The purpose of this study was to clarify the relationship between the kick start performance and legs muscular strength in competitive swimming. Six male competitive swimmers performed maximal efforts in 20 m of front crawl swimming using kick start. The start time was measured as the time when swimmer’s head passed across 5 m line using a digital camera operating at 30 Hz. Moreover, the starting movements were recorded by a high speed camera (100 Hz) and the 2-DLT method was used for calculating the kinematical data. The maximal voluntary isometric and isokinetic (60 deg/s, 120 deg/s) knee extension moments of front and rear legs were determined by using an isokinetic dynamometer. High correlation coefficients (r = -0.821, P ＜ 0.05, r = 0.962, P ＜ 0.01) were observed between the start time, the horizontal velocity of center of mass at take-off and the isometric knee extension moment of front leg, whereas there was no significant correlation for the other parameters. These results of this study suggested a possibility some trainings for isometric strength of the front leg would improve the resultant start performance.
The aim of this study is to investigate the usefulness of a new swimming power measurement apparatus. This apparatus is called the Drag Boat (DB). DB is as large as a floating kickboard. The body is made of wood, and the load can be selected from five different levels. Drag force and swimming power can be calculated by measuring swimming velocity. Calibration of this system was performed using a towing apparatus (Active Drag System, ADS). Towing velocity was in the range of 0.4~2.2m/sec. The subjects were ten male competitive swimmers. They swam 25m front crawl at maximum effort under two conditions. One was conducted in free swimming, and the other was semi-tethered swimming using DB and ADS. Significant linear relationship was observed between drag force and swimming velocity when the subjects swam towing DB. The swimming power calculated using DB was found to be significantly correlated with velocity of 25m sprint swimming (r = 0.73, p<0.05). There was also a significant correlation between swimming power and velocity of 25m sprint swimming, which were calculated using ADS (r = 0.82, p<0.01). The swimming power calculated using DB and the swimming power calculated using ADS were found to have a significant correlation (r = 0.83, p<0.01). The above results show that power measurement using DB is efficient.