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Mechanical energy variations in rowing 1982

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MECHANICAL ENERGY VARIATIONS IN ROWING by WALTER OLSEN MARTINDALE B. P. E. A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION i n THE FACULTY OF GRADUATE STUDIES S c h o o l Of P h y s i c a l E d u c a t i o n And R e c r e a t i o n We ac c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA December 1982 © W a l t e r O l s e n M a r t i n d a l e , 1982 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p urposes may be g r a n t e d by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of P h y s i c a l Education,1,December,1982 The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: i i A b s t r a c t The purpose of t h i s s tudy was t o q u a n t i f y and c o n t r a s t the i n s t a n t a n e o u s segmental and t o t a l body energy p a t t e r n s of rowing a s i n g l e s c u l l s r a c i n g s h e l l w i t h rowing a G j e s s i n g (Norway) rowing ergometer, and t o c o n t r a s t energy s a v i n g s t h r o u g h exchanges of m e c h a n i c a l energy among segments and c o n v e r s i o n s of energy w i t h i n segments. Four s c u l l e r s , two male and two female, were f i l m e d a t t h r e e s t r o k e r a t e s w h i l e rowing on a G j e s s i n g rowing ergometer (RE), the RE mounted on a wheeled c a r t , and rowing i n s i n g l e s c u l l s r a c i n g s h e l l s . D i g i t i z e d c o o r d i n a t e s of j o i n t markers were combined w i t h e s t i m a t e d body segment i n e r t i a l p a r a m e t e r s , and e v a l u a t e d w i t h l i n k - s e g m e n t methods a f t e r d i g i t a l f i l t e r i n g t o remove d i g i t i z a t i o n n o i s e . M e c h a n i c a l energy and i n t e r n a l work a n a l y s i s a l l o w e d c a l c u l a t i o n of energy s a v i n g s due t o exchange and i n t e r c o n v e r s i o n of segmental energy. The i n t e r n a l work was l e a s t i n the wheeled RE and g r e a t e s t i n the b o a t . S a v i n g of energy t h r o u g h exchange was g r e a t e s t i n the b o a t , and l e a s t i n the s t a t i o n a r y RE. S a v i n g of energy t h r o u g h i n t e r c o n v e r s i o n was g r e a t e s t i n the wheeled RE. The i n t e r c o n v e r s i o n s ( e x p r e s s e d as a p e r c e n t a g e of t o t a l work) were l o w e r , and q u i t e s i m i l a r f o r both the boat and the s t a t i o n a r y RE. S i m i l a r i t y of energy s a v i n g s c o r e s between the boat and the wheeled RE a l l o w the c o n c l u s i o n t h a t rowing ergometer t e s t i n g might p e r m i t a t h l e t e s t o work a t s t r o k e r a t e s more s i m i l a r t o r a c i n g l e v e l s . i i i T a b l e of C o n t e n t s A b s t r a c t i i L i s t of T a b l e s i v L i s t of F i g u r e s y Acknowledgements v i I n t r o d u c t i o n 1 Purpose 3 Methods 4 S u b j e c t s 4 P r o c e d u r e s 4 M a r k e r s 5 Rowing S e s s i o n 5 Ergometer S e s s i o n s 6 Data C o l l e c t i o n And A n a l y s i s 6 Segmental Energy 8 T o t a l Body Energy 8 I n t e r n a l Work 9 R e s u l t s And D i s c u s s i o n 13 Cinematography 13 Boat T r i a l s 13 Ergometer T r i a l s 13 I n t e r n a l Work 16 Energy Exchange And I n t e r c o n v e r s i o n 23 Average D r i v e Power 29 C o n c l u s i o n s 32 Recommendations 32 R e f e r e n c e s 34 APPENDIX 1 - DEFINITIONS 36 Rowing Terms 36 Energy A n a l y s i s Terms 37 APPENDIX 2 - SYMBOLS USED IN THE PAPER 40 APPENDIX 3 - ENERGY PLOTS OF SUBJECTS 2, 3, AND 4 41 APPENDIX 4 - REVIEW OF LITERATURE 45 Anthropometry 45 Energy And Work 50 Mechanics And Rowing 56 BIBLIOGRAPHY 62 i v L i s t of T a b l e s 1. B a s i c S u b j e c t I n f o r m a t i o n 4 2. I n t e r n a l Work For S c u l l i n g T r i a l s 17 3. I n t e r n a l Work For Wheeled Ergometer T r i a l s 18 4. I n t e r n a l Work For S t a t i o n a r y Ergometer T r i a l s 19 5. Power, S t r o k e R a t e , And V e l o c i t y , S c u l l i n g T r i a l s ....25 V L i s t of F i g u r e s IA. D r i v e Phase Of Rowing A S t a t i o n a r y Ergometer 15 IB. D r i v e Phase Of Rowing A Wheeled Ergometer 16 2. K i n e t i c Energy, Boat, Ergometers, S u b j e c t 1 21 3. K i n e t i c Energy, S u b j e c t 1 And Boat 28 4. K i n e t i c Energy, S u b j e c t 2 42 5. K i n e t i c Energy, S u b j e c t 3 43 6. K i n e t i c Energy, S u b j e c t 4 44 v i Acknowledgement I w i s h t o thank Dr. D. Gordon E. Ro b e r t s o n f o r the guidance and p a t i e n c e he has p r o v i d e d me i n the p r e p a r a t i o n of t h i s t h e s i s . The p a t i e n c e and encouragement of the members of my t h e s i s committee, Dr. K. D. C o u t t s , Dr. D. C. McKenzie, and Mr. B. K l a v o r a were i m p o r t a n t i n my c a r r y i n g t h r o u g h w i t h t h i s paper t o the c o m p l e t i o n . The encouragement of my c l a s s m a t e s and of my f r i e n d s on the U n i v e r s i t y rowing crew a r e a l s o g r a t e f u l l y acknowledged. 1 INTRODUCTION T e s t i n g oarsmen's p h y s i o l o g i c a l c a p a b i l i t i e s w i t h o f f - w a t e r rowing s i m u l a t o r s i s not new. Henderson and Haggard (1925) r e p o r t use of an h y d r a u l i c rowing s i m u l a t o r t o t e s t the 1924 Y a l e U n i v e r s i t y r owing crew. Hagerman and c o - w o r k e r s , i n s e v e r a l s t u d i e s (1971, 1972, 1975a, 1975b, 1978, 1979) have r e p o r t e d p h y s i o l o g i c a l t e s t i n g of s e v e r a l hundred oarsmen s i n c e the e a r l y 1970's u s i n g the Lyons (Gamut E n g i n e e r i n g , Redwood C i t y , C a l i f o r n i a ) r o wing ergometer. The Canadian Amateur Rowing A s s o c i a t i o n uses G j e s s i n g rowing ergometers ( h e r e a f t e r r e f e r r e d t o as RE) (E. G j e s s i n g , P l a s t . r e k o n s t r . avd., H o s p i t a l e t B e t a n i e n , Bergen, Norway) t o t e s t Canadian oarsmen i n t h e i r t r a i n i n g f o r n a t i o n a l rowing teams. The Lyons ergometer s i m u l a t e s "sweep" r o w i n g , i n which the oarsman h a n d l e s one oar on one s i d e of the b o a t . An oarsman accustomed t o rowing on one s i d e of the boat i s a t a d i s a d v a n t a g e when he i s t e s t e d on a L y o n s - t y p e RE b u i l t f o r p e o p l e accustomed t o the o t h e r s i d e of the b o a t ; s c u l l e r s , accustomed t o rowing w i t h two o a r s i n a s y m m e t r i c a l motion a r e a t a d i s a d v a n t a g e as w e l l . The G j e s s i n g RE i s a " c e n t e r - p u l l " machine. A l l sweep oarsmen a r e a t a s i m i l a r ( s l i g h t ) d i s a d v a n t a g e on t h i s machine, as the h a n d l e does not p i v o t about a p o i n t a t e i t h e r s i d e of t h e boat. I n s t e a d , the h a n d l e i s g u i d e d s t r a i g h t backwards and f o r w a r d s by a bar a t t a c h e d t o the " o a r " h a n d l e . S c u l l e r s a r e a t the l e a s t d i s a d v a n t a g e on the G j e s s i n g machine, as they need o n l y a l t e r t h e i r arm m o t i o n , w h i l e sweep-oar rowers must adapt by removing the normal t w i s t and l e a n of t h e i r b o d i e s from t h e i r 2 rowing s t r o k e . The c h i e f d i s a d v a n t a g e t o the G j e s s i n g RE i s t h a t i t i s d i f f i c u l t t o row a t normal r a c i n g s t r o k e r a t e s f o r more th a n a few m i n u t e s , w h i l e i t i s n e c e s s a r y t o row a r a c i n g s h e l l f o r 6 t o 7.5 m i n u tes t o complete most r a c e s ( s t r i k i n g between 32 and 40 s t r o k e s per m i nute, u s u a l l y , depending on the r a c e ) . An RE c a p a b l e of s i m u l a t i n g the rowing motion and of s i m u l a t i n g the work o u t p u t r e q u i r e m e n t s of r a c e rowing i s a v a l u a b l e t o o l f o r use i n team s e l e c t i o n , t r a i n i n g , and i n t e c h n i c a l c o a c h i n g . The p r e s e n t G j e s s i n g machine a f f o r d s an a p p r o x i m a t i o n of the r owing m o t i o n . C u r r e n t p r a c t i s e i n the Canadian rowing community i s t o t e s t oarsmen f o r 6 minutes on a G j e s s i n g RE w i t h a r e s i s t a n c e of "3 kp" ( a p p r o x i m a t e l y 29.4 N) a p p l i e d t o each f l y w h e e l r e v o l u t i o n . The oarsman does "3 kp.m" or 29.4 J of work f o r each f l y w h e e l r e v o l u t i o n . These "rows" a r e u s u a l l y done w i t h s t r o k e r a t e s between 26 and 29 s t r o k e s per m inute; use of h i g h e r r a t e s o f t e n r e s u l t i n the oarsman p e r f o r m i n g p o o r l y because of e x c e s s i v e f a t i g u e i n the second h a l f of the t e s t . Lower s t r o k e r a t e s than 24-26 (depending upon the s i z e of the rower, the l a r g e r , s t r o n g e r rowers do v e r y w e l l a t the low end of t h i s continuum) r e s u l t i n p o o r e r s c o r e s because the f l y w h e e l ' s r e v o l u t i o n r a t e drops to o much between s t r o k e s , and e x c e s s i v e e f f o r t i s spent t o r e t u r n t h e f l y w h e e l t o a " c o m f o r t a b l e " speed. I t would be v a l u a b l e t o the rowing community i f the r e a s o n ( s ) f o r the d i f f i c u l t y i n rowing a t the s t r o k e r a t e s e x p e r i e n c e d i n normal r a c i n g c o u l d be d e f i n e d , so t h a t t h e G j e s s i n g RE c o u l d be r e d e s i g n e d t o s i m u l a t e the f e e l of r o wing more a c c u r a t e l y than i t does now. P r i o r t o any d e s i g n 3 changes, however, i t is necessary to study the rowing machine in comparison with real rowing to assess existing differences between rowing the Gjessing machine and the boat. Purpose The purpose of th i s study was to quantify and contrast the instantaneous segmental and t o t a l body mechanical energy patterns of rowing in a s i n g l e - s c u l l s racing s h e l l with rowing a Gjessing RE, and to contrast energy savings through exchanges of mechanical energy among segments and conversions of energy within segments. 4 METHODS S u b j e c t s S u b j e c t s i n c l u d e d 2 male s c u l l e r s and 2 female s c u l l e r s . One of each of t h e male and female s c u l l e r s were e x p e r i e n c e d i n i n t e r n a t i o n a l c o m p e t i t i o n . The o t h e r two s u b j e c t s were s i g n i f i c a n t l y l e s s e x p e r i e n c e d i n r a c e s c u l l i n g . B e f o r e any t e s t i n g or measuring each s u b j e c t was i n f o r m e d of the n a t u r e of the study and c o n s e n t e d t o p a r t i c i p a t e . B a s i c i n f o r m a t i o n about the s u b j e c t s i s i n T a b l e 1. T a b l e 1. Age, h e i g h t , and body mass of s u b j e c t s and masses of r a c i n g s h e l l s used i n rowing t r i a l s . S u b j e c t Sex Age H e i g h t Mass Boat Mass (cm) (kg) (kg) 1 m 23 187.5 85.4 17.6 2 m 20 197.0 90.5 22.5 3 f 22 1 68.5 64.5 20. 