A new index of coordination for the crawl: description and usefulness.

This study analyzes stroke phases and arm and leg coordination during front crawl swimming as a function of swim velocity and performance level. Forty-three swimmers constituted three groups based on performance level. All swam at three different swim velocities, corresponding to the paces appropriate for the 800 m, 100 m, and 50 m. The different stroke phases and the arm and leg coordination were identified by video analysis. Arm coordination was quantified using a new index of coordination (IdC), which expresses the three major modalities opposition, catch-up and superposition. Opposition, where one arm begins the pull phase when the other is finishing the push phase; catch up, which has a lag time (LT) between propulsive phases of the two arms; and superposition, which describes an overlap in the propulsive phases. The IdC is an index which characterizes coordination patterns by measure of LT between propulsive phases of each arm. The most important results showed that duration of the propulsive phases (B + C) increased significantly with increasing velocity: 43.1 +/- 3.3% for V800; 46.5 +/- 3% for V100 and 49 +/- 3% for V50. The arm and leg synchronization was modified in the sense of an increase in six-beat kick. The IdC increased significantly with velocity: IdCV800 = -7.6 +/- 6.4%; IdCV100 = -3.2 +/- 5.1% and IdCV50 = -0.9 +/- 5.6%. IdC increased also significantly with performance level: IdCG3 = -6.07 +/- 5.3%; IdCG2 = -3.9 +/- 4.2% and IdCG1 = -1.76 +/- 5.6% for the mean of the 3 velocity. The two extreme IdC were IdCG3V800 = -9.4 +/- 5.4% and IdCG1V50 = +2.53 +/- 4.4%.