Alberty Morgan, Sidney Michel, Pelayo Patrick, Toussaint Huub M
Laboratory of Human Movement Studies, Faculty of Sport Sciences, University of Lille, Ronchin, France.
Med Sci Sports Exerc. 2009 Mar;41(3):637-44. doi: 10.1249/MSS.0b013e31818acfba.
Race analyses during swimming reveal how exercise duration affects both clean swimming speed (v), stroke rate (SR), and stroke length (SL). The aim of this study is to provide an explanation for the change of SL and SR during paced exercise swimming the front crawl through an analysis of intracycle changes in motor organization.
Trained swimmers (N = 10) swam three times to exhaustion (TTE in seconds) at predetermined velocities corresponding to 95%, 100%, and 110% of the mean speed attained in a 400-m race (V 400). During TTE tests, SR, SL, durations of the glide + catch, pull, push, and recovery phases (s) were measured. Assessment of arm coordination was made through the calculation of the index of coordination (IdC). The time allotted to propulsion per distance unit was estimated (T prop).
For all tested speeds, fatigue development induced a gradual increase of SR with concomitant decrease of SL. The duration of the nonpropulsive phases decreased, whereas the duration of the propulsive phases per stroke remained constant. The IdC increased reflecting a reduction of the lag time between two consecutive propulsive actions. Consequently, T prop increased.
Fatigue development induced an increase of the SR to compensate for the reduced capacity to generate a propulsive impulse per stroke. The change in arm coordination allows a better chain of the propulsive actions and leads to a greater time allotted to propulsion per distance unit. Such motor adaptation ensures that the overall propulsive impulse remained constant whereas average propulsive force per arm stroke is reduced.
游泳过程中的种族分析揭示了运动持续时间如何影响净游泳速度（v）、划水频率（SR）和划水长度（SL）。本研究的目的是通过分析运动组织的周期内变化，为自由泳定速运动过程中SL和SR的变化提供一种解释。
训练有素的游泳运动员（N = 10）以对应于400米比赛中达到的平均速度（V 400）的95%、100%和110%的预定速度游三次至力竭（以秒为单位的TTE）。在TTE测试期间，测量SR、SL、滑行+抓水、划水、推水和恢复阶段的持续时间（秒）。通过计算协调指数（IdC）来评估手臂协调性。估计每距离单位分配给推进的时间（T prop）。
对于所有测试速度，疲劳发展导致SR逐渐增加，同时SL降低。非推进阶段的持续时间减少，而每划水的推进阶段持续时间保持不变。IdC增加，反映出两个连续推进动作之间的滞后时间减少。因此，T prop增加。
疲劳发展导致SR增加，以补偿每划水产生推进冲动的能力下降。手臂协调性的变化允许推进动作有更好的连贯性，并导致每距离单位分配给推进的时间增加。这种运动适应确保了总的推进冲动保持不变，而每手臂划水的平均推进力降低。