1 4 f 23 173.5 65.7 20.1 P r o c e d u r e s S u b j e c t s were f i l m e d rowing i n s i n g l e s c u l l s r a c i n g s h e l l s f o r s e v e r a l r owing s t r o k e c y c l e s a t s t r o k e r a t e s a t , above, and below t h e i r normal r a c i n g r a t e s . Rowing t r i a l s took p l a c e a t the Burnaby Lake Canada Games (1973) rowing c o u r s e . On a s e p a r a t e o c c a s i o n , s u b j e c t s were f i l m e d r owing a G j e s s i n g rowing ergometer (RE) a t s i m i l a r s t r o k e r a t e s t o those used i n the 5 rowing t r i a l s . A l l f i l m i n g was done u s i n g a m o t o r - d r i v e n Locam 16 mm camera (Redlake I n d u s t r i e s ) . A l l f i l m i n g was a t 25 frames per second ( f / s ) . M a r k e r s . Markers were p l a c e d a t the a n k l e ( l a t e r a l m a l l e o l u s ) , knee ( l a t e r a l f e m o r a l e p i c o n d y l e , about 2 cm s u p e r i o r t o the j o i n t l i n e ) , h i p ( g r e a t e r t r o c h a n t e r of femur), s h o u l d e r (acromion p r o c e s s ) , elbow ( l a t e r a l e p i c o n d y l e of the humerus), w r i s t ( s p i n o u s p r o c e s s of the u l n a ) , and neck ( p o s t e r i o r l y , on the s p i n o u s p r o c e s s of the f i r s t t h o r a c i c v e r t e b r a ( T 1 ) ) . The opening of the o u t e r ear was used as a marker f o r the head. A l l markers were p l a c e d on the s u b j e c t s ' r i g h t s i d e and a l l rowing was done w i t h the s u b j e c t s f a c i n g the r i g h t of the camera's image, f o l l o w i n g the c o n v e n t i o n of h a v i n g the s u b j e c t f a c e t h e p o s i t i v e x - a x i s of a normal C a r t e s i a n c o o r d i n a t e system. B e f o r e a l l water t r i a l s , markers were p l a c e d 3 m a p a r t on the p o r t s i d e (the s i d e n e a r e s t the camera) of the s u b j e c t ' s r a c i n g s h e l l . B e f o r e the ergometer t r i a l s , two markers were p l a c e d on the RE t o i d e n t i f y motion of the RE. S u b j e c t s ' body masses were measured w i t h a s c a l e a c c u r a t e t o w i t h i n 50 g or w i t h a K i s t l e r f o r c e p l a t e . Rowing S e s s i o n . S u b j e c t s were p r e p a r e d f o r t h e i r f i l m t r i a l s a f t e r rowing workouts ( w i t h i n 40 m i n ) . When ready, s u b j e c t s w a i t e d i n the a p p r o p r i a t e r a c i n g l a n e ( l a n e t h r e e of the Burnaby Lake c o u r s e , about 57 m from the camera), about 250 m t o the r i g h t of the camera. The s u b j e c t s t a r t e d t o row, 6 and was t o l d of his stroke rates so that he could adjust his tempo to equal that chosen for the t r i a l being rowed at the time. The subject's stroke rate was checked with a cal i b r a t e d "rate watch" just before his or her passing the camera. Ergometer Sessions. Subjects were permitted to row the RE u n t i l they f e l t comfortably "warmed up". When ready for filming, subjects started rowing the machine and used about six to eight strokes to atta i n their designated stroke rates, after which the rates were estimated with a stopwatch. The stroke rate was adjusted or maintained as required. When the subject was rowing at the correct tempo, f l o o d l i g h t s were turned on, and the camera was run for the time required to complete about 3 complete rowing cycles. During the filming, the stroke rate was checked as accurately as possible to make sure that the subject maintained the correct rate throughout the t r i a l . After each t r i a l the subject rested momentarily. The filming was repeated at the other stroke rates. The RE t r i a l s were repeated with the RE mounted on a wheeled ca r t . Manufacturer's s p e c i f i c a t i o n s for the Gjessing RE are such that the machine i s mounted on wheels aligned with the longitudinal axis of the ergometer. The CARA-owned machine has no wheels. Data C o l l e c t i o n and Analysis Films were projected onto a d i g i t i z i n g table one frame at a time. The cartesian coordinates of a l l markers in each frame were " d i g i t i z e d " with a Numonics Graphics Calculator interfaced 7 w i t h a microNova computer (Data G e n e r a l C o r p . ) . One f u l l s t r o k e c y c l e of each t r i a l was d i g i t i z e d ( c a t c h - t o - c a t c h ) . Programmes used l a t e r i n the d a t a p r o c e s s i n g r e q u i r e d t h a t 6 frames b e f o r e the b e g i n n i n g of the s t r o k e and 6 frames a f t e r the end of the s t r o k e were d i g i t i z e d . Data were then t r a n s m i t t e d t o an Amdahl 470/V8 computer f o r e r r o r c h e c k i n g , k i n e m a t i c , and energy quant i f i c a t i o n . P e r s p e c t i v e e r r o r i n the c o o r d i n a t e d a t a , caused by the camera p o s i t i o n b e i n g such t h a t t h e movement was not p e r p e n d i c u l a r t o the o p t i c a l a x i s of the camera, was removed w i t h a m a t r i x t r a n s f o r m a t i o n adapted from t h a t d e s c r i b e d i n W o l t r i n g (1975, 1976). Data were then smoothed by two passes (one f o r w a r d and one backward t o e l i m i n a t e p h a s e - s h i f t ) of a low-pass d i g i t a l f i l t e r u s i n g a 5 Hz c u t o f f f r e q u e n c y f o r the ergometer d a t a . Data f o r the boat t r i a l s were f i l t e r e d u s i n g 2.5 Hz as the c u t o f f f o r the d i g i t a l f i l t e r t o r e t a i n as much of the " s i g n a l " as p o s s i b l e w h i l e r e d u c i n g h i g h f r e q u e n c y n o i s e . The d i g i t a l f i l t e r i n g method of r e d u c i n g " n o i s e " i n f i l m c o o r d i n a t e d a t a has been v a l i d a t e d by Pe z z a c k , Norman, and W i n t e r (1977). A n t h r o p o m e t r i c d a t a f o r each s u b j e c t were t a k e n from t a b l e s p r o v i d e d by Dempster ( i n W i n t e r , 1979b), based on s u b j e c t w e i g h t . L i n k segment a n a l y s i s of the f i l m d a t a gave the i n s t a n t a n e o u s (frame-by-frame) l i n e a r and a n g u l a r d i s p l a c e m e n t s , v e l o c i t i e s and a c c e l e r a t i o n s of the segments; e n e r g i e s and r a t e s of change of m e c h a n i c a l e n e r g i e s of a l l segments and of the t o t a l body were c a l c u l a t e d . E n e r g i e s of a l l segments were c a l c u l a t e d assuming t h a t a l l segments r e t u r n e d t o the same 8 p o s i t i o n a t the c o m p l e t i o n of each s t r o k e . In t h i s s i t u a t i o n , t h e r e i s no net e x t e r n a l work done on the body or by the body, as t h e r e i s no change from s t r o k e t o s t r o k e i n the h e i g h t of the body or i n i t s v e l o c i t y . Segmental Energy. E n e r g i e s of the segments and of the t o t a l body were c a l c u l a t e d as d e s c r i b e d by W i n t e r , (1979a). The energy of each segment (E ) was c a l c u l a t e d w i t h the f o r m u l a : s E = P o t e n t i a l energy (E ) s p + T r a n s l a t i o n a l k i n e t i c energy (E ) kt + R o t a t i o n a l k i n e t i c energy (E ) kr = mgh + 1/2 mv 2 + 1/2 Ia>2 (1) where m = segment mass i n kg g = g r a v i t a t i o n a l a c c e l e r a t i o n (9.8 m/s 2) h = h e i g h t of segment mass c e n t r e i n m v = a b s o l u t e v e l o c i t y of the segment mass c e n t r e i n m/s I = r o t a t i o n a l moment of i n e r t i a of the segment i n kg.m 2 co = r o t a t i o n a l v e l o c i t y of the segment i n r a d / s . T o t a l Body Energy. The i n s t a n t a n e o u s energy of the t o t a l body (E ) was c a l c u l a t e d by summing the e n e r g i e s of a l l of the t segments i n each f i l m frame: B E = Z E (2) t s=1 s where B was the number of segments and, E was the t o t a l energy of segment s i n each f i l m frame, s 9 I n t e r n a l Work. C a l c u l a t i o n o f t h e t o t a l i n t e r n a l work i n t h e r o w i n g s t r o k e r e q u i r e d i n c l u s i o n o f i n t e r n a l a n d e x t e r n a l w o r k . A c o n c e n t r i c ( s h o r t e n i n g ) m u s c l e c o n t r a c t i o n i s s a i d t o do p o s i t i v e work on a seg m e n t , i n c r e a s i n g t h e t o t a l e n e r g y o f t h a t s e g m e n t ; an e c c e n t r i c ( l e n g t h e n i n g a g a i n s t t h e c o n t r a c t i o n c a u s e d by some e x t e r n a l moment) c o n t r a c t i o n i s s a i d t o do n e g a t i v e w o r k , d i s s i p a t i n g m e c h a n i c a l ( k i n e t i c ) e n e r g y a n d d e c r e a s i n g t h e t o t a l body e n e r g y ( W i n t e r , 1 9 7 9 a ) . S i n c e r o w i n g i s u s u a l l y done on a f l a t o r n e a r l y f l a t s u r f a c e ( i . e., w i t h no a p p r e c i a b l e c u r r e n t ) t h e r e s h o u l d be l i t t l e i f a n y c h a n g e i n t h e m e c h a n i c a l e n e r g y o f t h e s y s t e m f r o m one s t r o k e t o t h e n e x t . The s y s t e m d o e s c h a n g e i t s d r a f t a n d h o r i z o n t a l v e l o c i t y d u r i n g a s t r o k e , b u t a t s t e a d y p a c e r o w i n g t h e c h a n g e s a r e r e p e a t e d e v e r y s t r o k e . The b o a t a n d r o w e r r e t u r n t o t h e same h e i g h t a n d v e l o c i t y a n d t h u s t o t h e same m e c h a n i c a l e n e r g y a t c o r r e s p o n d i n g p o i n t s o f c o n s e c u t i v e s t r o k e s . I n p r e v i o u s s t u d i e s o f m e c h a n i c a l e n e r g y ( e . g., P i e r r y n o w s k i , e t a _ l . , 1980, 1 981 ) t o t a l e n e r g i e s have been f o u n d t o v a r y s l i g h t l y a t c o r r e s p o n d i n g s t a g e s o f c y c l i c movements ( w a l k i n g a n d l o a d e d w a l k i n g ) . The s l i g h t c h a n g e b e t w e e n f i n i s h i n g e n e r g y (E ) a n d s t a r t i n g e n e r g y t n (E ) a p p e a r s a s e x t e r n a l work (W ) due t o movement o f t h e t o t a l to t body o r c h a n g e s i n i t s movement: N W = Z AE t i=1 - t i =E - E (3) t n tO I n t h i s s t u d y i t was p r e s u m e d t h a t t h e r e was no c h a n g e i n t o t a l e n e r g y ( t h u s no W ) b e t w e e n c o r r e s p o n d i n g p o i n t s o f c o n s e c u t i v e t 10 s t r o k e s . T h i s c o n s t r a i n e d a l l segmental energy components t o r e t u r n t o t h e i r o r i g i n a l l e v e l s a t the end of each s t r o k e . W , t t h e n , a c c o u n t e d f o r e x t e r n a l work done i n the t r i a l , and was s u b t r a c t e d from the t o t a l energy of the s t r o k e p r i o r t o c a l c u l a t i o n of t h e exchanges among or i n t e r c o n v e r s i o n s w i t h i n segments. " T h i s c o r r e c t i o n assumes t h a t the t o t a l body b e g i n s and ends a t the same energy l e v e l and t h i s i s t r u e a c r o s s many..." s t r o k e s u n l e s s t h e s u b j e c t i s c h a n g i n g h i s or her average v e l o c i t y w i t h each s t r o k e ( q u o t a t i o n from P i e r r y n o w s k i , 1978). The t o t a l i n t e r n a l work (W ) ( d e f i n e d by W i n t e r , 1979a) of i t h e s c u l l i n g s t r o k e was c a l c u l a t e d by t a k i n g the sum of the a b s o l u t e changes of the t o t a l body energy (AE ) over the number t of frames of the s t r o k e (N). T h i s c a l c u l a t i o n d e t e r m i n e d i n t e r n a l work assuming t h a t energy can be both i n t e r c o n v e r t e d and exchanged where i n t e r c o n v e r s i o n of energy w i t h i n a segment i m p l i e s c o n v e r s i o n from p o t e n t i a l energy t o k i n e t i c energy or v i c e - v e r s a , and exchange of energy i m p l i e s the t r a n s m i s s i o n of m e c h a n i c a l energy from segment t o segment. N W = -W + Z |AE | (4) i t i=1 t i The t o t a l work r e q u i r e d assuming t h a t t h e r e was energy exchange among segments but no i n t e r c o n v e r s i o n of energy w i t h i n segments (W ) was g i v e n by: e 11 N B W = -W + L I |AE | (5) e t i = 1 s=1 s i T o t a l work i f t h e r e was n e i t h e r exchange nor i n t e r c o n v e r s i o n (W ) was c a l c u l a t e d by summing the a b s o l u t e v a l u e s of the n changes i n the segmental energy components over t h e number of segments (B) and over the number of frames (N) i n the movement: W = -w + n t N B L L ( | AE | + | AE | + | AE | ) (6) i=1 s=1 p s i k t s i k r s i I t i s p o s s i b l e t o use the t h r e e v a l u e s W , W , and W t o n i e c a l c u l a t e the amount of energy "saved" or " p r e s e r v e d " i n the motion by i n t e r c o n v e r s i o n o f , or exchange of m e c h a n i c a l energy. The appearance of t h e s e exchanges or c o n v e r s i o n s of m e c h a n i c a l energy reduce the need f o r the muscles t o a b s o r b energy i n one p l a c e w h i l e g e n e r a t i n g energy i n a n o t h e r . Energy saved ( c . f . , " c o n s e r v e d " W i n t e r , 1979b) due t o i n t e r c o n v e r s i o n s w i t h i n segments (S ) was c a l c u l a t e d as the d i f f e r e n c e between the work i a l l o w i n g n e i t h e r exchange nor c o n v e r s i o n (W ) and the work n a l l o w i n g exchange but no c o n v e r s i o n (W ). The amount of energy e saved t h r o u g h i n t e r c o n v e r s i o n s w i t h i n segments i s e x p r e s s e d as a p e r c e n t a g e of the t o t a l work t h a t would have been r e q u i r e d i f no energy had been c o n v e r t e d or exchanged (W ) ( i . e., i f muscles n were needed t o g e n e r a t e or a b s o r b a l l energy changes, and no c o n v e r s i o n of energy o c c u r r e d ) . S = 100 (W - W ) / W . (7) i n e n 12 Energy saved due t o exchanges among segments (S ) was e c a l c u l a t e d as the d i f f e r e n c e between W and the i n t e r n a l work n a l l o w i n g exchange and t r a n s f e r (W ). T h i s f i g u r e was e x p r e s s e d i as a p e r c e n t a g e of W : n S = 100 (W - w ) / W . (8) e e i n The change i n energy of the t o t a l system (body and boat) from i t s l o w e s t v a l u e j u s t b e f o r e the c a t c h t o i t s h i g h e s t v a l u e j u s t b e f o r e the f i n i s h may be used t o d e r i v e the average power of the d r i v e phase of the s t r o k e . The d a t a f o r the t o t a l energy of the system was scanned, and t h e s c o r e s f o r the l o w e s t and h i g h e s t m e c h a n i c a l e n e r g i e s were r e c o r d e d , w i t h t h e i r r e s p e c t i v e t i m e s . The average d r i v e power (P ) was c a l c u l a t e d a s : d ( h i g h e s t M. E. - l o w e s t M. E.)