thirds of people have suffered from i t , one- th i rd have been disabled by i t " , but th is may be ' re la ted to-the young age of the sample. The th i rd and fourth decades of l i f e have been i d e n t i f i e d as the times of peak occurrence of LBP (Hult , 1954; Nachemson, 1975), and i t is of course more common to have been disabled by LBP l a t e r in- that per iod . The present study's sample of subjects (teachers) is atypical demographically, because the LBP l i t e r a t u r e usual 1y involves samples of manual workers. However, as noted in the Introduct ion, there is no c lear re-la t ionsh ip between the incidence of LBP and the heaviness of work performed. However, i t is often bel ieved in c l i n i c a l set t ings that equivalent LBP symptoms are more d isab l ing for manual workers than for more sedentary workers (H i rsch , 1966). I n i t i a l phases of analys is revealed,sex di f ferences in he ight , weight, COLD PRESSOR performance, total PONG score , 95 ABEMG a c t i v i t y , and SC. Demonstration of mean height and weight d i f ferences between men and women adds l i t t l e to the s c i e n t i f i c fund of knowledge. S i g n i f i c a n t l y fewer women than men tolerated the three-minute hand-immersion time in the COLD PRESSOR ice water bath, ind ica t ing that the women tended to have a lower pain tolerance than the men. This f inding is consistent with current knowledge, based on recent research and reviews of the l i t e r a t u r e (Notermans & Tophoff, 1975; Woodrow, Friedman, Siegelaub & C o l l e n , 1975). Perhaps the lower pain tolerance shown by women accounts for another observation in the present study; that i s , that the women more frequently r e s t r i c t e d the i r a c t i v i t i e s and/or sought medical at tent ion because of LBP than the men d i d . The total PONG scores were found to be s i g n i f i c a n t l y lower for the men than for the women, ind ica t ing that the men were more p r o f i c i e n t at th is hand-eye coordinat ion game than were the women. Though these video games are becoming quite common, casual observation during the i n i t i a l pract ice sessions l e f t l i t t l e doubt in the experimenter's mind that the women frequently had negative at t i tudes and expectancies about the gadgetry, where-as the men frequently were del ighted at the prospect of playing the game and often acknowledged previous experience with very s imi la r equipment. These at t i tude and pract ice d i f f e rences , though not formally documented, are held to be an adequate explanation for the observed d i f ferences in performance. 96 With regard to psychophysiological parameters, the most consistent d i f ferences between sexes occurred with regard to SC, with the women seemingly showing higher i n i t i a l values and greater responsiveness than the men. While there ex is t widely discrepant reports concerning sex d i f ferences in electrodermal a c t i v i t y , higher tonic SC leve ls have previously been observed in males (Ketterer & Smith, 1977; Kopacz & Smith, 1971). A greater responsiveness from such leve ls of males has also been observed (Kopacz & Smith, 1971), though an even greater v a r i -a b i l i t y in reports ex ists in th is regard along with the i d e n t i -f i c a t i o n of a l l manner of mediating inf luences from var iables such as type of task, level of task s t ressfu lness or d i f f i c u l t y , handedness of subjects , e tc . In the present research, however, there may be another explanation for the observed di f ferences in tonic SC l e v e l s . As described prev ious ly , for ethical reasons a l l male subjects had the i r electrodes attached by the male experimenter while a l l female subjects had theirs attached by a female laboratory a s s i s t a n t . Technique in attaching the SC e lec t rodes , in conjunction with l i k e l y di f ferences between subjects of the two sexes in ava i lab le areas and curvatures of the attachment s i t e s , may have led to measured SC di f ferences by way of systematic electrode contact d i f fe rences . In other analyses, there were no ind icat ions of SC di f ferences related to LBP or Control group membership, or of an in teract ion of sex of the subjects with such group membership. 97 The greater abdominal EMG a c t i v i t y shown by women in the i n i t i a l phases of the research session is more d i f f i c u l t to account for in that such di f ferences have not rout ine ly been shown for EMG measures. Where sex di f ferences in EMG a c t i v i t y have been found, they appeared to be d i r e c t l y re lated to gross strength d i f ferences (Goldste in , 1972). The abdominal oblique muscles are , of course, also an unusual s i te for psychophysio-log ica l monitoring. However, the sex di f ferences in abdominal EMG a c t i v i t y were evident only in the ear ly part of the exper i -mental s e s s i o n , suggesting that there may have been some type of habituation phenomenon operat ing. Perhaps the women sat more s t i f f l y or primly i n i t i a l l y than did the men. In other analyses performed on the ABEMG data, there appeared to be no systematic d i f ferences related to LBP or Control group s ta tus , except for one in teract ion between sex of the subjects and LBP status (LBP females showed higher values than other groups). This in terac t ion occurred in analyses of data re lated to the f i r s t experimental s t ressor and, standing in i s o l a t i o n among other i n s i g n i f i c a n t r e s u l t s , cannot be meaningfully in terpreted . Turning to the comparisons between the LBP and control groups, the f i r s t notable observation is the lack of s i g n i f i c a n t psychometric d i f ferences with regard to the Eysenck Personal i ty Inventory measures. Support of the Sternbach model of psycho-somatic et io logy tested in the present research would have required the LBP group,to show higher neuroticism scores than 98 the control group or the normal populat ion. In f a c t , both study groups were found to