Effects Of Drop Landing Height On Bilateral Asymmetry On Ground Reaction Forces During Depth Jumps

Previous research considering depth jumps at heights of .2m, .4m and .6m.demonstrated greater bilateral vertical ground reaction force (vGRF) and time asymmetry at lower heights compared to higher. Because depth jumps are often conducted from heights greater than .6m, there is a need for further research. PURPOSE: To determine the effect of height on vGRF differences and temporal differences between dominant and nondominant limbs during depth jumps. METHODS: Twenty-nine physically-active male college-age subjects (22.7±2.6yrs, 1.78±.07m, 80.5±14.3kg) with prior plyometric training experience performed DJ from heights of .30m, .45m, .60m, .75m, and .90m in random order. Four trials from each height were completed. Subjects dropped onto two forceplates, immediately performed a maximal jump and then landed back onto the forceplates a second time. Peak vGRF difference between the limbs for both the drop and second landing phases were determined and expressed in body weight units. Ground contact (GC) and ground off (GO) time differences (TD) between the dominant and nondominant limbs for the depth phase were also computed. Two factor (phase by height) analysis of variance (ANOVA) was conducted for peak vGRF difference, while separate one factor (height) ANOVA were conducted on GC and GO TD. RESULTS: A significant phase by height interaction was revealed for peak vGRF difference (PP=.001) than the second landing peak vGRF at .30m, whereas the drop peak vGRF was significantly greater than the second landing peak vGRF at .75m (PP CONCLUSIONS: As DJ height increases, the peak forces became more asymmetrical between limbs (dominant\u3enondominant). This may have implications on training adaptations and increase risk of impact related injuries. Future research should consider changes to exercise execution and instructions given to clients