Introduction: maximal speed in swimming events (Vmax) depends on the maximal power output the swimmer is able to generate (POmax); however, in water locomotion the power useful for propulsion is only a fraction of POmax: this fraction being defined as propelling efficiency (hp). It can thus be expected that both these factors (POmax and hp) interact in determining Vmax. Methods: 13 subjects were recruited for the study. They were requested to complete a maximal incremental test at the armo-ergometer to determine their maximal oxygen uptake (VO2max) and the corresponding power output (POmax). Moreover, they were requested to swim the front crawl (SFC) and to swim with arms only (SAO) at 6 self selected incremental speeds (from very slow to maximal). These experiments allowed us to calculate hp.

Results and Discussion: Multiple regression analysis indicated that Vmax can indeed be explained by a combination of POmax and hp (R = 0.631, p = 0.079 for SFC and R = 0.756, p = 0.014 for SAO). The lower correlation for SFC depends on the fact that in this case the contribution of the legs for propulsion is not accounted for in the determination of POmax. These results indicate that, as expected, both hp and POmax are important factors in determining Vmax in swimming. This finding is not so trivial since, even if it is generally acknowledged that improving hp and POmax is mandatory to improve performance, no studies have been conducted so far to investigate the interplay between these factors.