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Control of subtalar motion with the use of ski-boot footbeds Greenberg, Susan B 1990

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CONTROL OF SUBTALAR MOTION WITH THE USE OF SKI-BOOT FOOTBEDS By SUSAN B. GREENBERG B.A., York U n i v e r s i t y , 1986 THESIS SUBMITTED IN PARTIAL FULFILLMENT THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION i n THE FACULTY OF GRADUATE STUDIES (School of P h y s i c a l Education) We accept t h i s t h e s i s as conforming to the req u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA JUNE, 1990 ^ Susan B. Greenberg In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of P H V S J C A l E > > O C A T / ^ The University of British Columbia Vancouver, Canada Date DE-6 (2/88) ABSTRACT Research shows that up to 80% of r e c r e a t i o n a l s k i e r s have lower limb alignments which can impede t h e i r a b i l i t y to t u r n t h e i r s k i s p r o p e r l y (Subotnick,1982). The most d i f f i c u l t of these alignment problems to c o n t r o l w i t h i n a ski-boot i s the varus alignment of the s u b t a l a r j o i n t (Macintyre and Matheson, 1988). The use of custom molded footbeds made s p e c i f i c a l l y f o r use i n s i d e of s k i boots has been suggested as one method of compensating f o r a varus a l i g n e d f o o t . This study compared the e f f e c t i v e n e s s of one brand of custom molded s k i boot footbed with that of a non-custom i n s o l e i n c o n t r o l l i n g the motions of the lower limb a s s o c i a t e d w i t h s u b t a l a r varus. S p e c i f i c a l l y these motions were those of the r e a r f o o t and the n a v i c u l a r t u b e r c l e , along w i t h the alignment of the t i b i a l t u b e r o s i t y w i t h respect to the m i d - l i n e of the s k i boot. In a d d i t i o n , subjects were given the opportunity to assess t h e i r s u b j e c t i v e f e e l i n g s of edge c o n t r o l , pain, and f a t i g u e while s k i i n g w i t h both the custom molded footbeds and non-custom i n s o l e s . The subject group f o r t h i s study c o n s i s t e d of 13 advanced l e v e l adult s k i e r s who demonstrated more than three degrees of s u b t a l a r varus when non-weight bearing. Each subject r e c e i v e d a p a i r of custom molded s k i boot footbeds at the beginning of the study. Sk i boots that had been cut away at the rear and the medial s i d e were used i n the l a b o r a t o r y i n order t o observe the motions of the n a v i c u l a r t u b e r c l e and the r e a r f o o t as i i t h e s u b j e c t t r a n s f e r r e d t h e i r weight i n a s i m u l a t e d s k i i n g m o t i o n . The r i g h t and l e f t n a v i c u l a r t u b e r c l e , t i b i a l t u b e r c l e , and t h e i n s e r t i o n o f t h e A c h i l l e s a t t h e c a l c a n e u s o f each s u b j e c t were l o c a t e d by p a l p a t i o n and marked. A f t e r s u f f i c i e n t p r a c t i c e o f t h e weight t r a n s f e r m o t i o n , two t r i a l s o f each landmark were photographed u s i n g 35mm s l i d e f i l m . The s u b j e c t s were f i r s t photographed w h i l e u s i n g t h e non-custom i n s o l e s and a g a i n u s i n g t h e custom molded f o o t b e d s . The s l i d e s were d i g i t i z e d and comparisons were made between t h e two t y p e s o f i n s o l e s f o r b o t h t h e s t a r t and end l o c a t i o n s o f t h e landmarks as w e l l as f o r t h e ranges o f motion t h r o u g h which t h e landmarks t r a v e l e d . S t a t i s t i c a l a n a l y s e s o f t h e group r e s u l t s i n d i c a t e d t h a t t h e r e was s i g n i f i c a n t l y l e s s (p= 0 . 0 0 0 ) n a v i c u l a r m otion d u r i n g t h e s h i f t from t h e s t a r t t o t h e end p o s i t i o n s w i t h t h e use o f t h e custom molded f o o t b e d s as compared t o t h e non-custom i n s o l e s . The r e a r f o o t a n g l e was s i g n i f i c a n t l y l e s s a t b o t h t h e s t a r t (p= 0 . 0 0 0 ) and end (p= 0 . 0 0 0 ) p o s i t i o n s w i t h t h e use o f t h e custom f o o t b e d s as compared t o t h e non-custom i n s o l e s . There was no s t a t i s t i c a l d i f f e r e n c e between t h e amount o f r e a r f o o t motion a l l o w e d by e i t h e r t y p e o f i n s o l e . The t i b i a l t u b e r c l e was p o s i t i o n e d s i g n i f i c a n t l y (p= 0 . 0 0 0 ) c l o s e r t o t h e m i d - l i n e o f t h e s k i boot when u s i n g t h e custom f o o t b e d s t h a n w i t h t h e use o f t h e non-custom i n s o l e s . These r e s u l t s i n d i c a t e t h a t t h e custom f o o t b e d s do i i i m a i n t a i n t h e s u b t a l a r j o i n t i n a more n e u t r a l p o s i t i o n t h a n do non-custom i n s o l e s . D u r i n g t h e s k i i n g s e c t i o n o f t h e s t u d y t h e s u b j e c t s r a t e d t h e custom f o o t b e d s as p r o v i d i n g b e t t e r edge c o n t r o l (p=0.000) and r e s u l t i n g i n l e s s f a t i g u e (p=0.000) t h a n non-custom i n s o l e s . There was no s t a t i s t i c a l s i g n i f i c a n c e when comparing t h e r a t i n g s g i v e n by t h e group f o r t h e l e v e l o f p a i n e x p e r i e n c e d w i t h t h e use o f e i t h e r t y p e o f i n s o l e . There was 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 improvement (p=0.000) i n r a c e t i m e s f o r t h e group when u s i n g t h e custom f o o t b e d s as compared t o t h e non-custom i n s o l e s . The r e s u l t s o f t h i s s tudy i n d i c a t e t h a t custom molded s k i boot f o o t b e d s are a b l e t o c o n t r o l s u b t a l a r m o t i o n more e f f e c t i v e l y t h a n a non-custom i n s o l e . I t appears t h a t t h i s c o n t r o l o f s u b t a l a r motion enhances the s k i i n g e x p e r i e n c e by i n c r e a s i n g edge c o n t r o l and r e d u c i n g t h e amount o f f a t i g u e e x p e r i e n c e d . i v TABLE OF CONTENTS ABSTRACT i i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS i x 1. INTRODUCTION 1 Statement of the Problem 2 Hypotheses 3 S i g n i f i c a n c e of the Study 4 D e f i n i t i o n of Terms 4 D e l i m i t a t i o n s 6 Assumptions 7 2. REVIEW OF LITERATURE 8 Mechanics of S k i i n g 8 Lower Limb Alignment and S k i i n g 10 O r t h o t i c s , Footbeds, and S k i i n g 12 Footbed Con s t r u c t i o n 13 Pain A n a l y s i s 15 3. PROCEDURES 18 Subjects 18 Research Design 18 Laboratory Section 19 I n i t i a l Assessment 19 Footbed P r e p a r a t i o n 20 Sk i Boot Pre p a r a t i o n 20 Data C o l l e c t i o n 22 Data A n a l y s i s 24 S t a t i s t i c a l A n a l y s i s 24 v S k i i n g Section 24 Data C o l l e c t i o n 24 Data A n a l y s i s 26 S t a t i s t i c a l A n a l y s i s 26 4. RESULTS AND DISCUSSION 27 D e s c r i p t i o n of Subjects 27 Laboratory Section 27 N a v i c u l a r Drop 27 Rearfoot Angle 34 T i b i a l Rotation 36 Summary 38 S k i i n g Section 39 Edge C o n t r o l 39 Pain 39 Fatigue 40 Timed Runs 40 Summary 4 0 5. CONCLUSIONS AND RECOMMENDATIONS 44 Conclusions 46 Recommendations 47 REFERENCES 4 8 APPENDIX A - DETERMINATION OF LOWER LIMB ALIGNMENT 50 APPENDIX B - FOOTBED MOLDING PROCEDURE 51 APPENDIX C - GENERAL DESCRIPTIVE DATA FOR ALL SUBJECTS...53 APPENDIX D - COMPLETE NAVICULAR DATA 54 APPENDIX E - COMPLETE REARFOOT DATA. 61 APPENDIX F - COMPLETE TIBIAL TUBEROSITY DATA 64 vi APPENDIX G - COMPLETE RATINGS DATA APPENDIX H - COMPLETE RACE DATA v i i LIST OF FIGURES l a . Medial Window of S k i Boot Exposing the N a v i c u l a r Tubercle 21 l b . Rear Window of S k i Boot Exposing the I n s e r t i o n of the A c h i l l e s at the Calcaneus 21 l c . Front View of S k i Boot With T i b i a l Tuberosity 21 2a. N a v i c u l a r Start/End P o s i t i o n s , X D i r . , Right Foot....29 2b. N a v i c u l a r Start/End P o s i t i o n s , X D i r . , L e f t Foot 29 3a. N a v i c u l a r Start/End P o s i t i o n s , Y D i r . , Right Foot....30 3b. N a v i c u l a r Start/End P o s i t i o n s , Y D i r . , L e f t Foot 30 4. N a v i c u l a r Motion i n the X D i r e c t i o n ...32 5. N a v i c u l a r Motion i n the Y D i r e c t i o n 33 6a. Rearfoot Angles at S t a r t and End, Right Foot 35 6b. Rearfoot Angles at S t a r t and End, L e f t Foot 35 7. T i b i a l Tubercle, H o r i z o n t a l Distance From M i d l i n e . . . . 37 8a. Edge C o n t r o l Ratings f o r Short Radius Turns 41 8b. Edge C o n t r o l Ratings f o r Long Radius Turns 41 9a. Pain Ratings 42 9b. Fatigue Ratings 42 10. Race R e s u l t s 43 v i i i ACKNOWLEDGEMENT S I would l i k e to acknowledge the c o n t r i b u t i o n s of se v e r a l people without whom t h i s p r o j e c t would not have been made p o s s i b l e . To my t h e s i s and graduate advisor, Dr. Jack Taunton f o r h i s d i r e c t i o n , enthusiasm, and encouragement as w e l l as f o r h i s e xtensive network of valuable resource people. To Dr. James Macintyre f o r h i s i n s i g h t , e x p e r t i s e , and c o n t r i b u t i o n s i n the area of s k i research. To Dr. David Sanderson f o r h i s e x p e r t i s e and devotion to h i s f i e l d , h i s uncompromising standards, and most impo r t a n t l y f o r h i s a p p r o a c h a b i l i t y and genuine i n t e r e s t i n h i s students. To Mr. Paul P a r i s who has the a b i l i t y to get water from a stone i n the form of time and equipment donations and whose own s a c r i f i c e of valuable time and e f f o r t was the tr u e t u r n i n g p o i n t f o r t h i s p r o j e c t . To my f r i e n d s at U.B.C, p a r t i c u l a r l y those i n the Biomechanics Laboratory who k i n d l y adopted an o u t s i d e r and gave me a home base from which to operate. F i n a l l y , t o my fami l y who support me i n a l l t h a t I undertake. Support provided by Bud Ryckman/ MJD Agencies, Norvinca Inc., P a r i s O r t h o t i c s , John C o l p i t t s , David Steers, and Grouse Mountain Resorts L i m i t e d i s g r a t e f u l l y acknowledged. i x Chapter 1 INTRODUCTION Over two m i l l i o n Canadians p a r t i c i p a t e i n the sport of a l p i n e s k i i n g . S k i i n g i s unique i n that i t i s the only sport i n which a l e v e r system i s r i g i d l y attached t o the body. This system c o n s i s t s of the s k i , b i n d i n g , and boot. The s k i boot i s the main l i n k i n t r a n s f e r r i n g forces from the s k i e r t o the s k i . The a b i l i t y of the s k i e r to r i d e a f l a t s k i ( i e . m a i n t a i n i n g ground contact with both edges of the s k i simultaneously) without a l t e r i n g t h e i r n a t u r a l stance i s important. From t h i s p o s i t i o n the s k i e r i s able to p i v o t , edge, and pressure the s k i through a carved t u r n w i t h minimal l e g a c t i o n s . The s k i e r whose n a t u r a l stance places them on t h e i r s k i edges has d i f f i c u l t i e s i n i t i a t i n g a t u r n . Research i n d i c a t e s that up to 80% of r e c r e a t i o n a l s k i e r s have lower limb alignments which prevent them from r i d i n g a f l a t s k i while i n a n a t u r a l stance (Subotnick, 1982). The most common c o n d i t i o n s which c o n t r i b u t e to the i n a b i l i t y to r i d e a f l a t s k i are varus alignments of the t i b i a and f o o t . This research i n v e s t i g a t e d one suggested method f o r overcoming the problems as s o c i a t e d w i t h a varus alignment of the f o o t . The need t o compensate f o r imperfect l e g alignments has r e s u l t e d i n the improvement of s k i boot design. A d j u s t a b l e boot c u f f s can be a l i g n e d to approximate the angle of the 1 t i b i a w hile a l l o w i n g the base of the boot to remain l e v e l . The s k i e r w i t h a l l but the most severe amounts of t i b i a vara i s thus able t o r i d e a f l a t s k i . Forefoot and r e a r f o o t varus t y p i c a l l y r e s u l t i n excessive pronation during weight bearing. Excessive pronation i s i d e n t i f i e d by the accompanied increase of t i b i a l r o t a t i o n , a decreased a b i l i t y to reduce the t r a n s m i s s i o n of shock- up the l e g , and d i f f i c u l t y i n r e s u p i n a t i n g during unweighting. Excessive pronation i s a d i f f i c u l t c o n d i t i o n to c o r r e c t w i t h i n a s k i boot. The nature of the modern s k i boot i s such that the r i g i d p l a s t i c s h e l l and t i g h t f i t can increase the amount of pronation experienced by most s k i e r s by causing the l o n g i t u d i n a l arch to f l a t t e n . The manufacturers of custom molded s k i boot footbeds c l a i m that these devices can maintain the foot i n a n e u t r a l p o s i t i o n and c o n t r o l excess pronation thereby reducing the p a i n , f a t i g u e , and edge c o n t r o l problems a s s o c i a t e d w i t h excessive pronation (Peterson Tech. Manual, Superfeet Tech. Manual). To date there are no r e l i a b l e data supporting these b e l i e f s . Statement of the Problem This research was designed t o i n v e s t i g a t e the e f f e c t i v e n e s s of one type of custom molded footbed to c o n t r o l r e a r f o o t motion, n a v i c u l a r drop, and t i b i a l r o t a t i o n , three events a s s o c i a t e d with p r o n a t i o n . The focus of the study was t o obtain q u a n t i t a t i v e measures of the 2 a b i l i t y o f t h e f o o t b e d t o c o n t r o l motion w i t h i n a s k i boot i n an e f f o r t t o d e t e r m i n e t h e mechanism o f c o n t r o l . A second f o c u s was t h e q u a n t i f i c a t i o n o f t h e s u b j e c t i v e f e e l i n g s o f edge c o n t r o l , p a i n , and f a t i g u e w h i c h t o d a t e have o n l y been r e p o r t e d a n e c d o t a l l y . Hypotheses 1. I t was h y p o t h e s i z e d t h a t t h e r e i s s i g n i f i c a n t l y l e s s p r o n a t i o n , as measured by a ) n a v i c u l a r drop, b ) r e a r f o o t m o t i o n , and c ) t i b i a l r o t a t i o n w h i l e weight b e a r i n g w i t h f e e t p l a c e d on custom f o o t b e d s t h a n on non-custom i n s o l e s . 