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1 Edinburgh Reserch Explorer Kinemtic nd Electromyogrphic Chnges During 00 m Front Crwl t Rce Pce Cittion for published version: Figueiredo, P, Snders, R, Gorski, T, Vils-Bos, JP & Fernndes, RJ 0, 'Kinemtic nd Electromyogrphic Chnges During 00 m Front Crwl t Rce Pce' Interntionl Journl of Sports Medicine, vol., no., pp DOI: 0.055/s Digitl Object Identifier (DOI): 0.055/s Link: Link to publiction record in Edinburgh Reserch Explorer Document Version: Publisher's PDF, lso known s Version of record Published In: Interntionl Journl of Sports Medicine Publisher Rights Sttement: Kinemtic nd Electromyogrphic Chnges During 00 m Front Crwl t Rce Pce. / Figueiredo, P.; Snders, R.; Gorski, T.; Vils-Bos, J. P.; Fernndes, R. J. In: Interntionl Journl of Sports Medicine, Vol., No., 0.0, p Generl rights Copyright for the publictions mde ccessible vi the Edinburgh Reserch Explorer is retined by the uthor(s) nd / or other copyright owners nd it is condition of ccessing these publictions tht users recognise nd bide by the legl requirements ssocited with these rights. Tke down policy The University of Edinburgh hs mde every resonble effort to ensure tht Edinburgh Reserch Explorer content complies with UK legisltion. If you believe tht the public disply of this file breches copyright plese contct openccess@ed.c.uk providing detils, nd we will remove ccess to the work immeditely nd investigte your clim. Downlod dte: 0. Oct. 08

2 Trining & Testing 9 Kinemtic nd Electromyogrphic Chnges During 00 m Front Crwl t Rce Pce Authors P. Figueiredo, R. Snders, T. Gorski, J. P. Vils- Bos,, R. J. Fernndes, Affilitions Centre of Reserch, Eduction, Innovtion nd Intervention in Sport, Fculty of Sport, University of Porto, Porto, Portugl PESLS, University of Edinburgh, Edinburgh, United Kingdom Institute of Antomy, University of Bern, Bern, Switzerlnd Porto Biomechnics Lbortory, University of Porto, Porto, Portugl Key words swimming technique front crwl segmentl kinemtics muscle ctivity blood lctte ccepted fter revision June 5, 0 Bibliogrphy DOI /s Published online: August 7, 0 Int J Sports Med 0; : 9 55 Georg Thieme Verlg KG Stuttgrt New York ISSN 07-6 Correspondence Dr. Pedro Figueiredo Centre of Reserch Eduction Innovtion nd Intervention in Sport Fculty of Sport University of Porto Ru Dr. Plácido Cost Porto Portugl Tel.: + 5//50776 Fx: + 5//50776 spfg@vodfone.pt Abstrct The purpose of this study ws to nlyse eventul kinemtic nd electromyogrphic chnges during mximl 00 m front crwl t rce pce. 0 mle interntionl level swimmers performed 00 m mximl front crwl test. Imges were recorded by bove nd under wter cmers, nd electromyogrphic signls (EMG) of 7 upper nd lower limbs muscles were nlysed for stroke cycle in ech 50 m lp. Cpillry blood lctte concentrtions were collected before nd fter the test. The vribles of interest were: swimming speed, stroke length, stroke nd kick frequency, hnd ngulr velocity, upper Introduction In front crwl swimming, the production of propulsive forces to overcome velocity-dependent wter resistnce (i. e., hydrodynmic drg force) is minly generted by the rm stroke motion. The contribution of the rm ction to the totl front crwl propulsion generted in front crwl is estimted to be bout 85 % [7, ]. Nevertheless, propulsion genertion in swimming is not yet fully understood [5, 0 ], it is know tht propelling forces re strongly linked to kinemtic hnd prmeters, s observed in different models of hnd force clcultion [7, 0, 5, ]. It ws lso suggested tht swimming speed (v) could be prtly explined by hnd displcements in the horizontl (ligned with the direction of the motion) nd verticl xes during the rm stroke [ 7 ], with hnd speed being one of the min fctors predicting swimming speed [9 ]. Studies regrding the effect of ftigue on the rm stroke kinemtics during high intensity swimming re limited. Deschodt [ 7 ] reported significnt decrese in horizontl wrist displcement in 6 50 m front crwl set t mximl speed. In limb nd foot displcement, elbow ngle, shoulder nd roll ngle, durtion of stroke phses, nd EMG for ech