The Relationship Between The Operation Of Kick Start And Isokinetic Knee Strength In Swimmers

Abstract

PURPOSE: The purpose of this study was to examine the relationship between the operation of kick start and isokinetic knee strength in swimmers using three-dimensional (3D) analysis. METHODS: This study included 11 male university student swimmers, who usually used the kick-start technique. We filmed the operation of kick start using 3 high-speed cameras (300 scenes; shutter speed, 1/250 s). The cameras could record over an area measuring 6.05 × 1.90 × 2.00 m. After we took a video of operation, we vertically set up calibration-pole which applied the control-point at intervals of 0.5m at the seven places within the range of taking a picture as ground and the surface of the water. Motion analysis was performed using Frame-DIASIV System (DKH) software. The 3D coordinates of 23 points on each subject’s body were determined using direct linear transformation. Tests of isokinetic knee strength were performed using an isokinetic dynamometer (BIODEX, System 4). For each measurement, we set the angular velocity as 60, 180, and 300°/s, and repetitions were conducted 5, 10 and 15 times, respectively. In the analysis, we divided muscle strength by weight, for each participant. We used Spearman’s rank correlation coefficient to assess the relationship between the operation of kick start and isokinetic strength. Statistical significance was set at 5%. RESULTS: There was a significant relationship between the average center of gravity, horizontal acceleration before take-off, and flexion muscle strength of the front knee at 60°/s (r = 0.718) and 180°/s (r = 0.636) and extension muscle strength of the rear knee at 300°/s (r = 0.500). Similarly, there was a significant relationship between the time from the start signal to take-off and flexion muscle strength of the front knee at 60°/s (r = -0.651) and 180°/s (r = -0.651) and extension muscle strength of the rear knee at 300°/s (r = -0.433). CONCLUSION:These results suggest that swimmers with high muscle strength of the front knee at flexion can obtain a high horizontal acceleration in the acceleration phase, because they can quickly move the body forward. In addition, it is thought that this may shorten the take-off time