2. I t was h y p o t h e s i z e d t h a t t h e r e i s a s i g n i f i c a n t d e c r e a s e i n t h e l e v e l s o f p e r c e i v e d f o o t and l e g p a i n w i t h t h e use o f a custom f o o t b e d as compared t o a non-custom i n s o l e . 3. I t was h y p o t h e s i z e d t h a t t h e r e i s a s i g n i f i c a n t d e c r e a s e i n t h e l e v e l o f p e r c e i v e d f o o t f a t i g u e w i t h t h e use o f a custom f o o t b e d as compared t o a non-custom i n s o l e . 4. I t was h y p o t h e s i z e d t h a t t h e r e i s a s i g n i f i c a n t i n c r e a s e i n t h e l e v e l o f p e r c e i v e d edge c o n t r o l w i t h t h e use o f a custom f o o t b e d as compared t o a non-custom i n s o l e . 5. I t was h y p o t h e s i z e d t h a t t h e i n c r e a s e d l e v e l o f edge c o n t r o l would r e s u l t i n improved performance on a t i m e d r a c e c o u r s e . 3 S i g n i f i c a n c e of the Study This study served to t e s t the manufacturers claims as to the e f f e c t i v e n e s s of custom molded footbeds i n c o n t r o l l i n g the events a s s o c i a t e d with pronation and improving s k i i n g a b i l i t y and enjoyment. I t was the i n t e n t i o n of t h i s study to develop a method f o r q u a n t i t a t i v e assessment of motion w i t h i n a s k i boot i n order t o determine the e f f e c t i v e n e s s of s k i boot footbeds. D e f i n i t i o n of Terms Forefoot Varus. Medial border of the foot i s r a i s e d at the metatarsal heads while i n a non-weight bearing p o s i t i o n (Root et a l . , 1971). Subtalar Varus. Medial border of the foot i s r a i s e d at the heel while i n a non-weight bearing p o s i t i o n (Root et a l . , 1971). Pr o n a t i o n . P o s i t i o n described by ankle e v e r s i o n , abduction, and d o r s i f l e x i o n ; i n t e r n a l r o t a t i o n of the t i b i a occurs secondary to s u b t a l a r eversion (McKenzie, Clement, and Taunton, 1985). N a v i c u l a r Drop. The forward and downward motion of the n a v i c u l a r t u b e r c l e that t y p i c a l l y occurs w i t h weight bearing. Rearfoot Angle. The angle of i n s e r t i o n of the A c h i l l e s tendon at the calcaneus with respect to an imaginary l i n e which i s perpendicular to the ground. 4 T i b i a l R o t a t i o n . The a l i g n m e n t o f t h e t i b i a l t u b e r o s i t y w i t h r e s p e c t t o t h e mid-seam of t h e t o e p i e c e o f a s k i b o o t . The t i b i a l t u b e r o s i t y i s r o t a t e d outward as t h e a r c h c o l l a p s e s w i t h p r o n a t i o n . T h i s r o t a t i o n o c c u r s as a r e s u l t o f t h e s u b t a l a r j o i n t ' s a t t e m p t s t o m a i n t a i n p r o p e r a l i g n m e n t w i t h t h e t i b i a d e s p i t e t h e e f f e c t s o f p r o n a t i o n . O r t h o t i c . D e v i c e d e s i g n e d t o a s s i s t i n b i o m e c h a n i c a l c o n t r o l o f t h e l ower e x t r e m i t y ; s t a b i l i z e s t h e j o i n t i n a n e u t r a l p o s i t i o n ( M a c i n t y r e and Matheson, 1988). Non-custom I n s o l e . Removeable i n s o l e found i n s i d e s k i b o o t s . Custom Molded S k i Boot Footbed. Custom molded i n s o l e t h a t b e g i n s as a f o o t shaped b l a n k . I n s o l e s a r e h e a t e d and shaped t o i n d i v i d u a l f o o t c o n t o u r s w h i l e t h e f o o t i s m a i n t a i n e d by some method i n a n e u t r a l p o s i t i o n ( C o l p i t t s , 1987). The f o o t b e d used i n t h i s s t u d y was c o n s t r u c t e d o f c o r k and molded i n a non-weight b e a r i n g , n e u t r a l p o s i t i o n by t h e use o f s u c t i o n . H o r i z o n t a l V i s u a l Analogue S c a l e . A 10cm h o r i z o n t a l l i n e w i t h s t o p s at b o t h ends at r i g h t a n g l e s t o t h e l i n e . The a d d i t i o n o f d e s c r i p t i v e terms produces a g r a p h i c r a t i n g s s c a l e ( S c o t t and H u s k i s s o n , 1979). 5 D e l i m i t a t i o n s R e s u l t s of t h i s study were r e s t r i c t e d to a d u l t , advanced l e v e l s k i e r s who e x h i b i t e d more than three degrees of s u b t a l a r varus i n each foot. The r e s u l t s were a l s o r e s t r i c t e d to the one make and model of custom molded footbed t e s t e d as w e l l as the make and model of t e s t boot used i n the l a b o r a t o r y . An e f f o r t was made to standardize the make and model of t e s t boots as Schaff et a l . (1987) have shown tha t while there i s l i t t l e or no v a r i a b i l i t y i n the f l e x p a t t e r n and pressure p r o f i l e s of var i o u s s i z e s of the same boot, there i s v a r i a b i l i t y between boot s t y l e s and makes. The e f f e c t i v e n e s s of the footbeds was r e s t r i c t e d to the a b i l i t i e s of the t e c h n i c i a n s to work wi t h the product. V a r i a b i l i t y i n c o n s t r u c t i o n was minimized by using only two t e c h n i c i a n s to make a l l the footbeds f o r t h i s study. A n a l y s i s of motion i n s i d e of the s k i boots was confined t o l a b o r a t o r y c o n d i t i o n s . S k i i n g maneuvers create forces which are not e a s i l y reproduced i n the lab (Schattner et a l . , 1985). Windowing of the s k i boots minimally a l t e r e d f l e x and support c h a r a c t e r i s t i c s . Accuracy of the r e s u l t s may have been a f f e c t e d by these experimental c o n d i t i o n s . 6 Assumptions This research operated under the assumption th a t i f custom molded s k i boot footbeds d i d reduce pai n and f a t i g u e , and increase edge c o n t r o l they d i d so by reducing p r o n a t i o n . Although the l i t e r a t u r e speculated that t h i s i s the un d e r l y i n g mechanism of t h e i r e f f e c t i v e n e s s there were no r e l i a b l e data a v a i l a b l e at the time of t h i s study. I t was assumed that each subject was at a s k i i n g l e v e l which was s u f f i c i e n t l y high so as to allow them t o a c c u r a t e l y judge the su b t l e d i f f e r e n c e s i n edge c o n t r o l , p a i n , and f a t i g u e experienced with the use of v a r i o u s types of i n s o l e s . In the l a b o r a t o r y i t was assumed th a t a l l markers were p r o p e r l y p o s i t i o n e d on t h e i r intended landmarks. 7 Chapter 2 REVIEW OF LITERATURE This review i s d i v i d e d i n t o f i v e major s e c t i o n s : (a) mechanics of s k i i n g ; (b) lower limb alignment and s k i i n g ; (c) o r t h o t i c s , footbeds, and s k i i n g ; (d) footbed c o n s t r u c t i o n ; (e) pain a n a l y s i s . Mechanics of S k i i n g The carved p a r a l l e l t u r n i s the most e s s e n t i a l s k i l l of a l p i n e s k i i n g . P i v o t i n g , edging, and pressure c o n t r o l are the three elements i n v o l v e d i n the t u r n . Ankle e v e r s i o n , valgus angulation of the f l e x e d knee, and h i p f l e x i o n are the motions used to pressure the i n s i d e edge of the d o w n h i l l s k i (Macintyre and Matheson, 1988). This pressure causes the s k i to f l e x and carve an arc. Upon completion of the arc the s k i e r unweights , p i v o t s toward a new d i r e c t i o n , and pressures the i n s i d e edge of the new d o w n h i l l s k i c r e a t i n g another a r c . While the motions of the ankle, knee, and h i p during a s k i t u r n can be e a s i l y observed, the motion of the foot w i t h i n the s k i boot i s completely hidden from view. During the s k i t u r n the foot i s subjected to a p a t t e r n of weight s h i f t i n g s i m i l a r t o that of normal g a i t (Macintyre and Matheson, 1988). The often documented walking and running p a t t e r n of s u p i n a t i o n - p r o n a t i o n - r e s u p i n a t i o n occurs during the s k i t u r n as the s k i e r ' s weight s h i f t s from the heel to the f o r e f o o t (Macintyre and Matheson, 1988). Because of the 8 l o c k i n g e f f e c t o f t h e b u c k l e d s k i boot t h e r e i s no t r u e h e e l s t r i k e o r t o e - o f f e x p e r i e n c e d ( M a c i n t y r e and Matheson, 1988). U s i n g t r a n s d u c e r s l o c a t e d i n t h e f o o t b e d and tongue o f a s k i b o o t , Medoff et a l . (1985a) found t h e f o o t t o go t h r o u g h a r e p e t i t i v e p a t t e r n o f motion b e g i n n i n g w i t h a h e e l t h r u s t , f o l l o w e d by an even d i s t r i b u t i o n o f f o r c e s on t h e h e e l and f o r e f o o t , and f i n a l l y a p u s h - o f f on t h e f o r w a r d p a r t o f t h e f o o t . In a d d i t i o n i t was o b s e r v e d t h a t s h o r t r a d i u s s l a l o m t y p e t u r n s showed a more r a p i d , i n c o n s i s t e n t p a t t e r n t h a n t h a t o b s e r v e d d u r i n g l o n g r a d i u s t u r n s (Medoff e t a l . , 1985a). The f o r c e s i n v o l v e d i n c a u s i n g t h e s k i t o a r c d u r i n g a t u r n a r e t r a n s f e r r e d from th e s k i e r t h r o u g h t h e s k i b o o t s t o t h e s k i (Medoff e t a l , 1985a). At t h e same t i m e f o r c e s a r e b e i n g t r a n s f e r r e d from th e snow t h r o u g h th e boot and back up t o t h e s k i e r (Medoff et a l , 1985a). The boot i s t h e main l i n k i n t h i s system of a c t i o n and r e a c t i o n , and as such i t i s o f v i t a l i m p o r t a n c e t h a t t h e f o o t t o boot f i t be as c l o s e as p o s s i b l e (Medoff et a l , 1985a). For example, t h e a n k l e e v e r s i o n r e q u i r e d t o i n i t i a t e a s k i t u r n i s a s u b t l e m o t i o n . T h i s s u b t l e a c t i o n w i l l not be t r a n s f e r r e d t o t h e s k i i f t h e r e i s t o o much room between the f o o t and t h e b o o t . I n s t e a d , t h e f o r c e o f t h e a c t i o n i s l o s t i n s i d e o f t h e boot as t h e r e has been l i t t l e or no c o n t a c t between t h e f o o t and t h e boot d u r i n g t h e m o t i o n . E x a g g e r a t i o n o f such a m o t i o n i s d i f f i c u l t due t o t h e l i m i t a t i o n s o f motion c r e a t e d by t h e r i g i d p l a s t i c s h e l l and t h i c k foam l i n e r o f t h e s k i b o o t . 