The arm stroke efficiency in front crawl swimming: updating the state of the art

The main topic of this thesis was the arm stroke efficiency in front crawl swimming. Hence, it was developed in three original articles aiming to: (1) investigate the interplay between propelling efficiency and arm’s power output in determining the maximal speed in front crawl swimming, (2) estimate the effects of leg kick on the swimming speed and on arm stroke efficiency in front crawl, and (3) to compare different methods to assess the arm stroke efficiency and to identify the main biophysical predictors of maximal speed in 200 m swimming with the arms only. Different approaches were used to quantify the arm stroke efficiency. For instance, the paddle-wheel model (studies 1, 2, and 3), the ratio forward speed/hand speed (study 3), and the MAD System approach (study 3). The leg kick contribution was estimated individually, considering the differences in speed at paired stroke frequencies, in a range of speeds. Useful and non-useful components of the total mechanical power exerted by the arm stroke were obtained from dry land (using a customized arm-crank ergometer; study 1) and swimming protocols (using the MAD System; study 3), combined to the assessment of physiological and biomechanical parameters, including the arm stroke efficiency. The maximal speed in 200 m was determined by the balance between biomechanical (75% of the variances explained by the external mechanical power and the arm stroke efficiency; 98% of the variances explained by the external mechanical power, the arm stroke efficiency and the speed-specific drag) and physiological parameters (98% of the variances explained by the total metabolic power and the energy cost of swimming). Moreover, leg kick contribution to forward speed increased from low to maximal stroke frequencies (and speeds) and individual adjustments to the leg kick contribution should be considered when assessing the arm stroke efficiency in “full stroke” front crawl. Furthermore, the different methods provided significantly different values of arm stroke efficiency, although they agreed with each other. Therefore, arm stroke efficiency data should be interpreted carefully, considering the method used.