Force-displacement differences in the lower extremities of young healthy adults between drop jumps and drop landings

The Within-Subjects Effects of Practice on Performance of Drop Landing in Healthy, Young Adults

Most studies of high-speed lower body movements include practice repetitions for facilitating consistency between the trials. We investigated whether 20 repetitions of drop landing (from a 30.5-cm platform onto a force plate) could improve consistency in maximum ground reaction force, linear lower body stiffness, depth of landing, and jump height in 20 healthy, young adults. Coefficient of variation was the construct for variability used to compare the first to the last five repetitions for each variable. We found that the practice had the greatest effect on maximum ground reaction force (p = .017), and had smaller and similar effects on lower body stiffness and depth of landing (p values = .074 and .044, respectively), and no measurable effect on jump height. These findings suggest that the effect of practice on drop landing differs depending upon the variable measure and that 20 repetitions significantly improve consistency in ground reaction force.