Arm-pull thrust in human swimming and the effect of post-activation potentiation

The aim of this study was to analyse the front-crawl arm-pull kinetics and kinematics, comparing it before and after post-activation potentiation (PAP), and the associations between variables describing of the arm-pull kinetics. Twelve male competitive swimmers were randomly assigned to perform two different warm-ups in a crossover manner: (i) non-PAP (control condition); and (ii) PAP (experimental condition). PAP consisted of 2x5 arm-pulls with resistance bands by both upper-limbs. Eight minutes later, participants underwent a 25m all-out trial in front-crawl arm-pull. Kinetics (i.e., peak thrust, mean thrust and thrust-time integral) and kinematics (i.e., speed and speed fluctuation) were collected by an in-house customised system composed of differential pressure sensors, speedo-meter and underwater camera. There was a significant and large improvement of the arm-pull kinetics after completing the warm-up with PAP sets (0.010<P<0.054, 0.50<d<0.74). There were non-significant and small effects of PAP on speed (P=0.307, d=0.18) and speed fluctuation (P=0.498, d=0.04). Correlation coefficients among kinetic variables were significant with large associations (0.51<R<0.90, 0.001<P<0.088). In conclusion, warm-ups including PAP conditioning sets elicit a large improvement in the thrust, but with small improvement in performance. Variables used to characterise thrust are strongly correlated and hence can be used interchangeably.