Lower Limb Force Asymmetries During Landing and Jumping Exercises: A Pilot Study.

Significant asymmetries can exist between the lower limbs' force production during the take-off phase of bilateral jumping exercises. Some studies have indicated that similar asymmetries can also exist during the landing phase. It has not been demonstrated if the magnitude of lower body asymmetry was similar between the landing (L) and take-off (TO) phases of bilateral jumping movements. The main purpose of this study was to compare the asymmetry measured during the L and TO phases of bilateral jumping exercises to determine if there was a difference in asymmetry between the phases. In order to quantify the degree of the asymmetry, the vertical ground reaction force (vGRF) produced by each leg was measured during execution of vertical-jump (VJ) and drop-jump (DJ) exercises. Eleven recreationally trained individuals completed three VJ and DJ trials while two force plates recorded vGRF. A two-way repeated measures ANOVA was used to compare the asymmetry levels with the phase (within- subject: L and TO) and the exercise (within- subject: VJ and DJ) being factors. A significant difference in the asymmetry was found between the L and TO phases (p < .05). These findings suggested that there was greater asymmetry in the distribution of vGRF during landing than during take-off.