SLOWING IN SWIMMING RACES IS ASSOCIATED WITH A LOWERING OF STROKE RATE
Toussaint, H. M., Carol, A., Kranenborg, H., & Truijens, M. J. (2006). Effect of fatigue on stroking characteristics in an arms-only 100-m front-crawl race. Medicine and Science in Sports and Exercise, 38, 1635-1642.
Race analyses during swimming competitions provide information on the time-dependent values of variables such as swimming speed velocity, stroke rate, and stroke length. The effects of fatigue on and changes in those three variables were investigated. Lap-averaged values of velocity, stroke rate, and stroke length while swimming a short-course 100 m all out with arms only (trial 1) were related to the decline in mechanical power output measured during an all-out 100-m swim on the MAD system (trial 2), with legs immobilized in both trials.
Swimming a 100-m front-crawl sprint using arms only led to a significant 24% decrease in lap-averaged mechanical power output (from 200 to 153 W). This reduction in power-generating capacity led to a 12.4% decrease in velocity when lap 1 was compared with lap 4 (from 1.69 to 1.48 m/s). Stroke rate declined throughout the race by 10.6% from 0.85 Hz (lap 1) to 0.76 Hz (lap 4). The decrease in stroke rate was linearly related to the decrease in velocity. The reduction in stroke rate reflected the reduced propulsive force required to overcome the velocity-dependent, and therefore lower, drag.
Implication. Decreases in swimming velocity throughout a 100-m front-crawl race are the result of decreases in the power-producing capacity of the swimmer (fatigue), which is associated with a reduction in drag. [Drag increases with the velocity of progression.]. Stroke rate and not stroke length is associated with the loss in propulsive power.
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