/Atime (9) where - Atime was the e l a p s e d time of the energy change The average v e l o c i t y (v) d u r i n g the s t r o k e was c a l c u l a t e d a s : ( d i s p l a c e m e n t , c a t c h t o c a t c h ) / A t i m e (10) where - Atime was the time r e q u i r e d t o complete the s t r o k e from c a t c h t o c a t c h . 13 RESULTS AND DISCUSSION Cinematography Boat T r i a l s . A f i e l d of view of a p p r o x i m a t e l y 20 m i n the movement p l a n e was r e q u i r e d t o p e r m i t f i l m i n g of a t l e a s t one complete s t r o k e c y c l e ( c a t c h - t o - c a t c h or f i n i s h - t o - f i n i s h ) and ten frames b e f o r e and a f t e r t he c y c l e ' s end p o i n t s . The p r o j e c t e d images c o u l d not be e n l a r g e d t o more than about 3 % of l i f e s i z e due t o the l i m i t e d span of the d i g i t i z e r , about 55 cm). W e l l s and C a l d w e l l (1982) r e p o r t the r o o t mean square of the d i f f e r e n c e s between f i l t e r e d and u n f i l t e r e d f i l m d a t a (RMSD) as an i n d i c a t i o n of d i g i t i z a t i o n n o i s e . The RMSD i n c r e a s e d as the r a t i o of t r u e s i z e t o image s i z e i n c r e a s e d . The l a r g e s t such r a t i o e x p e r i e n c e d by W e l l s and C a l d w e l l (1982) was about 16:1, w h i l e the same r a t i o f o r the d a t a f o r the rowing t r i a l s i n t h i s s t u d y was about 34:1. RMSD was g r e a t e s t i n the x- c o o r d i n a t e of the a n k l e (23±4 mm, meant 1 s t a n d a r d d e v i a t i o n ) and l e a s t i n the y - c o o r d i n a t e d a t a f o r the boat (11±2) mm). The RMSD i n most of the rowing d a t a were s i m i l a r t o or s l i g h t l y g r e a t e r than t h a t of W e l l s and C a l d w e l l , u s i n g images a p p r o x i m a t e l y one h a l f of the s i z e found i n the p r e v i o u s s t u d y . T h i s s i m i l a r i t y , u s i n g images as s m a l l as 3 % l i f e - s i z e s u g g e s t s t h a t the a c c u r a c y of the d i g i t i z a t i o n was of s u f f i c i e n t a c c u r a c y t o p e r m i t d i s c u s s i o n of m e c h a n i c a l energy w i t h r e s p e c t t o the rowing t r i a l s . Ergometer T r i a l s . The t r u e s i z e t o image s i z e r a t i o s i n th e RE t r i a l s were about 9:1 f o r a l l t r i a l s ; t h e RMSD of t h e f i l m d a t a i n t h i s case was l e s s than 5 mm f o r a l l of the marker 14 c o o r d i n a t e s . The x - c o o r d i n a t e of the a n k l e marker a g a i n showed the g r e a t e s t v a r i a b i l i t y (average RMSD = 4.2±1.2 mm). T h i s s m a l l RMSD i n the RE f i l m d a t a s u g g e s t s t h a t the d i g i t i z a t i o n of the RE t r i a l s was a c c u r a t e . T r i a l s were a s s i g n e d codes t o i d e n t i f y t h e d a t a f o r the a n a l y s i s . "RB1A1," f o r example, r e f e r s t o Rowing, Boat, s u b j e c t j _ , s t r o k e r a t e "A" (a low s t r o k e r a t e - "B" i m p l i e s a medium r a t e , and "C" a h i g h r a t e ) , t r i a l j _ . A "W" was used t o denote wheeled RE t r i a l s , and "S" was used t o denote t r i a l s u s i n g the s t a t i o n a r y t r i a l s . S t i c k f i g u r e s of the movements of a s u b j e c t rowing on t h e s t a t i o n a r y RE and on the wheeled RE a r e p r e s e n t e d i n F i g u r e s 1A and 1B, r e s p e c t i v e l y . Note t h a t the s u b j e c t ' s body t r a n s l a t e s on the ergometer w h i l e the RE does not move ( c . f . the " a n k l e " p o s i t i o n i n F i g . 1A). On the wheeled RE, however, the s u b j e c t ' s body t r a n s l a t e s v e r y l i t t l e , and the RE i s moved ( c . f . the n e a r l y s t a t i o n a r y " h i p " and the moving " a n k l e " p o s i t i o n s i n F i g . 1B). I n t e r n a l Work A l l i n t e r n a l work measures (W , W ,W ) were g r e a t e s t i n i e n the rowing t r i a l s and l e a s t i n the wheeled RE t r i a l s ( T a b l e s 2 t o 4 ) . The major d i f f e r e n c e s between work s c o r e s i n rowing t r i a l s and i n ergometer t r i a l s were due t o the d i f f e r e n c e s i n the t r a n s l a t i o n a l energy of the t e s t d e v i c e s . These t r a n s l a t i o n a l e n e r g i e s were g r e a t e s t i n the rowing t r i a l s because t h e system of rower and boat moved s e v e r a l metres d u r i n g each s t r o k e ; t h e s e movements o c c u r r e d a t c h a n g i n g v e l o c i t i e s DRIVE PHASE OF ROWING A STATIONARY ERGOMETER FIGURE 1 A. DRIVE PHASE OF ROWING A WHEELED ERGOMETER FIGURE 1 B 17 T a b l e 2. I n t e r n a l work ( j o u l e s ) and energy s a v i n g s ( p e r c e n t ) f o r the s c u l l i n g t r i a l s . S u b j e c t W S S T r i a l i e i Code 832.2 27.6 18.7 RB1A1 1 1153. 1 27.6 13.5 RB1B2 970.7 38.1 14.8 RB1C3 1657.6 22.8 15.0 RB2A1 2 1267.6 36.4 9.9 RB2B2 1655.2 19.5 12.2 RB2C3 594.0 32. 1 16.8 RB3A1 3 909.6 32.3 11.6 RB3B2 788.2 33. 1 15.0 RB3C3 696.2 27.0 15.7 RB4A1 4 756. 1 31.0 13.8 RB4B2 794.4 40.4 12.3 RB4C4 MEAN SD 30.6 6.1 14.2 2.4 18 Table 3. Internal work (joules) and energy savings (percent) for the wheeled RE t r i a l s . iject W S S T r i a l i e i Code 245.6 31 .2 17.7 RW1A1 1 280.9 29.0 16.9 RW1B2 336.5 24.7 15.3 RW1C3 310.7 28.8 19.5 RW2A1 2 314.0 25.2 21.7 RW2B2 335.3 25.5 18.0 RW2C3 213.3 22.3 17.3 RW3A4 3 211.7 30.0 1 1 .8 RW3B5 212.0 32.6 16.1 RW3C6 181.0 23.3 22.6 RW4A1 4 1 93.4 21 .4 22.4 RW4B2 236.0 17.6 21 .8 RW4C3 MEAN SD 26.0 4.5 18.9 3.3 19 T a b l e 4. I n t e r n a l work ( j o u l e s ) and e n e r g y s a v i n g s ( p e r c e n t ) f o r t h e s t a t i o n a r y RE t r i a l s . lub j e c t W S S T r i a l i e i Code 361 .4 24.1 13.0 RS 1A4 1 3 6 7 . 9 2 3 . 0 11.8 RS1B5 551 .9 1 1.9 8 .2 RS1C7 4 6 8 . 8 2 2 . 2 1 1 .2 RS2A4 2 3 5 3 . 6 30.1 18.2 RS2B5 4 5 8 . 6 2 4 . 3 11.4 RS2C6 2 3 3 . 0 2 5 . 4 13.2 RS3A1 3 2 6 5 . 4 2 2 . 6 10.6 RS3B2 2 5 6 . 8 2 8 . 7 12.6 RS3C3 199.7 2 9 . 2 16.2 RS4A4 4 2 8 2 . 4 2 0 . 7 14.1 RS4B5 3 2 0 . 3 16.0 15.5 RS4C6 MEAN 2 3 . 2 13.0 SD 5.3 2.7 20 w i t h i n the s t r o k e s . I n the RE t r i a l s t h e r e was v e r y l i t t l e movement of the body o t h e r than t h a t on the s l i d e . W i t h no movement of the RE r e l a t i v e t o the e x t e r n a l environment (as e x i s t s i n t h e b o a t ) , t h e r e was no measure of the change of energy of the system of s u b j e c t - R E t h a t was p r o b a b l y r e f l e c t e d i n t he changes i n the a n g u l a r v e l o c i t y of the f l y w h e e l of t h e RE. M o t i o n of the RE i n the wheeled t r i a l s was not g r e a t enough t o cause s i g n i f i c a n t changes of energy i n the system of s u b j e c t and RE. The d i f f e r e n t i n t e r n a l work v a r i a b l e s enumerate changes i n the components of t h e e n e r g i e s of the segments. The c u r v e s shown i n F i g u r e 2 show the k i n e t i c e n e r g i e s of s e l e c t e d energy v a r i a b l e s a t t h e same s t r o k e r a t e on t h e d i f f e r e n t d e v i c e s . The to p c u r v e d e m o n strates the g r e a t e r changes i n the t o t a l m e c h a n i c a l energy of the s u b j e c t i n t h e rowing t r i a l s . The W i t e rm i s made up of t h e frame-by frame changes i n t h e t o t a l body energy, of which the t o p cu r v e i n F i g u r e 2 l a c k s o n l y the p o t e n t i a l energy (which i s e s s e n t i a l l y a b i a s , i n rowing) of t h e e n t i r e system and the energy of the bo a t . In the rowing t r i a l s , the changes i n the energy of the system ( t h e work) r e f l e c t t h e s u b j e c t s ' e f f o r t s t o move the boat t h r o u g h the m a n i p u l a t i o n s of the o a r s . The magnitude of the changes i n energy t h r o u g h t h e d r i v e , c o u p l e d w i t h the d u r a t i o n of the d r i v e ( i . e., power) r e f l e c t t he e f f e c t i v e n e s s of the rowing m o t i o n s . These powers a r e d i s c u s s e d l a t e r i n t h i s paper. The i n t e r n a l work v a l u e s seen i n t a b l e s 2 t o 4 may be compared w i t h i n t e r n a l work s c o r e s between 48.5 and 251.7 f o r l e v e l w a l k i n g (Winter 1979a). P i e r r y n o w s k i , e t a l . , (1980), 21 TOTAL BODY AND TQRSQ^THIGHS KINETIC ENERGY SUBJECT 1. TRIAL CODE: SUBJ 1 A — A BODY UN BOAT) TIME (SECONDS) FIGURE 2 . 22 found work v a l u e s i n t r e a d m i l l w a l k i n g which averaged 165.7 (W ), 340.2 (W ), and 500.9 (W ); v a l u e s f o r i n t e r n a l work i e n c a r r y i n g a v a r i e t y of e x t e r n a l l o a d s d u r i n g t r e a d m i l l w a l k i n g ranged from 328 t o 423 (W ) ( P i e r r y n o w s k i , e t a l . , 1981). These e r e s e a r c h e r s were a b l e t o i n c l u d e the speed of the t r e a d m i l l b e l t i n t h e i r i n v e s t i g a t i o n s , t o g i v e an e s t i m a t e of the " v e l o c i t y " of t h e i r s u b j e c t s m o t i o n s . Such a measure was not p o s s i b l e d u r i n g the p r e s e n t s t u d y , as the equipment a v a i l a b l e , and time and f i n a n c i a l c o n s t r a i n t s p r e v e n t e d development of and adequate measure of the a n g u l a r v e l o c i t y of the f l y w h e e l d u r i n g the RE t r i a l s . S c o r e s f o r W i n the boat t r i a l s i n the p r e s e n t s t u d y i were c o n s i d e r a b l y h i g h e r than s c o r e s f o r the w a l k i n g t r i a l s i n t h e s e o t h e r s t u d i e s . The work d a t a f o r the s t a t i o n a r y RE are s l i g h t l y h i g h e r than f o r the wheeled RE. The reason f o r t h i s i s a p p arent i n comparing F i g u r e s 1A and 1B and i n the bottom s e t s of c u r v e s i n F i g u r e 2. The l a c k of motion i n the s t a t i o n a r y RE causes the s u b j e c t t o have t o a c c e l e r a t e and d e c e l e r a t e most of h i s body a t each end of the s t r o k e i n a d d i t i o n t o moving the RE's oar h a n d le t h r o u g h the s t r o k e . T h i s i s not l i k e rowing a b o a t , i n which the boat moves w i t h the rower, and a l l o w s the s u b j e c t t o move the boat (which weighs about 20-25% of the s u b j e c t ) r e l a t i v e t o h i m s e l f , i n s t e a d of a l l of the s u b j e c t ' s motions b e i n g a b s o l u t e w i t h r e s p e c t t o the environment. i . e . , The s u b j e c t ' s movements i n a s h e l l cause the boat t o change i t s v e l o c i t y r e l a t i v e t o b o t h the s u b j e c t and t h e e x t e r n a l r e f e r e n c e system, w h i l e the i m m o b i l i t y of the s t a t i o n a r y RE f o r c e s a l l of the s u b j e c t ' s 23 motions t o be r e l a t i v e o n l y t o the e x t e r n a l system of r e f e r e n c e s i n c e the frame of the RE does not move p e r c e p t i b l y i n response t o the s u b j e c t ' s a c t i o n s . The g e n e r a l shape of the bottom s e t s of c u r v e s i n F i g u r e 4 i s due t o the need f o r the s u b j e c t t o come t o a complete s t o p a t each end of the s l i d e . A f t e r s t o p p i n g the movement of the d r i v e , the s u b j e c t was then r e q u i r e d t o a c c e l e r a t e h i s e n t i r e body i n the o p p o s i t e d i r e c t i o n f o r the r e c o v e r y . The h i g h peak of the s u b j e c t ' s energy d u r i n g the d r i v e was due t o the v e l o c i t y w i t h which the s u b j e c t moved d u r i n g the d r i v e . The lower peak i n the energy of the system i n the r e c o v e r y was due t o the s u b j e c t p e r f o r m i n g e s s e n t i a l l y the r e v e r s e of the d r i v e phase, but more s l o w l y . W i t h no measure of the f l y w h e e l ' s i n s t a n t a n e o u s r o t a t i o n a l v e l o c i t y t h e r e i s no c l e a r way t o compare the i n t e r n a l work i n the ergometer c o n d i t i o n s w i t h the i n t e r n a l work i n t h e rowing t r i a l s . The e f f e c t of the rower's movements on the boat a r e e v i d e n t i n the i n s t a n t a n e o u s changes i n the v e l o c i t y of the system. The a n g u l a r v e l o c i t y of the f l y