muscle in ech stroke phse. Generlly, the kinemtic prmeters decresed, nd reltive durtion incresed for the entry nd pull phses nd decresed for the recovery phse. Muscle ctivtion of flexor crpi rdilis, biceps brchii, triceps brchii, peitorl mjor nd upper trpezius incresed during specific stroke phses over the test. Blood lctte concentrtion incresed significntly fter the test. These findings suggest the occurrence of ftigue, chrcterised by chnges in kinemtic prmeters nd selective chnges in upper limbs muscle ctivtion ccording to muscle ction. ddition, Suito et l. [9 ] showed tht hnd speed nd pek ngulr velocity of shoulder dduction were significntly reduced from the first to the second hlf of n ll-out 00 m front crwl, in greement with the reports of Toussint et l. [0 ]. On the other hnd, Aujounnet et l. [5 ] found unchnged sptil fingertip s trjectory, despite the occurrence of ftigue, during protocol of 50 m front crwl t mximl intensity. These ltertions in kinemtic prmeters due to ftigue my be ssocited with eventul chnges in muscle ctivtion. For instnce, n increse in the verge musculr ctivity ws found fter n exhustive 00 yrds front crwl test for the shoulder externl rottors (suprspintus, infrspintus, nd teres minor), nd internl rottors (subscpulris) muscles [7 ]. Furthermore, some uthors found increses in the integrted EMG of the deltoid muscle during swimming t speed of. nd. m.s in swimming flume [ ], nd of the flexor crpi ulnris (considering the whole stroke cycle) nd triceps brchii (during the insweep nd outsweep phses) over 00 m protocol conducted t 85 % of the 00 m front crwl speed [ ]. More recently, Stirn et l. Downloded by: Universidde do Porto. Copyrighted mteril. Figueiredo P et l. Kinemtic nd Electromyogrphic Chnges Int J Sports Med 0; : 9 55

3 50 Trining & Testing [ 8 ] evluted muscle ftigue in upper body muscles during 00 m ll-out front crwl; lthough no chnges in EMG mplitude of the pectorlis mjor, ltissimus dorsi nd triceps brchii muscles were found, it incresed for the triceps brchii nd the lower prt of the ltissimus dorsi. Although the contribution of the lower limbs to the totl propulsion in front crwl is known to be low [ 6, ], the kick plys n importnt role in providing stbility for the whole stroke by fcilittion of body position, optimizing propulsion nd minimizing resistnce [ ], s well s in ssisting n economicl body roll, s it is linked to the hydrodynmic forces [ 5 ], implying physiologicl chnges (e. g., oxygen consumption) [ 8 ]. In ddition, proper kicking is required s foundtion for development of good coordintion in the globl front crwl technique [ 6 ]. In this wy, the chnges tht might occur in the lower limbs ctions during high-intensity swim should be tken into ccount. In spite of the bove-mentioned findings, to the best of our knowledge, no studies hve been conducted to nlyse the chnges of such kinemtic nd electromyogrphic prmeters during high intensity swim competition distnce. The present study imed to investigte kinemtic nd electromyogrphic chnges during mximl 00 m front crwl t rce pce, s it is described tht ftigue evolves during this event. Chnges on generl stroke prmeters, with the decrese of the velocity nd stroke length nd increse of the stroke frequency [, ], on bioenergetics, with the increse of energy cost [ 9 ], long the effort were reported. Methods Prticipnts 0 interntionl level mle front crwl swimmers (men ± SD of.6 ±. yers old; 76. ± 6. kg of body mss;.85 ± 0.07 m of height;.89 ± 0.08 m of rm spn), 00 m specilists (9.6 ±. % of the 5 m pool world record verge speed), volunteered to prticipte in the study. All procedures were performed in ccordnce with the ethicl stndrds proposed by Hrriss nd Atkinson [ ] nd the locl ethics committee pproved the study. All swimmers provided written informed consent. Swimmers were mrked with white hlf spheres ttched to blck complete swimsuit, llowing mnul digitistion for further -dimensionl reconstruction. ntomicl lndmrks were used: the vertex of the hed, 7 th cervicl vertebr, mndible (mentl protubernce), nd the right nd left tip of the third distl phlnx of the