Counter Movement Jump Characteristics Pre and Post Fatiguing Strength Exercise in Elderly Individuals

Abstract

Failure to perform functional motor task in elderly individuals may be linked to muscle fatigue. Leg muscle peak power generation obtained during counter movement jump (CMJ) test has previously demonstrated close correlations to various functional motor tasks in old individuals. It is not known, however, which impact fatiguing leg strength exercise has on the various descriptive parameters of the CMJ-test. PURPOSE: To examine changes in CMJ parameters pre and post fatiguing leg strength exercise in elderly women and to correlate changes in jump height and mechanical CMJ output, respectively. METHODS: Eighteen elderly women (age 69.7 ±3.4 years, mean ± SD) were randomly assigned CMJ tests with or without prior fatiguing leg muscle exercise. The fatiguing protocol consisted of 5 sets of 10 RM incline leg press. Maximal CMJs were performed on a force plate (Kistler 9281 B). Peak upward acceleration (apeak) was measured in the eccentric phase, while maximal jump height (JH), peak power (Ppeak) and mean power (Pmean) were calculated for concentric phase. Ppeak was further decomposed into its velocity (Vppeak) and force (Fppeak) components. Furthermore, plantar flexor phase mean power (PF Pmean) was denned in the final part of the concentric phase where the position of the center of mass is lifted vertically above the starting position. A separate familiarization session was performed 1–4 days prior to the test session. Students paired t-test was used to evaluate differences in mean values pre versus post fatiguing leg exercise and linear correlation of JH-changes and descriptive parameters were evaluated by the Pearson product-moment method. RESULTS: A significant decrease in JH (−9.3%) was followed by decreases in Pmean (−3.8%), Vppeak (−2.9%), and apeak (−20.4%). When correlating the decrease in JH with the decreases in mechanical CMJ output the Pmean and PF Pmean explained a large proportion of the variation in JH-decrease (77.6% and 84.6%, respectively). Moderate correlations were observed for Ppeak, Vppeak, and apeak (range: 24.8% and 30.2%). CONCLUSIONS: Changes in PF Pmean and Pmean largely explained the decrease in JH. Fatigue related decrements in plantar flexor function and functional consequences of muscle fatigue should be evaluated further in elderly subjects.