w h e e l would r e f l e c t t h e s e e f f o r t s i n the ergometer, and c o u l d be used t o g i v e energy v a l u e s which c o u l d be used t o compare the i n t e r n a l work s c o r e s of the d i f f e r e n t t e s t d e v i c e s . F u t u r e r e s e a r c h i n t h i s a r e a must i n c l u d e such a measure. Energy Exchanges and I n t e r c o n v e r s i o n s C a l c u l a t i n g s a v i n g s of energy by exchange and i n t e r c o n v e r s i o n a v o i d s the problem of comparing i n t e r n a l work s c o r e s by p e r m i t t i n g the comparison of the p r o p o r t i o n a l d i f f e r e n c e s between the "work" v a l u e s . Energy s a v i n g s c a l c u l a t e d from E q u a t i o n s 7 and 8 a r e p r e s e n t e d i n the second 24 and t h i r d d a t a columns of T a b l e s 2, 3, and 4. The S and S e i v a l u e s a r e e x p r e s s e d as p e r c e n t a g e s of the t o t a l m e c h a n i c a l work i f n e i t h e r exchange nor c o n v e r s i o n of energy a r e p e r m i t t e d . The energy exchange term (S ) may be used t o d i s c u s s some e of t h e d i f f e r e n c e s between rowing and rowing e r g o m e t e r s . A l a r g e r p r o p o r t i o n of the t o t a l apparent "work" (W ) appears t o n be t r a n s m i t t e d from the body t o the d e v i c e i n s c u l l i n g t han i n e i t h e r RE c o n d i t i o n , w i t h v i s i b l e e f f e c t on t h e s h e l l . T h i s i s a p p a r e n t from the l a r g e r S s c o r e s i n the s c u l l i n g d a t a e ( T a b l e 5 ) . That the S i n the wheeled RE was g r e a t e r than the e S i n t h e s t a t i o n a r y RE but l e s s than t h a t i n the boat, and t h a t e the o n l y r e a l d i f f e r e n c e between the two RE c o n d i t i o n s was the motion of the RE ( r e f e r t o F i g u r e 1 A and B) d u r i n g the s t r o k e r e i n f o r c e s t h i s s u g g e s t i o n . As w e l l , s u b j e c t s c l a i m e d t h a t the wheeled RE " f e l t " s l i g h t l y more l i k e r e a l r o wing than d i d rowing the s t a t i o n a r y RE. I n t e r c o n v e r s i o n of energy w i t h i n segments (S ) was g r e a t e s t i i n t h e wheeled RE and was v e r y s i m i l a r f o r the s c u l l i n g and the s t a t i o n a r y RE d a t a . The main sou r c e of t h e d i f f e r e n c e i n e s t i m a t e d S may have been the presence or absence of l a r g e i amounts of t r a n s l a t i o n a l energy changes i n t h e segments. In the wheeled RE most of the motion of the t h i g h s and lower l e g s segments, f o r example, was e i t h e r r o t a t i o n a l or t r a n s l a t i o n a l i n the v e r t i c a l d i r e c t i o n o n l y . W i t h the s t a t i o n a r y RE and w i t h 25 T a b l e 5. Power i n d r i v e , average v e l o c i t y , s t r o k e r a t e and average power. T r i a l D r i v e Average S t r o k e Average E s t . Code Power V e l . Rate Power 2000 i (W) (m/s) (/min) (W) Time RB1A1 377 3.75 25.6 161 8'53" * RB1B2 859 4.57 32 459 7' 18" * RB1C3 962 4.74 32 514 7' 02" RB2A1 462 3.66 20.4 157 9'07" RB2B2 434 3.87 24. 1 174 8' 37" * RB2C3 757 4.42 32 404 7' 32" RB3A1 309 3.51 24.7 127 9*29" RB3B2 468 4.07 29.5 230 8' 1 1 " RB3C3 655 4.21 32 350 7'55" RB4A1 521 3.72 26 226 8*57" RB4B2 566 4.21 30.7 290 7'55" RB4C4 560 4.59 36.6 343 7' 15" 26 the rowing s h e l l , t h e r e was a l a r g e h o r i z o n t a l t r a n s l a t i o n a l component t o the motion i n a d d i t i o n t o the r o t a t i o n a l and v e r t i c a l movement components. Thus the c h i e f d i f f e r e n c e between the s t a t i o n a r y and the wheeled c o n d i t i o n s i s due t o the c o m p u t a t i o n of the S w h i c h , as a p e r c e n t a g e of the t o t a l i a p p a r e nt change i n energy, i s i n c r e a s e d i n the wheeled RE because of the absence of the r e l a t i v e l y l a r g e h o r i z o n t a l components seen i n t h e motions of the s u b j e c t i n the s t a t i o n a r y RE and boat t r i a l s . There was no apparent r e l a t i o n s h i p between the p e r c e n t a g e of energy saved i n the t h r e e d e v i c e s and the s t r o k e r a t e . A l t h o u g h t h e r e was an i n s u f f i c i e n t number of s u b j e c t s t o warrant i n f e r e n t i a l s t a t i s t i c s , the d i f f e r e n c e s between the means shown i n T a b l e s 2 t o 4 a r e worth n o t e . The mean S f o r the boat was e s i g n i f i c a n t l y d i f f e r e n t from the v a l u e s f o r both ergometer c o n d i t i o n s (t=2.14, p ^ 0 . 0 5 , boat v e r s u s wheeled RE, and t = 3 . l 9 , p ^ 0.01 ,boat v e r s u s s t a t i o n a r y e r g o m e t e r ) . These d i f f e r e n c e s suggest t h a t f u r t h e r i n v e s t i g a t i o n of exchange of energy i n rowing may be w o r t h w h i l e . (No attempt may be made t o use the d a t a from t h i s s t u d y t o p r e d i c t the m e c h a n i c a l energy s a v i n g s of o t h e r s c u l l e r s because of the s m a l l sample s i z e i n the s t u d y and because of the v a s t d i f f e r e n c e s between the a b i l i t i e s of the e x p e r i e n c e d and i n e x p e r i e n c e d s u b j e c t s . ) I d e n t i f i c a t i o n of the s o u r c e s of energy exchange among segments ( i n c l u d i n g the r a c i n g s h e l l ) may be a method f o r a t t e m p t i n g t o m a n i p u l a t e rowing t e c h n i q u e s t o maximize b o t h exchange of m e c h a n i c a l energy and the average v e l o c i t y of the r a c i n g s h e l l . 27 The p o s s i b i l i t y of the presence of exchanges of energy between the s u b j e c t and the s h e l l i s r e i n f o r c e d by the p a t t e r n s of t h e c u r v e s f o r the s u b j e c t and boat i n F i g u r e 3. Between t h e low e s t p o i n t of the s u b j e c t ' s E c u r v e ( a t about 1.75 s) and kt t he c a t c h ( i n d i c a t e d by "CAT") a t about 2.00 s, the energy of the boat f e l l , w h i l e t h a t of the s u b j e c t i n c r e a s e d . The k i n e t i c energy of the s h e l l was e x p e c t e d t o f a l l , as i t was under the i n f l u e n c e of drag from the water. The energy of the s u b j e c t was not e x p e c t e d t o i n c r e a s e b e f o r e t h e c a t c h , s i n c e t h e s u b j e c t was s t i l l a p p r o a c h i n g the f r o n t of the s l i d e w i t h h i s o a r s out of the water. D u r i n g the r e c o v e r y phase of a s t r o k e rowers t r y t o mi n i m i z e d i s t u r b a n c e s of the motion of a boat by r e d u c i n g e x c e s s motion t o a minimum. The o n l y s o u r c e from which the s u b j e c t c o u l d have r e c e i v e d energy a t t h a t p o i n t was the b o a t . The p a t t e r n of the E c u r v e s between about 0.75 s and about 1.75 s kt ( d u r i n g the r a p i d d e c r e a s e i n the energy of the s u b j e c t ) p e r m i t s s p e c u l a t i o n t h a t f u r t h e r energy s a v i n g e x i s t s as exchange from s u b j e c t t o b o a t . In t h a t e n t i r e second, d u r i n g which the E of k t the s u b j e c t f e l l from i t s peak t o i t s l o w e s t p o i n t i n the c y c l e , the E of the boat i n c r e a s e d almost c o n t i n u o u s l y . The energy kt c a u s i n g the b o a t ' s energy t o i n c r e a s e must have come from the s u b j e c t t h r o u g h h i s c o n n e c t i o n t o the boat a t the f e e t , s i n c e the o n l y o t h e r s o u r c e of energy change i n the system was the v i s c o u s d r a g of the w a t e r . C l e a r l y , t h e d r a g of t h e water d i d not add t o the energy of the b o a t . These exchanges of energy among boat and crew have been e v i d e n t f o r y e a r s , and a r e 28 TOTAL BODY AND BOAT KINETIC ENERGY SUBJECT 1 TRIAL CODE'. RB1C3. A — A SUBJECT K. E. TIME 1SECOND-SJ FIGURE 3 . 29 a p p arent i n the changes of h u l l v e l o c i t y d u r i n g the s t r o k e ( e . g., M a r t i n and B e r n f i e l d , 1980). A l i t e r a t u r e s e a r c h found no p r e v i o u s a t t e m p t s t o q u a n t i f y the exchanges of energy between boat and rower. That the S and p a r t i c u l a r l y t h e S v a l u e s a r e h i g h e r i n i e t h e wheeled RE c o n d i t i o n a l l o w the s p e c u l a t i o n t h a t an oarsman would be c a p a b l e of p r o d u c i n g g r e a t e r work o u t p u t i n a 6 min RE t e s t on an ergometer mounted on wheels or r o l l e r s . The f e a s i b i l i t y of such a t e s t might be i n c r e a s e d by t e t h e r i n g the RE a t each end of the machine w i t h a "damped e l a s t i c , " as t h e r e i s a tendency f o r the machine t o t r a v e l " s t e r n w a r d " d u r i n g r o wing when mounted on wheels. Average D r i v e Power The powers of the d r i v e phase (P of the s c u l l i n g s t r o k e s , d t h e average . v e l o c i t y of t h e s h e l l t h r o u g h o u t the s t r o k e s ( c a t c h - t o - c a t c h ) , t h e s t r o k e r a t e , the average power of each s t r o k e , and an e s t i m a t e d 2000 m r a c e time a r e p r e s e n t e d i n T a b l e 5. Powers c a l c u l a t e d f o r the d r i v e phase of some of the s c u l l i n g s t r o k e s i n t h i s paper ( i n d i c a t e d by "*") a r e h i g h e r than the average power e s t i m a t e d f o r maximal rowing ergometer t e s t s of American n a t i o n a l - team c a n d i d a t e s . Hagerman e t a l . , (1978) r e p o r t average power i n 310 s u b j e c t s , of 360113.8 W, w i t h a maximal v a l u e of 407 W, c a l c u l a t e d from the number of f l y w h e e l r e v o l u t i o n s i n 6 min maximal rowing ergometer t e s t s . The average power r e q u i r e d t o s c o r e 5000 f l y w h e e l r e v o l u t i o n s w i t h the G j e s s i n g RE used i n t h i s s t u d y i s s l i g h t l y g r e a t e r than 30 400 W (1 r e v o l u t i o n = 29.4 J , time=360 s ) . The main d i f f e r e n c e between t h e powers shown i n t h i s paper and th o s e e s t i m a t e d i n p r e v i o u s rowing ergometer t e s t s may be due t o the l a c k of a t o t a l m e c h a n i c a l work measure i n the ergometer t e s t s ( i . e., o n l y the e f f o r t a p p l i e d t o the f l y w h e e l has been measured i n the p a s t ) , and t o the absence of any p r e v i o u s e s t i m a t e s of the i n t e r n a l work and the i n t r a - s t r o k e work of ro w i n g . A m e c h a n i c a l energy s t u d y of REs i s r e q u i r e d w i t h a measure of the a n g u l a r v e l o c i t y of the RE's f l y w h e e l b e f o r e c o r r e c t c o n t r a s t s may be drawn between the m e c h a n i c a l energy p a t t e r n s of s c u l l i n g and rowing an RE. The methods used t o e s t i m a t e the average power i n the s h e l l f o r the e n t i r e s t r o k e (average power = (P x ( s t r o k e r a t e ) ) / 6 0 s) d i n c l u d e s b o t h the work r e q u i r e d t o move the s c u l l e r ' s body t h r o u g h t h e rowing s t r o k e and t h e e f f e c t s of the s u b j e c t ' s e f f o r t s on the v e l o c i t y of the r a c i n g s h e l l . B oth of the e s t i m a t e d average powers f o r s u b j e c t 1 s c u l l i n g a t 32 s t r o k e s per minute ( t r i a l s RB1B2 and RB1C3) a r e g r e a t e r than the average powers of the b e s t oarsmen r e p o r t e d by Hagerman (e t a _ l ) . , ( 1978). T h i s s u g g e s t s t h a t the average power c a l c u l a t e d from f l y w h e e l ergometry i n rowing f a l l s s h o r t of the r e a l power e x e r t e d i n s c u l l i n g . F u r t h e r study of the power i n rowing i s n e c e s s a r y and s h o u l d i n c l u d e measurement of the f o r c e s a p p l i e d e i t h e r a t the o a r l o c k , the o a r , or the f o o t b o a r d s , as w e l l as s i m u l t a n e o u s f i l m i n g f o r a power a n a l y s i s . Another s u g g e s t i o n i s t h a t f u r t h e r i n v e s t i g a t i o n of the m e c h a n i c a l e n e r g i e s i n rowing a G j e s s i n g RE i s w a r r a n t e d , u s i n g a measure 31 of the i n s t a n t a n e o u s work a p p l i e d t o the f l y w h e e l of the RE, as w e l l as the i n t e r n a l work due t o the s u b j e c t s ' segmental e n e r g i e s . 32 CONCLUSIONS The d a t a p r e s e n t e d above s u p p o r t the f o l l o w i n g c o n c l u s i o n s : 1. Based on the d i f f e r e n c e s between energy s a v i n g s i n the boat and energy s a v i n g s i n the RE c o n d i t i o n s , t h e r e e x i s t s i g n i f i c a n t d i f f e r e n c e s between the movements of the s c u l l e r when s c u l l i n g and tho s e movements when rowing an ergometer. 