finger, wrist xis, elbow xis, shoulder xis, hip xis, knee xis, nkle xis, fifth mettrsophlngel joint, nd the tip of the first phlnx. Dt collection After moderte intensity individul wrm-up totlling 000 m, subjects underwent 00 m mximl front crwl test, using push off strt nd open turns to eliminte the influence of the dive in the nlysis of the first stroke cycle nd due to the EMG pprtus. One complete non-brething stroke cycle, t midpool, ws recorded for ech 50 m of the 00 m front crwl. The stroke cycle ws defined s the period between consecutive hnd entries of the right hnd. Swimmers were instructed to void brething while swimming through the clibrted spce. The swimming test ws recorded by 6 synchronised video cmers (Sony DCR-HCE) under nd bove the wter. All cmers recorded the motion of the swimmer t smpling frequency set t 50 fields per second nd n electronic shutter speed of /50 s. The recorded swimming spce ws clibrted using frme of the following dimensions:.0 m length (x),.0 m height (y), nd.0 m (z) width (ccurcy nd relibility estblished by Figueiredo et l. [ 8 ] ). -dimensionl reconstruction of the body lndmrks, digitised mnully nd frme by frme using APAS (Ariel Dynmics Inc), ws computed using DLT [ ], Ztsiorsky ntomicl model dpted by de Lev [5 ], nd 6 Hz low pss digitl filter. Tests were conducted in 5-m indoor swimming pool (7.5 C). The EMG ctivity ws mesured t smpling frequency of 000 Hz, with 6-bit nlogue to digitl conversion (BIOPAC System, Inc). The EMG signl of 7 muscles (flexor crpi rdilis, FCR; biceps brchii, BB; triceps brchii, TB; pectorlis mjor, PM; upper trpezius, UT; biceps femoris, BF; nd rectus femoris, RF), which hve been shown to hve high ctivity during front crwl swimming (for review see Clrys nd Cbri [ ] ), ws recorded from the right side of the body using bipolr (inter-electrode distnce of cm) Ag AgCl circulr surfce electrodes, with premplifiers (AD 6 BN). The electrodes were plced prllel to the direction of muscle fibres on the surfce of the muscle belly ccording to interntionl stndrds [ ]. Before electrode fixtion, the skin surfce ws shved, brded, nd clened with lcohol. Afterwrds, electrodes were covered with n dhesive bndge (Opsite Flexifix ) to void contct with wter [, ]. All cbles were fixed to the skin by dhesive tpe to minimise the perturbtion of the nturl movement nd interference with the signl. In ddition, swimmers wore complete swimsuit (Fstskin, Speedo ) with cble entrnce opened in the medium-dorsl position; over the wter, steel cble ws extended with sheve to which the cbles corresponding to ech one of the electrodes were fixed. A reference electrode ws ttched to the skin of the ptell. The totl gin of the mplifier ws set t 00 with common mode rejection rtio of 0 db [ ]. To synchronise EMG nd video, n electronic flshlight signl/ electronic trigger ws mrked simultneously on the video nd EMG recordings. Cpillry blood smples (5 μl) were collected from the er lobe to ssess rest nd post exercise blood lctte by mens of portble lctte nlyser (Lctte Pro, Arkry, Inc.). Blood lctte ws mesured before nd t,, 5, nd 7 min fter the test; the pek vlue ws used for further nlysis s n indictor of exercise intensity. Dt nlysis Kinemticl dt nlysis ws done using APAS (Aril Dynmics, Inc.). The men horizontl speed ws clculted by dividing the swimmer s men whole-body centre of mss (CM) horizontl displcement by the time spent to complete stroke cycle. Stroke frequency (SF) ws the inverse of the time to complete stroke cycle. Stroke length (SL) ws the horizontl displcement of the CM during stroke cycle. Angulr speed of the hnd ws derived through digitising procedure nd considered to be the men ngulr speed of the line from the midpoint of the wrist to the fingertip projected onto the xy plne of the externl reference system. Kick frequency (KF) ws the inverse of the time to complete kick cycle, defined s the period between consecutive mximum verticl coordintes of the right foot. The bckwrd displcement mplitude nd slip mplitude were clculted through the difference between the coordintes of the most forwrd point nd the most bckwrd position of the Downloded by: Universidde do Porto. Copyrighted mteril. Figueiredo P et l. Kinemtic nd Electromyogrphic Chnges Int J Sports Med 0; : 9 55