have s l i g h t l y lower scores than those reported for a normal population by the' Eysencks (1972). Beyond not supporting the Sternbach model , ' - this .observation of normal neuroticism scores character iz ing a . LBP population is also counter to reports in the l i t e r a t u r e , reviewed in the Intro-duction s e c t i o n , descr ib ing abnormal neuroticism scores in LBP pat ients . The l i t e r a t u r e reviewed, however, usual ly concerned c l i n i c a l populations of ind iv idua ls who were complaining of LBP and a c t i v e l y seeking professional help , often surgery, repeat surgery, or a l ternat ives t o - f a i l e d surgery. It may well be that such c l i n i c a l populations represent a s e l f - s e l e c t e d subclass of people with LBP who continue to seek help , while non-neurotic people with LBP may tend to consult physicians a few times and then to lerate the i r symptoms.. A l t e r n a t i v e l y perhaps, as some have suggested (Caldwell & Chase, 1977; Mersky & Boyd, 1978; Sternbach, 1977), the protracted experience of s i g n i f i c a n t LBP symptoms may give r ise to the neuroticism features seen in c l i n i c a l populat ions. S i m i l a r l y , the absence of group di f ferences with regard to pain tolerance is of in terest in' that observations from former research ( W i l f l i n g , 1973) with a c l i n i c a l population would have led to expectations of such d i f fe rences . Again, however, s e l f -se lec t ion of a c l i n i c a l populat ion, or developing intolerance to pain with protracted experience of i t , may explain the d i s -crepancies between these research f ind ings . 99 Though not bearing on a central hypothesis of the present research , i t is in te res t ing to note the lack of s i g n i f i c a n t d i f ferences in the subject ive descr ipt ions of the LBP experience, as documented by the McGill Pain Assessment-Questionnaire, between ; those who have personal 1y experienced LBP and those who have not. In that LBP is so"very common in the populat ion, i t is possib le that the control subjects of the present study had observed many ind iv idua ls with LBP, had heard the i r des-c r i p t i o n s of the experience, and were thus able to describe LBP accurate ly on the quest ionnaire . The psychophysiological parameters of the present study present the most in teres t ing f i n d i n g s . The tota l absence of group d i f ferences with regard to i n i t i a l baseline and response magnitude and "durat ion-character is t ics- .o f the.HR, SC and VM var iables c e r t a i n l y suggests that general ized psychophysiological d i f ferenees-do not d i f f e ren t ia te ' . ind iv idua l s with a h istory of LBP from normal subjects . Furthermore, the lack of group d i f ferences with regard to the ABEMG a c t i v i t y suggests that general ized skeleta l muscle a c t i v i t y abnormalit ies do not char-acter ize ind iv idua ls with a h is tory of LBP. The central hypothesis of the present research relates to a c t i v i t y of the posterior"1umbar'muscies. On the basis of the Sternbach model , i t was hypothesized that these muscles in LBP subjects would hyper-respond to any s t r e s s , both in greater magnitude and for a longer duration before returning 100 to basel ine values, as compared to these muscles in normal subjects . The p r o f i l e analyses performed on data from the present research, however, provide no support for th is hypo-t h e s i s . To the contrary , the subjects of the LBP group con-s i s t e n t l y showed less baseline EMG a c t i v i t y in the c r i t i c a l anatomical region as compared to normals, with' this i n f e r i o r i t y being maintained af ter s t r e s s , with no gains or losses in mag-nitude or duration of response being shown in comparison to the response curve shapes of the normal control subjects . That i s , the base! ine , response , and recovery por t ions 'o f the curves for the LBP and control groups were para l l e l but widely separ-ated, often to a s t a t i s t i c a l l y s i g n i f i c a n t degree. It is d i f f i c u l t to bel ieve that the observed di f ferences between the LBP and Control groups with regard to BKEMG a c t i v i t y could be due to systematic b iases . The experimenter's subcon-scious desire to support his hypothesis, i f subtly manifested by qua l i ty of skin preparation for electrode attachment, by mot ivat ion- inducing d i f ferences in i n i t i a l i n s t r u c t i o n s , or by any s imi la r procedural d i f f e r e n c e , would have biased the resu l ts in the opposite d i r e c t i o n . Furthermore, the experimental condit ions were standardized by a l l ins t ruct ions and st imul i occurr ing during the experimental session being tape recorded, electrodes being placed by measurement, from body landmarks, a l l . physiograph records being scored by a d is in teres ted tech-n ic ian bl ind to the experimental cond i t ions , and so fo r th . 101 Examination of the hypothesis concerning the presence of a poster ior lumbar muscle indiv idual response stereotypy in LBP subjects led to rather meagre observat ions, as might have been expected by the consistent para l le l i sm seen between the response curves of the two groups in the e a r l i e r p r o f i l e ana l -yses . After adjustment of the response magnitudes for the e f fec ts of basel ine d i f ferences had been made, there was a weak (not s t a t i s t i c a l l y s i g n i f i c a n t ) i n d i c a t i o n , in the analysis of ranked responses, that the LBP subjects in fact•responded less from the i r basel ine leve ls than did the control subjects from t h e i r s . The f indings of a s i g n i f i c a n t tendency for LBP subjects to show greater increases in RR in response to the various experimental manipulations than the Control subjects is both methodological ly and t h e o r e t i c a l l y i n t e r e s t i n g . From the methodological point of view, the lack of s i g n i f i c a n t separa-t ions of the LBP and Control group RR curves, as evidenced