Development of the technology to measure active drag ofswimmers by the method of small perturbations

The research aimed at further improvement of the technology of measuring swimmers' active drag by the small perturbation method (SPM) at the average maximal swimming velocity (v_0max). For better reliability and accuracy of measurements, a standard variant of SPM was developed to measure automatically active drag (F_r(ad)), dimensionless coefficient of hydrodynamic force (C_x) and total external mechanical power P_to in different competitive swimming techniques during a single 50 m trial. The study involved twelve elite swimmers who specialized in front crawl at the distances of 100 and 200 m (780-850 FINA Points). From our measurements, in front crawl the results are following: v_0max = 1.909 ± 0.017 m·s^-1, F_r(ad) = 106.892 ± 7.276 N, C_x = 0.311 ± 0.028 and P_to = 204.033 ± 13.221 W. For objective estimation of the results, a verification variant of SPM was applied: v_0max = 1.911 ± 0.018 m·s^-1, F_r(ad) = 107.033 ± 7.232 N, C_x = 0.311 ± 0.030 and P_to = 204.467 ± 12.982 W. The correlation analysis of the results obtained by the standard and verification variants of SPM confirms high accuracy and reliability of the method used (r = 0.988 for v_0max; r = 0.979 for F_r(ad); r = 0.988 for C_x(ad); r = 0.979 for P_to). The measurement error, including the method error and the devices error, does not exceed 2.4 %. This method has also a systematic error that reduces the measured data in the same direction from the actual values (min = -2.1 %; max = -2.9 %). This error should be taken into account when analyzing and evaluating the measured hydrodynamic characteristics of swimmers.