4 Trining & Testing 5 fingertip, nd of the entry nd exit of the fingertip, respectively ( Fig. ). The verticl motion of the upper limb ws represented by displcements of the fingertip, wrist, nd elbow. The y displcement of the first phlnx tip ws representtive of the foot s verticl motion. Both the y direction motion of the upper limb nd foot were referenced to n externl point. The lterl motion of the upper limb ws clculted s the bsolute z displcement, referenced to the swimmer s CM. Shoulder roll ngle ws determined by the rc-tngent (Sy/Sz), where Sy nd Sz re the y nd z components of the shoulder unit vector, i. e., the ngle between the unit vector of the line joining the shoulders, projected onto the yz plne (the plne perpendiculr to the swimming direction) nd the horizontl. The -dimensionl elbow ngle ws clculted in time moments within the underwter stroke cycle ( Fig. ): (i) entry of the hnd in the wter (A entry); (ii) beginning of finger bckwrd movement (B first bck); (iii) finger verticlly ligned with the shoulder (C shoulder x); (iv) end of bckwrd movement (D end bck). These time moments were clculted bsed on the horizontl displcement of the finger nd shoulder during the stroke cycle. The elbow ngle rnge during the pull nd push phses ws clculted s: C B nd D C, respectively. seprte phses were identified within every stroke cycle ( Fig. ), from the swimmer s (-dimensionl model) horizontl (x) nd verticl displcement (y) of the digitized finger coordintes nd noting the time corresponding to these displcements using APAS (Aril Dynmics, Inc.): entry, pull, push, nd recovery [0, 6 ]. Time ws expressed in seconds nd s percentge of the stroke cycle. Kick cycle phses were clculted bsed on the verticl displcement of the foot: the downbet, from the mximl to minimum verticl coordintes; nd, the upbet, from the minimum to mximl verticl coordintes. Verticl xis (m) Fig A - entry end bck Push phse Bckwrd displcement Amplitude slip Entry phse D - exit C - shoulder x mximl depth Recovery phse B - first bck Pull phse Antero-posterior xis (m) Exmple of the underwter trjectory of the right hnd. The EMG dt nlysis ws performed using the MATLAB 008 softwre environment (MthWorks Inc., Ntick, Msschusetts, USA). The rw EMG signls were bnd-pssed filtered (8 500 Hz), full-wve rectified nd smoothed with th order Butterworth filter (0 Hz) for the liner envelope. The integrtion of the rectified EMG (iemg) ws clculted, per unit of time, to eliminte the stroke phses durtion effect (iemg/t). The signl ws prtitioned in 0 ms windows to find the mximl iemg vlue for ech swimmer over every stroke cycle in the mid-pool. To normlise the results, iemg/t ws expressed s percentge of iemg mximum vlue obtined during the 00 m [ 9 ]. Sttisticl nlysis All dt were checked for normlity nd expressed s mens nd SD. The compound symmetry, or sphericity, ws checked using the Muchley test [ ]. A -wy repeted mesures nlysis of vrince (ANOVA) ws used to ssess chnges in the mesured vribles over the lps during the rce. When significnce ws determined, post-hoc comprisons were conducted with Bonferroni nlysis. A repeted mesures t-test ws used to compre blood lctte concentrtion between the beginning nd end of the effort. Sttisticl significnce ws set t p All sttisticl tests were performed using STATA 0. softwre (SttCorp, Inc.). Effect size between lps nd between beginning nd end of the 00 m were computed with Cohen s f nd Cohen s d, respectively. The criteri for interpreting the effect size were bsed on Cohen s [ ] suggestion tht f effect sizes of 0. re smll, 0.5 moderte, nd 0. lrge nd d effect sizes of 0. re smll, 0.5 moderte, nd 0.8 lrge. Results Men ± SD, p, f nd F vlues of the repeted mesures ANOVA re displyed in Tble for the generl biomechnicl prmeters, hnd ngulr v nd KF, in Tble for the rm nd foot lengths, nd in Tble for the ngle vribles computed. Chnges in rce prmeters were observed s denoted by the significnce level nd lrge effect sizes. Swimming