9 L i k e w i s e , compensation f o r a poor f i t by t i g h t l y b u c k l i n g t h e b o o t s can d i s r u p t t h e t r a n s m i s s i o n of f o r c e s by l o c k i n g t h e f o o t i n t o a p r o n a t e d p o s i t i o n ( M a c i n t y r e and Matheson, 1988). Lower Limb A l i g n m e n t and S k i i n g A l l s k i i n g s k i l l s o r i g i n a t e from a n e u t r a l g l i d e p o s i t i o n w h i c h r e q u i r e s t h e s k i e r t o r i d e on b o t h edges o f t h e i r s k i s i m u l t a n e o u s l y w h i l e i n a n a t u r a l s t a n c e . T h i s p o s i t i o n i s r e f e r r e d t o as r i d i n g a f l a t s k i . R i d i n g on e i t h e r o f t h e s k i ' s edges w h i l e g l i d i n g w i l l p r e d i s p o s e t h e s k i e r t o c a t c h i n g an edge on t h e snow, and p r e v e n t them from p i v o t i n g s u c c e s s f u l l y . S u b o t n i c k (1982) found 80% o f t h e s k i e r s t h a t he t e s t e d t o e x h i b i t lower l i m b a l i g n m e n t s which p r e v e n t e d them from r i d i n g a f l a t s k i w i t h o u t a d j u s t i n g t h e i r n a t u r a l s t a n c e . The most common a l i g n m e n t s w h i c h can a d v e r s e l y a f f e c t t h e a b i l i t y o f a s k i e r t o p r o p e r l y r i d e a f l a t s k i are t i b i a v a r a , f o r e f o o t v a r u s , and r e a r f o o t v a r u s . Most p e o p l e e x h i b i t an average o f two t o t h r e e degrees o f r e a r f o o t or s u b t a l a r v a r u s (James, 1979). M a c i n t y r e and Matheson (1988) o u t l i n e d t h e e f f e c t s o f v a r u s a l i g n m e n t s o f t h e t i b i a and f o o t on s k i i n g . V a r us a l i g n m e n t o f t h e t i b i a i s t r a n s f e r r e d t h r o u g h t h e boot t o t h e s k i . I f t h e boot c u f f i s s e t p e r p e n d i c u l a r t o t h e boot base t h e s k i e r w i t h t i b i a v a r a w i l l s t a n d on t h e o u t s i d e o f t h e s k i s . The knees w i l l c o n s e q u e n t l y be i n a v a r u s p o s i t i o n . I n i t i a t i n g a t u r n from t h i s p o s i t i o n i s 10 d i f f i c u l t . Because they are locked onto t h e i r outside edges, s k i e r s w i t h t h i s c o n d i t i o n tend to jump from one t u r n to the next i n s t e a d of c a r v i n g l i n k e d t u r n s . A l i g n i n g the boot c u f f t o the angle of the t i b i a while the base of the boot remains l e v e l allows the s k i e r to r i d e a f l a t s k i while i n a n a t u r a l stance. A more d i f f i c u l t c o n d i t i o n to c o n t r o l w i t h i n the s k i boot i s a varus alignment of the f o o t . The c o n d i t i o n may not appear u n t i l the s k i e r assumes a f u n c t i o n a l s k i i n g p o s i t i o n . During weight bearing the varus a l i g n e d foot w i l l pronate e x c e s s i v e l y . ( M a c i n t y r e and Matheson, 1988) Pronation i s a combination of ankle eversion, abduction, and d o r s i f l e x i o n . During running pronation i s necessary f o r decreasing the forces experienced by the l e g , but excessive pronation causes an increased amount of t i b i a l r o t a t i o n and a decreased a b i l i t y to reduce shock (Nigg, 1986). C o n t r i b u t i n g to pronation i n s k i e r s i s the ankle eversion necessary f o r t u r n i n i t i a t i o n as w e l l as the s k i boot i t s e l f . A t i g h t l y buckled boot i s b e l i e v e d t o f l a t t e n the l o n g i t u d i n a l arch, preventing the foot from s u p i n a t i n g a f t e r unweighting (Macintyre and Matheson, 1988). Excessive pronation can place the s k i e r i n a p o s i t i o n c h a r a c t e r i z e d by the s k i t i p s p o i n t i n g outward and the knees p o i n t i n g inward. This p o s i t i o n r e s u l t s i n poor s k i i n g technique and p a i n . The extreme valgus p o s i t i o n of the knee r e q u i r e d f o r t u r n i n g from t h i s p o s i t i o n causes the upper body and the hips to r o t a t e i n t o the h i l l . Instead of 11 c a r v i n g , t h e s k i e r banks t h e i r t u r n s . T h i s r e s u l t s i n a s h i f t i n g o f t h e c e n t e r o f g r a v i t y o u t s i d e o f t h e base o f s u p p o r t and t h e s k i e r f a l l s u p h i l l . P a i n may r e s u l t from t h e extreme r o t a t i o n o f t h e t i b i a a t t h e knee w h i c h accompanies e x c e s s i v e p r o n a t i o n . A ttempts t o s t a b i l i z e t h e f o o t by c u r l i n g t h e t o e s or t i g h t e n i n g t h e b u c k l e s l e a d s t o c o l d , cramped f e e t . ( M a c i n t y r e and Matheson, 1988) O r t h o t i c s , Footbeds, and S k i i n g I t has been su g g e s t e d t h a t t h e s o l u t i o n t o t h e problems a s s o c i a t e d w i t h p r o n a t i o n i s t h e s t a b i l i z a t i o n o f t h e f o o t i n a n e u t r a l p o s i t i o n w i t h i n t h e s k i boot ( M a c i n t y r e and Matheson, 1988). Running s t u d i e s have shown o r t h o t i c s t o reduce r e a r f o o t motion and o v e r a l l p r o n a t i o n when used i n r u n n i n g shoes ( C l a r k e e t a l , 1984). There a r e v a r i o u s t h e o r i e s as t o t h e mechanism by which o r t h o t i c s reduce r e a r f o o t m o t i o n and p r o n a t i o n . Smith et a l . (1983) found r u n n i n g shoe o r t h o t i c s t o - r e d u c e c a l c a n e a l e v e r s i o n d u r i n g r u n n i n g and s u g g e s t e d t h a t t h i s d e c r e a s e may be a s i g n i f i c a n t mechanism f o r t h e r e d u c t i o n o f symptoms by o r t h o t i c s . B a tes et a l . (1979) found t h a t p r o n a t i o n began l a t e r and ended sooner d u r i n g r u n n i n g t r i a l s w i t h o r t h o t i c s t h a n w i t h o u t t h e use o f o r t h o t i c s . In i n d e p e n d e n t l y run s t u d i e s B a t e s e t a l . ( 1 9 7 9 ) and N i g g and L e u t h i (1980) b o t h found t h a t t h e use o f o r t h o t i c s by i n j u r e d r u n n e r s a l t e r e d t h e mechanics o f t h e lower e x t r e m i t y enough t o d e c r e a s e t h e amount o f p r o n a t i o n e x p e r i e n c e d t o l e v e l s s i m i l a r t o t h o s e e x p e r i e n c e d by non i n j u r e d r u n n e r s ( S t a c o f f and L e u t h i , 1986). A n o t h e r s t u d y found a d e c r e a s e i n r e a r f o o t m otion w i t h t h e i n c r e a s e d h e i g h t o f t h e o r t h o t i c (Cavanagh, 1980) . The m a n u f a c t u r e r s o f s k i boot f o o t b e d s c l a i m t h a t t h e i r p r o d u c t s can c o n t r o l p r o n a t i o n i n s i d e o f a s k i boot s i m i l a r l y t o t h e c o n t r o l found t o o c c u r w i t h t h e use o f o r t h o t i c s d u r i n g r u n n i n g . In a d d i t i o n t h e i r l i t e r a t u r e m a i n t a i n s t h a t c o n t r o l l i n g t h e e x c e s s i v e motions a s s o c i a t e d w i t h p r o n a t i o n can reduce p a i n and f a t i g u e , and i n c r e a s e edge c o n t r o l ( P e t e r s o n Tech. Manual, S u p e r f e e t Tech. M a n u a l ) . F o o t b e d C o n s t r u c t i o n . The p r i m a r y f u n c t i o n o f any o r t h o t i c f o o t b e d i s t h e b i o m e c h a n i c a l c o n t r o l o f t h e f o o t (McKenzie, Clement, and Taunton, 1985). S k i boot f o o t b e d m a n u f a c t u r e r s agree w i t h s p o r t s m e d i c i n e p r a c t i t i o n e r s t h a t t h e i d e a l p o s i t i o n o f t h e f o o t i s one i n which t h e s u b t a l a r j o i n t i s n e u t r a l (McKenzie, Clement, and Taunton, 1985). M a n u f a c t u r e r s d i f f e r on t h e i r methods of c r e a t i n g a f o o t b e d i n w h i c h t h e s u b t a l a r j o i n t i s h e l d n e u t r a l . The f o o t b e d s u t i l i z e d i n t h i s s t u d y were molded w i t h t h e s u b j e c t i n a s e a t e d p o s i t i o n w i t h no w e i g h t b e i n g p l a c e d on t h e f e e t ( S u p e r f e e t Tech. M a n u a l ) . The f o o t i s m a i n t a i n e d i n a n e u t r a l p o s i t i o n t h r o u g h o u t t h e m o l d i n g p r o c e s s by t h e t e c h n i c i a n ( S u p e r f e e t Tech. M a n u a l ) . Other s k i boot f o o t b e d s are molded i n a w e i g h t b e a r i n g p o s i t i o n w i t h h i g h d e n s i t y foam p l a c e d under 13 the foot t o maintain a n e u t r a l p o s i t i o n (Peterson Tech. Manual). There are no data a v a i l a b l e comparing the successes of these two techniques i n c r e a t i n g a footbed which can maintain the foot i n a n e u t r a l p o s i t i o n . Footbed m a t e r i a l s vary with manufacturer. The footbeds u t i l i z e d i n t h i s study were made from cork w i t h a n o n - s l i p , breathable top cover (Superfeet Tech. Manual). The m a t e r i a l chosen f o r a footbed must be f i r m . A f l e x i b l e footbed can c o l l a p s e under the pressures a s s o c i a t e d w i t h the s k i t u r n (Superfeet Tech. Manual). The footbed must a l s o withstand the pressures exerted by the b u c k l i n g of the boots. Running shoe o r t h o t i c s t y p i c a l l y end j u s t a f t e r the metatarsal heads to allow f o r f l e x i b i l i t y at the toes and reduce the chance of cramping (McKenzie, Clement, and Taunton, 1985.). This i s j u s t i f i a b l e i n such o r t h o t i c s as i t has been shown that a l l the biomechanical c o n t r o l that takes place does so from the heel to immediately proximal t o the metatarsal heads (McKenzie, Clement, and Taunton, 1985). S k i boot o r t h o t i c s are f u l l length as the manufacturers b e l i e v e t h a t t h i s increases the s t a b i l i t y o f f e r e d by the footbed w h i l e b a l a n c i n g the o v e r a l l support and f u n c t i o n (Superfeet Tech. Manual). No data were a v a i l a b l e t o i n d i c a t e the mechanism of c o n t r o l i n any brand of s k i boot footbed. Studies have found s i g n i f i c a n t d i f f e r e n c e s between the biomechanical parameters of i n d i v i d u a l s ' r i g h t and l e f t legs suggesting that there i s a need to c o n t r o l each foot 14 i n d i v i d u a l l y (McKenzie, Clement, and Taunton 1985). A l l custom molded f o o t b e d s d e a l w i t h each f o o t s e p a r a t e l y , m o l d i n g one f o o t b e d a t a t i m e . T h i s s t u d y o p e r a t e d under t h e same i d e o l o g y and as such a n a l y s e s were d e s i g n e d t o l o o k a t each f o o t as a s e p a r a t e v a r i a b l e b e l o n g i n g t o one s u b j e c t . T h i s a l l o w e d f o r t h e i n v e s t i g a t i o n o f w i t h i n s u b j e c t v a r i a b i l i t y between f e e t as w e l l as between t y p e o f i n s o l e . P a i n A n a l y s i s U n f o r t u n a t e l y , p a i n i s a p a r t o f many p e o p l e ' s s k i i n g e x p e r i e n c e . A l t h o u g h common, p a i n i s a d i f f i c u l t parameter t o d e f i n e . I t i s a complex phenomenon encompassing t h e s e n s a t i o n s evoked by t i s s u e - d a m a g i n g s t i m u l i as w e l l as t h e s u b j e c t ' s r e a c t i o n t o t h a t s t i m u l i (Medoff e t a l , 1985b). V a r i a b i l i t y i n response t o p a i n f u l s t i m u l i has been a t t r i b u t e d t o f a c t o r s such as age , gender, c u l t u r a l background, p r e v i o u s t r a i n i n g , and t h e i n f l u e n c e o f s u g g e s t i o n (Medoff e t a l , 1985b). P a i n i n s k i i n g i s o f t e n t h e r e s u l t o f a f a l l , c o l l i s i o n , c o l d i n j u r y , o r as i t r e l a t e s t o t h i s s t u d y , i m p r o p e r l y f i t t e d b o o t s o r t i g h t l y b u c k l e d b o o t s . R a t i n g p a i n u s i n g d e s c r i p t i v e s c a l e s can be approached from two d i r e c t i o n s . Sensory s c a l e s u t i l i z e words t h a t r e l a t e t o q u a l i t y and i n t e n s i t y such as t h e words weak and moderate (Medoff e t a l , 1985b). A f f e c t i v e p a i n s c a l e s use words such as u n p l e a s a n t and d i s t r e s s i n g , w hich r e l a t e t o the m o t i v a t i o n a l and emotional v a r i a b l e s a s s o c i a t e d w i t h the p a i n experience (Medoff et a l , 1985b). The sensory type of s c a l e was chosen f o r t h i s study as i t u t i l i z e s terms which are more appropriate f o r d e s c r i b i n g the e f f e c t i v e n e s s of footbeds. V i s u a l analogue s c a l e s have been shown to be s a t i s f a c t o r y measurement t o o l s i n the assessment of pain (Huskisson, 1983). According to Huskisson (1983) the greatest advantage of the v i s u a l analogue s c a l e i s the u n i f o r m i t y of d i s t r i b u t i o n of r e s u l t s . The s c a l e may c o n s i s t of e i t h e r a v e r t i c a l or h o r i z o n t a l l i n e w i t h stops at both ends at r i g h t angles to the l i n e (Huskisson, 1983). Both s c a l e s have proven s a t i s f a c t o r y although i t i s recommended that only one of the two be used over the course of any one study i n order to maintain consistency (Scott and Huskisson, 1979). The v e r t i c a l s c a l e has as a source of e r r o r the angle at which i t i s viewed (Dixon and B i r d , 1981). Viewing angle does not a f f e c t the h o r i z o n t a l s c a l e which was t h e r e f o r e chosen f o r use i n t h i s study. Further sources of e r r o r encountered when using r a t i n g s c a l e s can be a r e s u l t of inadequate i n s t r u c t i o n s and subject compliancy (Dixon and B i r d , 1981). Some researchers f e e l that r a t i n g s c a l e s r e f l e c t what the subject b e l i e v e s they ought to f e e l r a t h e r than t h e i r t r u e f e e l i n g s (Dixon and B i r d , 1981). The h o r i z o n t a l v i s u a l analogue scale was u t i l i z e d i n t h i s study f o r the purpose of r a t i n g edge c o n t r o l and f a t i g u e as w e l l as the t r a d i t i o n a l use as a pain s c a l e . This was done i n an 16 e f f o r t to maintain consistency while minimizing the amount of i n s t r u c t i o n s r e q u i r e d . 