Abstract
The different characteristics of the four swimming strokes affect the interplay between the four limbs, acting as a constraint to the force produced by each hand and foot. The purpose of this study was to analyze the symmetry of force production with a varying number of limbs in action and see its effect on velocity. Fifteen male swimmers performed four all-out bouts of 25-m swims in the four strokes in full-body stroke and segmental actions. A differential pressure system was used to measure the hands/feet propulsive force and a mechanical velocity meter was used to measure swimming velocity. Symmetry index was calculated based on the force values. All strokes and conditions presented contralateral limb asymmetries (ranging from 6.73% to 28% for the peak force and from 9.3% to 35.7% for the mean force). Backstroke was the most asymmetric stroke, followed-up by butterfly, front crawl, and breaststroke. Kicking conditions elicited the higher asymmetries compared with arm-pull conditions. No significant associations were found between asymmetries and velocity. The absence of such association suggests that, to a certain and unknown extent, swimming may benefit from contralateral limb asymmetry.
Highlights
IntroductionSegmental actions act as propellers producing propulsive forces
All strokes and conditions showed a contralateral asymmetry in the force production which were not correlated to swimming velocity
The present results showed that Symmetry Index of Fpk (SI_Fpk) was positively and significantly related to Symmetry Index of Fm (SI_Fm) with large effect size, in every controlling condition
Summary
Segmental actions act as propellers producing propulsive forces. When swimming the full stroke, the upper-limbs produce propulsion by doing arm-pulls; whereas, the lower-limbs by kicking. Propulsive force is related to limbs’ velocity, stroke frequency, stroke length, and to performance [1]. Each swim stroke presents its unique set of coordination constraints between the four limbs [2], plus unique trajectories under and above the water [3]. These features affect the production of propulsive forces, and affect thrust, velocity, and complexity, making some strokes faster and more complex than others [4]
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