Effects Of Different Levels Of Assisted Jumping On Vertical Jump Height And Relative Ground Reaction Force

Overspeed exercises are commonly integrated into a training program to help athletes perform at a speed greater than what they are accustomed. Overspeed methods such as downhill sprinting or tow training, has been shown to decrease sprinting time, thus assisted training applied to vertical jumping may enhance jump performance. PURPOSE: To examine different assisted jump conditions on vertical jump height (VJH) and relative ground reaction force (GRF/Mass with reduction %). METHODS: Twenty recreationally trained college students completed three testing sessions, which consisted of a 5-minute warm-up, followed by randomized experimental conditions of 0%, 10%, 20%, 30%, and 40% body weight reduction (BWR). In all BWR experimental sessions subjects wore a full body harness while attached to two elastic cords, which were attached to the ceiling. Subjects performed three maximal countermovement jumps with arm swing for all conditions on a force plate. One minute of rest was given between each jump and two minutes of rest were provided between conditions. Maximum values from the peak velocity repetition for each condition were used for analysis. RESULTS: Analysis of variance (ANOVA) revealed no interaction of condition by sex for VJH or relative GRF, however there were significant main effects for condition for both variables. As BWR increased, VJH and relative GRF significantly (p<.05) increased with the exception of 0% and 10% (VJH-42.67±9.81cm and 43.90±9.71cm, GRF-13.19±2.97N/kg and 13.54±2.52N/kg). Significant (p<.05) increases were found between all other BWR conditions for VJH (20%-50.41±10.39cm, 30%-58.10±10.04cm and 40%-63.37±11.60cm) and relative GRF (20%-15.39±3.11N/kg, 30%-17.69±3.20N/kg and 40%-21.10±5.49N/kg). CONCLUSIONS: These results suggest 20%, 30% and 40% BWR via elastic cords increases VJH and relative GRF. Therefore, these conditions may elicit a jumping performance increase when applied in a training study.BR>