in the p r o f i l e analyses, makes the appearance of s i g n i f i c a n t d i f ferences in the indiv idual response stereotypy (IRS) analyses s u r p r i s i n g . However, response data for the IRS analyses were derived by subtract ing the basel ine a c t i v i t y value from the maximal response value and correct ing the response for the LIV, whereas the data for the p r o f i l e analyses consisted of mult iple uncorrected a c t i v i t y values across be fore - , d u r i n g - , and after--the -s t ressor parts of the response curves. From the theoret ica l 102 point of view, the f inding that.LBP subjects tend to breathe faster than Control subjects during environmental events or motor tasks is in teres t ing in l i g h t of the biomechanical "balloon e f fec t" described in the Introduct ion. To the degree that the lumbar spine is unloaded and protected.by an increase in i n t r a -abdominal pressure (the balloon e f f e c t ) , and th is increase is in ter fered with or prohibi ted by breathing, breathing during the occurrence of environmental events or movement could increase the r isk of in jury to the lumbar spine. A second way of.approaching the issue of indiv idual res-ponse stereotypy and i t s importance to the psychosomatic process re lates more c l o s e l y . t o the Sternbach model and addresses i t s e l f to the question of "organ s p e c i f i c i t y " of the psychosomatic process. Other condit ions in the Sternbach model being s a t i s -f i e d , i t would be the most psychophysio logica l ly responsive organ or system of an i n d i v i d u a l ' s body that would sustain damage with repeated a c t i v a t i o n . This would account, for example, for why one person develops ulcers while another develops card io -vascular problems in response to repeated or prolonged s t r e s s . Pathophysiological processes stemming from hypoactive physio-log ica l systems are also well recognized, and i t would thus seem advisable to examine ind iv idual response stereotypy patterns with regard both to the most and the least responsive psycho-physio logica l funct ions . In th is regard, of course, no support was found for e i ther of the poster ior lumbar muscle indiv idual 103 response stereotypy patterns (very high or very low a c t i v i t y ) in the LBP subjects , and the abdominal muscles also did not contr ibute to a LBP indiv idual response stereotypy. However, in the resu l ts of th is analysis there also appeared to be e v i -dence of IRS, with regard to the RR var iab le . That i s , of those subjects that showed the least increase in RR fol lowing st ressors or motor tasks, a d isproport ionate ly low number belonged to the LBP group. As noted above, these RR response di f ferences would in te r fe re with the hydraul ics of the abdominal "balloon e f fec t" and would leave the spine poorly supported and protected against trauma. The hypoact iv i ty of the poster ior lumbar muscles of LBP subjec ts , as .descr ibed above, in a l l 1 ike l ihood contr ibutes further (in addit ion to the e f f e c t s ' o f the decreased "balloon e f fec t" ) to poor s t a b i l i z a t i o n and protect ion of the lumbar spine. By way of a number of well establ ished biomechanical p r i n c i p l e s , hypoact iv i ty of the poster ior muscles would be expected to lead to destruct ive forces acting on the lumbar d i s c s . The resul tant pathophysiological process is probably very much more damaging than the compression-based process i n i t i a l l y hypothesized in this research. B r i e f l y , the spine can be l ikened to a mast, rod, , or beam composed of a stack of poorly joined sect ions"(the vertebrae) which are inherently unstable or free to move in re la t ionsh ip to each other. Linear r i g i d i t y and weight-carrying capacity 104 is achieved in such a mast by guying i t at mult iple l e v e l s , as is done with a t a l l antenna mast. Just as the guy wires of an antenna allow i t to remain erect when i t could not do so of i t s own i n t e g r i t y , so the muscles surrounding the spine guy i t and hold i t e rect . Such a biomechanical model of the spine has long been described (Asmussen & Klausen, 1962; Farfan et a l . , 1 970; Parke & S c h i f f , 1971; White & Panjabi , 1 978). In addit ion to the s t a b i l i z i n g ef fect of this guying, the preload placed on the spine ac tua l ly s t i f f e n s i t (White & Panjabi , 1978) or enhances i t s "beam strength" (Parke & S c h i f f , 1971) and in the process the a r t i c u l a r processes are pushed together, pro-tect ing the spine from excessive rotat ion (Farfan et a l . , 1 970). Just as loosening the guy wires of an antenna mast would allow curvatures to develop in i t s length , u l t imately leading to buckling and to the introduct ion of tors ional and shear forces between the indiv idual s e c t i o n s , so too would one expect s imi lar forces to be exerted on poor!y stabi1 ized spines , such as those which character ized the LBP subjects in the present study. The poor s t a b i l i z a t i o n would resu l t in tors ional and shear forces on the d i s c s , which are much more destruct ive and l i k e l y to produce eventual degeneration of the discs than are the com-pressive forces impl icated in the o r ig ina l hypotheses of th is study (Farfan et a l . , 1970; Troup, 1966). Numerous researchers (see Farfan et a l . , 1970; Frymoyer & Pope, 1978; White & Panjabi , 1978; Wi l tse , 1971), have shown the in terver tebra l disc to 105 be quite res is tan t to compression but to be very eas i l y damaged by tors ion or shear, and Wickstrom (1978) and White & Panjabi (1978) have discussed how tors ional or shear forces can d i r e c t l y cause d isrupt ion and tearing of the long, s t r i n g y , organic molecules comprising the annulus f ibrosus of the d i s c . The probable importance of tors ional and shear forces is also evident on a c l i n i c a l basis in that most acute episodes of LBP treated at Compensation Boards appear to be i n i t i a t e d by t w i s t i n g / l i f t i n g movements (Brown, 1977). The introduct ion of tors ional and shear forces has also been discussed in re la t ion to the poorly s t a b i l i z e d spine (Troup, 1977) or a spine l e f t poorly protected by fat igue (Brown, 1977) or sudden unexpected physical e f fo r t (Magora, 1973). Thus, a ser ies of shearing mini-traumas to the disc may well be responsible for the accumulation of small f i ssures of the annulus f i b r o s u s , f i ssures which lead to i t s gradual weakening, de te r io ra t ion , ' and ultimate d isrupt ion by a minimal " f ina l straw" force (Farfan et al . , 1 970; Ri tchie & Fahrni , 1970; Wickstrom, 1978). Before the ultimate d i s -ruption of the d i s c , leakages of in t rad isca l materials through the smal1 f i ssures resu l t ing from mini-traumas can give r i se to local inflammation and per iods 'o f LBP (Brown, 1971; H i rsch , 1966; Nachemson, 1975; White & Panjabi , 1978). Another manner in which the observations of the present study seem to be important re lates to Farfan's (1975) demon-s t ra t ion that there must ex is t a dynamic mechanical balancing 106 between the abdomen's oblique and f lexor muscles and the pos-t e r i o r muscles of the back. If not, destruct ive shear forces w i l l be exerted on the discs in l i f t i n g and even in the course of maintaining posture. It is pert inent to note that , while the LBP and Control subjects showed equivalent abdominal muscle a c t i v i t y , they d i f fe red with regard to the i r back muscle ac-t i v i t i e s . Of the two groups, i t is most probably the LBP subjects who are unbalanced o r , in the vernacular of the model c i ted e a r l i e r , "have the i r guy wires s lack" . Yet another pathophysiological condit ion involv ing the in terver tebra l d i s c s , a condit ion which may fol low from hypo-act ive poster ior lumbar muscles, relates to nu t r i t ion of the d i s c s . In adult l i f e the discs are not vascu la r i zed , and i t is thought that they acquire the nutr ients to maintain the i r i n t e g r i t y by f l u i d d i f f u s i o n through the vertebral endplates. This f l u i d movement.is promoted by a mechanical pumping action which comes from c y c l i c loading and unloading forces on the d i s c , a decrease in which would, in a l l p r o b a b i l i t y , lead to accelerated degeneration due to nut r i t iona l d e f i c i t s (Nachemson, 1975). Since the LBP subjects of th is study do not appear to be loading the i r d iscs as much as the normal subjects , they may be decreasing th is pumping action and nut r i t iona l process. Possible Origins of . the Observed Psychophysiological Anomalies  of LBP Subjects Stated in the most extreme and s imp l i f i ed ve rs ion , the 107 RR IRS character iz ing LBP subjects would be akin to not holding the breath while l i f t i n g . This would of course subject the spine to overloads and damaging compression, t o r s i o n , and shear fo rces . Not r e s t r i c t i n g the breathing during'the occurrence of environmental s t ressors and l ight .motor tasks would also leave an i n d i v i d u a l ' s spine unprotected against unexpected heavy loads that may well fol low on such st ressors and modest tasks. How the behaviour of breath-holding during 1 i f t i n g is acquired is uncer ta in , but i t may be learned in that overt ins t ruc t ions to do so are commonplace. What is even less cer ta in is how the behaviour o f . r e s t r i c t i n g RR, as an ant ic ipatory biomechan-i c a l l y protect ive response, might be acquired. Why the LBP subjects-of ' . the: present" study should have had hypoactive poster ior lumbar muscles cannot be answered on the basis of the study, but the hypoact iv i ty may simply be one of those physio logica l ind iv idual d i f f e r e n c e s , as is ind iv idual response stereotypy, which is perhaps related to ear ly learning or genetic endowment (Roessler & Engel , 1 974). The f inding may have other explanat ions, however, which could lead to in te r -est ing and productive questions for further research. One p o s s i b i 1 i t y might be that even a-minimal h is tory of LBP, such as that which had been experienced.by the subjects of th is study, may promote learning during symptomatic periods of s u b t l e , pain r e l i e v i n g postural posi t ions associated with poster ior muscle l a x i t y , postures which are then maintained 1 0 8 during asymptomatic per iods. Fordyce (1974) has described how learning of disturbed posture or gait can take place during periods of pain and, because i t is instrumental in reducing or avoiding the pa in , how the learned posture or gait may be maintained long af ter the organic les ion has resolved. Thus, a study of habitual postures of LBP and normal subjects would be most i n t e r e s t i n g . A second p o s s i b i l i t y is that the back muscle hypoact iv i ty observed in the LBP subjects of the present study may have resulted from par t ia l denervation of the poster ior lumbar muscles which are supplied at segmental l eve ls ' by the poster ior primary rami (Mack, 1950). Such par t ia l denervation has been i d e n t i f i e d q in post-surgery LBP patients (Larson, 1975; Mack, 1950) but has been a t t r ibuted to the e f fec ts of surgery. Perhaps, however, the denervated condit ion predates surgery and is of e t i o l o g i c a l s ign i f i cance to LBP. This p o s s i b i l i t y would appear to warrant invest iga t ion by d iagnos t ic , qual i tat ive-EMG examination of a group of subjects with a minimal h istory of LBP, such as the group involved in the present study. Implications of the Present Findings for LBP Therapies and  Further Research The unexpected f inding of an IRS involv ing the RR var iable 9. McCracken, Wi l l iam. Medical D i rec tor , Ontario WCB. Personal d iscussion concerning recent ly completed research, May 1979. 