The Effect of Load Placement on Lower Extremity Joint Biomechanics in Landing

Abstract

Landing is a critical component to athletic performance. Many studies have investigated the effect that added mass has on landing biomechanics finding when load is added to the body during a landing task, an increase in both vertical (VGRF) and anterior-posterior ground reaction forces is observed. These studies have focused primarily on adding mass to the trunk segment. It is unclear, however, if these adaptations would persist if mass was added to other body segments. We hypothesize that altering the load placement on the body will alter the kinetics and kinematics of lower extremity joints during landing. The purpose of this study is to determine the effect of load placement on joint biomechanics during jump landing compared to unloaded jump landing. 7 healthy college-aged individuals participated in this study. Participants were outfitted for bilateral lower-extremity 3D motion capture. VGRFs were collected from two force platforms. Each participant completed 3 successful jump landings in 3 conditions (unloaded, loaded thigh, and loaded trunk). 10% of the participant's mass was added to the trunk via a weighted vest and 5% was added to each thigh via weighted pants during the loaded conditions. Landing height was standardized to 50 (± 2.5) cm. Student's paired samples T-tests were used to detect any mean differences with (p < 0.05) indicating significance. A significant reduction (p = .004) in peak VGRF was found between the loaded thigh condition (1935.4N ± 419.9N) and the loaded trunk condition (1755.7N ± 308.9N). Results showed that during the loaded thigh condition, participants landed with more extended knees (-12.3 ± 5.9 deg) than the unloaded (-13.1 ± 4.6 deg) and loaded trunk (-15.0 ± 6.5 deg) conditions however these results were not significant. Hip flexion angle increased in the loaded trunk condition (-22.5 ± 9.3 deg) compared to loaded thigh (-15.3 ± 7.6 deg) and unloaded (19.6 ± 6.2 deg) although these results were not significant. Our results supported our hypothesis that altering the load placement on the body will alter lower extremity joint biomechanics during landing from a drop jump.