Front crawl and backstroke are characterized by trunk rotations and upper/lower limbs propulsive actions allowing a continuous displacement. Despite of their similarity, swimmers accomplish faster velocities in front crawl with comparable upper limbs frequency and distance and intracycle velocity variation at aerobic velocities. At higher efforts, high hydrodynamic drag configures different conditions for maintaining technique, usually deteriorated due to muscle fatigue. Considering that backstroke is mainly performed in short races, we aimed to compare the kinematics of both techniques at sprint pace. Nine junior female elite swimmers were recorded performing 2 x 25 m maximal sprint each swimming technique. Aerial and underwater cameras placed in the sagittal plane followed the swimmers for kinematic calculations. Mean, maximum and minimum velocities, intracycle velocity variation, upper limbs frequency and distance, index of coordination, stability and complexity were calculated. An independent samples t-test compared kinematics between swimming techniques (p.0.05). Front crawl mean, maximum and minimum velocities were higher than in backstroke (1.69}0.03 vs. 1.50}0.07, 2.03}0.16 vs. 1.88}0.11, 1.30}0.13 vs. 1.15}0.10 m/s, p<0.05). Intracycle velocity variation (10.49}2.21 vs. 11.79}2.70%), relative minimum and maximum velocities (1.23}0.04 vs. 1.25}0.06 and 0.93}0.41 vs. 0.77}0.06%), upper limbs frequency (49.8}10.8 vs. 48.0}4.0 cycles/min) and distance (1.87}0.24 vs. 1.89}0.18 m, respectively), upper limbs index (3.19 } 0.38 vs. 2.84 } 0.33 m2/s), index of coordination (-9.5}4.6 vs. -7.8}4.2%), stability (0.26}0.18 vs. 0.18}0.05) and complexity (0.99}0.30 vs. 0.97}0.35) presented no differences between the swimming techniques. In short races, hydrodynamic drag increases contributing for a more demanding mechanical effort. The current study did not allow to determine what makes backstroke slower than front crawl in the same swimmers but propelling efficiency may be the main discriminator. Dynamic variables showed comparable adaptation in both swimming techniques, suggesting that the swimmer-environment-task complex interaction behaves similarly.
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