17 Chapter 3 PROCEDURES The p r i m a r y purpose o f t h i s s t u d y was t o d e t e r m i n e q u a n t i t a t i v e l y t h e e f f e c t i v e n e s s o f custom molded s k i boot f o o t b e d s i n c o n t r o l l i n g t h e motions a s s o c i a t e d w i t h p r o n a t i o n . The second purpose o f t h e s t u d y was t o q u a n t i f y t h e s u b j e c t i v e e x p e r i e n c e s o f s k i e r s i n a c o n t r o l l e d s t u d y . S u b j e c t s The s t u d y u t i l i z e d a s u b j e c t group o f 15 advanced l e v e l a d u l t s k i e r s r e c r u i t e d t h r o u g h t h e use o f p o s t e r s d i s p l a y e d a t a major u n i v e r s i t y , s k i shops, and l o c a l s k i h i l l s . The s u b j e c t s a l l d i s p l a y e d a minimum o f t h r e e degrees o f s u b t a l a r v a r u s i n b o t h f e e t . No s u b j e c t had p r i o r e x p e r i e n c e s k i i n g on t h e b r a n d o f custom molded f o o t b e d used i n t h e s t u d y . P r i o r t o t e s t i n g , each s u b j e c t was i n f o r m e d as t o t h e n a t u r e o f t h e s t u d y and gave w r i t t e n consent t o p a r t i c i p a t e . The l a b o r a t o r y s e c t i o n o f t h e s t u d y was c o n d u c t e d u s i n g o n l y 13 out o f t h e o r i g i n a l group o f s u b j e c t s due t o a t t r i t i o n . R e s e a r c h D e s i g n The independent v a r i a b l e s f o r b o t h t h e l a b o r a t o r y and t h e s k i i n g p o r t i o n s o f t h i s s t u d y were t h e non-custom i n s o l e s and t h e custom molded f o o t b e d s . The l a b o r a t o r y 18 p o r t i o n o f t h e r e s e a r c h a l s o l o o k e d a t t h e r i g h t and l e f t f e e t , w h i l e t h e s k i i n g p o r t i o n o f t h e s t u d y c o n t r o l l e d f o r s h o r t r a d i u s and l o n g r a d i u s t u r n s . The dependent v a r i a b l e s f o r t h e l a b o r a t o r y p o r t i o n o f t h e s t u d y were n a v i c u l a r drop, t h e a n g l e o f i n s e r t i o n o f t h e A c h i l l e s tendon at t h e c a l c a n e u s ( r e a r f o o t a n g l e ) , and t h e a l i g n m e n t o f t h e t i b i a l t u b e r o s i t y w i t h r e s p e c t t o t h e mid-seam o f t h e b o o t ' s t o e p i e c e . These v a r i a b l e s were chosen as t h e y r e f l e c t e d t h e e v e n t s a s s o c i a t e d w i t h p r o n a t i o n and were e a s i l y m o n i t o r e d i n t h e l a b o r a t o r y . The dependent v a r i a b l e s f o r t h e s k i i n g p o r t i o n o f t h e s t u d y were l e v e l o f p e r c e i v e d edge c o n t r o l , l e v e l o f p e r c e i v e d p a i n , l e v e l o f p e r c e i v e d f a t i g u e , and r a c e r e s u l t s . The s t u d y was d e s i g n e d as a t e s t / r e t e s t s i t u a t i o n w i t h each s u b j e c t r e p e a t i n g t h e same p r o c e d u r e s w i t h b o t h t h e custom molded f o o t b e d s and t h e non-custom i n s o l e s i n a random o r d e r . L a b o r a t o r y S e c t i o n I n i t i a l Assessment. A l l s u b j e c t s were a s s e s s e d f o r s u b t a l a r v a r u s , f o r e f o o t v a r u s , and f u n c t i o n a l h y p e r m o b i l i t y by one i n v e s t i g a t o r f o l l o w i n g t h e p r o t o c o l s o u t l i n e d i n Appendix A. F o r e f o o t v a r u s and f u n c t i o n a l h y p e r m o b i l i t y were a s s e s s e d o n l y f o r t h e i r p r e s e n c e . S u b t a l a r v a r u s was measured t o t h e n e a r e s t degree and r e c o r d e d i n Appendix C. 19 F o o t b e d P r e p a r a t i o n . Custom molded f o o t b e d s ( S u p e r f e e t brand) were p r e p a r e d f o r each s u b j e c t by one o f two t e c h n i c i a n s f o l l o w i n g t h e p r o t o c o l o u t l i n e d i n Appendix B. S k i Boot P r e p a r a t i o n . A t o t a l o f f i v e p a i r s o f f o u r b u c k l e o v e r l a p d e s i g n s k i b o o t s , women's s i z e s 6.5, 7.5, and men's s i z e s 8.5, 10.5, 11.5 were used i n t h e l a b o r a t o r y s e c t i o n o f t h i s s t u d y . A l l o f t h e b o o t s were o f t h e same make and comparable model. These b o o t s were c u t away a t t h e r e a r and m e d i a l s i d e s t o a l l o w f o r t h e o b s e r v a t i o n o f t h e i n s e r t i o n o f t h e A c h i l l e s a t t h e c a l c a n e u s and t h e n a v i c u l a r t u b e r c l e r e s p e c t i v e l y . These a r e a s o f t h e boot s h e l l were ground down u s i n g a b e l t g r i n d e r and c u t open w i t h a j i g s a w . Edges were smoothed and f i n i s h e d by k n i f e . The boot l i n e r s were t h e n p l a c e d i n s i d e o f t h e s h e l l s and t h e o u t l i n e s o f t h e windows were t r a c e d . L i n e r s were removed, c u t open by k n i f e , and p l a c e d back i n t o t h e boot s h e l l . A l l b o o t s were checked on t e s t s u b j e c t s t o ensure a c l e a r v i e w o f t h e r e q u i r e d landmarks. M a r k e r s were p l a c e d a l o n g t h e mid-seam o f t h e t o e and h e e l p i e c e s o f t h e boot as w e l l as t o t h e f r o n t o f t h e m e d i a l a r c h window as shown i n F i g u r e 1. These marks s e r v e as s t a n d a r d p o i n t s o f r e f e r e n c e f o r l a t e r a n a l y s e s . S k i b o o t s were l a b e l e d f o r s i z e and f o o t on t h e f r o n t , r e a r , and m e d i a l s i d e f o r easy i d e n t i f i c a t i o n d u r i n g d i g i t i z i n g . As w e l l , each s u b j e c t was i d e n t i f i e d on t h e boot d u r i n g t h e i r t r i a l s . 20 F i g u r e l a . M e d i a l window o f s k i boot e x p o s i n g t h e \ • / \ I n a v i c u l a r t u b e r c l e F i g u r e l b . Rear window o f s k i boot e x p o s i n g t h e i n s e r t i o n o f t h e A c h i l l e s a t t h e c a l c a n e u s . F i g u r e l c . F r o n t view o f s k i boot w i t h t i b i a l t u b e r o s i t y . 21 Data C o l l e c t i o n . The s u b j e c t removed b o t h socks and shoes and was f i t t e d f o r t e s t s k i b o o t s u s i n g a s i z e r p r o v i d e d by t h e boot company. A l l s u b j e c t s were p a l p a t e d and marked on b o t h l e g s by one i n d i v i d u a l . The f o l l o w i n g landmarks were marked: a. N a v i c u l a r t u b e r c l e ; b. The attachment o f t h e A c h i l l e s tendon t o t h e c a l c a n e u s , a p o i n t 1.5 cm d i s t a l t o t h e attachment s i t e , and two more p o i n t s spaced between t h e t o p o f t h e s k i boot and t h e p o p l i t e a l space on t h e m i d l i n e o f t h e l e g as o u t l i n e d i n James (1979); c. M i d p o i n t o f t h e t i b i a l t u b e r o s i t y . The s u b j e c t put on t h e r i g h t boot w i t h t h e non custom i n s o l e and b u c k l e d t h e boot as t h e y would f o r s k i i n g . A l l windows were checked f o r an u n o b s t r u c t e d v i e w o f t h e landmarks. The s u b j e c t t h e n s t o o d on a f l u s h mounted K i s t l e r Model 9261-A f o r c e p l a t f o r m such t h a t t h e mid-seam o f t h e f r o n t and r e a r o f t h e boot were a l i g n e d w i t h t h e y a x i s o f t h e p l a t f o r m and t h e m e t a t a r s a l heads c r o s s e d t h e x a x i s . An o s c i l l o s c o p e was used t o d e t e c t t h e d i s p l a c e m e n t o f t h e c e n t e r o f p r e s s u r e on t h e f o r c e p l a t f o r m and c o n v e r t t h i s i n t o a s i n g l e v e c t o r . When t h e c e n t e r o f p r e s s u r e was l o c a t e d on t h e x a x i s o f t h e p l a t f o r m , t h e l i n e on t h e scope r e p r e s e n t i n g m otion i n t h e 'y' p l a n e was a l i g n e d w i t h t h e scope's z e r o l i n e . When t h e c e n t e r o f p r e s s u r e i s moved t o t h e r e a r f o o t t h e 'y' p l a n e l i n e o f t h e scope dropped below t h e z e r o l i n e . 22 The s u b j e c t i n i t i a l l y s t o o d on t h e r i g h t f o o t o n l y . S k i p o l e s were used t o a s s i s t , i n m a i n t a i n i n g b a l a n c e w i t h o u t s u p p o r t i n g t h e l o a d . The c e n t e r o f p r e s s u r e was t r a n s f e r r e d t o t h e r e a r o f t h e f o o t . T h i s p o s i t i o n was deemed t h e " s t a r t p o s i t i o n " . The s u b j e c t t h e n t r a n s f e r r e d p r e s s u r e t o t h e m e t a t a r s a l heads w h i l e m a i n t a i n i n g h e e l c o n t a c t w i t h t h e f o r c e p l a t f o r m . T h i s "end p o s i t i o n " i s c o n f i r m e d on t h e scope by t h e a l i g n m e n t o f t h e •y 1 p l a n e l i n e w i t h t h e z e r o l i n e . These s t a r t and end p o s i t i o n s were chosen f o r use i n t h i s s t u d y as t h e y mimic t h e a c t i o n s o f u n w e i g h t i n g and w e i g h t i n g d u r i n g a c a r v e d p a r a l l e l t u r n . B o t h t h e s t a r t and end p o s i t i o n s were h e l d f o r f i v e seconds each. The s u b j e c t p r a c t i s e d moving from t h e s t a r t p o s i t i o n t o t h e end p o s i t i o n u n t i l t h e y c o u l d c o n s i s t e n t l y match up t h e l i n e s on t h e scope. T h i s t o o k a mean o f 13.07 t r i a l s . When t h e s u b j e c t had s u c c e s s f u l l y c o mpleted t h e p r a c t i s e t r i a l s , photographs were t a k e n o f t h e s t a r t and end p o s i t i o n s o v er two t r i a l s u s i n g 35mm s l i d e f i l m . The n a v i c u l a r was photographed f i r s t , f o l l o w e d by t h e r e a r f o o t . The s u b j e c t ' s f r o n t lower l e g was t h e n photographed i n a p o s i t i o n i n w h i c h c e n t e r o f p r e s s u r e was n e u t r a l . The s u b j e c t r e p e a t e d t h e p r o t o c o l u s i n g t h e r i g h t f o o t w i t h t h e custom f o o t b e d , t h e l e f t f o o t u s i n g t h e non custom i n s o l e , and t h e l e f t f o o t u s i n g t h e custom f o o t b e d . A 30 cm r u l e r was p l a c e d b e s i d e t h e s u b j e c t d u r i n g a l l photographs t o a c t as a s c a l i n g r o d i n l a t e r a n a l y s e s . 23 Data A n a l y s i s . P r o c e s s e d s l i d e s were p r o j e c t e d onto w h i t e paper t a p e d t o a w a l l . Images o f t h e marked p o i n t s on b o t h t h e s u b j e c t and t h e boot were t r a c e d onto t h e paper. A g r i d was c o n s t r u c t e d on each i n d i v i d u a l d a t a page u s i n g t h e boot landmark as t h e o r i g i n . The d i s t a n c e o f t h e a n a t o m i c a l landmark from t h e x and y axes was measured and r e c o r d e d as a s e t o f c o o r d i n a t e s . A n g l e s were measured by p r o t r a c t o r . S c a l i n g f a c t o r s were c a l c u l a t e d f o r each frame by m e a s u r i n g t h e image o f t h e s c a l i n g r o d . R e a l l e n g t h c o o r d i n a t e s were c a l c u l a t e d by image l e n g t h / s c a l i n g f a c t o r . D i f f e r e n c e s i n s t a r t and end p o s i t i o n s f o r a l l measurements were c a l c u l a t e d and r e c o r d e d . S t a t i s t i c a l A n a l y s i s . L a b o r a t o r y d a t a were e n t e r e d i n t o t h e computer program L o t u s 1-2-3 where averages were c a l c u l a t e d a c r o s s t h e two t r i a l s f o r each s u b j e c t i n each v a r i a b l e . Averages were t r a n s f e r r e d t o a n o t h e r computer program, S y s t a t f o r a n a l y s i s as two f a c t o r models w i t h two l e v e l s f o r each f a c t o r and r e p e a t e d measures on each l e v e l at a s i g n i f i c a n c e o f 0.05. Graphs were produc e d u s i n g t h e H a r v a r d G r a p h i c s computer program. S k i i n g S e c t i o n Data C o l l e c t i o n . L e v e l s o f p e r c e i v e d p a i n , f a t i g u e , and edge c o n t r o l were a s s e s s e d u s i n g h o r i z o n t a l v i s u a l analogue s c a l e s . Each s c a l e c o n s i s t e d o f 10cm h o r i z o n t a l l i n e w i t h s t o p s a t b o t h ends, a t