Differences in countermovement jump landing characteristics and joint works across levels of perceived effort

The way in which different levels of effort affect countermovement jump (CMJ) landing characteristics and strategies remains unclear. The purpose of this study was to investigate differences in CMJ landing performance and related joint-level strategies across various levels of perceived effort. Twenty-four recreationally active individuals (12 Male: age = 23 ± 5 years, mass = 83.8 ± 14.5 kg, height = 1.8 ± 0.1 m; 12 Female: age = 23 ± 2 years, mass = 62.6 ± 12.0, height = 1.6 ± 0.1) performed five sets of three CMJs. Three-dimensional kinematic and ground reaction force (GRF) data were collected for each trial. Landing performance index (LPI), peak vGRF, and durations of the loading, attenuation, and control phases of the landing were obtained. Total lower body joint work (TW) as well as hip, knee and ankle contributions were calculated for 100 %, 75 %, 50 %, and 25 % perceived effort level for each phase of the landing. One-way repeated measures ANOVA tests (α = 0.05) were used to identify differences between each of the effort levels for all variables of interest. The best landing performances occurred during the 100 % condition, and while patterns in significant differences between levels of effort were not observed throughout all variables of interest, the TW during attenuation phase exhibited the most significant variability between levels of perceived effort. In addition, changes in the dependent variables did not coincide with proportional changes in level of effort. The results of the joint contributions suggest that levels of perceived effort may not stimulate desired changes in landing performance or joint mechanics.