Intracycle velocity variations in swimming: deeper analysis and new insights

Abstract

Swimming performance may be optimised by reducing velocity variations and, consequently, energy expenditure, transforming the movement into as uniform as possible. The current thesis deeply analysed the intracycle velocity variation assessment and give new insights into its usefulness for swimming performance enhancement. A systematic scoping review identified the main gaps in the literature showing that 61% of the studies used the coefficient of variation to represent intracycle velocity variation. Swimmers of different competitive levels were evaluated in the four techniques at various paces, recording their displacement along 25 m with aerial and underwater cameras for 2D kinematic analysis. Intracycle velocity variation was assessed combined with other variability measures. Minimum and maximum velocities, stroke rate, length and index, phases duration and velocity, indexes of coordination and synchronization were the kinematical variables examined. Results showed that, although the coefficient of variation is a sensitive method for assessing velocity dispersion around the mean, it was unable to differentiate swimmers of varying competitive levels, except in butterfly. The relative power to velocity was proposed to overcome the intracycle velocity variation limitations, since it integrates the individual characteristics regarding the drag conditions. The power necessary to velocity variation increases in absolute magnitude but decreases in relative terms as mean velocity increases. It also enables to predict its effect on the swimmers performance. This variable revealed that butterfly and front crawl emerged as the swimming techniques that most effectively combined the ability to minimize drag with higher mean velocities. Breaststroke presented the highest mechanical demands, especially at higher intensities, reflecting its biomechanical complexity. This thesis offers comprehensive insights into the velocity variations in swimming and contributes to swimming performance enhancement.