r i g h t a n g l e s t o t h e l i n e . The s t o p s were l a b e l e d "none" and " s e v e r e " f o r b o t h t h e p a i n and t h e 24 f a t i g u e s c a l e s and "none" and " t o t a l " f o r t h e edge c o n t r o l s c a l e s . The s u b j e c t s were asked t o make a mark on t h e l i n e s a t t h e p o i n t which t h e y f e l t c o r r e s p o n d e d t o t h e i r e x p e r i e n c e s . The v i s u a l analogue s c a l e was chosen as i t was s i m p l e enough t o be a d m i n i s t e r e d on t h e h i l l i m m e d i a t e l y f o l l o w i n g each s k i r u n . O n - h i l l s k i t e s t i n g t o o k p l a c e over t h e c o u r s e o f one s k i day. S u b j e c t s s k i e d i n t h e i r own s k i b o o t s . A draw was made t o randomly a s s i g n each s u b j e c t t o one o f two t e s t g r oups. One group s k i e d t h e f i r s t h a l f o f t h e day u s i n g non custom i n s o l e s w h i l e t h e o t h e r group used t h e custom molded f o o t b e d s . A l t h o u g h t h e s u b j e c t s were not i n f o r m e d as t o whic h o f t h e two groups t h e y had been a s s i g n e d , t h e d i f f e r e n c e s i n f e e l o f t h e two t y p e s o f i n s o l e s make a t r u l y b l i n d s t u d y i m p r o b a b l e . A l l s u b j e c t s spent two hours f r e e s k i i n g t o adapt t o w h i c h e v e r i n s o l e t h e y were u s i n g . A f t e r two hours t h e group g a t h e r e d f o r a s e t o f assessment r u n s . These runs were s k i e d on i n t e r m e d i a t e t e r r a i n c o n s i s t i n g o f a g r a d u a l s l o p e , groomed c o n d i t i o n s , and o n l y a few s m a l l bumps. The s u b j e c t s s k i e d one run u s i n g s h o r t r a d i u s t u r n s , and one run u s i n g l o n g r a d i u s t u r n s . F o l l o w i n g each o f t h e s e runs t h e s u b j e c t s c o m p l e t e d a v i s u a l analogue s c a l e t o a s s e s s p e r c e i v e d edge c o n t r o l d u r i n g t h e r u n . A f t e r c o m p l e t i n g b o t h runs t h e s u b j e c t s s k i e d two t i m e d runs each t h r o u g h a r a c e c o u r s e . A l l t i m e s were r e c o r d e d . F o l l o w i n g t h e t i m e d runs each s u b j e c t completed v i s u a l analogue s c a l e s f o r b o t h 25 p a i n and f a t i g u e l e v e l s a t t h e end o f t h e s e s s i o n . The groups t h e n changed assignments and r e p e a t e d t h e p r o t o c o l w i t h t h e i r new f o o t b e d / i n s o l e . Data A n a l y s i s . V i s u a l analogue s c a l e s were measured f o r d i s t a n c e from t h e l e f t s t o p t o t h e s u b j e c t ' s mark and a l l d i s t a n c e s were r e c o r d e d . Race t i m e s were r e c o r d e d . S t a t i s t i c a l A n a l y s i s . S k i i n g d a t a were e n t e r e d i n t o t h e computer program L o t u s 1-2-3 where averages were c a l c u l a t e d f o r each s u b j e c t i n each v a r i a b l e . Averages were t r a n s f e r r e d i n t o t h e S y s t a t computer program f o r a n a l y s i s as one f a c t o r models w i t h two l e v e l s and r e p e a t e d measures on each l e v e l a t a s i g n i f i c a n c e o f 0.05. Graphs were p r o d u c e d u s i n g H a r v a r d G r a p h i c s computer program. 26 Chapter 4 RESULTS AND DISCUSSION D e s c r i p t i o n o f S u b j e c t s The s u b j e c t group u t i l i z e d i n t h i s s t u d y c o n s i s t e d o f 15 advanced l e v e l a d u l t s k i e r s who e x h i b i t e d more t h a n t h r e e degrees o f s u b t a l a r v a r u s i n each f o o t . As i n d i c a t e d i n Appendix C, t h e mean age, h e i g h t , and mass o f t h e s u b j e c t group was 25.13 + 3.96 y e a r s , 171.17 +5.69 cm, and 70.47 + 7.25 kg r e s p e c t i v e l y . The group e x h i b i t e d an average o f 5.6 + 1.5 degrees o f s u b t a l a r v a r u s i n t h e r i g h t f o o t , and 4.9 +_ 1.2 degrees o f s u b t a l a r v a r u s i n t h e l e f t f o o t , a d i f f e r e n c e w h i c h was 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 (p=0.156). The average number o f y e a r s o f s k i i n g e x p e r i e n c e was 15.47 +_ 3.15 y e a r s . A l l s u b j e c t s p a r t i c i p a t e d i n t h e s k i i n g s e c t i o n o f t h e s t u d y . A subgroup c o n s i s t i n g o f 13 o f t h e o r i g i n a l group o f s u b j e c t s p a r t i c i p a t e d i n t h e l a b o r a t o r y s e c t i o n . L a b o r a t o r y S e c t i o n The p o s i t i o n o f t h e n a v i c u l a r t u b e r c l e , d i s p l a c e m e n t o f t h e t i b i a l t u b e r o s i t y from t h e c e n t e r l i n e o f t h e bo o t , and r e a r f o o t a n g l e were m o n i t o r e d as t h e y r e f l e c t e d t h e e v e n t s a s s o c i a t e d w i t h p r o n a t i o n and c o u l d be e a s i l y m o n i t o r e d i n t h e l a b o r a t o r y . N a v i c u l a r Drop. As weight i s t r a n s f e r r e d f o r w a r d a l o n g t h e f o o t d u r i n g t h e c a r v i n g phase o f t h e s k i t u r n t h e n a v i c u l a r t u b e r c l e t y p i c a l l y moves b o t h f o r w a r d and downward 27 i n r e l a t i o n t o i t s p o s i t i o n d u r i n g t h e unweighted phase o f t h e t u r n . T h i s n a v i c u l a r motion, r e f e r e d t o i n t h i s s t u d y as n a v i c u l a r drop, i s s i m i l a r t o t h a t e x p e r i e n c e d d u r i n g w a l k i n g as t h e f o o t moves from t h e h e e l s t r i k e phase t h r o u g h t o t h e p o i n t j u s t p r i o r t o t o e - o f f . N a v i c u l a r drop a l o n g b o t h t h e x and y axes o f t h e s a g g i t a l p l a n was c a l c u l a t e d f o r each s u b j e c t ' s r i g h t and l e f t f o o t o v er a t o t a l o f f o u r t r i a l s . Two t r i a l s were p e r f o r m e d u s i n g t h e non custom i n s o l e s and two t r i a l s used t h e custom molded f o o t b e d s . L o c a t i o n o f t h e n a v i c u l a r t u b e r c l e was d e t e r m i n e d a t b o t h t h e s t a r t and end p o s i t i o n s as o u t l i n e d i n t h e p r o c e d u r e s s e c t i o n . The l o c a t i o n o f t h e n a v i c u l a r t u b e r c l e on b o t h t h e x and y axes f o r t h e s t a r t and end p o s i t i o n s u s i n g b o t h t h e non-custom i n s o l e s and t h e custom molded f o o t b e d s a r e summarized i n F i g u r e s 2-3. The non-custom i n s o l e s a r e r e f e r r e d t o as "boot" and t h e custom molded i n s o l e s a r e shown as " f o o t b e d " on a l l c h a r t s . In t h e s t a r t p o s i t i o n f o r b o t h t h e r i g h t and l e f t f e e t t h e r e was 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 d i f f e r e n c e between t h e l o c a t i o n o f t h e n a v i c u l a r t u b e r c l e i n b o t h t h e x and y d i r e c t i o n when comparing t h e boot t o t h e f o o t b e d . The n a v i c u l a r was p o s i t i o n e d b o t h h i g h e r and f a r t h e r backward when t h e s u b j e c t was s t a n d i n g on t h e f o o t bed as compared t o s t a n d i n g on t h e non-custom i n s o l e . T h i s d i f f e r e n c e can be a t t r i b u t e d t o t h e t h i c k n e s s o f t h e f o o t b e d as compared t o t h e non-custom i n s o l e as w e l l as t o t h e r e a l i g n m e n t o f t h e 28 cm SB vs SF sig., p • 0.034 EB vs EF sig., p • 0.000 10.0 i START END • i BOOT E3 FOOTBED Figure 2a. Navicular start/end positions, x dir., right foot cm SB vs SF sig., p • 0.000 EB vs EF sig., p • 0.000 10.0 i START END H BOOT EZ3 FOOTBED Figure 2b. Navicular start/end positions, x dir., left foot SB - S t a r t Boot SF - S t a r t Footbed EB - End Boot EF - End Footbed 2 9 cm SB vs SF sig., p • 0.000 EB vs EF sig., p - 0.000 10.0 i — • START END • i BOOT EZ2 FOOTBED Figure 3a. Navicular start/end positions, y dir., right foot 10.0 8.0 cm SB vs SF sig., p • 0.000 EB vs EF sig., p • 0.000 2,0 0.0 START END • I BOOT ¥22 FOOTBED Figure 3b. Navicular start/end positions* y dir., left foot SB - S t a r t Boot SF - S t a r t Footbed EB - End Boot EF - End Footbed 30 f o o t by t h e f o o t b e d . There was a s i m i l a r s i g n i f i c a n c e when comparing end p o s i t i o n s o f t h e n a v i c u l a r t u b e r c l e . The n a v i c u l a r was s i t u a t e d h i g h e r and f a r t h e r back i n t h e boot when t h e s u b j e c t was s t a n d i n g i n t h e end p o s i t i o n on t h e custom f o o t b e d t h a n i t was when s t a n d i n g i n t h e end p o s i t i o n on t h e i n s o l e . F i g u r e s 4-5 show t h e range t h r o u g h w h i c h t h e n a v i c u l a r t u b e r c l e moves when t h e s u b j e c t s h i f t s from t h e s t a r t t o t h e end p o s i t i o n . T h i s range was d e t e r m i n e d by c a l c u l a t i n g t h e d i f f e r e n c e s between t h e s t a r t and end p o s i t i o n s o f t h e n a v i c u l a r . There i s 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 d i f f e r e n c e i n t h e amount o f n a v i c u l a r m otion e x p e r i e n c e d when u s i n g t h e two t y p e s o f i n s o l e s . The custom f o o t b e d s a l l o w e d s i g n i f i c a n t l y l e s s f o r w a r d and downward motion t h a n d i d t h e non-custom i n s o l e s . These f i n d i n g s i n d i c a t e t h a t t h e custom i n s o l e s changed t h e p o s i t i o n o f t h e f o o t and r e d u c e d t h e amount o f motion e x p e r i e n c e d i n s i d e o f t h e boot, s p e c i f i c a l l y t h a t n a v i c u l a r m otion which i s a s s o c i a t e d w i t h t h e f l a t t e n i n g o f t h e a r c h d u r i n g p r o n a t i o n . I t was n o t e d t h a t one s u b j e c t d i s p l a y e d a s l i g h t backward and downward motion o f t h e l e f t n a v i c u l a r t u b e r c l e w h i l e u s i n g t h e non-custom i n s o l e . One s t u d y c o n d u c t e d by a boot m a n u f a c t u r e r has shown t h i s t o be a somewhat common phenomena w i t h t h e use o f o v e r l a p d e s i g n b o o t s due t o s l i p p a g e a t t h e h e e l (Walkhoff and Baumann, 1987). The s u b j e c t d i s p l a y e d t h e more t y p i c a l f o r w a r d and downward mot i o n when u s i n g t h e custom molded f o o t b e d . 31 1.00 0.80 0.60 0.40 0.20 0.00 cm R vs L not sig.; B vs F sig., p • 0.000 RIGHT LEFT H BOOT ¥ZA FOOTBED Figure 4. Navicular motion in the x direction. R - R i g h t Foot B - Boot L - L e f t Foot F - Footbed 32 cm R vs L not sig.; B vs F sig., p • 0.000 0.60 0.40 H 0.20 0.00 RIGHT LEFT H BOOT EZ3 FOOTBED Figure 5. Navicular motion in the y direction. R - R i g h t Foot L - L e f t Foot B - Boot F - Footbed 33 There was no s i g n i f i c a n t d i f f e r e n c e between t h e n a v i c u l a r motions o f t h e r i g h t and l e f t f e e t o f t h e s u b j e c t group. There was no s i g n i f i c a n t i n t e r a c t i o n between t y p e o f i n s o l e and f e e t . R e a r f o o t A n g l e . The a n g l e c r e a t e d by t h e m i d l i n e o f t h e lo w e r l e g as i t moves away from t h e p e r p e n d i c u l a r was t a k e n as t h e r e a r f o o t a n g l e i n t h i s s t u d y . Photographs were t a k e n of t h e r e a r f o o t i n t h e s t a r t and end p o s i t i o n s u s i n g b o t h non-custom i n s o l e s and custom f o o t b e d s . These a n g l e s , e x p r e s s e d i n degrees a re d i s p l a y e d i n F i g u r e 6. The group r e s u l t s comparing t h e r e a r f o o t a n g l e a t t h e s t a r t p o s i t i o n o f t h e non-custom i n s o l e s t o t h a t a t t h e s t a r t p o s i t i o n o f t h e custom f o o t b e d s f o r t h e r i g h t f o o t showed a s i g n i f i c a n t d i f f e r e n c e . 