During maximal freestyle swimming it is generally accepted within the literature that the arms contribute approximately 90% to the total swimming velocity in elite swimmers [1, 2]. This contribution has also been shown to be valid irrespective of swimming ability [3]. While some authors have taken this finding to imply that the leg kick contributes to only 10% of the velocity [4, 5], others have found that, when swimming with the leg kick only, swimmers can achieve approximately 60-65% of the velocity attained during whole body swimming [3]. Thus, when the reported contribution of the arms (~90%) is summed with the contribution of the legs (~60%), the result far exceeds the velocity achieved during whole body swimming (100%). Previous research has also investigated the contributions of the arm stroke and leg kick to whole body energy expenditure. In studies where the anaerobic and aerobic capacities of arm stroke, leg kick and whole body freestyle swimming have been measured, the summation of arm stroke and leg kick energy expenditure have exceeded the total energy expenditure observed in whole body swimming [6-8]. Authors have suggested that synergistic stabilising muscles (e.g. trunk muscles) could be active in both the arms only and legs only trials. As a result, these muscles require 0 2 in both instances and this energy overlap when summing the VO2 values from arms only and legs only trials is not accounted for in whole body swimming. While this may be true, the difference between whole body swimming VO2 and the sum of the VO2 of arms only and legs only swimming is too great to be solely attributed to the double-up of the VO2 requirements of the synergistic stabilising muscle groups [6]. Possible reasons for the discrepancy in previous findings could relate to the lack of measurement and control over stroke and kick rate across trials, as these parameters can influence swimming velocity as well as metabolic cost [5, 9]. If a swimmer's stroke rate in the arms only trial exceeds that attained in the whole stroke trial, the swimmer is likely to achieve a higher velocity with higher energy expenditure compared to what would be observed if the stroke rate of the arms only trial matched that of the whole stroke trial. Allowing participants to swim the whole stroke trial, and the arms only and legs only trials with varying stroke and kick rate means that the internal mechanical power and metabolic demands are bound to exceed 100% when summed together. The contribution of the arm stroke and leg kick to swimming velocity, and the associated energy expenditure, while controlling for stroke and kick rate, is yet to be examined. The purpose of this study was to: 1) determine the contribution of the legs and arms to velocity in submaximal, steady-state freestyle swimming while controlling stroke and kick rate, and 2) determine the metabolic cost associated with whole stroke, arm stroke only and kick only freestyle swimming. A comprehensive understanding of the contribution of the upper and lower limbs to swimming velocity and metabolic cost will inform training prescription, with the aim of decreasing the metabolic costs associated with these movements while increasing the velocity contributions of the arm stroke and leg kick.
© Copyright 2014 XIIth International Symposium for Biomechanics and Medicine in Swimming. Veröffentlicht von Australian Institute of Sport. Alle Rechte vorbehalten.