INTRODUCTION: An elite swimmer`s success is primarily dependent upon their ability to minimise active drag, whilst optimising propulsive force. The aim of this study was to quantify passive and active drag, as a force-time profile. The secondary aim was to examine the force-time profile to determine which part of the stroke phase an athlete produced min and max force, and provide feedback to coaches and athletes. METHODS: Elite freestylers (n=18) completed 3 max swim velocity trials, followed by 3 passive and active drag trials using a towing device mounted upon a force platform. The computed active drag and the propulsive force profiles were represented as a force-time graph synchronised with video footage, allowing identification of intra-cyclic force fluctuations. RESULTS: The mean velocity for the females and males were 1.72 m/s, 1.89 m/s respectively. The mean passive drag for the females and males were 49.7 ± 1.8 N, 78.9 ± 1.6 N, respectively and the mean active drag for the females and males were 164.4 ± 11.7 N, 228.4 ± 10.8 N, respectively. DISCUSSION: The mean passive drag values measured are comparable to those previously reported. Kolmogorov and Duplishcheva (1992) observed male and female passive drag ranging from 69.7 - 103.0 N and 44.2 - 56.9 N, respectively at velocities 1.73 - 1.91 m/s and 1.52 - 1.67 m/s, respectively. Active drag did not concur with the literature. Toussaint et al. (2004) compared the values collected with MAD and VPM systems. The values at a mean velocity of 1.64 m/s were 66.9 N and 53.2 N, respectively. There was significant variation between min and max propulsive force range for left and right stroke phases, between and within participants. It was evident that mean min propulsive force was generated during the first `pull` phase of the stroke cycle. The results indicated that the max propulsive force production occurred during the final `push` phases of the stroke cycle. This study demonstrated the importance of representing active drag as instantaneous force, rather than a mean value. This provided unique and valuable insight into the intra-cyclic force fluctuations within a stroke cycle. REFERENCES: 1. Kolmogorov SV, Duplishcheva OA. (1992). Active drag, Useful Mechanical Power Output and Hydrodynamic Force Coefficient in Different Swimming Strokes at Max Velocity. J Biomech, 25 (3):311-318. 2. Toussaint HM, Roos PE, Kolmogorov S. (2004). The determination of drag in front crawl swimming. J Biomech, 37(11): 1655-1663.
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