2. The main d i f f e r e n c e s i n s a v i n g s a re due t o the motion of the boat r e l a t i v e t o the s u b j e c t , which does not oc c u r on a s t a t i o n a r y RE. 3. The t o t a l body m e c h a n i c a l energy and i n t e r n a l work of rowing a r a c i n g s h e l l i s g r e a t e r than t h a t of rowing a rowing ergometer. 4. S i n c e the t o t a l energy s a v i n g s t h r o u g h exchanges and c o n v e r s i o n s i n the wheeled RE a r e g r e a t e r than those i n the s t a t i o n a r y ergometer, t h e r e i s support f o r a p r o p o s a l t h a t f u t u r e t e s t i n g of oarsmen be co n d u c t e d u s i n g some form of wheeled c a r t under the RE t o p e r m i t use of h i g h e r , more r a c e - l i k e s t r o k e r a t e s i n ergometer t e s t i n g . Recommendations Based on the u n d e r s t a n d i n g g a i n e d w i t h the f i n d i n g s of t h i s s t u d y , the f o l l o w i n g recommendations f o r the study of rowing b i o m e c h a n i c s a r e w a r r a n t e d . 1. The c o m b i n a t i o n of f i l m s t u d y and f o r c e r e c o r d i n g i n the o a r l o c k or the oar would p e r m i t f u r t h e r u n d e r s t a n d i n g of the m e c h a n i c a l energy changes and power f l o w s between the oarsman 33 and t h e b o a t . 2. A moving camera system, t o p e r m i t l a r g e r image s i z e s , i s n e c e s s a r y f o r t h e r e d u c t i o n of n o i s e i n the f i l m d a t a of r o w i n g , i f a whole s t r o k e i s t o be a n a l y z e d . The Olympic rowing c o u r s e i n M o n t r e a l would be i d e a l f o r such a s t u d y , as s e v e r a l c o n s e c u t i v e s t r o k e s c o u l d be s t u d i e d , perhaps under r a c e c o n d i t i o n s . 3. The changes i n s c u l l i n g t e c h n i q u e t h a t may o c c u r w i t h f a t i g u e d u r i n g a r a c e might be examined by f i l m i n g s t r o k e s a t the s t a r t and a t each 250 or 500 m through t h e r a c e . 4. An i n s t a n t a n e o u s measure of the f l y w h e e l a n g u l a r v e l o c i t y of any rowing ergometer must be i n c l u d e d i n any f u t u r e s t u d y of the m e c h a n i c a l energy and i n t e r n a l work of rowing ergometers. 34 REFERENCES 1. E l f t m a n , H. F o r c e s and energy changes i n the l e g d u r i n g w a l k i n g . Am. J . P h y s i o l . 125:339-356 (1939). 2. Hagerman, F. C , and W. D. Lee. Measurement of oxygen consumption, h e a r t r a t e , and work output d u r i n g rowing Med. S c i . S p o r t s . 3(4):155-160, (1971). 3. Hagerman, F. C , W. A d d i n g t o n , and E. A. G a e n s l e r . A comparison of s e l e c t e d v a r i a b l e s among o u t s t a n d i n g c o m p e t i t i v e oarsmen. J _ S p o r t s Med. Phys. F i t n e s s 12(1 ) : 12-22 ( 1972). 4. Hagerman, F. C , M. D. M c K i r n a n , and J . A. Pompei. Maximal oxygen consumption of c o n d i t i o n e d and u n c o n d i t i o n e d oarsmen. J . S p o r t s Med. Phys. F i t n e s s 15(3):43-48, (1975a) 5. Hagerman, F. C , W. W. A d d i n g t o n , and E. A. G a e n s l e r . Severe s t e a d y s t a t e e x e r c i s e a t sea l e v e l and a t a l t i t u d e i n Olympic oarsmen. Med. S c i . S p o r t s 7(4):275-279 (1975b). 6. Hagerman, F. C , M. C. Connors, J . A. G a u l t , G. R. Hagerman, and W. J . P o l i n s k i . Energy e x p e n d i t u r e d u r i n g s i m u l a t e d r o w i n g . J _ A p p l . P h y s i o l . 45(1):87-93, (1978) . 7. Hagerman, F. C , G. R. Hagerman, and T. C. M i c k l e s o n . P h y s i o l o g i c a l p r o f i l e s of e l i t e r owers. P h y s i c i a n and S p o r t s m e d i c i n e 7(7):74-83, (1979). 8. Henderson, Y., and H. W. Haggard. The maximum of human power and i t s f u e l . Am. J . P h y s i o l . 72:264-282, (1925). 9. P e z z a c k , J . C , R. W. Norman, and D. A. W i n t e r . An assessment of d e r i v a t i v e d e t e r m i n i n g t e c h n i q u e s used f o r motion a n a l y s i s . J _ Biomechanics 10, 377-382, (1977). 10. P i e r r y n o w s k i , M. R. Energy l e v e l s of human body segments d u r i n g l o a d c a r r i a g e on a t r e a d m i l l . M. Sc. T h e s i s ; U n i v e r s i t y of W a t e r l o o , (1978) 11. P i e r r y n o w s k i , M. R., D. A. W i n t e r , and R. W. Norman. T r a n s f e r s of m e c h a n i c a l energy w i t h i n the t o t a l body and m e c h a n i c a l e f f i c i e n c y d u r i n g t r e a d m i l l w a l k i n g . Ergonomics 23(2):147-156, (1980). 12. P i e r r y n o w s k i , M. R., R. W. Norman, and D. A. W i n t e r . M e c h a n i c a l energy a n a l y s e s of the human d u r i n g l o a d c a r r i a g e on a t r e a d m i l l . Ergonomics 24(1):1-14, (1981). 13. R o b e r t s o n , D. G. E., and D. A. W i n t e r . M e c h a n i c a l energy g e n e r a t i o n , a b s o r p t i o n and t r a n s f e r amongst segments d u r i n g w a l k i n g . J _ Biomechanics 13:845-854, (1980). 35 14. ' W i n t e r , D. A. and D. G. E. R o b e r t s o n . J o i n t t o r q u e and energy p a t t e r n s i n normal g a i t . B i o l o g i c a l C y b e r n e t i c s 29:137-142, (1978). 15. W i n t e r , D. A. A new d e f i n i t i o n of m e c h a n i c a l work done i n human movement. J _ A p p l . P h y s i o l . 4 6 ( 0 : 7 9 - 8 3 , (1979a). 16. W i n t e r , D. A. Biomechanics of Human Movement W i l e y , T o r o n t o , (1979b) 17. W o l t r i n g , H. J . C a l i b r a t i o n and measurement i n 3- d i m e n s i o n a l m o n i t o r i n g of human motion by o p t o e l e c t r o n i c means. I . P r e l i m i n a r i e s and t h e o r e t i c a l a s p e c t s . B i o t e l e m e t r y 2:169-196, (1975). 18. W o l t r i n g , H. J . C a l i b r a t i o n and measurement i n 3- d i m e n s i o n a l m o n i t o r i n g of human motion by o p t o e l e c t r o n i c means. I I E x p e r i m e n t a l r e s u l t s and d i s c u s s i o n . B i o t e l e m e t r y 3:65-97, (1976). 36 APPENDIX _ - DEFINITIONS Rowing Terms. The f o l l o w i n g rowing terms were o p e r a t i o n a l l y d e f i n e d f o r d i s c u s s i o n of rowing a c t i o n s : c a t c h - n o r m a l l y t h a t p a r t of the rowing s t r o k e i n which the rower p u t s the b l a d e p o r t i o n of the o a r ( s ) i n t o the water t o b e g i n p u l l i n g t o p r o p e l the b o a t ; f o r t h i s s t u d y the " c a t c h " was the p o s i t i o n of the rower when he or she was no l o n g e r moving f o r w a r d on the s l i d e d u r i n g r e c o v e r y , and had not y e t s t a r t e d t o move back on the s l i d e i n the d r i v e ( t h i s p o s i t i o n was i d e n t i f i e d by the p o s i t i o n of the oar h a n d l e when i t was a t i t s f u r t h e s t p o i n t from the rower's body, and was n e i t h e r moving f o r w a r d nor backward w i t h r e s p e c t t o the rower. d r i v e - t h a t p a r t of the rowing s t r o k e i n which the rower was p u l l i n g the oar handle w i t h the b l a d e p o r t i o n of the oar s quared, and beneath the s u r f a c e of the w a t e r ; the d r i v e i s the p a r t of the s t r o k e used t o p r o p e l the b o a t . f i n i s h - n o r m a l l y t h a t p a r t of the rowing s t r o k e i n which the rower c o m p l e t e s the d r i v e , s t o p s p u l l i n g the oar h a n d l e ( s ) , removes the b l a d e ( s ) from the w a t e r , and f e a t h e r s the b l a d e ( s ) t o b e g i n the r e c o v e r y ; f o r t h i s s tudy f i n i s h meant the p o s i t i o n of the s u b j e c t when the oar h a n d l e had stopped moving backwards (toward the bow of the boat) a t the end of the d r i v e , and had not s t a r t e d moving f o r w a r d w i t h r e s p e c t t o the rower d u r i n g the r e c o v e r y - the o p p o s i t e end of the s t r o k e from the c a t c h p o s i t i o n . r a t e - or - s t r o k e r a t e - the s t r o k e f r e q u e n c y e x p r e s s e d i n 37 s t r o k e s per minute, eg., "rowing a t 30", "30 s t r o k e s per minute", and " s t r i k i n g 30," and o t h e r s i m i l a r e x p r e s s i o n s a r e c o n s i d e r e d e q u i v a l e n t , r a t e watch - a c a l i b r a t e d stopwatch w h i c h d i s p l a y s the s t r o k e r a t e e x t r a p o l a t e d from the time r e q u i r e d t o complete 3 or 4 s t r o k e s (depending upon the c a l i b r a t i o n of the watch f a c e ) , r e c o v e r y - t h a t p a r t of the rowing s t r o k e f o l l o w i n g the f i n i s h and b e f o r e the c a t c h , when the rower p r e p a r e s f o r the next s t r o k e . s c u l l i n g - r o w i n g i n a boat u s i n g two o a r s ( s c u l l s ) per p e r s o n , one on each s i d e of the boat ( c . f . "sweep"). s h e l l - a boat used f o r f l a t water r a c e rowing - a l s o c a l l e d a " s k i f f " . s l i d e - t h e t h e t r a c k s which g u i d e t h e movement of t h e wheels of the rower's s e a t i n a s h e l l , s t r e t c h e r - the p a r t of the s h e l l used t o p o s i t i o n the rower's f e e t d u r i n g r owing; a l s o c a l l e d " f o o t b o a r d " sweep - rowing i n a boat u s i n g one oar (sweep) on one s i d e of the s h e l l ; sweeps r e q u i r e a minimum of two rowers w h i l e s c u l l i n g may be done a l o n e or w i t h p a r t n e r s . Energy A n a l y s i s Terms. D i s c u s s i o n of m e c h a n i c a l energy i n t h i s s t u d y r e q u i r e d the o p e r a t i o n a l d e f i n i t i o n of the f o l l o w i n g - terms: c o n v e r s i o n - see " i n t e r c o n v e r s i o n " , below. 38 i n t e r c o n v e r s i o n - (energy i n t e r c o n v e r s i o n ) the change i n the e x p r e s s i o n of the m e c h a n i c a l energy w i t h i n a body segment i . e., when an o b j e c t i s dropped from a h e i g h t p o t e n t i a l energy i s c o n v e r t e d or i n t e r c o n v e r t e d t o k i n e t i c energy, exchange - (energy exchange) the t r a n s m i s s i o n of m e c h a n i c a l energy from one body p a r t t o an o t h e r e. g., energy " g e n e r a t e d " i n the a n t e r i o r d e l t o i d muscle by c h e m i c a l r e a c t i o n s between a c t i n , myosin, and adenosine t r i p h o s p h a t e i s t r a n s f e r r e d t o the fo r e a r m segment i n the a c t i o n of s h o u l d e r f l e x i o n ( d e s c r i b e d i n E l f t m a n (1939), W i n t e r and Ro b e r t s o n (1978), and i n Robertson and W i n t e r (1980). Energy i s exchanged among segments when the d e c e l e r a t i o n of one segment causes a c c e l e r a t i o n of an a d j a c e n t or nearby segment. These d e f i n i t i o n s of i n t e r c o n v e r s i o n and exchange of m e c h a n i c a l energy d i f f e r from those p r e v i o u s l y used. C a l d w e l l (1980) used exchange t o d i s c u s s both c o n v e r s i o n and exchange. P i e r r y n o w s k i , e t a l . (1980) used t r a n s f e r t o e x p r e s s the two v a l u e s . The use of two terms whose d i c t i o n a r y d e f i n i t i o n s a r e more s u i t e d t o the d e s c r i p t i o n of d i f f e r e n t e f f e c t s of motion on the m e c h a n i c a l energy of an o b j e c t i s perhaps l e s s ambiguous than u s i n g the same term, whether exchange or t r a n s f e r , t o d i s c u s s d i f f e r e n t s o u r c e s of energy s a v i n g . T h i s may be p a r t i c u l a r l y i m p o r t a n t f o r p e o p l e l e s s f a m i l i a r w i t h the c o n c e p t s and t e r m i n o l o g y of t h i s s t u d y and o t h e r s l i k e i t . work - used t o d e s c r i b e the change i n the t o t a l m e c h a n i c a l energy of a segment or of a body; a l s o c a l l e d pseudowork or i n t e r n a l work; the energy change r e q u i r e d t o move body p a r t s i n space - d i s t i n c t from e x t e r n a l work, which i s the energy 39 change r e q u i r e d t o e f f e c t a change i n the immediate s u r r o u n d i n g s of the body a g a i n s t g r a v i t y . 