109 has rather d i rec t impl icat ions for the development of LBP, as described prev ious ly . To protect the spine from injury and to unload the discs during physical e f f o r t , i t would obviously be desi rable to teach ind iv idua ls to hold the i r breaths and act ivate the abdominal hydraul ics of the "balloon e f fect" at the appropriate times. The appropriate times would probably include not only times of physical e f f o r t , such as l i f t i n g but also times f o i l owing immediately on environmental s t r e s s o r s , which may signal the subsequent demand for rapid and extreme physical e f fo r t or responses. Many treatment centres, such as the BCWCB C l i n i c , include educational programs concerning back care and l i f t i n g techniques in the overa l l therapy for LBP, but these programs concern themselves mainly with maintaining muscle strength and appro-pr iate postures. It would appear that much could be gained by also attending to breathing habits of the LBP patients in these programs. Perhaps the desired breath-holding could be accom-pl ished in these programs by simple ins t ruc t ions and pract ice for the pa t ien ts , in that RR is e a s i l y contro l led v o l u n t a r i l y . A l t e r n a t i v e l y , even the 've ry 'c rudes t 'o f ' physio!ogical monitoring or biofeedback equipment (i'. e. ; .a - l i q u i d - f i l l e d surgical tube e n c i r c l i n g the chest , connected to a makeshift manometer) could be used to monitor the pat ients ' RR behaviours during various st ressors and motor tasks , thus incorporat ing a biofeedback paradigm into th is t r a i n i n g . 110 Whatever the cause(s) of the low baseline back EMG a c t i v i t y l eve ls shown by the LBP subjects of th is study, they were capable of substant ia l EMG responses. Furthermore, researchers using maximal tests of gross back and abdominal muscle strength have not found s i g n i f i c a n t d i f ferences between LBP patients and normal subjects (Nachemson & Lindh, 1969; Nachemson, 1975). It would thus seem that LBP.subjects probably have normal back muscle capaci ty or strength a v a i l a b l e , but simply.are not using i t . Because i t would in a l l p robab i l i t y be biomechanical1y benef ic ia l to ind iv idua ls with a LBP history to s t a b i l i z e the i r spines more during the everyday a c t i v i t i e s of maintaining posture, moving around, and performing work, an in teres t ing idea presents i t s e l f : It should be possible to increase substant ia l l y the EMG a c t i v i t y 1evel of the poster ior 1umbar muscles, both during rest and.with a c t i v i t y , in these ind iv idua ls by using a neuro-muscular re-education biofeedback technique ( I n g l i s , Campbell & Donald, 1976). What prophylact ic value such biofeedback t ra in ing in the e a r l i e s t stages of a LBP history would have for prevention of further LBP would ce r ta in ly be an in te res t ing topic for study. However, in l i g h t of the f indings and b io-mechanical analyses presented in th is paper, there cer ta in ly should be.considerable caution exercised in applying a poorly-reasoned LBP treatment cons is t ing of biofeedback reduction of poster ior lumbar muscle a c t i v i t y . Such treatment is being undertaken by several ind iv idua ls l o c a l l y and has been reported I l l by others elsewhere (Krav i t z , Moore, Glaros & Stauf fe r , 1978; Malpe & Yue, 1979). Indeed, prel iminary c l i n i c a l research along these l ines (Douglas, Crocket t , W i l f l i n g , Craig & Wing, 1979) included a LBP patient whose symptoms increased with lumbar muscle EMG reduct ion. This observat ion, which is consistent with the f indings and biomechanical analyses of the present study, is discrepant with the reports of K r a v i t z , et a l . (1978) and Malpe and Yue (1979), who reported LBP r e l i e f as the resu l t of an EMG biofeedback reduction procedure. Steger Cl979) has reported that , in his c l i n i c a l experience, very few LBP patients exhib i t abnormally high EMG values of the poster ior back muscles, but those that do respond well to an EMG biofeedback reduction procedure. Steger did not comment on whether or not he has observed unusually low poster ior back muscle EMG a c t i v i t y in any of his pat ients . Perhaps the somewhat summary and universal c l i n i c a l observat ion, "Some get Bet ter , Some get Worse", of psychologists at the Ontario WCB 1 0 who have also used EMG b io -feedback to reduce poster ior muscle a c t i v i t i e s in LBP pat ients , most accurately r e f l e c t s the current status of knowledge with regard to such treatment. Perhaps, as also seems un iversa l ly t rue , there is more than one possible mechanism accounting for any one presenting symptom and, in f a c t , perhaps both increased and decreased 10. Doxey, N. 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The pain can be of different types, such as feelings of tightness or cramping, dull aches, sharp, searing or cutting, etc. The answers to this questionnaire, as all research data, are strictly confidential. Age Sex Occupation Have you f i l led out this questionnaire before? Have you ever had low back pain? How many times have you had low back pain in the past year? When did you last have low back pain, and how long did i t last? ' Have you ever had to limit your non-work activities because of low back pain? During the past year? What extent of restriction? Have you ever missed work because of low back pain? During the past year? (how many days) Have you ever seen a Doctor because of low back pain? During the past year? (How often) Have you ever seen a specialist about low back pain? Have you ever taken medication for low back pain? What kind?_ Have you ever had x-rays of your low back? Have you ever had physiotherapy or chiropractic treatment for low back pain? Have you ever had a back operation? Are you presently receiving treatment for low back pain? Have you ever seriously injured your low back? How?