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 d i f f e r e n c e was a l s o found when comparing t h e r e a r f o o t a n g l e s a t t h e end p o s i t i o n s o f t h e two t y p e s o f i n s o l e s . I n b o t h c a s e s t h e a n g l e o f t h e r e a r f o o t was d e c r e a s e d when u s i n g t h e custom f o o t b e d s as compared t o t h e a n g l e e x h i b i t e d when u s i n g t h e i n s o l e s . The r e s u l t s were t h e same f o r t h e l e f t f o o t . T h i s d i f f e r e n c e i n a n g l e s can be a t t r i b u t e d t o t h e change i n f o o t a l i g n m e n t b r o u g h t about by t h e custom molded f o o t b e d s . N e i t h e r t h e non-custom i n s o l e n or t h e custom f o o t b e d a l l o w e d any s i g n i f i c a n t change i n a n g l e when moving from t h e s t a r t t o t h e end p o s i t i o n w i t h e i t h e r f o o t . The i n t e g r i t y o f t h e boot a t t h e r e a r may i n f l u e n c e t h e amount o f motion e x p e r i e n c e d by t h e r e a r f o o t . The r e s u l t s i n d i c a t e t h a t 34 SB vs SF sig., p • 0.000; EB vs EF sig., p • 0.000 SB vs EB not sig.; SF vs EF not sig. 7.0 i BOOT FOOTBED • START 1ZZ2-END Figure 6a. Rearfoot angles at start and end, right foot. SB vs SF sig., p • 0.000; EB vs EF sig., p • 0.000 SB vs EB not sig.; SF vs EF not sig. 7.0 | 6.0 -BOOT FOOTBED • i START E22 END Figure 6b. Rearfoot angles at start and end, left foot. SB - S t a r t Boot SF - S t a r t Footbed EB - End Boot EF - End Footbed 35 w h i l e n e i t h e r t y p e o f i n s o l e a l l o w s any s i g n i f i c a n t r e a r f o o t m o t i o n , t h e custom f o o t b e d s m a i n t a i n t h e l e g s i g n i f i c a n t l y c l o s e r t o t h e p e r p e n d i c u l a r b o t h at t h e s t a r t and a t t h e end p o s i t i o n . There was a s i g n i f i c a n t d i f f e r e n c e found i n b o t h t h e s t a r t and end p o s i t i o n s when comparing t h e r e a r f o o t a n g l e s o f t h e r i g h t f o o t t o t h e l e f t f o o t . A l t h o u g h t h e non-weight b e a r i n g measurements o f s u b t a l a r v a r u s t a k e n d u r i n g t h e i n i t i a l s c r e e n i n g p r o c e s s showed no s i g n i f i c a n t d i f f e r e n c e between f e e t , added f a c t o r s such as w e i g ht b e a r i n g , and knee and h i p a l i g n m e n t s c o u l d h e l p t o a m p l i f y any d i f f e r e n c e s w h i c h d i d e x i s t . T h i s r e s u l t i s c o n s i s t e n t w i t h o t h e r r e s e a r c h f i n d i n g s w h i c h have i n d i c a t e d t h e d i f f e r e n c e s i n b i o m e c h a n i c a l parameters when comparing r i g h t and l e f t f e e t (McKenzie, Clement, and Taunton, 1985). T h i s f i n d i n g s u p p o r t s t h e concept of c r e a t i n g f o o t b e d s f o r each f o o t s e p a r a t e l y . There was no s i g n i f i c a n t i n t e r a c t i o n between t h e t y p e o f i n s o l e and f e e t . T i b i a l R o t a t i o n . T i b i a l r o t a t i o n was measured by t h e h o r i z o n t a l d i s p l a c e m e n t (x d i r e c t i o n ) o f t h e t i b i a l t u b e r c l e from a l i n e l y i n g p e r p e n d i c u l a r t o t h e f l o o r and p a s s i n g t h r o u g h t h e midseam o f t h e b o o t . T h i s v a r i a b l e was measured i n one p o s i t i o n o n l y . T h i s p o s i t i o n p l a c e d each s u b j e c t on one l e g a t a t i m e w i t h w e i g ht e q u a l l y d i s t r i b u t e d a c r o s s t h e f o o t . The r e s u l t s a r e shown i n F i g u r e 7. 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 d i f f e r e n c e was found between t h e p o s i t i o n s o f t h e t i b i a l t u b e r o s i t y when comparing t h e two t y p e s o f 36 cm B vs F sig., p • 0.000; R vs L sig., p • 0.037 0.0 RIGHT LEFT H BOOT E D FOOTBED Figure 7. Tibial tubercle horizontal distance from midline. RB - R i g h t Boot LB - L e f t Boot RF - R i g h t F o otbed LF - L e f t Footbed 37 i n s o l e s . The t u b e r o s i t y was s i g n i f i c a n t l y c l o s e r t o t h e m i d l i n e when t h e s u b j e c t s were u s i n g t h e custom molded f o o t b e d s . T h i s f i n d i n g was t r u e f o r b o t h t h e r i g h t and l e f t f e e t . T h i s r e s u l t was a t t r i b u t e d t o t h e custom molded f o o t b e d a l t e r i n g t h e p o s i t i o n o f t h e f o o t w h i c h i n t u r n changed t h e a l i g n m e n t o f t h e lower l i m b . There was 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 d i f f e r e n c e between t h e l o c a t i o n o f th e t u b e r o s i t y f o r t h e r i g h t and l e f t f e e t . S e p a r a t e s t a t i s t i c a l a n a l y s e s p e r f o r m e d on each t y p e o f i n s o l e a l o n e showed t h a t t h i s s i g n i f i c a n c e o c c u r r e d when u s i n g t h e non-custom i n s o l e s . The custom molded f o o t b e d s showed no s i g n i f i c a n t d i f f e r e n c e between t h e p o s i t i o n o f t h e t i b i a l t u b e r o s i t y o f t h e r i g h t and l e f t f e e t . T h i s r e s u l t i n d i c a t e d t h a t t h e custom molded f o o t b e d s b o t h d e c r e a s e d t h e amount o f t i b i a l r o t a t i o n and m i n i m i z e d t h e between l e g d i f f e r e n c e s . Summary. The custom molded f o o t b e d s m a i n t a i n e d t h e n a v i c u l a r t u b e r c l e i n a p o s i t i o n i n s i d e o f t h e s k i boot w h i c h was b o t h h i g h e r and f a r t h e r back as compared t o t h e non-custom i n s o l e s a t b o t h t h e s t a r t and end p o s i t i o n s . T h i s was due t o t h e t h i c k n e s s o f t h e f o o t b e d as w e l l as t o th e change i n f o o t p o s i t i o n brought about by t h e f o o t b e d . F u r t h e r , t h e custom f o o t b e d s a l l o w e d l e s s f o r w a r d and downward motion o f t h e n a v i c u l a r t h a n d i d t h e i n s o l e s when moving from t h e s t a r t t o t h e end p o s i t i o n . The r e a r f o o t a n g l e was s m a l l e r a t b o t h t h e s t a r t and end p o s i t i o n when u s i n g t h e custom f o o t b e d as compared t o 38 t h e non-custom i n s o l e . T h i s was due t o t h e r e p o s i t i o n i n g o f t h e f o o t by t h e f o o t b e d . There was no d i f f e r e n c e between t h e amount o f motion t h a t e i t h e r o f t h e t y p e s o f i n s o l e s a l l o w e d when moving from t h e s t a r t t o t h e end p o s i t i o n . The custom molded f o o t b e d s m a i n t a i n e d t h e t i b i a l t u b e r o s i t y i n a p o s i t i o n c l o s e r t o t h e m i d - l i n e t h a n d i d t h e non-custom i n s o l e s . A g a i n , t h i s i s due t o t h e r e p o s i t i o n i n g o f t h e f o o t by t h e f o o t b e d . S k i i n g S e c t i o n H o r i z o n t a l v i s u a l analogue s c a l e s were u t i l i z e d by t h e s u b j e c t s i n o r d e r t o r a t e t h e i r e x p e r i e n c e s w i t h edge c o n t r o l , p a i n , and f a t i g u e w h i l e s k i i n g . The group d a t a from t h e s e s c a l e s are d i s p l a y e d i n F i g u r e s 8-10. Edge C o n t r o l . The s u b j e c t s gave t h e custom molded f o o t b e d s s i g n i f i c a n t l y h i g h e r marks t h a n t h e non-custom i n s o l e s i n t h e c a t e g o r y o f edge c o n t r o l . T h i s was t r u e f o r b o t h t h e s h o r t r a d i u s and t h e l o n g r a d i u s t u r n s . P a i n . A l t h o u g h t h e s u b j e c t s e x p e r i e n c e d s l i g h t l y more p a i n w i t h t h e use o f t h e custom molded f o o t b e d s t h a n w i t h t h e i r own non custom i n s o l e s , t h e f i g u r e s were not s i g n i f i c a n t . The s l i g h t i n c r e a s e i n p a i n was a t t r i b u t e d t o an i n s u f f i c i e n t b r e a k - i n p e r i o d when u s i n g t h e new custom f o o t b e d s . A d j u s t m e n t s such as b u c k l e t i g h t n e s s and sock t h i c k n e s s w i t h t h e use o f any new f o o t b e d o r s k i boot t a k e more t i m e t h a n was a v a i l a b l e d u r i n g t h i s s t u d y . I t was n o t e d t h a t most s u b j e c t s e x p e r i e n c e d l e s s p a i n as t h e y spent more t i m e i n t h e custom f o o t b e d s but were i n s t r u c t e d t o complete t h e r a t i n g s s c a l e based on t h e i r o v e r a l l i m p r e s s i o n d u r i n g t h e e n t i r e t e s t p e r i o d . F a t i g u e . The s u b j e c t s found t h e i r f e e t and l e g s t o be s i g n i f i c a n t l y l e s s f a t i g u e d a f t e r s k i i n g w i t h t h e custom f o o t b e d s t h a n w i t h t h e non-custom i n s o l e s . Timed Runs. S u b j e c t s were t i m e d f o r a t o t a l o f f o u r t r i a l s t h r o u g h a r a c e c o u r s e . The average t i m e s f o r t h e group were s i g n i f i c a n t l y f a s t e r when u s i n g t h e custom molded f o o t b e d s as compared t o t h e non custom i n s o l e s . I n a d d i t i o n i t was n o t e d t h a t a l l s u b j e c t s had e q u i v a l e n t o r f a s t e r t i m e s when u s i n g t h e custom f o o t b e d s as compared t o t h e non custom i n s o l e s . A l t h o u g h each s u b j e c t s k i e d t h e same r a c e c o u r s e a l l f o u r t i m e s , t h e e f f e c t s o f l e a r n i n g were c o n t r o l l e d by t h e d i v i s i o n o f t h e group i n t o two subgroups. W h i l e h a l f o f t h e s u b j e c t s s k i e d t h e i r t h i r d and f o u r t h runs u s i n g t h e custom f o o t b e d s , t h e o t h e r h a l f o f t h e group s k i e d t h e i r f i r s t and second runs u s i n g t h e custom f o o t b e d s . Summary. The s u b j e c t group r a t e d t h e custom f o o t b e d s as s i g n i f i c a n t l y b e t t e r t h a n t h e custom i n s o l e s i n p r o v i d i n g edge c o n t r o l f o r b o t h s h o r t and l o n g r a d i u s t u r n s . The f o o t b e d s were a l s o r a t e d as c a u s i n g s i g n i f i c a n t l y l e s s f a t i g u e t h a n non-custom i n s o l e s . The s u b j e c t group d i d not f i n d any s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s i n t h e l e v e l o f p a i n e x p e r i e n c e d w h i l e u s i n g e i t h e r t y p e o f i n s o l e s . 40 B vs F sig., p • 0.000 100 i B vs F sig.. p • 0.001 100 i BOOT , FOOTBED Figure 8b. Edge control ratings for long radius turns. B - Boot F- Footbed 41 B vs F not sig. S C o R E 1 0 0 100 75 50 25 S C O R E / 1 0 0 100 75 50 25 S.O. 17.886 S.D. 17.91 BOOT FOOTBED Figure 9a. Pain ratings. B vs F sig., p - 0.005 S.D. 18.27 S.D. 20.149 BOOT FOOTBED Figure 9b. Fatigue ratings. B - Boot F - Footbed 42 19.00 18.50 18.00 17.50 17.00 TIME (SEC) B vs F sig., p • 0.000 17.76 • / - 1.15 BOOT FOOTBED Figure 10. Race results. B - Boot F - Footbed 43 Chapter 5 CONCLUSIONS AND RECOMMENDATIONS T h i s i n v e s t i g a t i o n was d e s i g n e d t o t e s t t h e h y p o t h e s i s t h a t custom molded s k i boot f o o t b e d s c o u l d c o n t r o l t h e e v e n t s a s s o c i a t e d w i t h p r o n a t i o n more e f f e c t i v e l y t h a n non-custom i n s o l e s . The c o n t r o l o f p r o n a t i o n was t e s t e d by a n a l y z i n g t h e r e l a t e d motions o f v a r i o u s f o o t and lo w e r l e g landmarks. N a v i c u l a r drop was m o n i t o r e d as i t r e f l e c t s t h e c o l l a p s i n g o f t h e m e d i a l a r c h which accompanies t h e a b d u c t i o n and a n k l e e v e r s i o n a s s o c i a t e d w i t h p r o n a t i o n . R e a r f o o t a n g l e was chosen as an o t h e r i n d i c a t o r o f a b d u c t i o n and a n k l e e v e r s i o n . The l o c a t i o n o f t h e t i b i a l t u b e r c l e was m o n i t o r e d because t i b i a l r o t a t i o n has been shown t o accompany p r o n a t i o n . The r e s u l t s o f t h e i n v e s t i g a t i o n showed t h e custom f o o t b e d s t o c o n t r o l n a v i c u l a r drop and t i b i a l r o t a t i o n more e f f e c t i v e l y t h a n t h e non-custom i n s o l e s . The amount o f r e a r f o o t a n g l e a t b o t h t h e s t a r t and end p o s i t i o n s was s i g n i f i c a n t l y changed w i t h t h e use o f custom f o o t b e d s even though o v e r a l l motion was not a f f e c t e d . I t was h y p o t h e s i z e d t h a t custom f o o t b e d s c o u l d improve edge c o n t r o l , d e c r e a s e p a i n and d e c r e a s e f a t i g u e as compared t o non-custom i n s o l e s . The r e s u l t s o f t h e i n v e s t i g a t i o n i n d i c a t e d t h a t t h e t e s t group f e l t t h a t custom f o o t b e d s d i d i n c r e a s e edge c o n t r o l i n b o t h s h o r t and l o n g r a d i u s t u r n s , and d e c r e a s e d t h e amount o f f a t i g u e e x p e r i e n c e d . The group d i d not r e p o r t any s i g n i f i c a n t d i f f e r e n c e s i n t h e l e v e l o f p a i n e x p e r i e n c e d . These r e s u l t s were based on p u r e l y s u b j e c t i v e a n a l y s e s . Timed runs t h r o u g h a r a c e c o u r s e r e s u l t e d i n f a s t e r t i m e s f o r s k i e r s when u s i n g t h e custom f o o t b e d s as compared t o t h e non-custom i n s o l e s . I t was b e l i e v e d t h a t m a i n t a i n i n g t h e s u b t a l a r j o i n t i n a more n e u t r a l p o s i t i o n would r e s u l t i n a l l t h e s k i i n g improvements p r e v i o u s l y d i s c u s s e d . From t h e d i f f e r e n c e s i n