Effect of acceleration on the rate of power development and neural activity of the leg extensors across the adult life span.

Abstract

The rate of power development (RPD) represents the capacity to rapidly generate power during a dynamic muscle contraction. As RPD is highly susceptible to aging, its decline can have important functional consequences. However, the effect of age on RPD in response to rapid changes in movement velocity (cfr. fall incidence) is not yet clear. Therefore, the present study aimed to examine the effect of age on RPD and neural drive in response to different accelerations. Three maximal isokinetic leg extensor tests at 540°/s with different initial acceleration phases at 3200, 5700 and 7200°/s2 were performed. RPD, which is the slope of the power-time curve during the acceleration phase, was calculated for 83 subjects aged between 20 and 69years. Mean electromyography signal amplitude was determined for rectus femoris (RF), vastus lateralis (VL) and biceps femoris muscles. The average annual age-related decline rate of RPD at highest acceleration was - 2.93% and was - 1.52% and - 1.82% higher compared to lower acceleration rates (p < 0.001). This deficit can probably be explained by an age-related impairment in neural drive during the first 75ms of the acceleration phase, as evidenced by a reduced RF and VL neuromuscular activity of - 0.30% and - 0.36% at highest versus lowest acceleration (p < 0.05). These findings highlight the inability of aged individuals to quickly respond to abrupt changes in movement velocity, which requires more focus in training and prevention programs.