_ What sort of things make you get low back pain? Do you think that muscle tension is involved in your low back pain? How? •  If you would like to be a subject in this low back pain research - - - people without back pain are also needed for study — then please f i l l in the in-formation blanks below. This is not a final consent to be a subject - be-fore giving that, I'll tell you everything about the study and answer any questions. Name (Please print): Summer address: Telephone or way to contact: APPENDIX B Subject Consent Form 1 3 0 Basic Rights and Privileges of Volunteer Subjects\ Any person who volunteers to participate in experiments conducted by fu l l or part-time members of the faculty of the Department of Psychology at the University of Br i t ish Columbia, by their employees, or by the graduate and undergraduate students working under the direction of faculty members of the above-named Department, is entit led to the following rights and privi leges. 1. The subject may terminate and withdraw from the experiment at any time without being accountable for the reasons for such an action. 2. The subject shall be informed, prior to the beginning of an experiment, of the maximum length of time the experiment might take and of the general nature of the experiment. 3. The subject shall be informed, prior to the beginning of an experiment, of the nature and function of any mechanical and e lectr ic equipment which is to be used in the experiment. In cases where the subject is in direct contact with such equipment, he shall be informed of the safety measures de-signed to protect him from physical injury, regardless of how sl ight the possib i l i ty of such injury i s . 4. The subject shall be informed prior to the beginning of an experiment, of the aspects of his behavior that are to be observed and recorded and how this is to be done. 5. Any behavioral record that is obtained during the course of the experiment is confidential . Any behavioral records that are made public through either journal papers or books, public addresses, research col loquia, or classroom presenta-tions for teaching purposes, shall be anonymous. 6. The subject shall be offered, at the end of an experiment, a complete explanation of the purpose of the experiment, either oral ly by the experimenter or, at the option of the experimenter, in writ ing. The subject shall also have the opportunity to ask questions pertaining to the experiment and shall be ent i t led to have these questions answered. 7. The subject has the right to inform the Chairman of the Departmental Committee on Research with Human Subjects of any perceived violations of, or questions about, the afore-mentioned rights and privi leges. TITLE OF STUDY: DATE: I have read the above statement of my rights as a volunteer subject, understand the conditions of this experiment and am participating volun-ta r i l y . SIGNED: APPENDIX C Laboratory Interview Form LABORATORY INTERVIEW FORM S# Sex Handedness Date Time Any diagnosed LB path? Description of LBP Any medications 24 hrs. Unusual activity 24 hrs. History of major med. probs. Current med. probs. Periodicity, day APPENDIX D Eysenck Personality Inventory 134 PERSONALITY INVENTORY Occupation INSTRUCTIONS Please answer each question by putting a circle around the "YES" or the "NO" following the question. There are no right or wrong answers, and no trick questions. Work quickly and do not think too long about the exact meaning of the question. REMEMBER TO ANSWER EACH QUESTION 1. Does your mood often go up and down? YES NO 2. Are you a talkative person? YES NO 3. Have you ever taken the credit for something you knew some-one else had really done? YES NO 4. Do most things taste the same to you? YES NO 5. Do you ever feel 'just miserable' for no good reason? YES NO 6. Can you usually let yourself go and enjoy yourself a lot at a fun party? YES NO 7. Were you ever greedy by helping yourself to more than your share of anything? YES NO 8. Would it upset you a lot to see a child or an animal suffer? YES NO 9. Do you often worry about things you should not have done or said? YES NO 10. Do you have many different hobbies? YES NO 11. If you say you will do something do you always keep your promise no matter how inconvenient it might be? YES NO 12. Do you think that marriage is old-fashioned and should be done away with? YES NO 13. Are your feelings rather easily hurt? YES NO 14. Do you like going out a lot? YES NO 15. Have you ever blamed anyone for doing something you knew was really your fault? YES NO 16. Do you love your mother? YES NO 17. Are you an irritable person? YES NO 18. Do you have many friends? YES NO 19. Are a j _ your habits good and desirable ones? YES NO 20. Do you enjoy hurting people you love? YES NO •135 2 21. Are you often troubled about feelings of guilt? YES NO 22. Do you hate being in a crowd who play harmless jokes on one another? YES NO 23. Have you ever taken anything (even a pin or a button) that belonged to someone else? YES NO 24. Can you easily understand the way people feel when they tell you their troubles? YES NO 25. Would you call yourself tense or highly strung? YES NO 26. Are you rather lively? YES NO 27. Do you sometimes talk about things you know nothing about?.. YES NO 28. Would you like to think that other people are afaid of you?. YES NO 29. Do you worry about awful things that might happen? YES NO 30. Can you easily get some life into a rather dull party? YES NO 31. Do you always say you are sorry when you have been rude? . . . YES NO 32. Would you take drugs which may have strange or dangerous effects? YES NO 33. Would you call yourself a nervous person? YES NO 34. Do you prefer reading to meeting people? YES NO 35. Have you ever broken or lost something which belonged to someone else? YES NO 36. Do you enjoy practical jokes which sometimes hurt people? . . YES NO 37. Do you worry about your health? YES NO 38. Are you mostly quiet when you are with other people? YES NO 39. Do you sometimes boast a l i t t le? — YES NO 40. Is your mother a good person? YES NO 41. Do you suffer from sleeplessness? YES NO 42. Do you 1 iike having long chats on the telephone? YES NO 43. Have you ever said anything nasty or bad about anyone? YES NO 44. Have you always been known