40 APPENDIX 2 - SYMBOLS USED IN THE PAPER E - k i n e t i c energy k E - t r a n s l a t i o n a l k i n e t i c energy kt E - r o t a t i o n a l k i n e t i c energy kr E - p o t e n t i a l energy P P - average power i n the d r i v e phase of a s t r o k e d S - energy "saved" by exchange among segments e x p r e s s e d as a e pe r c e n t a g e of the t o t a l m e c h a n i c a l work r e q u i r e d w i t h n e i t h e r exchange nor c o n v e r s i o n of m e c h a n i c a l energy. S - energy "saved" by i n t e r c o n v e r s i o n w i t h i n segments, i e x p r e s s e d as a p e r c e n t a g e of the t o t a l m e c h a n i c a l work r e q u i r e d w i t h n e i t h e r exchange nor c o n v e r s i o n of m e c h a n i c a l energy. W - work r e q u i r e d t o move the segments of the body i f exchange e of energy was p e r m i t t e d , but i n t e r c o n v e r s i o n of energy was not p e r m i t t e d . ( E q u a t i o n #5) W - work r e q u i r e d t o move the segments of the body a l l o w i n g i b o t h exchange and i n t e r c o n v e r s i o n of m e c h a n i c a l energy ( E q u a t i o n #4) W - Work r e q u i r e d t o move the segments of the body i f n e i t h e r n exchange nor i n t e r c o n v e r s i o n of energy was p e r m i t t e d ( E q u a t i o n #6). 41 APPENDIX 3 - ENERGY PLOTS OF SUBJECTS 2. 3. AND 4 42 TOTAL BODY AND TORSO+THIGHS KINETIC ENERGY SUBJECT 2 400 _L 0.00 0.25 0.50 FIGURE 4 . 0 . 7 5 I'.OO 1.25 1.50 1.75 TIME [SECONDS] 2.00 2.25 2.50 2. 43 TOTAL BODY AND TORSO+THIGHS KINETIC ENERGY SUBJECT 3 TRIAL CODE: SUBJ 3 FIGURE 5. TIME (SECONDS) 44 flnn TOTAL BODY AND TORSO+THIGHS KINETIC ENERGY SUBJECT 4 o.oa 0 . 2 5 FIGURE 6. 0 . 7 5 1.00 1.25 1.50 TIME ISECONDS) 45 APPENDIX 4 - REVIEW OF LITERATURE The s t u d y of the m e c h a n i c a l energy v a r i a t i o n s of rowing r e q u i r e s f a m i l i a r i t y w i t h t h r e e a r e a s i n the l i t e r a t u r e : a nthropometry as a p p l i e d t o human movement, m e c h a n i c a l energy s t u d i e s of human movement, and m e c h a n i c a l a s p e c t s of the rowing s t r o k e . T h i s r e v i e w c o n t a i n s a b r i e f s u r v ey some commonly used anthropometry s t u d i e s and a s h o r t r e v i e w of some r e c e n t s t u d i e s of the i n e r t i a l p r o p e r t i e s of human body segments. As w e l l , an e f f o r t has been made t o su r v e y the development of the m e c h a n i c a l energy methods used i n t h i s s t u d y , w i t h the aim of f o l l o w i n g the development of t h e s e methods r a t h e r than l i s t i n g e v e r y paper r e p o r t i n g use of t h e s e methods. The s e c t i o n on the mechanics of rowing i s i n c o m p l e t e , as most of the r e p o r t s p u b l i s h e d on m e c h a n i c a l a s p e c t s of rowing a r e more s u b j e c t i v e than s c i e n t i f i c . The aim i n the rowing s e c t i o n of t h i s r e v i e w was t o be as complete as p o s s i b l e i n s u r v e y i n g the E n g l i s h language m a t e r i a l u s i n g o b j e c t i v e measures of m e c h a n i c a l a s p e c t s of ro w i n g . Anthropometry The s t u d y of the m e c h a n i c a l p r o p e r t i e s of human movement r e q u i r e s a knowledge of or a model d e s c r i b i n g the mass d i s t r i b u t i o n and i n e r t i a l p r o p e r t i e s of the body and i t s segments. There have been r e l a t i v e l y few s t u d i e s of the i n e r t i a l p r o p e r t i e s of the human body, m a i n l y because of the c o m p l e x i t y of such s t u d i e s and the d i f f i c u l t y i n o b t a i n i n g good sample d i s t r i b u t i o n s r e p r e s e n t a t i v e of the human p o p u l a t i o n ( C h a n d l e r , e t a l . 1975; M c C o n v i l l e , e t a l . 1980). 46 The c e n t r e of g r a v i t y (CG) i s measured i n a number of ways, i n c l u d i n g r e a c t i o n b oards, b a l a n c e b o a r d s , and " g r a v i t y l i n e s " ( i . e., l o c a t i n g the e.g. a t the i n t e r s e c t i o n of v e r t i c a l l i n e s drawn down from 3 or more d i f f e r e n t p o i n t s of s u s p e n s i o n ) . Moments of i n e r t i a can be measured i n a few segments i n l i v e s u b j e c t s by h o l d i n g the segment a g a i n s t a maximal c o n t r a c t i o n , r e l e a s i n g the segment s u d d e n l y , measuring the a c c e l e r a t i o n of the segment i m m e d i a t e l y a f t e r r e l e a s e , and u s i n g the a p p r o p r i a t e c o m p u t a t i o n . The u s u a l method f o r whole body and cadaver segment study i s t h a t of the compound pendulum, which i n v o l v e s "suspending the body [or segment] from some f i x e d p o i n t [which may be e x t e r n a l t o the o b j e c t ] , s e t t i n g i t i n motion by s h i f t i n g i t a few degrees from i t s e q u i l i b r i u m p o s i t i o n , and d e t e r m i n i n g i t s p e r i o d of o s c i l l a t i o n . . . " (Hay, 1974). T h i s p e r i o d i s then e n t e r e d i n the e q u a t i o n : I = WhT 2/4 ( 7 r ) 2 o where - (I i s the moment of i n e r t i a of the body or p a r t about an o a x i s t h r o u g h the p o i n t of s u s p e n s i o n 0, W i s the weight of the body or p a r t , h i s the d i s t a n c e from 0 t o the CG of the o b j e c t , and T i s the p e r i o d of o s c i l l a t i o n . Two o t h e r v a l u e s , the moment of i n e r t i a about the CG (I ) and eg the r a d i u s of g y r a t i o n (k) may be c a l c u l a t e d u s i n g : I = 1 - mh 2, and eg o k = s q r t d /m) o o 47 where m i s the mass of the o b j e c t . Braune and F i s c h e r (1889) and F i s c h e r (1906) p r e s e n t e a r l y s t u d i e s of the CG and of t h e moments of i n e r t i a , r e s p e c t i v e l y , of human c a d a v e r s and cadaver segments. These German language papers have been summarized and a b r i d g e d by Krogman and J o h n s t o n (1963) and r e v i e w e d by Hay (1973,1974). The Braune and F i s c h e r d a t a and the F i s c h e r d a t a have been used i n a number of e a r l y b i o m e c h a n i c s s t u d i e s e. g., Fenn (1930) and E l f t m a n (1939). Use of the Braune and F i s c h e r (1889) and the F i s c h e r (1906) d a t a f o r s t u d y i n g the k i n e t i c p r o p e r t i e s of human motion ( p a r t i c u l a r l y i n a t h l e t e s ) i s not recommended f o r a number of r e a s o n s . F i r s t , the c a d a v e r s used by Braune and F i s c h e r were g e n e r a l l y s m a l l i n s t a t u r e , w h i l e the one cadaver used by F i s c h e r i n 1906 was v e r y s m a l l (44.057 kg, and 150.5 cm) (Krogman and J o h n s t o n , 1963). Second, the c a d a v e r s used i n the e a r l i e r s tudy were not p o s i t i o n e d a c c u r a t e l y ; the saw c u t s used t o segment the s u b j e c t s were thus i n a c c u r a t e due t o the i n c o n s i s t e n t p o s i t i o n i n g of the c a d a v e r s (Hay, 1973). The next major study of the mass d i s t r i b u t i o n and i n e r t i a i p r o p e r t i e s of humans i s t h a t of Dempster (1955). That paper has a l s o been condensed by Krogman and J o h n s t o n (1963), and reviewed by Hay (1973,1974). Dempster's study i n c l u d e d the CG of the body and i t s segments, the r a t i o s of d i s t a n c e between the CG and each segment's ends, the mass f r a c t i o n s of the segments (segment mass / t o t a l -body mass), and moments of i n e r t i a and r a d i i of g y r a t i o n of each segment s t u d i e d . Dempster's seven c a d a v e r s were s m a l l e r , l i g h t e r , and o l d e r (the youngest l i s t e d cadaver age was 52) than the average w h i t e male or m i l i t a r y p e r s o n n e l 48 (Dempster, 1955). Dempster's d a t a have been used t o r e p l a c e t h a t of Braune and F i s c h e r , but a r e s t i l l not r e p r e s e n t a t i v e of the p o p u l a t i o n of a t h l e t e s from which the sample i n t h i s s t u d y was drawn. Hay (1974) s u g g e s t s t h a t d a t a f o r the cadaver i n Dempster's t a b l e s of d a t a most n e a r l y matched w i t h each s u b j e c t be used f o r k i n e t i c s s t u d i e s , r a t h e r than average d a t a . More r e c e n t s t u d i e s i n t h i s a r e a have s t u d i e d the i n e r t i a l p r o p e r t i e s of humans w i t h the aim of p r o v i d i n g r e l i a b l e and v a l i d r e g r e s s i o n e q u a t i o n s f o r the e s t i m a t i o n of i n d i v i d u a l s u b j e c t i n f o r m a t i o n . F u t u r e r e s e a r c h i n the k i n e m a t i c s and k i n e t i c s of humans s h o u l d attempt t o use t h i s new i n f o r m a t i o n t o d e s c r i b e the i n e r t i a l p r o p e r t i e s of i n d i v i d u a l s u b j e c t s . S e v e r a l s t u d i e s have been completed of the mass d i s t r i b u t i o n and the i n e r t i a l p r o p e r t i e s of the human body s i n c e Dempster's. Most worthy of note a r e those of C l a u s e r , e t a l . (1969), C h a n d l e r , e t a l . (1975), and M c C o n v i l l e , e t a l . (1980). C l a u s e r , e t a l , (1969) s t u d i e d the l o c a t i o n of the CG i n 13 embalmed c a d a v e r s , i n two s e p a r a t e p l a n e s ( i n most segments). The p o s i t i o n of the segmental CGs were g i v e n as p r o p o r t i o n s of the d i s t a n c e between segment ends, and between c e r t a i n a n t e r i o r and p o s t e r i o r landmarks. Data from t h a t s t u d y were q u i t e s i m i l a r t o those of Dempster's (1955). The main d i f f e r e n c e between C l a u s e r , e t a l _ . , (1976) and Dempster was i n the mass f r a c t i o n s r e p r e s e n t e d by the head segment and by the t o r s o segments. These d i f f e r e n c e s a r e p r o b a b l y due t o C l a u s e r e t a l . h a v i n g used a h i g h e r p o s i t i o n on the neck t o s e p a r a t e the two segments than d i d Dempster. 49 C h a n d l e r , e t a l . (1975), p r o v i d e a t h r e e - d i m e n s i o n a l s t u d y of the i n e r t i a l p r o p e r t i e s of s i x f r o z e n embalmed male c a d a v e r s . The s m a l l sample s i z e , and the use of two groups of t h r e e c a d a v e r s i n d i f f e r e n t p o s i t i o n s reduced the a c c u r a c y of the proposed model. C h a n d l e r et a_l. s t a t e , almost c a t e g o r i c a l l y , t h a t the d a t a and r e g r e s s i o n e q u a t i o n s p r e s e n t e d are not r e f l e c t i o n s of the p o p u l a t i o n of a d u l t males, and s h o u l d not be used as such. M c C o n v i l l e , e t a_l. ( 1980) s t u d i e d 31 l i v i n g males u s i n g s t e r e o m e t r i c photography t o a s s e s s t o t a l body and segmental moments of i n e r t i a i n t h r e e axes. The compound pendulum method was used as c r i t e r i o n t o a s s e s s the a c c u r a c y of the s t e r e o m e t r i c measure f o r t o t a l body moments. ( A c c o r d i n g t o t h o s e a u t h o r s , i f the pendulum method and the p h o t o g r a p h i c method had not a g r e e d i n a t r i a l s u b j e c t , the s t u d y may not have been completed.) T h i s appears t o be the f i r s t s t u d y u s i n g a n a t o m i c a l landmarks t o d e f i n e the p r i n c i p a l axes f o r the moment of i n e r t i a , r a t h e r than u s i n g some p r i n c i p a l a x i s system e x t e r n a l t o the segment b e i n g s t u d i e d . In a l l segments except t h e head and t h e neck, th e r e g r e s s i o n e q u a t i o n s d e v e l o p e d t o p r e d i c t the moments about th e p r i n c i p a l x-, y-, and z-axes were s i g n i f i c a n t l y more a c c u r a t e than the mean v a l u e s , as i n d i c a t e d by reduced s t a n d a r d e r r o r s of e s t i m a t e compared w i t h the s t a n d a r d d e v i a t i o n s of the moments' means. The main f a u l t w i t h t h i s s t u d y was t h a t the o r i g i n of the p r i n c i p a l axes was l o c a t e d a t the segmental c e n t r e s of volume, u s u a l l y found d i s t a l t o the c e n t r e of mass, w h i l e the mass c e n t r e i s the u s u a l p o s i t i o n about which i n e r t i a l p r o p e r t i e s a r e s t u d i e d ( M c C o n v i l l e , e t a l . , 1980). 