INDEX OF CO-ORDINATION – A MEASURE OF CRAWL STROKE TIMING
Chollet, D., Chalies, S., & Chatard, J. C. (2000). A new index of co-ordination for the crawl: Description and usefulness. International Journal of Sports Medicine, 21, 54-59.
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, is where one arm begins the pull phase when the other is finishing the push phase; catch-up, 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 lag-time 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 three velocities. The two extreme Indexes of Coordination were IdCG3V800 = -9.4 ± 5.4% and IdCG1V50 = +2.53 ± 4.4%.
Index of Coordination – Useful concepts .
Catch-up Timing in Crawl Stroke: There is a period of time between successive propulsive phases where no propulsive forces exist (lag-time) and the swimmer slows. The velocity curve is wave-like but demonstrates negative values during the lag-time.
Opposition Timing in Crawl Stroke: When the propulsive phase of one arm finishes the other arm begins. The velocity curve of this coordination is wave-like, falling to lower levels between the loss of propulsion in one arm and the building of propulsion in the other.
Superposition Timing in Crawl Stroke: When the propulsive phase of one arm is finishing, the other begins. The overlap of reasonable levels of force application produces a wave-like velocity curve with only a minor dip in each wave.
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