Kinematic analysis of the backstroke start: differences between backstroke specialists and non-specialists |
| |
| Authors: | Tsuyoshi Takeda Osamu Itoi Hideki Takagi Shozo Tsubakimoto |
| |
| Institution: | 1. School of Sport Sciences, Waseda University, Tokorozawa, Japantsuyoshi561981@yahoo.co.jp;3. Gifu National Sports Festival Promotion Department, Gifu, Japan;4. Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Japan |
| |
| Abstract: | AbstractThe purpose of this study was to clarify factors to perform the hole-entry technique in the backstroke start. A total of 16 well-trained Japanese competitive swimmers were divided into two groups (backstroke specialists and non-specialists) to compare their backstroke start motions. Their backstroke motions were videotaped, and two-dimensional co-ordinates for the swimmers were obtained from the video images using direct linear transformation methods. A non-paired t-test and Mann–Whitney U-test were used to analyse the statistical difference of the kinematic variables between the groups. Backstroke specialists showed a significantly shorter 5 m time (P = 0.009, effect size = –1.54), a significantly higher position of the toe (P = 0.010, effect size = 1.47) at signal and of the hip at toe-off (P = 0.002, effect size = 1.94), a significantly larger hip joint angle at toe-off (P = 0.007, effect size = 1.60) and a significantly higher angular velocities of the hip joints (45–85%; P < 0.05) for the normalised time as compared to that of non-specialists. An earlier initiation of the extension and the maintenance of a higher extension speed at the hip joints were important factors in achieving an arched-back posture, which facilitated and water entrance with a small entry range. |
| |
| Keywords: | motion analysis water entry angular momentum |
|
|