50 Energy and Work E a r l y r e p o r t s d e s c r i b i n g m e c h a n i c a l energy i n human motion a r e those of Fenn (1930), and E l f t m a n (1939). Fenn used h i g h - speed f i l m i n g t o study the changes i n the k i n e t i c energy of the body and i t s segments i n s p r i n t i n g . The s u b j e c t s ' b o d i e s were used as r e f e r e n c e p o i n t s f o r the segmental motions t o s i m p l i f y t h e c a l c u l a t i o n of changes i n the KE of the arms and l e g s , and t o t r y t o e l i m i n a t e c a l c u l a t i o n of energy exchanges from body t o l i m b s or from l i m b s t o body. The c a l c u l a t e d work v a l u e was e x t r e m e l y h i g h s i n c e no a l l o w a n c e was made f o r t r a n s f e r s or exchanges of energy. Cavagna, e t a_l. ( 1 964) s t u d i e d r u n n i n g , r e c o r d i n g from a t r i - a x i a l a c c e l e r o m e t e r p l a c e d near the CG. A c c e l e r a t i o n s were i n t e g r a t e d w i t h r e s p e c t t o time t o o b t a i n the v e l o c i t y of t h e CG. V e l o c i t y d a t a were then used i n c a l c u l a t i n g the k i n e t i c energy of the t r u n k . Cavagna e t a l . (1964) a l s o s t u d i e d the e n e r g i e s of the l i m b s w i t h the t r u n k as a r e f e r e n c e " p o i n t " . F l a w s i n the use of t r u n k a c c e l e r a t i o n d a t a t o d e r i v e t o t a l body energy p a t t e r n s (e. g., Cavagna, e t a l . , (1964); Gage, ( 1964); G e r s t e n , e t a l . , (1969)) a r e d i s c u s s e d l a t e r i n t h i s r e v i e w ( W i n t e r , 1979). Other s t u d i e s have used f o r c e p l a t e s t o s t u d y th e v e l o c i t y as d e r i v e d from f o r c e s (hence a c c e l e r a t i o n s ) t o c a l c u l a t e KE (eg . , Cavagna and M a r g a r i a (1966), Cavagna, e t a l . , ( 1 971,1976)). The problems a s s o c i a t e d w i t h t h i s approach a r e s i m i l a r t o those a s s o c i a t e d w i t h u s i n g the a c c e l e r a t i o n of the CG f o r energy assessment. Both the Fenn (1930) and the Cavagna (1964) r e p o r t s e s t i m a t e the KE of the l i m b s i n c o r r e c t l y . Smith 51 (1975) i n d i c a t e s t h a t Fenn's c a l c u l a t i o n s a p p l y o n l y when the segmental v e l o c i t y i s p e r p e n d i c u l a r t o t h a t of the body, a r a r e o c c u r r e n c e , and t h a t a b s o l u t e segmental v e l o c i t y ( b o t h v e r t i c a l and h o r i z o n t a l components, i n a two d i m e n s i o n a l s t u d y ) must be used t o c a l c u l a t e the KE of a l i m b o r segment. In a c l a s s i c s tudy of the k i n e t i c s and k i n e m a t i c s of w a l k i n g , E l f t m a n (1939) s y n c h r o n i z e d f o r c e - p l a t e d a t a w i t h f i l m d a t a t o examine the r a t e s of t r a n s f e r of m e c h a n i c a l energy among segments. Energy exchange was not s t u d i e d . R e p l i c a t i o n of E l f t m a n ' s s t u d y i s d i f f i c u l t , because t h e r e i s no i n d i c a t i o n of the formulae used t o compute the energy-time p a t t e r n s . The c h i e f h i n d r a n c e t o E l f t m a n was the need t o use manual t e c h n i q u e s t o d i f f e r e n t i a t e d i s p l a c e m a n t d a t a t o o b t a i n segment v e l o c i t y and a c c e l e r a t i o n i n f o r m a t i o n from the f i l m . These manual t e c h n i q u e s a l s o a f f e c t e d the a c c u r a c y of Fenn's s t u d y . I n t r o d u c t i o n of computer t e c h n o l o g y t o g a i t s t u d i e s has g r e a t l y i n c r e a s e d the q u a n t i t y , and, i t i s hoped the q u a l i t y , of d a t a t h a t can be s t u d i e d . E r r o r s a s s o c i a t e d w i t h manual d a t a c o l l e c t i o n have a l s o been reduced, by r e d u c i n g the o p p o r t u n i t y f o r humans t o c o l l e c t d a t a . The c h i e f r e m a i n i n g s o u r c e of human e r r o r i s now a t the s t a g e of f i l m d a t a c o l l e c t i o n ( W i n t e r , e t a l . ( 1 9 74), P e z z a c k , e t a l . ( 1 9 7 7 ) ) . Quanbury, W i n t e r , and Reimer (1975) s t u d i e d the m e c h a n i c a l energy p a t t e r n s i n w a l k i n g , u s i n g a t e l e v i s i o n - c o m p u t e r i n t e r f a c e t o c o l l e c t raw k i n e m a t i c d a t a a u t o m a t i c a l l y . J o i n t f o r c e s and power f l o w s were computed f o r a l l segments, s t a r t i n g w i t h the s w i n g i n g l e g , and wo r k i n g back t h r o u g h the p e l v i s t o t h e s u p p o r t i n g l e g . These c a l c u l a t i o n s were done o n l y f o r the s i n g l e l e g s u p p o r t phase of 52 the w a l k i n g s t r i d e . An e s t i m a t e of ground r e a c t i o n f o r c e (GRF) t o the s u p p o r t i n g f o o t was computed. I t may be t h e o r e t i c a l l y p o s s i b l e t o c a l c u l a t e GRF from k i n e m a t i c d a t a , but the human body i s not i d e a l l y s u i t e d t o the a n a l y s i s , as i t v i o l a t e s the assumptions of the l i n k - s e g m e n t model i n a number of ways. Quanbury, e t a l . (1975) were unable t o c o r r o b o r a t e t h e i r c a l c u l a t e d GRF w i t h r e a l f o r c e p l a t e d a t a . Smith (1975) c o n t r a s t e d the use of a b s o l u t e v e l o c i t y and the r o t a t i o n a l v e l o c i t y of segments w i t h Fenn's (1930) method of c a l c u l a t i n g KE, i n s t u d y i n g a jumping movement. I t was shown t h a t Fenn's method ( a l s o used by Cavagna, e t a l . (1964)) was i n s e n s i t i v e t o a s i g n i f i c a n t amount of the KE p r e s e n t i n most human movements, as i t was o n l y v a l i d a t the v e r y r a r e i n s t a n c e when a segment's v e l o c i t y was p e r p e n d i c u l a r t o the body's v e l o c i t y . Norman, et §_. (1976) c o i n e d the term " m e c h a n i c a l pseudowork" t o d e s c r i b e the changes i n m e c h a n i c a l energy of the l i m b s and segments d u r i n g w a l k i n g . Pseudowork was computed as the sum of the a b s o l u t e v a l u e s of a l l p o t e n t i a l and k i n e t i c energy changes, f o r a l l segments i n a l i n k - s e g m e n t model, f o r a l l of the time i n t e r v a l s ( f i l m frames) i n c l u d e d i n the movement. T h i s "pseudowork" i s e q u i v a l e n t t o the term "W " n ( e q u a t i o n #6), used i n the p r e s e n t s t u d y . U s i n g the a b s o l u t e v a l u e s of a l l i n t r a - s e g m e n t energy changes, as i n Wn, c r e a t e s an a r t i f i c i a l l y h i g h "work" term. W i n t e r , (1979) expanding on the concept of pseudowork, d e f i n e s " i n t e r n a l " work of human movement as a l l p o t e n t i a l and k i n e t i c energy changes t h a t o c c u r i n a l l segments of the body d u r i n g movement. The d i s t i n c t i o n drawn between i n t e r n a l and 53 e x t e r n a l work i s t h a t e x t e r n a l work i s a measure of movement of an o b j e c t ( the body) through some v e r t i c a l d i s p l a c e m e n t i . e., a change i n PE or an i n c r e a s e i n v e l o c i t y ; i n t e r n a l work i s a measure of the energy changes (PE and KE) o c c u r i n g i n a l l segments w h i l e moving, perhaps d u r i n g e x t e r n a l work. I n t e r n a l work i s the sum of the t o t a l m e c h a n i c a l e n e r g i e s of a l l segments, i n a l l time i n t e r v a l s of a movement. T h i s c a l c u l a t i o n d i f f e r s from pseudowork (Norman, e t a l . (1976) i n t h a t i n t e r n a l work i s the "raw" sum of the energy changes, w h i l e pseudowork i s the sum of the a b s o l u t e v a l u e s of those energy changes. The t r i a n g l e i n e q u a l i t y (|a+b| ^ |a|+|b|) d i c t a t e s t h a t i n t e r n a l work i s always l e s s than or ( r a r e l y ) e q u a l t o pseudowork. W i n t e r ' s (1979) term " i n t e r n a l work" i s e q u i v a l e n t t o the W i computed e a r l i e r i n t h i s paper ( e q u a t i o n #4). A minor problem i n the c a l c u l a t i o n s p r e s e n t e d by Win t e r i s t h a t , a l t h o u g h the e x t e r n a l work i s assumed t o e q u a l z e r o the d i g i t i z i n g p r o c e s s u s u a l l y i n t r o d u c e s some s m a l l amount of e x t e r n a l work. T h i s o c c u r s when the t o t a l body energy a t the end of a movement c y c l e i s d i f f e r e n t from t h a t a t the b e g i n n i n g of t h e c y c l e . O f t e n , i n c o n t r o l l e d s i t u a t i o n s , the e r r o r i s due t o s m a l l e r r o r s ( n o i s e ) i n t he d i g i t i z e d d a t a , i n t r o d u c e d by the human o p e r a t i n g the d i g i t i z e r . T h i s e r r o r was r e c o g n i z e d and c o r r e c t e d f o r by P i e r r y n o w s k i , e t a l . (1980). W i n t e r ' s i n t e r n a l work term i s c r e d i t e d w i t h i d e n t i f y i n g changes i n the m e c h a n i c a l energy of the body and segments which a r e not d e t e c t e d by s t u d y i n g t h e motion of t h e t o t a l body CG. Movement of the l i m b s i n r e c i p r o c a l movements such as w a l k i n g and r u n n i n g r e q u i r e s some work from the m u s c l e s , a l o n g w i t h 54 p a s s i v e energy changes. M o t i o n s of the l i m b s a r e not d e t e c t e d by f o l l o w i n g the CG, as i n Cavagna, et a l . (1964). W i n t e r (1979) compared the energy p a t t e r n s of the CG w i t h the i n t e r n a l work (W ) of the body, and showed t h a t the CG "work" i u n d e r e s t i m a t e d the a c t u a l m e c h a n i c a l work of w a l k i n g (measured w i t h the method f o r W , t h i s paper) by 16 t o 40 p e r c e n t . i P i e r r y n o w s k i , W i n t e r , and Norman (1980) f u r t h e r adapted the c a l c u l a t i o n s of the energy a n a l y s i s . The "work" c a l c u l a t i o n was f u r t h e r p a r t i t i o n e d t o p e r m i t ( m a t h e m a t i c a l l y ) the exchange of energy w i t h i n segments, but not the t r a n s f e r of energy among segments. T h i s was done by a d d i n g the a b s o l u t e v a l u e s of the " i n s t a n t a n e o u s " changes of the segment t o t a l e n e r g i e s . The e q u i v a l e n t c a l c u l a t i o n i s t h a t of "W " ( e q u a t i o n #5, t h i s e p a p e r ) . P i e r r y n o w s k i , e t a l . (1980) then removed apparent e x t e r n a l work (W , e q u a t i o n #3, t h i s p a p e r ) , and c a l c u l a t e d t energy t r a n s f e r s and exchanges by s u b t r a c t i o n of the a p p r o p r i a t e "work" terms. P i e r r y n o w s k i , e_t a l . , ( 1980) a l s o c a l c u l a t e d an e f f i c i e n c y term, a t t e m p t i n g t o account f o r i n t e r n a l work, e x t e r n a l work, and t h e d i f f e r e n t e f f i c i e n c i e s of c o n c e n t r i c and e c c e n t r i c m u scular c o n t r a c t i o n . The c h o i c e of the numbers used t o r e p r e s e n t the m e t a b o l i c e f f i c i e n c i e s of the d i f f e r e n t c o n t r a c t i o n s appears t o have been somewhat a r b i t r a r y , however, and i s open t o q u e s t i o n . R o b e r t s o n and W i n t e r (1980) s t u d i e d j o i n t and muscle powers, and segmental energy p a t t e r n s of the lower l i m b i n 55 normal w a l k i n g . The l i n k - s e g m e n t model and f i n i t e d i f f e r e n c e a r i t h m e t i c were used t o d e r i v e i n s t a n t a n e o u s m e c h a n i c a l energy from f i l m d a t a . A f o r c e p l a t e was used i n c o n j u n c t i o n w i t h the f i l m d a t a t o study the j o i n t powers. T o t a l power and segmental energy c u r v e s were v e r y s i m i l a r f o r the e n t i r e s t r i d e i n the t h i g h and shank segments, and f o r most of the s t r i d e i n the f o o t . The f o o t segment e n e r g i e s showed l i t t l e change t h r o u g h the e n t i r e s t e p c y c l e , w h i l e the a n k l e j o i n t powers v a r i e d c o n s i d e r a b l y a t the weight a c c e p t a n c e and p u s h - o f f s t a g e s of the s t e p . T h i s d i f f e r e n c e between power and energy r e s u l t s f o r the f o o t was a t t r i b u t e d t o the l a r g e j o i n t power and muscle power components ( o p p o s i t e i n s i g n ) , where a s m a l l e r r o r i n measurement would cause c o n s i d e r a b l e change i n the t o t a l power d e l i v e r e d t o the f o o t . P i e r r y n o w s k i , Norman and W i n t e r , (1981) a p p l i e d the energy c a l c u l a t i o n s t o the s t u d y of l o a d c a r r i a g e on a t r e a d m i l l . One of the c o n c l u s i o n s of t h a t study was t h a t the methods p r e v i o u s l y used t o s t u d y normal and p a t h o l o g i c a l w a l k i n g c o u l d be a p p l i e d t o the study of l o a d c a r r i a g e and p o s s i b l y t o s t u d y of backpack d e s i g n . Another study u s i n g these methods f o r o t h e r forms of l o c o m o t i o n i s t h a t of C a l d w e l l (1980). C a l d w e l l s t u d i e d the m e c h a n i c a l c o s t and the energy t r a n s f e r s (and exchanges) i n two l e v e l s of c r o s s - c o u n t r y s k i e r s . More s k i l l e d ( i n t e r n a t i o n a l l y c o m p e t i t i v e ) s k i r a c e r s were found t o exchange and t r a n s f e r a g r e a t e r p r o p o r t i o n of the t o t a l "pseudowork" than n o v i c e s . Problems a s s o c i a t e d w i t h s t a t i o n a r y cameras o u t s i d e of the l a b o r a t o r y were i d e n t i f i e d a s : - c a m era-object d i s t a n c e has t o be l a r g e . 