speed, hnd ngulr v, SL, SF, mximl depths of finger, wrist nd elbow, elbow ngle t the end bck, shoulder roll nd KF significntly diminished long the 00 m. Wheres, mximl elbow width showed significnt increse. Men ± SD reltive nd bsolute durtions of stroke phses for ech lp, s well s the propulsion/non-propulsion rtio, re presented in Fig. (left nd right pnel, respectively). The entry nd pull phses presented n increse of the reltive durtion long the 00 m (F,7 = 5.5, p = 0.005, f = 0.; F,7 =.7, p = 0.0, f = 0.6, respectively), while decrese ws observed for the recovery phse (F,7 = 9.08, p < 0.00, f = 0.7). Absolute durtions of the entry phse incresed progressively from the Downloded by: Universidde do Porto. Copyrighted mteril. Tble Men ± SD dt nd sttisticl comprisons between the lps cross the 00 m front crwl for the generl biomechnicl prmeters, hnd ngulr velocity (v) nd kick frequency. Prmeter Lp Lp Lp Lp F,7 P f speed (m.s ).57 ± ± ± ± < stroke length (m).9 ± 0.. ± ± 0.,b,c. ± stroke frequency (Hz) 0.68 ± ± ± ± hnd ngulr v (rd.s - ) 0.08 ± ± ± ± kick frequency (Hz).0 ± ± ± ± ,b,c Significntly different from the first, second nd third lp, respectively. P < 0.05 Figueiredo P et l. Kinemtic nd Electromyogrphic Chnges Int J Sports Med 0; : 9 55

5 5 Trining & Testing Tble Men ± SD dt nd sttisticl comprisons between the lps cross the 00 m front crwl for the rm nd foot lengths. Prmeter Lp Lp Lp Lp F,7 P f bckwrd mplitude (m).6 ± ± ± ± bckwrd mplitude/ SL (m) 0.7 ± ± ± 0.07,b 0.75 ± mplitude slip (m) 0.56 ± ± ± ± mx. finger depth (m) 0.7 ± ± ± ± mx. wrist depth (m) 0.57 ± ± ± ± mx. elbow depth (m) 0.6 ± ± ± 0.0,b 0. ± mx. finger width (m) 0. ± ± ± ± mx. wrist width (m) 0. ± ± ± ± mx. elbow width (m) 0. ± ± ± ± finger width rnge (m) 0.5 ± ± ± ± wrist width rnge (m) 0.9 ± ± ± ± elbow width rnge (m) 0. ± ± ± ± depth right foot (m) 0.7 ± ± ± ± ,b Significntly different from the first, second nd third lp, respectively. P < 0.05 Tble Men ± SD dt nd sttisticl comprisons between the lps cross the 00 m front crwl for the computed ngles. Prmeter Lp Lp Lp Lp F,7 P f elbow ngle: entry ( ) 9. ±. 5. ±.0 9. ±. 6.0 ± elbow ngle: first bck ( ) 9.7 ±. 5.9 ± ± ± elbow ngle: shoulder x ( ) 0. ±. 0. ± ± ± elbow ngle: end bck ( ).0 ±..6 ± 7.6. ± 6.6,b 6. ± elbow ngle: rnge of pull ( ) 7.6 ± ± ± ± elbow ngle: rnge of push ( ) 0.8 ±.9. ± 9.. ±.8 0. ± shoulder roll ( ) 07.6 ± 5.8. ±. 8.9 ± 9.. ± ,b Significntly different from the first, second nd third lp, respectively. P < 0.05 Reltive durtion (% of complete stroke cycle) Lps entry pull push recovery prop/non-prop rtio,b Durtion (s) Lps entry pull push recovery Downloded by: Universidde do Porto. Copyrighted mteril. Fig. Stroke phse reltive durtions nd propulsion/non-propulsion rtio (left pnel), nd stroke phse bsolute durtions (right pnel). Men ± SD vlues re indicted over the 00 m front crwl., b Significntly different from the first nd second lp, respectively. p < first lp (F,7 = 7.56, p < 0.00, f = 0.), wheres n increse in the push phse ws observed only in the lst 50 m (F,7 =., p = 0.0, f = 0.7). Although the push nd recovery phses did not present significnt differences (F,7 =.7, p = 0.09, f = 0.9; F,7 =.67, p = 0.07, f = 0.9, respectively) p-vlues were lower thn 0.0 nd the effect size ws medium. Fig. shows upper body muscles ctivtion (FCR, BB, TB, PM, nd UT) seprted by phse nd lp. FCR presented differences during the entry, pull nd push phses between the second nd the fourth lp nd the third nd the fourth lp (F,7 = 7., p = 0.00, f = 0.; F,7 = 9.0, p < 0.00, f = 0.; F,7 =., p = 0.0, f = 0., respectively); BB for the pull phse between the third nd fourth lp (F,7 =.0, p = 0.0, f = 0.7); TB for the push phse between the first nd fourth lp (F,7 =., p = 0.0, f = 0.6); PM for the pull phse between the third nd fourth lp (F,7 =.60, p = 0.0, f = 0.0); nd UT for the recovery phse between the first nd fourth lp nd the second nd fourth lp (F,7 = 5.9, p = 0.0, f = 0.9). iemg men ± SD vlues of lower limbs muscles ctivtion (BF nd RF) re presented in Fig. ; no sttisticl significnt differences were found long the 00 m effort. Blood lctte incresed from.07 ± 0. mmol.l t rest to. ±.65 mmol.l fter the test (t =.7, p < 0.00, d = 9.0). Figueiredo P et l. Kinemtic nd Electromyogrphic Chnges Int J Sports Med 0; : 9 55

