Influence of sports background on the bouncing mechanism of running.

During running, the mechanical energy of the centre of mass of the body (COM) oscillates throughout the step like a spring-mass system, where part of its mechanical energy is stored during negative phases to be released during the following positive phases. This storage-release of energy improves muscle-tendon efficiency, which is related to lower-limb stiffness. This study explores the effect of sports background on the bouncing mechanism, by examining differences in stiffness and step spatiotemporal parameters between swimmers and football athletes. All athletes performed three consecutive running bouts on an instrumented treadmill at three different speeds (3.9, 4.4 and 5.0 m·s-1). The ground reaction forces were recorded. Vertical stiffness and step spatiotemporal parameters were analysed and compared using a two-way ANOVA. Vertical stiffness of football players was on average 21.0 ± 1.1% higher than swimmers. The modification of step spatiotemporal parameters also suggests a more elastic rebound by increasing the stretch of tendons relative to muscle within muscle-tendon units in football players. Compared to swimmers, they (1) decrease the effective contact time by 9.7 ± 2.4% and (2) decrease the duration of the push by 15.0 ± 6.4%, suggesting that background training adaptations influence spring-mass behaviour during running.

The rebound of the body during uphill and downhill running at different speeds.

When running on the level, muscles perform as much positive as negative external work. On a slope, the external positive and negative work performed are not equal. The present study analysed how the ratio between positive and negative work modifies the bouncing mechanism of running. Our goals are to: (1) identify the changes in motion of the centre of mass of the body associated with the slope of the terrain and the speed of progression, (2) study the effect of these changes on the storage and release of elastic energy during contact and (3) propose a model that predicts the change in the bouncing mechanism with slope and speed. Therefore, the ground reaction forces were measured on 10 subjects running on an instrumented treadmill at different slopes (from -9 to +9 deg) and different speeds (between 2.2 and 5.6 m s(-1)). The movements of the centre of mass of the body and its external mechanical energy were then evaluated. Our results suggest that the increase in the muscular power is contained (1) on a positive slope, by decreasing the step period and the downward movements of the body, and by increasing the duration of the push, and (2) on a negative slope, by increasing the step period and the duration of the brake, and by decreasing the upward movement of the body. Finally, the spring-mass model of running was adapted to take into account the energy added or dissipated each step on a slope.

The effects of multidisciplinary rehabilitation in patients with early-to-middle-stage Huntington's disease: a pilot study.

BACKGROUND AND PURPOSE: Despite advances in the understanding of Huntington's disease (HD), treatment remains symptomatic. Multidisciplinary rehabilitation, however, appears to impact disease progression. Here we show the feasibility, safety and efficacy of a 9-month multidisciplinary rehabilitation programme in a small cohort of patients with early-to-middle-stage HD. METHODS: Twenty patients with HD were assigned to two groups, equally matched for cognitive and motor scores. One group received the intervention, whilst the other served as control. The Unified-Huntington's-Disease-Rating-Scale-Total-Motor-Score was the primary outcome measure. Neurocognitive/psychological tests, body composition, postural stability, strength and quality of life assessments were secondary outcome measures. RESULTS: The intervention reduced motor and postural stability deterioration, with minor improvements in depression, cognition and quality of life. Significant gains were observed for fat-free mass and strength. CONCLUSION: This pilot study suggests that a prolonged multidisciplinary rehabilitation programme in early-to-middle-stage HD is feasible, well-tolerated and associated with therapeutic benefit. Further explorative, larger studies are warranted.