56 - a wide f i e l d of view i s needed t o ensure f i l m i n g a t l e a s t one complete movement c y c l e , - the two r e s t r i c t i o n s above combine t o g i v e v e r y s m a l l image s i z e , t h u s a low s i g n a l : n o i s e r a t i o ; In the p r e s e n t study the a c c u r a c y of the d i g i t i z i n g was r e s t r i c t e d as the p r o j e c t e d ( d i g i t i z e d ) image was o n l y about 3% l i f e s i z e . Komi, e t a l . , (1981) s t u d i e d the m e c h a n i c a l energy of n i n e r u n n e r s a t the speeds a t which b l o o d l a c t a t e b e g i n s t o a c c u m u l a t e . H i g h c o r r e l a t i o n s were found between the average power ou t p u t a t the measured v e l o c i t i e s and the p e r c e n t a g e of s l o w - t w i t c h muscle f i b r e s measured from b i o p s i e s of the v a s t u s l a t e r a l i s m u s c l e . S u b j e c t s were not t e s t e d , nor were m e c h a n i c a l e n e r g i e s a s s e s s e d a t r u n n i n g speeds o t h e r than the l a c t a t e " t h r e s h o l d " . F u t u r e r u n n i n g s t u d i e s w i t h m e t a b o l i c and energy measures s h o u l d t e s t a t a v a r i e t y of speeds i n each s u b j e c t , t o t e s t f o r f u r t h e r r e l a t i o n s h i p s between the m e c h a n i c a l and m e t a b o l i c f e a t u r e s of r u n n i n g . Mechanics and Rowing Few E n g l i s h - l a n g u a g e s t u d i e s e x i s t i n the m e c h a n i c a l a s p e c t s of r o w i n g . A s e a r c h of the l i t e r a t u r e found no s t u d i e s u s i n g the m e c h a n i c a l energy approach t o study the rowing s t r o k e c y c l e . Most e x i s t i n g l i t e r a t u r e on the mechanics or 57 b i o m e c h a n i c s of rowing c o n s i d e r hydrodynamics, boat and equipment d e s i g n f o r c e a t the o a r - h a n d l e (and c o n s e q u e n t l y , a t the b l a d e ) , or the e f f e c t s of s t r o k e r a t e on s h e l l v e l o c i t y . Most o t h e r l i t e r a t u r e (not r e p o r t e d here) c o n t a i n s r e l a t i v e l y s u b j e c t i v e o b s e r v a t i o n s of the k i n e m a t i c s of r o w i n g . A r e c e n t l y p u b l i s h e d r e v i e w of p h y s i o l o g i c a l and b i o m e c h a n i c a l a s p e c t s of rowing and p a d d l i n g s p o r t s i s u s e f u l as i t d i s c u s s e s some of the non E n g l i s h - l a n g u a g e papers on rowing ( Z s i d e g h , 1981). The e f f e c t of s t r o k e r a t e upon impulse ( i n each s t r o k e and over a timed i n t e r v a l ) , and s t u d i e s on s t r o k e t e c h n i q u e , f o r c e development, and r i g g i n g a r e mentioned. Z s i d e g h ' s r e v i e w i s u s e f u l f o r g u i d i n g a s e a r c h of the non- E n g l i s h work on the mechanics of r o w i n g . W i l l i a m s (1967) d e s c r i b e s the " i d e a l " motions r e q u i r e d of the oarsman i n t a k i n g a s t r o k e , and d i s c u s s e s the t i m i n g of the power a p p l i c a t i o n i n a rowing s t y l e not common i n modern r o w i n g . Cameron (1967) e v a l u a t e d s h e l l d e s i g n , oar s t i f f n e s s , and o t h e r s t r u c t u r a l a s p e c t s of rowing equipment; l i t t l e a t t e n t i o n was p a i d t o a c t u a l l y u s i n g the equipment. W e l l i c o m e (1967) e v a l u a t e d the v a r i o u s e f f e c t s of water d e p t h , boat b r e a d t h ( w i d e s t p o i n t ) and l e n g t h , oar d e s i g n , s h e l l c r o s s - s e c t i o n , s u r f a c e roughness, v i s c o u s d r a g , and wave dynamics on the r e l a t i v e v e l o c i t y of a rowing s h e l l . Pope (1973) d e s i g n e d a t h e o r e t i c a l model t o i n c l u d e f o r c e a t the o a r , power a p p l i c a t i o n w i t h r e s p e c t t o t h e p o s i t i o n of the o a r l o c k , and o t h e r f a c t o r s . The model s i m p l i f i e d t he e f f e c t s of asymmetric f o r c e a p p l i c a t i o n ( c a u s i n g yaw), and of the movement of the system's t o t a l CG d u r i n g the s t r o k e . Some 58 i n s i g h t s were g a i n e d r e g a r d i n g the p o t e n t i a l e f f e c t i v e n e s s of changes i n the p o s i t i o n of the o a r l o c k r e l a t i v e t o the p o s i t i o n of the f r o n t of the s l i d e . Pope appears t o r e c o g n i z e numerous human f a c t o r s e x e r t i n g a t l e a s t as much i n f l u e n c e on boat speed as the equipment. A f t e r d e v e l o p i n g the model a t l e n g t h , Pope s t a t e s , "... rowing i s an a f f a i r of men, and t h i s must be c l e a r l y u n d e r s t o o d . " McMahon (1971) s t u d i e d the e f f e c t of boat d e s i g n on the r a c i n g speeds of l i g h t w e i g h t and heavyweight crews. A t h e o r e t i c a l l i g h t w e i g h t s h e l l was m o d e l l e d t o be g e o m e t r i c a l l y s i m i l a r t o a heavyweight s h e l l , i n terms of the r a t i o s of crew weight t o t h e l e n g t h , b r e a d t h , and w e t t e d s u r f a c e a r e a of the s h e l l . I t was proposed t h a t s i m i l a r s h e l l s rowed by l i g h t w e i g h t and heavyweight crews s h o u l d f i n i s h a r a c e i n the same t i m e . Another approach t o mechanics i n rowing i s t h a t of B r e a r l e y (1977). The moment about t h e s t e r n of eight-man r a c i n g s h e l l s was c a l c u l a t e d f o r " s t a n d a r d " r i g and f o r an a l t e r n a t e r i g of the o a r s . The s t a n d a r d r i g , w i t h the sweeps s t a g g e r e d from bow t o s t e r n , w i t h bow (#1) on s t a r b o a r d and s t r o k e (#8) on the p o r t or l e f t s i d e of the s h e l l ) , was shown t o cause the boat t o waver i n i t s c o u r s e throughout each s t r o k e . T h i s w a vering i s due t o the d i f f e r e n c e between the sum of the d i s t a n c e s from the s t e r n t o the r i g g e r s on p r o t s i d e and the same sum on s t a r b o a r d . At d i f f e r e n t p a r t s of the s t r o k e , the g r e a t e r sum of d i s t a n c e s of the s t a r b o a r d r i g g e r s causes the bow of the boat t o be pushed or p u l l e d s l i g h t l y o f f c o u r s e a t t h e c a t c h and f i n i s h , r e s p e c t i v e l y . The a l t e r n a t e r i g , w i t h bow, 3, 5, and s t r o k e (#8) on the same s i d e , and 2, 4, 5, and 7 on the o p p o s i t e s i d e 59 e l i m i n a t e s the moment about the s t e r n , as t h e sums of the d i s t a n c e s from the s t e r n t o t h e r i g g e r s a r e the same f o r both s i d e s of the bo a t . I s h i k o (1971) measured the f o r c e a t the oar w i t h s t r a i n guages on the i n b o a r d p o r t i o n (between the end of the ha n d l e and the o a r l o c k ) of an o a r , and the a c c e l e r a t i o n of the s h e l l . F o r c e c u r v e s were found t o v a r y g r e a t l y from s u b j e c t t o s u b j e c t even among e l i t e members of the same crew. The a c c e l e r a t i o n s of the boat were r e l a t e d t o the f o r c e - t i m e p a t t e r n s of the o a r , but n e i t h e r f o r c e nor a c c e l e r a t i o n were a d e q u a t e l y r e l a t e d t o the k i n e m a t i c s of the s u b j e c t ' s m o t i o n s . Asami, e t a_l. ( 1978), and S c h n e i d e r , e t a l . ( 1978) r e p o r t f o r c e - t i m e c u r v e s f o r oar s or o a r l o c k s , d e t e r m i n e d w i t h s t r a i n gauges. F o r c e - t i m e c u r v e s were g e n e r a t e d i n rowing by a number of oarsmen w i t h d i f f e r e n t s k i l l l e v e l s . The f o r c e - t i m e c u r v e s were c o n s i d e r e d as p o s s i b l e i n s t r u c t i o n a l i n f o r m a t i o n t o a s s i s t i n t e a c h i n g oarsmen improved t e c h n i q u e , and t o i d e n t i f y s k i l l e d p e rformance. The c h i e f d i f f i c u l t y w i t h t h e s e d a t a i s t h a t the t e l e m e t r y equipment needed t o c o l l e c t f o r c e i n f o r m a t i o n a t the o a r l o c k or oar s h a f t i s p r o h i b i t i v e l y e x p e n s i v e . C e l e n t a n o , e t a_l. ( 1 974) s t u d i e d t h e f o r c e s i n the oar d u r i n g rowing a t s t r o k e r a t e s between about 20 and about 37 s t r o k e s per minute. The e f f e c t s of s t r o k e r a t e of the v e l o c i t y of a p a i r w i t h o u t coxwain, on s t r o k e (and d r i v e phase) d u r a t i o n , and t o t a l "work" done per s t r o k e were a l s o s t u d i e d . The s h e l l ' s f l u c t u a t i o n about i t s mean v e l o c i t y was found t o be reduced a t s t r o k e r a t e s g r e a t e r than 35 per minute. The power o u t p u t , f o r c e , and the p r o p o r t i o n of t h e s t r o k e t a k e n by the d r i v e phase 60 were found t o i n c r e a s e w i t h r a t e . M a r t i n and B e r n f i e l d (1980) s t u d i e d f i l m d a t a t o measure the v e l o c i t y of an e i g h t w i t h coxwain a t t h r e e s t r o k e r a t e s between 37 and 41 s t r o k e s per minute. The l e a s t f l u c t u a t i o n i n v e l o c i t y (a range of 2.65 m/s) o c c u r e d a t 39 s t r o k e s per minute. The g r e a t e s t mean v e l o c i t y was 6.41 m/s, and o c c u r r e d a t 41 s t r o k e s per minute. These r e s u l t s extended the f i n d i n g s of C e l e n t a n o , e t a_l. ( 1974). The c h i e f c o n t r i b u t i o n s t o the i n c r e a s e d v e l o c i t y of the s h e l l a t h i g h e r r a t e s were g r e a t e r f o r c e per s t r o k e , and the i n c r e a s e d p e r c e n t a g e of the t o t a l s t r o k e c y c l e time spent e x e r t i n g the f o r c e ( i . e., i n c r e a s e d i m p u l s e ) . S t u d i e s mentioned above as i n v e s t i g a t i o n s of the f o r c e s o c c u r r i n g i n the oar or i n the o a r l o c k (measured a t t h e p i n ) appear t o make no mention of the d i f f i c u l t y and expense i n v o l v e d i n t a k i n g t h e s e measures. In a d e s c r i p t i o n of a c o m p u t e r i z e d d a t a system f o r a f o u r - o a r e d s h e l l , K l a v o r a (1979) d e s c r i b e s s e v e r a l problems e x p e r i e n c e d by, f o r example, I s h i k o (1971), and by s e v e r a l o t h e r coaches and r e s e a r c h e r s . A system d e s c r i b e d by K l a v o r a was d e s c r i b e d as h a v i n g an " a t t r a c t i v e " p r i c e , f a r g r e a t e r than any f u n d i n g a v a i l a b l e f o r t h i s study ( i . e., the 1979 p r i c e was e s t i m a t e d a t about $10,000) A s t u d y of the p o s i t i o n of the oarsman a t the c a t c h , and the e f f e c t of t h a t p o s i t i o n of the f o r c e d e v e l o p e d i n the d r i v e phase of the s t r o k e showed l i t t l e , e xcept t h a t : u n l e s s s u b j e c t s a r e v e r y h i g h l y s k i l l e d they a r e l i k e l y t o be unable t o d u p l i c a t e a s k i l l e d motion r e l i a b l y and, the environment f o r t e s t i n g rowing motions must be made as s i m i l a r t o t h e r e a l 61 rowing motion as possible (Klavora, 1978). Very few studies have been published describing comparisons of the mechanics of rowing with ergometers and rowing in s h e l l s . Stuble, Erdman, and Stoner (1980) studied the kinematics of rowing in a boat and rowing two di f f e r e n t types of rowing ergometer. Eight subjects were filmed through several strokes in coxless pairs and in the two machines, and the kinematics of the hands and of several r e l a t i v e angles (e.g., thigh-trunk angle) were examined graphically. Stuble, et a l . were able to „ discern between members of d i f f e r e n t rowing clubs and between s k i l l l e v e l s . The movement out of the saggital plane occurring in sweep-oar rowing was ignored, and only motion in the x-y (vertical-anteroposterior) plane was examined, as in t h i s investigation. 62 BIBLIOGRAPHY Asami, T., N. A d a c h i , K. Yamamoto, K. I k u t a , and K. T a k a h a s h i . B i o m e c h a n i c a l a n a l y s i s of rowing s k i l l . i n : Asmussen, E., and K. Jjzfrgensen (eds.) Biomechanics VI-B U n i v e r s i t y Park P r e s s , pp. 109-114, (1978). Braune, W., and 0. F i s c h e r . 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