The purpose of this study was to examine the changes in both the coordination patterns of segmental actions and the dynamics of vertical jumping that accompany changes in vertical jump performance (VJP) occurring from trial to trial in single subjects. Ground reaction forces and video data were analyzed for 50 maximal vertical jumps for 8 subjects. It was possible to predict VJP from whole-body or even segmental kinematics and kinetics in spite of the small jump performance variability. Best whole-body models included peak and average mechanical power, propulsion time, and peak negative impulse. Best segmental models included coordination variables and a few joint torques and powers. Contrary to expectations, VJP was lower for trials with a proximal-to-distal sequence of joint reversals.
Luis F. Áragón-Vargas and M. Melissa Gross
Luis F. Aragón-Vargas and M. Melissa Gross
The purpose of this study was to investigate the kinesiological factors that distinguish good jumpers from poor ones, in an attempt to understand the critical factors in vertical jump performance (VJP). Fifty-two normal, physically active male college students each performed five maximal vertical jumps with arms akimbo. Ground reaction forces and video data were collected during the jumps. Subjects' strength was tested isometrically. Thirty-five potential predictor variables were calculated for statistical modeling by multiple-regression analysis. At the whole-body level of analysis, the best models (which included peak and average mechanical power) accounted for 88% of VJP variation (p < .0005). At the segmental level, the best models accounted for 60% of variation in VJP (p < .0005). Unexpectedly, coordination variables were not related to VJP. These data suggested that VJP was most strongly associated with the mechanical power developed during jump execution.
Jefferson W. Streepey, M. Melissa Gross, Bernard J. Martin, Sundravalli Sudarsan, and Catherine M. Schiller
The relationship between playing surface and muscle fatigue was examined in 22 male subjects performing a simulated basketball task on a conventional wood floor and less stiff composite floor. Force and electromyographic activity (EMG) were measured during maximum and submaximum (10% of maximum) voluntary contractions of knee extensor and ankle plantarflexor muscles before and after completion of the simulated basketball task. Jump height was evaluated during the task, and perceived fatigue was assessed at the end of the task. Although not all subjects jumped significantly higher on the composite floor compared to the wood floor. competitive basketball players showed a significant improvement in jump height (3.4 cm. 6%) when jumping on the composite floor. Perceived fatigue was significantly lower for the composite floor (21.7%) than the wood floor (30.2%). The objective measures indicated the occurrence of fatigue; however, force and EMG magnitudes obtained during maximum exertions were not sensitive lo floor types. Post-task increase in EMG magnitude indicated a significant fatigue effect for the soleus muscle on the wood floor only. These findings suggest that the composite floor may benefit human performance without increasing fatigue during basketball-related activities.