Breaststroke swimmers moderate internal work increases toward the highest stroke frequencies

A model to predict the mechanical internal work of breaststroke swimming was designed. It allowed us to explore the frequency-internal work relationship in aquatic locomotion. Its accuracy was checked against internal work values calculated from kinematic sequences of eight participants swimming at three different self-chosen paces. Model predictions closely matched experimental data (0.58\ub10.07 vs 0.59\ub10.05Jkg-1m-1; t(23)=-0.30, P=0.77), which was reflected in a slope of the major axis regression between measured and predicted total internal work whose 95% confidence intervals included the value of 1 (\u3b2=0.84, [0.61, 1.07], N=24). The model shed light on swimmers ability to moderate the increase in internal work at high stroke frequencies. This strategy of energy minimization has never been observed before in humans, but is present in quadrupedal and octopedal animal locomotion. This was achieved through a reduced angular excursion of the heaviest segments (7.2\ub12.9\ub0 and 3.6\ub11.5\ub0 for the thighs and trunk, respectively, P<0.05) in favor of the lightest ones (8.8\ub12.3\ub0 and 7.4\ub11.0\ub0 for the shanks and forearms, respectively, P