Arm coordination symmetry and breathing effect in front crawl.

This study analysed the relationships among arm coordination symmetry, motor laterality and breathing laterality during a 100-m front crawl, as a function of expertise. Ten elite swimmers (G1), 10 mid-level swimmers (G2), and 8 non-expert swimmers (G3) composed three skill groups, which were distinguished by velocity, stroke rate, stroke length, breathing frequency (BF) and the mean number of strokes between two breaths - the stroke breath (SB) - over a 100-m front crawl. Four stroke phases were identified by video analysis (catch, pull, push and recovery) and the index of coordination (IdC) measured the lag time between the propulsive phases of the two arms. The three modes of coordination are catch-up (IdC<0%), opposition (IdC=0%) and superposition (IdC>0%). The IdC was established as the mean of IdC1 and IdC2, which measured the lag time between the propulsive phases of the left and right arms, respectively. The coordination symmetry was analysed by comparing IdC1 and IdC2, and the breathing effect was studied by distinguishing IdC1 (and IdC2) with and without breathing. Motor laterality was determined by an adaptation of the Edinburgh Handedness Inventory. Breathing laterality was determined by a questionnaire and observation during the 100-m trial. Most of the front crawl swimmers showed asymmetric arm coordination, with propulsive discontinuity on one side and propulsive superposition on the other. This asymmetry was most often related to breathing laterality (a preferential breathing side for a unilateral breathing pattern) and motor laterality (arm dominance), with different profiles noted. More than the breathing laterality itself, the breathing actions of the non-expert swimmers amplified their asymmetric coordination on the breathing side. Conversely, the elite swimmers, who had higher and more stable spatial-temporal parameters (velocity and stroke lengths), a high coordination value (IdC) and lower breathing frequency (BF), managed their race better than the less proficient swimmers and their asymmetric arm coordination was not disturbed by breathing actions. By determining the dominant arm and the preferential breathing side, the coach can obtain a swimmer profile that allows both coach and swimmer to better understand and respond to excessive coordination asymmetry.