Biomechanics and Medicine in Swimming XI

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the ankles during 25 to 800 m all-out trials. It is likely that the larger increase in speed found in our study is due to the fabric composition of the suits from Bluesevnty TM , made of 75% nylon and 25% PU-CR (polyurethane that improves buoyancy), in contrary to the polyester and lycra composition of the FastSkin TM . Parsons and Day (1986) and Cordain and Kopriva (1991) analyzed the effects of wetsuits, allowed in triathlon competitions and made of low-density material, which is similar to the bodysuits analyzed in our study. The authors suggested that the performance enhancement was directly related to the improved buoyancy offered by the suit. According to Benjanuvatra et al. (2002), improved buoyancy allows a smaller energetic cost to sustain an optimal body position, and therefore greater force can be applied on generating propulsion. In the present study, the increase in speed was due to an increase in stroke length, since there was no difference in the stroke rate when using the bodysuit. Roberts et al. (2003) found similar results when comparing front crawl swimming using the Speedo Fastskin TM to ordinary suits. These authors, however, analyzed sub-maximal swimming intensities. Chatard and Wilson (2008) found a significant decrease of the energetic cost associated with an increase of the stroke length when using the Fastskin TM body suit, which means improved swimming economy. Our subjects showed a shorter duration of the entry and catch phase during the second split of the trial when using the bodysuits, resulting in a significant decrease in the duration of the non-propulsive stroke phase. This result took us to believe in a possible influence on the index of coordination, which was not confirmed. This result is in accordance with the ones presented by Hue et al. (2003) who found differences in the index of coordination when using a triathlon wetsuit only when analyzing long distance races, with no differences found during swimming at velocities similar to the 100 m and 50 m races. Analyzing the subjects individually, five subjects showed a similar index of coordination on both suit situations and one subject showed a greater continuity between the propulsive actions during the first 25 m split. During the second split four out of the six subjects showed a greater continuity of the propulsive phases using the suit and the other two did not change their index of coordination values. This suggests that the suit may have a greater influence on technique during the final portion of the race. Since the suit did not interfere with the duration of the propulsive phase of the stroke, the greater stroke length is probably as a result of more effective force application during the phase probably due to a decrease in drag. The propulsive effectiveness is dependent on the combination of a high displacement speed of the hand and its adequate trajectory during the propulsive phase, generating higher peak forces (Toussaint & Beek, 1992). It was not possible to evaluate the body compression caused by the suit, if any, and this is a limitation of this study. However, the subjects reported difficulties to put on the suits, taking a long time dress them properly. Kainuma (2009) suggests that the compression of the LZR Racer TM from Speedo, can modify the physiological systems by an alternative mechanism, where the compression would affect the blood circulation, forcing the use of anaerobic-glycolitic pathways. This would in turn enable an instantaneous increment in force generation, which could have some influence on short distance, more high-speed races. Even though we randomized the tests order and tried to verbally stimulate the athletes the same way on both trials, a possible placebo effect could not be controlled for. conclusIon Wearing a full bodysuit, covering from the shoulders to the ankles, from Blueseventy TM , significantly improves the swimming speed during an all-out 50 m front crawl swimming trial, mostly on the second half of the test. When wearing the suits, the subjects showed a greater stroke length during both 25 m splits and shorter duration of the non-propulsive phase of the arm stroke during the second half of the test. chaPter2.Biomechanics reFerences Benjanuvatra, N., Dawson, G., Blanksby, B.A., Elliott, B.C. (2002). Comparison of buoyancy, passive and net active drag forces between Fastskin TM and standard swimsuits. J Sci Med Sport, 5(2):115-123. Chatard, J.C., Wilson, B. (2008). Effect of Fastskin Suits on Performance, Drag, and Energy Cost of Swimming. Med Sci Sports Exerc, 40(6): 1149-1154. Chollet, D., Chalies, S., Chatard, J.C. (2000). A new index of coordination for the crawl: description and usefulness. Int J Sports Med, 21(1): 54-59. Cordain, L., Kopriva, R. (1991). Wet suits, body density and swimming performance. Br J Sports Med, 25: 31-33. Hue, O., Benavente, H., Chollet, D. (2003). The effect of wetsuit use by triathletes: An analysis of the different phases of arm movement. J Sports Sci, 21(12): 1025-1030. Kainuma, E., Watanebe, M., Chikako, T.M., Inoue, M., Kuwano, Y., Ren, H.W., Abo, T. (2009). Proposal of alternative mechanism responsible for the function of high-speed swimsuits. Biomed Res, 30(1): 69-70. Mollendorf, J.C., Termin, A.C., Oppenheim, E., Pendergast, D.R. (2004). Effect of swim suit design on passive drag. Med Sci Sports Exerc, 36(6): 1029-1035. Parsons, L., Day, S.J. (1986). Do wet suit affect swimming speed? Br J Sports Med, 20: 129-131. Roberts, B.S., Kamel, K.S., Hedrick, C.E., McLean, S.P., Sharp, R.L. (2003). Effect of a fastskin suit on submaximal freestyle swimming. Med Sci Sports Exerc, 35(3): 519-524. Seifert, L., Chollet, D., Rouard, A. (2007). Swimming constraints and arm coordination. Hum Mov Sci, 26(1): 68-86. Toussaint, H.M., Beek, P.J. (1992). Biomechanics of competitive front crawl swimming. Sports Med, 13(1): 08-24. AcKnoWledGeMents The authors want to express their gratitude to the athletes and coaches from Grêmio Náutico União, for the contribution in this study, and to Aquatic Sports Research group for their cooperation. 167
BiomechanicsandmedicineinswimmingXi Fatigue Analysis of 100 Meters All-Out Front Crawl Using Surface EMG stirn, I. 1 , Jarm, t. 2 , Kapus, V. 1 , strojnik, V. 1 1University of Ljubljana, Faculty of sports, Ljubljana, Slovenija 2University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia The aim of the study was to estimate fatigue in arm propelling muscles by analyzing electromyographic (EMG) signal. Eleven male competitive swimmers performed a 100 meters all-out front crawl. Trials were recorded to obtain kinematical data, lactate concentration after the swims were measured. EMG signals of latissimus dorsi (LD), pectoralis major (PM) and triceps brachii (TB) were recorded, also. Average lactate concentration was 14.1 ± 2.93 mmol.l -1 . Stroke length, stroke rate and swimming speed decreased. The EMG amplitude (ARV) for the lower part of LD and for TB increased and the mean frequency (MNF) decreased for 20.5 ± 9.1 to 24.6 ± 8.4 % for all muscles under observation (P
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Figure 1. General biomechanical par
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Fourteen highly trained male swimme
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Figure 2. Repeatability of the LTin
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Pahlen Norge AS Pahlen Norge AS Cha
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