6 Trining & Testing 5 FCR BB TB PM UT Entry Pull Push Recovery Percentge of the cycle (%) < 0% 0-9% 0-9% 0-9% 0-9% > 50% Fig. Upper limb muscles iemg during ech stroke phse cross the 00 m front crwl. FCR flexor crpi rdilis, BB biceps brchii, TB triceps brchii, PM pectorlis mjor, nd UT upper trpezius. The stick figure represents the key points tht define the phses. iemg (%) downbet upbet downbet upbet Biceps Femoris Rectus Femoris Lp Lp Lp Lp Fig. Men ± SD vlues of the lower limb muscles iemg during downbet nd upbet phses of the kick over the lps of the 00 m front crwl mximl effort. Discussion This study imed to nlyse if the chnges in kinemtic vribles nd muscle ctivity in response to high-intensity swimming test would reflect evidence of ftigue, s high blood lctte vlues were mesured fter the 00 m, confirming the high-intensity of the effort nd glycolytic prticiption. Stroke prmeters mngement chnged long the 00 m front crwl event s expected, s in the literture [,, 0 ]. SL decresed long the test with sttisticl mening in the lst 50 m lp, nd SF decresed in the third lp in comprison to the first, nd ugmented t the end of the effort to compenste the decrese in the SL (llowing mintennce of speed) [,, ]. Concomitnt with velocity decrese, ngulr velocity of the hnd diminished long the 00 m; once the upper limb is ssumed to be the min genertor of propulsive force, therefore decreses in swimming velocity re likely to be cused by reduced hnd velocity, s found for the 00 m front crwl [9, 0 ]. This chnge of hnd ngulr velocity hs implictions on the time durtion of the stroke phses, s the pull phse is incresed in reltive nd bsolute vlues, but without higher propulsive force genertion. The increse in reltive durtion of the pull phse, nd the decrese in reltive durtion of the recovery phse, is in greement with the results of Alberty et l. [ ] lso during 00 m test. Bckwrd mplitude ws higher thn the vlue reported by Deschodt et l. [ 6 ], probbly becuse of the different protocol velocities, s it chnges the SR-SL reltionship [ ], nd lower velocities re ssocited with higher SL [ 6 ]. However, bckwrd mplitude remined sttisticlly stble, suggesting tht the most forwrd point ugmented, possibly due to higher glide, in ccordnce with the increse in reltive nd bsolute durtion of the entry phse. When bckwrd mplitude ws normlised to SL, n increse in the lst lp ws observed, suggesting decrese of the propelling efficiency [ 9 ], s higher reltive durtion of the pull phse s hnd ngulr velocity decresed, but with lower propulsive impulses s SF incresed [ ]. The mesured depths were similr to the vlues previously described for 5 m mximl intensity swimming [6, 5, 9 ]. A decrese of the depths ws observed from the first to the lst lp, resulting in tendency for n bsolute decrese in elbow ngle t shoulder x point (not sttisticlly different, but with medium size effect). This occurred due to the incresed elbow width, lthough with the sme rnge. The vlues presented by the mximl finger width were in ccordnce with the literture [5, 9 ]. The observed chnges in the depth could be due to chnges in SF, s the shoulder roll presents the sme pttern (significnt decrese in the third lp), nd hve been linked to ech other [8,, 5 ]. The mgnitudes of shoulder roll in the present study were similr to those reported by Psychrkis nd Snders [ 0 ] nd McCbe et l. [ 5 ], t lest for the first lp, where the velocities were higher. However, the speed ws constnt during the lst lps, the shoulder roll incresed in the lst lp, nd yet the depths decresed. In this phse (pull) the PM nd BB showed gret importnce nd n increse of the ctivtion s previously reported [, ], suggesting tht the ttined stbility ws done by incresing the muscle effort, bsed on the dominnt contribution of shoulder dduction during this phse [ 9 ]. A high ctivtion of the TB in this phse suggests the ntgonist ction to mintin joint stbility nd supplement prime movers