landmark p o s i t i o n s i n b o t h s t a r t and end p o s i t i o n s when comparing t h e two t y p e s o f i n s o l e s , i t appears t h a t t h e custom f o o t b e d s e f f e c t i v e l y r e a l i g n e d t h e f o o t w i t h i n t h e s k i b o o t . Because o f t h e m o l d i n g t e c h n i q u e u t i l i z e d i n t h i s s t u d y , i t i s assumed t h a t t h e f o o t b e d does m a i n t a i n t h e f o o t i n a n e u t r a l p o s i t i o n d u r i n g w e i g ht b e a r i n g . I n a d d i t i o n t o t h e r e a l i g n m e n t o f t h e f o o t , t h e f o o t b e d s e r v e d t o f i l l i n any gaps under t h e f o o t and p r o v i d e a s o l i d , m i n i m a l l y c o m p r e s s i b l e base o f s u p p o r t . The c o m b i n a t i o n o f t h e s e two f a c t o r s l i k e l y a l l o w s f o r t h e c o n t r o l o f motion w i t n e s s e d d u r i n g t h i s i n v e s t i g a t i o n . I t i s a l s o b e l i e v e d t o be r e s p o n s i b l e f o r an improved t r a n s m i s s i o n o f f o r c e s between t h e s k i e r and t h e bo o t , r e s u l t i n g i n b e t t e r edge c o n t r o l and d e c r e a s e d e f f o r t t o c a r v e a t u r n . The s u b j e c t s u t i l i z e d i n t h i s s t u d y e x h i b i t e d more t h a n t h r e e degrees o f s u b t a l a r v a r u s when measured i n a non-w e i g h t b e a r i n g p o s i t i o n . The e f f e c t i v e n e s s o f t h e f o o t b e d s i n c o n t r o l l i n g t h e motion e x p e r i e n c e d by t h e s e s u b j e c t s c o u l d be tho u g h t t o i n d i c a t e a s i m i l a r e f f e c t i v e n e s s when f o o t b e d s a r e used by s k i e r s w i t h l e s s e r degrees o f 45 m a l a l i g n m e n t . However, t h e use o f t h i s p r o d u c t by such s k i e r s would not n e c e s s a r i l y be i n d i c a t e d . C o n c l u s i o n s Based upon t h e r e s u l t s o f t h i s s t u d y , t h e f o l l o w i n g c o n c l u s i o n s were made w i t h r e g a r d s t o t h e h y p o t h e s e s : 1. a) Custom molded f o o t b e d s c o n t r o l l e d t h e n a v i c u l a r drop a s s o c i a t e d w i t h p r o n a t i o n more e f f e c t i v e l y t h a n non-custom i n s o l e s . b) Custom f o o t b e d s r e a l i g n e d t h e s u b t a l a r j o i n t so as t o d e c r e a s e t h e r e a r f o o t a n g l e as compared t o t h a t e x p e r i e n c e d w i t h t h e use o f non-custom i n s o l e s . Custom f o o t b e d s d i d not reduce t h e amount o f r e a r f o o t m otion as compared t o t h a t e x p e r i e n c e d w i t h t h e use o f non-custom i n s o l e s . c) Custom molded f o o t b e d s r e a l i g n e d t h e f o o t and l o w e r l e g so as t o m a i n t a i n t h e t i b i a l t u b e r c l e i n a p o s i t i o n c l o s e r t o c e n t e r t h a n t h a t e x p e r i e n c e d w i t h t h e use o f t h e non-custom i n s o l e . 2. The h y p o t h e s i s t h a t custom f o o t b e d s d e c r e a s e t h e amount o f p a i n e x p e r i e n c e d w h i l e s k i i n g was not s u p p o r t e d by t h e f i n d i n g s o f t h i s s t u d y . 3. The use o f custom f o o t b e d s r e s u l t e d i n a s u b j e c t i v e d e c r e a s e i n t h e amount o f f a t i g u e r e p o r t e d by t h e s u b j e c t group as compared t o t h a t r e p o r t e d w i t h t h e use o f t h e non-custom i n s o l e s . 46 4. The use o f custom f o o t b e d s r e s u l t e d i n an improvement i n t h e amount o f edge c o n t r o l r e p o r t e d by t h e t e s t group. 5. The use o f custom f o o t b e d s r e s u l t e d i n improved r a c e t i m e s f o r t h e s u b j e c t group. Recommendations The a b i l i t y o f custom molded s k i boot f o o t b e d s t o c o n t r o l s u b t a l a r motion and enhance t h e s k i i n g e x p e r i e n c e i s s u p p o r t e d by t h i s s t u d y . These f i n d i n g s were based on t h e use o f one s t y l e o f f o o t b e d . At t h e p r e s e n t t i m e t h e r e a r e o t h e r s t y l e s o f custom f o o t b e d b e i n g marketed t o s k i e r s . S k i e r s s h o u l d be aware t h a t some o f t h e f o o t b e d s a v a i l a b l e do not p r o v i d e a s o l i d bottom and may t h e r e f o r e be h i g h l y c o m p r e s s i b l e , a l l o w i n g more motion a t t h e n a v i c u l a r w i t h f o r w a r d w e i g h t t r a n s f e r . In a d d i t i o n , t h e use o f d i f f e r e n t m a t e r i a l s i n t h e c o n s t r u c t i o n o f t h e f o o t b e d s , as w e l l as t h e method o f m o l d i n g t h e f o o t b e d s can a l t e r t h e amount o f c o n t r o l t h e y p r o v i d e . The consumer s h o u l d be aware o f t h e d i f f e r e n c e s i n t h e a v a i l a b l e p r o d u c t s i n o r d e r t o f u l l y b e n e f i t from t h e use o f a custom molded f o o t b e d . F u t u r e d i r e c t i o n s f o r r e s e a r c h i n t h i s a r e a s h o u l d i n c l u d e l a b o r a t o r y t e s t i n g i n c o r p o r a t i n g t h e p r o t o c o l u t i l i z e d i n t h i s s t u d y f o r t h e a n a l y s e s o f d i f f e r e n t t y p e s o f s k i boot f o o t b e d s . F i e l d r e s e a r c h s h o u l d be p e r f o r m e d documenting i n j u r y r a t e s among s k i e r s u s i n g custom molded f o o t b e d s . Such i n v e s t i g a t i o n s would be b e n e f i c i a l a d d i t i o n s t o t h e p r e s e n t r e s e a r c h . REFERENCES B a t e s , B.T., O s t e r i n g , L.R., Mason, B., and James, L.S. (1979). Foot o r t h o t i c d e v i c e s t o modify s e l e c t e d a s p e c t s o f lo w e r e x t r e m i t y mechanics. The American  J o u r n a l o f S p o r t s M e d i c i n e , 7 ( 6 ) , 338-342. Cavanagh, P.R. (1980). The Running Shoe Book. Anderson World, Mountain View, C a l i f o r n i a . pp.241-260. 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M e d i c i n e and  S c i e n c e i n S p o r t and E x e r c i s e , 1 5 ( 2 ) , 171. S t a c o f f , A., and L u e t h i , S.M. (1986). S p e c i a l a s p e c t s o f shoe c o n s t r u c t i o n and f o o t anatomy. I n N i g g , B.M. (Ed.), B i o m e c h a n i c s o f Running Shoes, 117-137. Human K i n e t i c s , Champaign, I l l i n o i s . S u b o t n i c k , S . I . (1982). Foot o r t h o s e s i n s k i b o o t s . The P h y s i c i a n and S p o r t s M e d i c i n e , 10, 61-68. S u p e r f e e t Inshoe System. T e c h n i c a l Manual. (1983). W a l k h o f f , K., and Baumann, C.W. (1987). A l p i n e s k i boot h y s t e r e s i s c h a r a c t e r i s t i c s i n t e r p r e t e d f o r s k i e r t a r g e t groups w i t h i n t h e c u r r e n t s t a n d a r d s . I n Mote J r . , C D . and Johnson, R.J. ( E d s . ) , S k i i n g Trauma and S a f e t y 6 t h  I n t e r n a t i o n a l Symposium, 127-144. ASTM, P h i l a d e l p h i a , P e n n s y l v a n i a . 49 APPENDIX A DETERMINATION OF LOWER LIMB ALIGNMENT. Leg - h e e l a l i g n m e n t ( s u b t a l a r v a r u s ) - s u b j e c t i n prone p o s i t i o n w i t h f e e t e x t e n d e d c l e a r o f t h e e x a m i n i n g t a b l e - mark m i d l i n e o f t h e c a l c a n e u s a t i n t e r s e c t i o n o f A c h i l l e s tendon and a t a p o i n t 1.5cm d i s t a l - p l a c e two a d d i t i o n a l marks on t h e m i d l i n e o f t h e d i s t a l 1/3 o f t h e l e g t o r e p r e s e n t t h e l o n g i t u d i n a l a x i s o f t h e t i b i a - p l a c e t h e s u b t a l a r j o i n t i n n e u t r a l p o s i t i o n : s t a b i l i z e t h e f o r e f o o t by a p p l y i n g p r e s s u r e under t h e f o u r t h and f i f t h m e t a t a r s a l heads and d o r s i f l e x u n t i l t h e p o i n t o f r e s i s t a n c e , t h e n i n v e r t / e v e r t t h e f o o t t h r o u g h t h e a r c o f m otion u n t i l t h e b a l a n c e p o i n t i s i d e n t i f i e d - measure t h e a n g l e between t h e l o n g i t u d i n a l a x i s o f t h e l e g and h e e l u s i n g a goniometer James(1979) F o r e f o o t - h e e l a l i g n m e n t ( f o r e f o o t v a r u s ) - p l a c e s u b j e c t i n prone p o s i t i o n w i t h f e e t e x t e n d e d c l e a r o f t h e e x a m i n i n g t a b l e - marks on c a l c a n e u s from th e p r e v i o u s measurement a r e u sed as r e f e r e n c e s f o r t h e h e e l , t h e p l a n e o f t h e m e t a t a r s a l heads i s used i n r e f e r e n c e t o t h e s e marks - v a r u s a l i g n m e n t i s s a i d t o be p r e s e n t i f t h e p l a n e o f t h e f o r e f o o t a t t h e m e t a t a r s a l head l e v e l i s such t h a t t h e m e d i a l s i d e o f t h e f o o t r i s e s above a p e r p e n d i c u l a r p l a n e James(1979) F u n c t i o n a l H y p e r m o b i l i t y - s u b j e c t i s weight b e a r i n g , s t a n d i n g on t h e f l o o r - o b s e r v e t h e movement o f t h e g r e a t t o e , t h e f l a t t e n i n g o f t h e a r c h / n a v i c u l a r drop, and t i b i a l r o t a t i o n / k n e e v a l g u s w i t h weight b e a r i n g 50 APPENDIX B FOOTBED MOLDING PROCEDURE. 1. R e a r / M i d f o o t M o l d i n g - s u b j e c t i s s e a t e d c o m f o r t a b l y , shoes and socks o f f - p o s i t i o n t h e " 3 / 4 t h o t i c s " on t h e h e a t i n g p a d d l e s , and i n s i d e t h e oven (160 ^ C) f o r approx. lOmin.; p o s i t i o n t h e b l a n k s above t h e oven t o p i c k up ambient heat - w h i l e p o s i t i o n i n g t h e 3 / 4 t h o t i c on t h e m o l d i n g cap, i n s e r t t h e r e a r p a r t o f t h e b l a n k i n t o t h e oven t o warm s l i g h t l y b e f o r e p o s i t i o n i n g t h e b l a n k on t h e 3 / 4 t h o t i c (max. t i m e i n oven i s 20 s e c , t h i s e n s u r e s p r o p e r b o n d i n g o f t h e b l a n k and t h e 3 / 4 t h o t i c ) - remove 3 / 4 t h o t i c from s p a t u l a by t a p p i n g a g a i n s t t h e bench - c e n t e r t h e 3 / 4 t h o t i c and b l a n k f l a n g e s f l u s h w i t h t h e f l a n g e s o f t h e m o l d i n g cap - t a c k a l l edges t o g e t h e r - c e n t e r t h e p a r t s a g a i n s t t h e bottom o f t h e f o o t and g e n t l y s l i d e t h e h e e l o f t h e f o o t i n t o t h e h e e l cup - f a s t e n t h e r e t a i n i n g s t r a p - check t h a t t h e h e e l i s i n t h e back o f t h e s k i t h o t i c , t h e l o n g a x i s o f t h e f o o t and t h e s k i t h o t i c a r e i n a l i g n m e n t w i t h t h e cap, and t h e s k i t h o t i c and t h e cap are p e r p e n d i c u l a r t o t h e l o n g a x i s o f t h e l e g - s l i p on t h e p l a s t i c sock, p u l l up from h e e l , and s e c u r e w i t h a n k l e c i n c h band - t u r n on vacuum pump. - as a i r e v a c u a t e s , g e n t l y h o l d down t h e f i r s t m e t a t a r s a l head - p o s i t i o n t h e f o o t i n a l o c k e d , n e u t r a l p o s i t i o n (as d e s c r i b e d i n James 197 9 - see Appendix A) - have s u b j e c t s t e p down on t h e o t h e r f o o t and s l o w l y put th e down t h e ' o r t h o t i c ' f o o t j u s t t o t h e p o i n t o f c o n t a c t w i t h t h e ground - no weight - t u r n o f f t h e vacuum - s u b j e c t f l e x e s b o t h knees f o r w a r d s l i g h t l y , g e n t l y t r a n s f e r s w e i g h t t o b o t h f e e t e q u a l l y - m a i n t a i n n e u t r a l , l o c k e d p o s i t i o n - t u r n vacuum back on, have t h e s u b j e c t l i f t t h e f o o t a g a i n and s i t down f o r 30 seconds - a l l o w p a r t s t o c o o l f o r 2 min b e f o r e s e p a r a t i n g t h e f o o t b e d from t h e m o l d i n g cap 2. F o r e f o o t M o l d i n g - p o s i t i o n f o o t b e d s about h a l f way i n t o t h e oven f o r 3 min - do not heat more th a n 3-4cm beyond t h e l e a d i n g edge o f t h e 3 / 4 t h o t i c so as not t o s o f t e n t h e m e d i a l a r c h o r c u b o i d a r e a s - p o s i t i o n t h e s k i t h o t i c and m o l d i n g cap s q u a r e l y on t h e f o o t w i t h an i n s u l a t i o n pad p l a c e d between t h e f o o t and f o o t b e d - have s u b j e c t s t e p down on t h e o t h e r f o o t and b r i n g f o o t b e d f o o t down t o t h e p o i n t o f c o n t a c t i n g t h e ground - no we i g h t 51 - check t h a t h e e l i s i n p o s i t i o n , b a l l o f f o o t and m e d i a l edges o f f o o t b e d and m o l d i n g cap a r e a l l f l u s h - g a t h e r t o e s t o g e t h e r as t h e y would be i n a s k i boot - h o l d t o e s and f o r e f o o t down, g e n t l y l i f t t h e h e e l w i t h t h e o t h e r hand - have s u b j e c t t r a n s f e r a l l t h e weight t o t h e f o o t b e d and h o l d f o r 5 seconds - t r a n s f e r w e i ght back t o t h e o t h e r f o o t and lo w e r t h e h e e l s l o w l y w i t h o u t weight - gu i d e t h e h e e l u n t i l c o n t a c t i s made - g e n t l y push t o e s down w i t h t h e palm o f your hand t o p h e l p i n c r e a s e d e f i n i t i o n - push down on t h e f i r s t m e t a t a r s a l head w h i l e t h e r e a r f o o t remains n e u t r a l - w i t h o u t weight 3. F i n i s h i n g t h e Footbeds - use s k i b o o t ' s s t a n d a r d i n s o l e t o t r a c e l e n g t h and shape onto f o o t b e d - t r i m back, l e a v i n g f o o t b e d s l i g h t l y l o n g e r t h a n t h e i n s o l e ( l e a v e even l o n g e r f o r r e a r e n t r y b o o t s ) - use a w i r e - b r u s h wheel t o g r i n d o f f ex c e s s c o r k i n t h e a r c h a r e a - use t h e edge o f a ston e wheel t o c u t back any o t h e r e x c e s s and t o l e a v e a smooth f i n i s h - keep t h e f l a n g e edge t h i n , but no l e s s t h a n 1mm - keep t h e h e e l cup as v e r t i c a l as p o s s i b l e - f i t t h e f o o t b e d i n t o t h e boot, t r i m i f n e c e s s a r y S u p e r f e e t T e c h n i c a l Manual(1983) 52 APPENDIX C GENERAL DESCRIPTIVE DATA FOR ALL SUBJECTS T a b l e C - l G e n e r a l D e s c r i p t i v e Data f o r a l l S u b j e c t s SV A g e ( y r s ) Height(cm) Weight(kg) S k i i n g ( y r s ) R L 28 170 70.4 20 6 5 24 170 76.4 16 7 8 21 177.5 81.8 12 4 4 23 162.5 61.4 13 5 4 27 175 77.3 15 5 6 24 177.5 65.9 18 9 4 18 180 70.4 12 6 4 23 175 80.4 10 5 4 36 177.5 79.5 21 8 6 23 167.5 61.4 14 4 6 23 172.5 68.2 17 7 5 25 162.5 56.8 16 4 3 28 167 .5 65. 