TAKE-OFF CHARACTERISTICS OF DOUBLE BACK SOMERSAULTS ON THE FLOOR

Backward take-offs are one of the most important and frequently used components of a floor routine in artistic gymnastics and usually occur at the beginning, middle, and at the finish of a routine. They also initiate the linear and rotational impulses for multiple somersaults with various body positions with or without twists. This study was undertaken to supplement the work done previously by Brueggemann (1983, 1987, 1994), Hwang et al. (1990) and Knoll(1993). The purpose of the study specifically, was to investigate the biomechanical characteristics of dynamic take-offs in double backward somersaults performed by ten male and eight female gymnasts on the floor at the world gymnastics championships in Brisbane, 1994. Data was captured at 50Hzby two video cameras; this permitted the calculation of 3D kinematic data. Mean and standard deviations of selected kinematic and temporal parameters were calculated in order to: compare differences of biomechanical characteristics between male and female gymnasts, identify the differences in take-offs between the different types of double back somersaults performed, and to compare the data to those reported previously. Analysis of the data for both male and female gymnasts revealed, that the most important performance factor determining somersault height, the vertical velocity of the CM, changed from 1.17±0.46 and2.35±0.60 m/s at touch-down to 4.2±0.46 and 3.54±0.85 m/s at take-off, respectively. The vertical velocity value for the male gymnasts (4.2k0.46 m/s)was lower, assuming their body mass is the same, compared to those of previously reported studies by Brueggemann 4.57 m/s (1983), Hwang et al. 4.46m/s (1990) and Newton et al. 5.8 m/s (1992). This was most likely due to localized leg muscle fatigue; 70% of the analyzed take-offs in this study were performed at the finishing acrobatic series of their floor exercise. Brueggemann(1983, 1987) and Hwang et al. (1990) reported, that the leg muscles played the dominant role in take-offs. The horizontal velocity at touch-down was 4.32 ±0.47and 4.05±0.47 m/s and decreased to 3.21±0.49 and 2.30±2.27 m/s at take-off, respectively. The take off period was 130 and 120 ms, respectively for males and females. The touch-down and take-off angles of the CM to ground contact and the horizontal was 64.1±6.1, 69.7±5.9 and 88.1±3 .0 and 90.6±5.0,respectively. Preliminary results from the angular momentum calculations confirm the values of previously reported studies by the above authors