ction [ ]. It would be of interest to understnd if less skilled swimmers perform in the sme wy or hve gret kinemticl chnges. In the push phse, the elbow ngles t end bck point vlues were slightly lower thn the ones presented by McCbe et l. [5 ] ; however the mesurement protocols were different, s they implemented bouts of 5 m t mximum speed. The decrements in this prmeter cross the effort could led to the specultion tht reduction of the power output [7, 0 ], nd lso decrese in the propulsive forces produced in the push phse occurs. It is suggested tht TB ftigues, lthough the push phse durtion ws stble, becuse of the decrese of ngulr hnd velocity. TB ctivtion during the push phse incresed significntly long the 00 m, in greement with the results of Aujounnet et l. [ 5 ]. The increse in EMG signl mplitude occurs in response to muscle ftigue to mintin the swimming speed through n dditionl recruitment of muscle fibres [6 ]. As SF incresed in the lst lp, chnges occurred in the reltive durtion of the recovery phse, s previously observed [, 7 ], but with decrese (medium effect size) of the bsolute durtion [6 ]. Concomitnt with these chnges the ctivtion of the Downloded by: Universidde do Porto. Copyrighted mteril. Figueiredo P et l. Kinemtic nd Electromyogrphic Chnges Int J Sports Med 0; : 9 55

7 5 Trining & Testing UT muscle occurred in the lst lp, resulting from the successive sub-mximl repetitions (bringing the upper limb out of the wter to the initil position to strt new stroke cycle), nd decresing the time between contrction nd relxtion. The ugmented ctivtion of FCR during the ctch, pull nd push phses throughout the test is likely to confirm the importnt role of this muscle in stbilising the wrist during these phses, s previously reported for the wrist flexor muscles [9 ], since the higher lod is underwter, presenting evidence of ftigue [ ]. The deteriortion of stroke mechnics is described in the literture, nd ws relted to locl ftigue due to severl biochemicl events, such s high blood lctte levels [ 9, 0 ]. The observed post exercise blood lctte vlues were similr to those found by other uthors fter 00 m front crwl swimming event [,, ], confirming the high intensity chieved by the prticipnts during the test, nd suggesting the ppernce of ftigue. Regrding the lower limbs, KF decresed in the third lp, s in the SF, suggesting tht swimmers mintined the sme rm-leg coordintion. The lower limbs seem to follow the upper limbs frequency, s the first ones hve lower importnce in the propulsion [7, ], which is reflected in the level of ctivtion of both BF nd RF muscles in comprison to the upper limb muscles in their min phses. As consequence, BF nd RF do not show electromyogrphic nd kinemtic evidences of ftigue, s their level of ctivtion remined the sme, predominntly in the downbet (RF) nd upbet (BF) kick, s they re gonistic/ ntgonistic muscles; their depth remined lso the sme, in spite of chnges in KF. Kick depth vlues were slightly higher thn those presented by McCbe et l. [ 5 ], probbly becuse in sprinting the KF is so much higher tht it reduces the mplitude of the kick. In ddition, the slightly higher ctivity of the BF nd RF in the first lp of the upbet nd downbet phse (respectively), suggested tht the higher speed in the first lp could be ssocited with higher lower limbs use; this would led to higher body position, decresing frontl drg, nd consequently requiring less work for the upper limbs (s found by Rourd et l. [ ] ). Conclusion Chnges in the sptil nd temporl kinemtics occurred during the 00 m front crwl. In ddition, musculr ctivtion of the upper limb muscles incresed during the event in the phses in which they were required. These chnges evidenced ftigue tht ws indicted by high blood lctte t the end of the event. The lower limb kinemtics nd muscle ctivity remined quite stble only chnging their KF in response to SF chnges, but not showing signs of ftigue. References Abdel-Aziz Y, Krr H. Direct liner trnsformtion: from comprtor coordintes into object coordintes in close rnge photogrmmetry. 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