as a loner? YES NO 45. Do you sometimes sulk? YES NO 46. Would you rather plan things than do things? YES NO 47. As a child were you ever cheeky to your parents? YES NO 48. Do your friendships break up easily without it being your fault? YES NO 49. Do you often feel l i fe is very dull? YES NO 50. Do you often take on more activities than you have time for? YES NO 136 3 51. Do you always wash before a meal? YES NO 52. Would you feel very sorry for an animal caught in a trap? . . YES NO 53. Have you often felt l istless or tired for no good reason? . . YES NO 54. Do you like telling jokes and telling funny stories to your friends? YES NO 55. Have you ever cheated at a game? YES NO 56. Are you always specially careful with other people's things? YES NO 57. Do you often feel fed up? YES NO 58. Do you like mixing with people? YES NO 59. Have you ever taken advantage of someone? YES NO 60. When you are in a crowd, do you worry about catching germs?. YES NO 61. Are you touchy about some things? YES NO 62. Do you nearly always have a 'ready answer' when people talk to you? YES NO 63. Are you always polite even to unpleasant people? YES NO 64. Do you try not to be rude to people? YES NO 65. Are you sometimes bubbling over with energy and sometimes very sluggish? YES NO 66. Would you call yourself happy-go-lucky? YES NO 67. Have you ever insisted on having your own way? YES NO 68. Do you sometimes get cross? YES NO 69. Do you worry too long after an embarrassing experience? YES NO J 70. Do you mind selling things or asking people for money for '••'[ some good cause? YES NO 71. Would you dodge paying taxes i f you were sure you would never be found? YES NO 72. Have you ever told a lie? YES NO 73. Do you suffer from 'nerves'? YES NO 74. Do you prefer to have few but special friends? YES NO 75. Have you ever deliberately said something to hurt someone's feelings? YES NO 76. Do good manners and cleanliness matter much to you? YES NO 77. Are you easily hurt when people find fault with you or the work you do? YES NO 78. Do you often do things on the spur of the moment? YES NO 79. Do you always practice what you preach? YES NO 80. Did you mind f i l l ing in this questionnaire? YES NO 137 APPENDIX E McGill Pain Assessment Questionnaire PAIN QUESTIONNAIRE 138 Patient's name Age F i l e No. Date C l i n i c a l category (e.g., cardiac, neurological, e t c . ) : Diagnosis: Analgesic ( i f already administered) 1. Type 2. Dosage 3. Time given i n r e l a t i o n to t h i s test Patient's i n t e l l i g e n c e : C i r c l e number that represents best estimate 1 (low) 2 3 4 5 (high) ********************** This questionnaire has been designed to t e l l us more about your pain.' Four major questions we ask are: 1. Where i s your pain? 2. What does i t f e e l l i k e ? 3. How does i t change with time? 4. How strong i s i t ? It i s important that you t e l l us how your pain f e e l s now. Please follow the in s t r u c t i o n s at the beginning of each part. © R. Melzack, Oct. 1970 Where i s your Pain? 139 Please mark, on the drawings below, the areas where you f e e l pain. Put E i f external, or I i f i n t e r n a l , near the areas which you mark. Put EI i f both external and i n t e r n a l . ALSO: If you have one or more areas which can tr i g g e r your pain when pressure i s applied to them, mark each with an X. Comments: Part 2. What Does Your Pain Feel Like? 140 Some of the words below describe your present pain. C i r c l e ONLY those words that best describe i t . Leave out any category that i s not s u i t a b l e . Use only a sing l e word'in each appropriate category — the one that applies best. 1 2 3 4 . F l i c k e r i n g Quivering Pulsing Throbbing Beating Pounding Jumping Flashing Shooting P r i c k i n g Boring D r i l l i n g Stabbing Lancinating Sharp Cutting Lacerating Pinching Pressing Gnawing Cramping Crushing Tugging P u l l i n g Wrenching Hot Burning Scalding Searing T i n g l i n g Itchy Smarting Stinging 10 11 12 D u l l Sore Hurting Aching Heavy Tender Taut Rasping S p l i t t i n g T i r i n g Exhausting Sickening Suffocating 13 14 15 16 F e a r f u l F r i g h t f u l T e r r i f y i n g Punishing G r u e l l i n g Cruel Vicious K i l l i n g Wretched Blinding Annoying Troublesome Miserable Intense Unbearable 17 18 19 20 Spreading Radiating Penetrating P i e r c i n g Tight Numb Drawing Squeezing Tearing Cool Cold Freezing Nagging Nauseating Agonizing Dreadful Torturing 141 Part 3. How Does Your Pairi Change With Time? 1. Which word or words would you use to describe the pattern of your pain? Continuous Rhythmic Brief Steady Periodic Momentary Constant Intermittent Transient 2. What kind of things relieve your pain? 3. What kinds of things increase your pain? Part 4. How Strong Is Your Pain? People agree that the following 5 words represent pain of increasing intensity. They are: 1 2 3 4 5 Mild Discomforting Distressing Horrible Excruciating 1. Which word describes your pain right now? 2. Which word describes i t at i t s worse? 3. Which word describes i t when i t is least? 4. Which word describes the worst toothache you ever had? 5. Which word describes the worst headache you ever had? 6. Which word describes the worst stomach-ache you ever had? Appendix F Psychophysiological Baselines and Stressor Effects Data Physiological Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG .2 0 4 8.00 1.42 5,32 .243 BKEMG 2 0 4 7.90 1.41 . • 5,33 .246 HR 2 0 4 158.17 28.21 5,33 .000 SC 2 0 4 63.76 11.41 5,34 .000 RR 2 0 4 5.71 1.02 5,34 .421 VM 2 0 4 39.88 6.84 5,24 .000 * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. i—> GO TONE DATA Physiological Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F.Stat. df. Sign, ABEMG 2 1 4 37.87 5.44 6,31 ,001 BKEMG .2 1 4 12.79 1.84 6,32 • .122 HP, 2 1 .4 355.93 50.85 6,30 .000 SC 2 1 4 156.48 22.65 6,33 .000 , RR 2 1 4 11.77 1.70 6,33 .151 VM 2 1 4 44.62 6.01 6,21 .000 * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. COUNT DATA Physiological Variable Data Points Before Stressor* Data Points During . Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG 2 6 4 25.72 1.69 11,26 .132 BKEMG 2 6 4 24.77 1.64 • .11,27 .143 HR 2 6 4 283.89 18.97 11,26 .000 SC 2 6 4 163.34 10.94 11,28' .000 ,-RR 2 6 4 205.85 13.78 11,28 .000 VM 2 6 4 109.40 5.97 11,15 .001 * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. i—• cn POm DATA Physiological Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG 2 3 3 51.11 5.11 7,14 .005 BKEMG 2 3 3 10.42 1.04 7,14 .446 HR 2 3 3 92.22 9.01 7,13 .000 SC 2 3 3 47.65 4.76. 7,14 . .006 RR 2 3 3 23.36 2.34 7,14 .084 VM MD MD MD MD MD MD i MD * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. i—* COLD PRESSOR DATA Physiological Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG 2 0 4 88.49 15.78 5,33 .000 BKEMG 2 0 4 51.98 9.24 " 5,32 .000 HR 2 0 . 4 778.79 138.45 5,32 .000 SC 2 0 4 65.59 11.74 5,34 .000 . RR 2 0 4 14.22 2.54 5,34 .056 VM MD MD MD MD MD ' MD MD * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. STAND DATA Physiologica' Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG L. 1 4 72.28 10.46 6,33 .000 BKEMG - 2 1 4 12.11 1.75 6,32 .143 HR 2 1 4 387.88 55.67 6,31 .000 SC 2 1 4 100.32 14.52 6,33 .000 ;. RR MD MD MD MD MD MD MD VM MD MD MD MD MD ' MD MD * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. VALSALVA DATA Physiological Variable Data Points Before Stressor* Data Points During Stressor* Data Points After Stressor* T-Square F Stat. df. Sign. ABEMG 2 1 2 30.20 6.95 4,35 .000 BKEMG 2 1 2 22.55 5.18 • 4,34 .002 HR 2 1 2 253.53 58.10 4,33 .000 SC 2 1 2 75.94 17.49 4,35- .000 RR 2 1 2 19.25 4.42 4,34 .006 VM MD MD MD MD MD ' MD MD * All data scored in 30-second intervals unless otherwise noted. MD = Missing Data. FLEX DATA APPENDIX G Eysenck Personality Inventory Data. Normative Values and Mean Values for Groups of Subjects in the Present Study. Eysenck Personal ity Inventory Scales Data Source Group Extraversion Neuroticism Psychoticism Lie Eysenck Population 12.55 10.95 2.16 .7.29 Normal Males 12.67 9.59 2.74 6.74 Population Females 12.43 12.31 1.57 7.84 Subjects Males 11.60 9.95 1.20 5.80 of the Females 12.35 8.60 1.20 7.60 Present LBP 12.55. 8.85 1.35 6.00 Study Non-LBP 11.40 9.70 1.05 7.40 152 APPENDIX H Individual Response Stereotypy Rank Data LBP SUBJECTS CONTROL SUBJECTS SUBJ NO. • TONE COUNT PONG COLD PRESS. STAND VALS. FLEX MEAN RANK SUBJ. NO. TONE COUNT PONG COLD PRESS. STAND VALS. FLEX- MEAN RANK 1 22 17 33 36 11 35 16 29 5 23 27 15 35 22 9 15 24 2 39 24 31 2 17 25 5 23 7 24 13 26 28 8 33 28 27 3 25 20 13 9 15 14 24 10 8 7 18 25 26 14 32 18 21 . 4 27 16 10 16 20 34 19 22 9 32 - - 38 39 2 38 39 6 26 32 36 18 25 22 30 36 10 31 26 34 29 28 37 3 35 13 5 35 21 10 26 28 7 17 11 18 37 14 19 35 23 36 31 16 - - - - - 10 26 - 12 12 6 5 11 . 10 27 11 3 17 9 23 35 . 37 32 31 39 38 14 35 3 11 . 1 1 29 8 4 18 36 36 3 21 16 20 31 28 15 33 30 30 32 13 15 33 34 19 20 19 19 6 30 ' 17 13 13 20 21 12 28 14 7 39 12 18 21 3 2 2 . 7 6 4 9 1 22 14 7 16 5 23 , 40 25 16 25 6 21 22 15 12 16 22 9 23 29 29 23 22 18 26 6 25 . 26 34 25 29 20 4 21 1 19 24 15 10 12 24 2 12 32 7 29 19 22 9 27 31 8 21 20 27 10 9 27 31 24 30 40 30 31 8 5 32 30 37 6 4 12 28 '. 4 8 4 17 3 18 23 2 33 11 14 24 25 19 13 20 . 14 ' 30 16 15 7- 12 29 36 14 15 35 28 11 8 8 9 11 34 8 32 13 4 6 3 .33 19 17 5.5 38 17 34 38 33 21 24 35 37 34 30 28 18 39 38 3 29 . 32.5 39 37 38 17 23 34 7 2 26 36 - 2 1 37 34 36 1 10 11 40 38 31 1 13 27 38 37 32.5 37 1 33 20 4 5 5 27 5.5 - = Missing Data ABEMG RANKED RESPONSE DATA. LBP SUBJECTS S U B J . TONE COUNT PONG COLD STAND V A L S . FLEX MEAN NOo PRESS, RANK 1 26 15.5 11 32 23 10 27 22 2 38 27 22 5 9 35 7 21 3 21 15.5 •9 31 18 15 9 11 . 4 32 30 26 28 15 8 29 28 6 21 15.5 3.5 19.5 5 9 4 5.E 13 33 32 24 35 19 12 30 31. 16 3 7 14 7 6 23 3 2 17 14 26 35 30 29 26 34 . 33.E 18 13 29 17 24 7 13 6 9 19 21 15.5 3.5 19.5 3 ' 4.5 1.5 4 21 21 15.5 7 22 14 32 26 18 25 17 10 29 13 35 2 25 15 26 10 28 16 9 22 3 38 ' 13 29 31 37 33 38 26 14 23 37 31 37 9 27 23 38 36 36 38 33 4 3 15 8 2 29 22 . 7 35 21 15.5 8 25 24 21 28 20 38 - - - - - - - -39 6 4 10 4 ' 10 20 35 8 40 5 24 20 6 17 34 11 10 - = Missing Data CONTROL SUBJECTS S U B J . NO. TONE COUNT PONG COLD PRESS. STAND V A L S . FLEX MEAN RANK 5 7.5 39 • 37 36 4 4.5 1.5 14 7 12 8 1 17 34 38 24 16 8 21 15.5 3.5 19.5 28 27 33 24 9 30 25 30 29 12 6 20 26 10 36 35 39 3 39 30 12 33.5 11 . 35 31 28 14 33 7 18 27 12 9 6 38 33 30 1 32 25 14 29 11 13 16 27 25 15 17 15 7.5 5 6 10 20 19 10 5.5 20 28 34 32 34 31 17 16 32 22 16 21 32 -15 36 • 37 39 35 23 11 36 21 12 25 24 17 23 24 21 15.5 3.5 19.5 37 31 14 19 27 34 20 25 27 21 39 31 36 28 15 38 36 37 8 28 21 30 30 17 22 12 26 32 18 37 29 32 39 33 34 39 . 11 33 19 39 34 25 23 23 11 13 16 8. 12 36 - 2 2 19 1 1 11 13 1 37 1 1 18 2 16 22 5 3 BKEMG RANKED RESPONSE DATA. LBP SUBJECTS CONTROL SUBJECTS SUBJ • TONE COUNT PONG COLD STAND VALS. FLEX MEAN SUBJ. TONE COUNT PONG COLD STAND VALS. FLEX MEAN NOo PRESS. RANK NO. PRESS. RANK 1 12 30 24 9.5 10 12 11 5 13.5 12 35 1 4 - 13 5 2 28 13 7 20 27 - 22 24 7 4.5 21 15 38 5 - 37 19 3 6 22 14 23.5 37 - 9 15.5 8 24 10.5 32 33.5 7.5 - 4 15.5 . 4 19 26 38 14.5 12.5 18.5 25. 9 27 29 6 37 3 7,5 14 6 13.5 14 19 9.5 25 _ 34 17 10 2 2 27 28 28 - 16 12 13 11 39 39 36 15 - 32 34 . 11 . 33 38 26 14.5 16 14 30 16 29.5 32 4.5 40 26 - 28 33 12 4.5 5.5 12 7 17 - 38 7.5 17 25 27 23 30 31.5 - 39 36.5 14 21 1 10 21 20 - 20 9.5 18 17 23 33 11 34 - 6 21 15 26 31 36 25.5 12.5 18.5 32 19 20 35 17 3 31.5 _ 31 28 20 39 24 22 12 18 - , 10 22' 21 36 40 25 16 6 - 21 .31 22 16 37 30 25.5 19 ' - 11 29 25 29.5 . 33 8 22 1 - 15 13 23 1 4 9 17 9 - 5 1 26 32 25 29 27 39 - 23 35 24 35 17.5 21 29 38 - 35 36.5 29 37 15 13 39 11 - 3 18 27 23 8 3 3 2 - 7.5 2 31 9 10.5 1 ,23.5 40 - - 7.5 28 10 7 2 19 30 - 2 3 33 22 5.5 18 32 21 - 29 23 30 7 0 20 8 14 - 22 6 35 40 16 37 33.5 35 - 25 40 32 34 28 16 35 • 7.5 - 1 20 38 15 34 40 31 33 - 30 39 34 8 3 4.5 6 23 - 26 . 4 39 38 36 34 18 24 - 27 38 36 - 3 20 11 13 22 - 24 . 9.5 40 18 17.5 31 5 29 36 27 37 31 19 28 3 36 - 17 26 - = Missing Data RR RANKED RESPONSE DATA. 

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