9 15 5 4 28 170 70 . 45 20 5 6 26 162.5 70. 9 13 4 5 25.13 171.17 70.48 15.47 5.6/4 .9 3.96 5.69 7.25 3.16 1.5/1 .2 SV - S u b t a l a r Varus ( R i g h t / L e f t ) 53 APPENDIX D COMPLETE NAVICULAR DATA. Ta b l e D - l R i g h t Foot - L o c a t i o n o f N a v i c u l a r ( c m ) , Average o f 2 T r i a l s SBX SFX EBX EFX 9 .595 9. 6 9 .035 9. 28 9 .225 9. 29 8 .0 9. 135 7 .335 8. 125 6 .56 7 . 975 8 .4 65 8. 575 7 .855 8 . 42 8 .225 10 .71 7 .275 10 .39 8 .81 9. 635 8 .165 9. 26 7 . 695 7. 855 7 .405 7 . 83 8 .03 8. 1 7 .08 7 . 965 8 .565 8. 595 7 . 66 8. 42 7 .8 7. 84 6 .84 7. 715 8 .46 9. 52 7 .675 9. 33 8 .01 8. 06 7 .07 7. 865 8 .36 8. 74 7 .575 8. 495 8 .352 8. 819 7 .553 8. 622 0 .619 0. 837 0 . 642 0. 801 SBY SFY EBY EFY 7. 38 7 .79 6. 825 6. 825 6. 39 7 .125 5. 715 7 . 11 6. 385 7 .79 5. 91 7. 73 6. 21 6 .70 5. 485 6. 595 6. 455 7 .16 6. 075 7. 045 6. 325 6 .84 6. 16 6. 83 7. 51 7 . 935 7. 06 7 . 64 6. 89 7 .48 6. 415 7. 45 6. 625 7 .385 6. 105 7. 34 5. 62 6 .765 5. 21 6. 745 5. 515 7 .75 5. 09 7 . 545 6. 36 7 .325 5. 825 7 . 26 6. 51 7 .03 6. 17 6. 925 6. 475 7 .313 6. 003 7. 157 0. 567 0 .419 0. 569 0. 367 SBX - S t a r t , b o o t , x a x i s EBX - End, b o o t , x a x i s SBY - S t a r t , b o o t , y a x i s EBY - End, boo t , y a x i s SFX - S t a r t , f o o t b e d , x a x i s EFX - End, f o o t b e d , x a x i s SFY - S t a r t , f o o t b e d , y a x i s EFY - End, f o o t b e d , y a x i s 54 T a b l e D-2 L e f t Foot - L o c a t i o n o f N a v i c u l a r ( c m ) , Average o f Two T r i a l s SBX SFX 8 .385 8 .78 8 .43 8 . 61 8 .11 8 .35 8 .765 9 .22 9 .075 9 .57 9 .535 10 .435 8 .895 8 .96 7 .23 7 .51 8 .26 8 .41 6 .665 7 .59 7 .55 7 . 6 7 .28 7 . 625 7 . 675 8 .03 8 .143 8 .515 0 .829 0 .882 EBX EFX 7.475 8.51 7.91 8.37 7.50 8.04 8.24 9.06 8.475 9.495 8.64 10.245 8.06 8.865 6.41 7.38 7.415 8.245 7.205 7.475 6.695 7.36 6.485 7.565 7.515 7.68 7.540 8.253 0.720 1.000 SBY SFY 6. 89 7. 535 5. 93 6. 83 6. 255 6. 995 6. 105 6. 62 7. 145 7. 67 7 . 085 7. 77 7. 225 7. 86 7. 125 7. 79 6. 735 7. 665 5. 79 6. 845 6. 695 6. 69 6. 845 7. 56 5. 615 6. 54 6. 572 7. 259 0. 563 0. 507 EBY EFY 6.59 7.51 5.295 6.77 5.54 6.935 5.68 6.425 6.77 7.56 6.915 7.74 7.005 7.75 6.56 7.62 6.235 7.56 5.45 6.80 5.99 6.62 6.3 7.41 5.345 6.495 6.129 7.169 0.617 0.501 SBX - S t a r t , b o o t , x a x i s EBX - End, boot, x a x i s SBY - S t a r t , b o o t , y a x i s EBY - End, bo o t , y a x i s SFX - S t a r t , f o o t b e d , x a x i s EFX - End, f o o t b e d , x a x i s SFY - S t a r t , f o o t b e d , y a x i s EFY - End, f o o t b e d , y a x i s 55 T a b l e D-3 N a v i c u l a r Range o f M o t i o n , Average o f Two T r i a l s RIGHT LEFT Boot Footbed Boot F o o t b e d (x y) (x y) (x y) (x y) .56 .55 .32 .085 .91 .3 .27 .025 1.225 .675 .155 .015 .52 .635 .24 .12 .77 .475 .15 .06 .61 .715 .31 .06 .71 .725 .155 .105 .525 .425 .16 .195 .95 .38 .32 .115 .6 .375 .075 .11 .645 .165 .375 .01 .895 .17 .19 .03 .29 .45 .025 .295 .835 .22 .095 .11 .95 .475 .135 .03 .82 .565 .13 .17 .905 .52 .175 .045 .845 .5 .165 .105 .91 .41 .125 .02 .54 .34 .115 .045 .785 .425 .19 .205 .855 .705 .24 .07 .94 .535 .15 .065 .795 .545 .06 .15 .785 .34 .245 .105 .655 .27 .35 .045 Mean .802 .472 .194 .089 .723 .443 .185 .095 SD .227 .143 .096 .082 .150 .182 .092 .055 56 T a b l e D-4 A n a l y s i s o f V a r i a n c e - R i g h t Foot, L o c a t i o n o f N a v i c u l a r Source Sums o f Mean DF F P Squares Squares R a t i o SBX vs SFX 1.417 1.417 1 5.701 0.034 E r r o r 2.983 0.249 12 EBX vs EFX 7.415 7.415 1 28.400 0.000 E r r o r 3.133 0.261 12 SBY vs SFY 4.570 4.570 1 34.710 0.000 E r r o r 3.133 0.261 12 EBY vs EFY 8.648 8.648 1 45.822 0.000 E r r o r 2.265 0.189 12 SBX - S t a r t , b o o t , x a x i s EBX - End, boot, x a x i s SBY - S t a r t , boot, y a x i s EBY - End, bo o t , y a x i s SFX - S t a r t , f o o t b e d , x a x i s EFX - End, f o o t b e d , x a x i s ' SFY - S t a r t , f o o t b e d , y a x i s EFY - End, f o o t b e d , y a x i s 57 T a b l e D-5 A n a l y s i s o f V a r i a n c e - L e f t F o o t , L o c a t i o n o f N a v i c u l a r Source Sums o f Mean DF F Squares Squares R a t i o SBX vs SFX 0.899 0 .899 1 23.503 E r r o r 0.459 0.038 . 12 EBX vs EFX 3.302 3.302 1 37.972 E r r o r 1.043 0.087 12 SBY vs SFY 3.067 3.067 1 87.660 E r r o r 0.420 0.035 12 EBY vs EFY 7.030 7.030 1 173.012 E r r o r 0.488 0.041 12 0.000 0.000 0.000 0.000 SBX - S t a r t , b o o t , x a x i s EBX - End, boot, x a x i s SBY - S t a r t , b o o t , y a x i s EBY - End, bo o t , y a x i s SFX - S t a r t , f o o t b e d , x a x i s EFX - End, f o o t b e d , x a x i s SFY - S t a r t , f o o t b e d , y a x i s EFY - End, f o o t b e d , y a x i s 58 T a b l e D-6 A n a l y s i s o f V a r i a n c e - Range o f M o t i o n , X D i r e c t i o n , Boot vs Fo o t b e d Source Sums o f Squares W i t h i n S u b j e c t s R vs L 0.025 E r r o r 0.345 B vs F 4.278 E r r o r 0.176 I n t e r a c t i o n 0.016 E r r o r 0.374 Mean DF Squares 0.025 1 0.029 12 4.278 1 0.015 12 0.016 1 0.031 12 F P R a t i o 0.877 0.368 292.314 0.000 0.506 0.491 59 T a b l e D-7 A n a l y s i s o f V a r i a n c e - Range o f M o t i o n , Y D i r e c t i o n , Boot vs Footbed " ' " Source Sums o f Squares W i t h i n S u b j e c t s R vs L 0.002 E r r o r 0.119 B vs F E r r o r 1.737 0.229 Mean Squares 0.002 0.010 1.737 0. 019 DF 1 12 1 12 F R a t i o 0.158 91.227 0.698 0.000 I n t e r a c t i o n 0.004 0.004 1 0.405 0.537 E r r o r 0.113 0.009 12 60 APPENDIX E COMPLETE REARFOOT DATA. Ta b l e E - l R e a r f o o t A n g l e , Average o f Two T r i a l s RBS RBE 6.75 6.0 5.5 5.25 5.75 5.5 4.25 3.5 8.5 8.75 7.5 7.5 6.5 5.75 3.0 4.5 6.25 4.5 7.0 5.5 5.0 4.25 5.75 6.0 4.25 3.5 Mean 5.846 5.423 SD 1.488 1.491 RFS RFE LBS 3.5 3.0 4.0 4.25 4.25 2.5 3.0 2.75 3.75 3.5 2.25 5.75 4.5 4 .75 4.25 3.5 3.0 3.0 3.0 2.25 5.5 2.75 4.0 5.75 3.5 3.75 4.0 4.25 3.5 4.0 3.25 3.0 3.75 3.25 2.75 5.25 2.0 1.25 4.25 3.404 3.115 4.288 0.673 0.939 1.015 LBE LFS LFE 3.5 1.25 1.0 2.0 1.5 1.25 3.5 2.0 2.0 5.5 3.0 3.5 4.0 1.5 1.75 2.75 1.75 2.0 5.25 2.0 1.5 4 .25 1.0 0.5 3.25 1.625 1.25 2.75 1.5 1.5 3.25 1.5 1.25 5.0 1.5 1.0 4.0 1.0 1.0 3.769 1.625 1.500 1.038 0.515 0.736 RBS - R i g h t , boot, s t a r t RBE - R i g h t , b o o t , end LBS - L e f t , boot, s t a r t LBE - L e f t , b o o t , end RFS - R i g h t , f o o t b e d , s t a r t RFE - R i g h t , f o o t b e d , end LFS - L e f t , f o o t b e d , s t a r t LFE - L e f t , f o o t b e d , end 61 T a b l e E-2 A n a l y s i s o f V a r i a n c e vs F o o t b e d - R e a r f o o t A n g l e , S t a r t P o s i t i o n , Boot Source Sums o f Squares W i t h i n S u b j e c t s R vs L 36.181 E r r o r 20.089 B vs F 84.724 E r r o r 5.421 I n t e r a c t i o n 0.159 E r r o r 9.704 Mean DF F P Squares R a t i o 36.181 1 21.612 0.001 1.674 12 84.724 1 187.557 0.000 0.452 12 0.159 1 0.197 0.665 0.809 12 62 T a b l e E-3 A n a l y s i s o f V a r i a n c e - R e a r f o o t A n g l e , End P o s i t i o n , Boot vs Fo o t b e d " ~ ' " Source Sum o f Mean DF F P Squares Squares R a t i o W i t h i n S u b j e c t s R vs L 34.736 34.736 1 16.832 0.001 E r r o r 24.764 2.064 12 B vs F 68.082 68.082 1 91.608 0.000 E r r o r 8.918 0.743 12 I n t e r a c t i o n 0.005 0.005 1 0.007 0.936 E r r o r 8.495 0.708 12 63 APPENDIX F COMPLETE TIBIAL TUBEROSITY DATA. Ta b l e F - l D i s p l a c e m e n t o f t h e T i b i a l T u b e r o s i t y From C e n t e r , Average o f Two T r i a l s RBX RFX 2.33 1.315 1.405 0.98 1.53 1.285 2.46 1.185 2.235 1.345 2.305 2.025 2.67 1.72 1.835 1.355 2.97 1.215 2.625 1.545 2.06 2.355 1.38 0.815 3.13 1.035 Mean 2.226 1.398 SD 0.567 0.427 LBX LFX 1 .85 0 .38 0 . 95 0 . 645 1 .22 0 .88 2 .065 2 .39 1 .205 0 .8 1 .25 0 .3 2 . 605 1 .72 2 . 185 1 . 61 2 .29 0 .78 1 .74 0 . 935 1 . 97 1 . 69 1 .8 0 .95 3 .05 1 .095 1 .860 1 .090 0 . 604 0 .599 RBX - R i g h t , b o o t , x d i r . LBX - L e f t , b o o t , x d i r . RFX - R i g h t , f o o t b e d , x d i r . LFX - L e f t , f o o t b e d , x d i r . 64 T a b l e F-2 A n a l y s i s o f V a r i a n c e - T i b i a l R o t a t i o n , D i s p l a c e m e n t i n t h e X D i r e c t i o n , Boot vs Footbed Source Sum o f Mean DF F P Squares Squares R a t i o W i t h i n S u b j e c t s R vs L 1.474 1.474 1 5.513 0.037 E r r o r 3.208 0.267 12 B v s F 8.292 8.292 1 26.405 0.000 E r r o r 3.768 0.314 12 I n t e r a c t i o n 0.011 0.011 1 0.131 0.724 E r r o r 1.003 0.084 12 RBX - R i g h t , boot, x d i r . RFX - R i g h t , f o o t b e d , x d i r . LBX - L e f t , b oot, x d i r . LFX - L e f t , f o o t b e d , x d i r . 65 APPENDIX G COMPLETE RATINGS DATA. Ta b l e G - l S u b j e c t i v e R a t i n g s Out o f 100 f o r Edge C o n t r o l , P a i n , and  F a t i g u e LRF LRB SRF SRB PF PB FF FB 76 40 81 31 11 31 10 40 66 32 70 39 59 44 31 43 53 21 53 23 62 43 25 44 72 39 66 31 58 50 55 64 72 42 81 44 40 30 28 40 83 27 98 30 75 75 63 84 58 84 79 77 46 3 2 11 73 44 79 41 53 37 24 70 62 41 62 35 18 40 24 58 83 68 89 62 33 27 61 62 73 46 69 57 33 42 34 49 48 65 66 65 41 59 70 56 90 59 74 64 43 66 24 27 85 56 78 46 24 22 29 31 85 65 74 61 60 33 53 52 71.9 48.6 74 . 6 47.1 43.7 40.13 35.5 48.7 12.5 17.2 11.1 16.2 17.9 17.9 20.1 18.3 LRF - Long r a d i u s , f o o t b e d SRF - S h o r t r a d i u s , f o o t b e d PF - P a i n , f o o t b e d FF - F a t i g u e , f o o t b e d LRB - Long r a d i u s , boot SRB - S h o r t r a d i u s , boot PB - P a i n , boot FB - F a t i g u e , boot 66 T a b l e G-2 A n a l y s i s o f V a r i a n c e - R a t i n g s f o r Edge C o n t r o l , P a i n , and  F a t i g u e , Boot v s . Footbed Source Sum o f Mean DF F Squares Squares R a t i o W i t h i n S u b j e c t s LRF vs LRB 4083. 333 4083.333 1 19 .587 E r r o r 2918. 667 208.476 14 SRF vs SRB 5685. 633 5685.633 1 34 . 975 E r r o r 2275. 867 162.562 14 PF vs PB 97. 200 97.200 1 0 .519 E r r o r 2623. 800 187.414 14 FF v s FB 1306. 800 1306.800 1 11 .271 E r r o r 1623. 200 115.943 14 0.001 0.000 0.483 0.005 LRF - Long r a d i u s , f o o t b e d SRF - S h o r t r a d i u s , f o o t b e d PF - P a i n , f o o t b e d FF - F a t i g u e , f o o t b e d LRB - Long r a d i u s , boot SRB - S h o r t r a d i u s , boot PB - P a i n , boot FB - F a t i g u e , boot 67 APPENDIX H COMPLETE RACE DATA. Tab l e H - l Race R e s u l t s , Average o f Two Runs Footbed Boot 17.145 17.45 17.19 17.47 16.115 16.735 17.5 17.785 17.685 17.99 18.585 18.585 20.235 20.535 19.55 19.78 18.315 18.7 17.32 17.45 16.4 16.905 16.365 16.65 18.435 18.73 17.39 17.645 18.21 18.485 Mean 17.763 18.060 SD 1.327 1.202 T a b l e H-2 A n a l y s i s o f V a r i a n c e - Race R e s u l t s , Boot vs Source Sum o f Mean DF F p Squares Squares R a t i o W i t h i n S u b j e c t s B vs F 0.662 0.662 1 66.420 0.000 E r r o r 0.139 0.010 14 69 

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