Effect of stimulation train characteristics on the dynamic performance of human skeletal muscle
Date
2006
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
The activation frequency of skeletal muscle affects the generation, maintenance, and decline (fatigue) of force. Although activities of daily living predominantly involve nonisometric contractions, the dynamic response of the muscle over a range of stimulation characteristics has not been rigorously investigated. The activation frequency, activation pattern, train durations, and number of stimulation pulses were considered as the train characteristics of interest in this study. The excursion-frequency (for a controlled train duration), and excursion-train duration (for controlled frequencies) relationships were each modeled as a 2-parameter exponential and the excursion produced as a function of the number of stimulation pulses was characterized by combining the excursion-frequency, and excursion-train duration relationships. In addition, for each frequency tested between 10 to 50Hz, variable-frequency trains that took advantage of the catchlike property of skeletal muscle produced greater excursions than constant-frequency trains. The variable-frequency trains were also able to achieve targeted trajectories with fewer pulses than constant-frequency trains. Results showed a predictable excursion-frequency relationship for trains over a wide range of durations and number of pulses and that similar to voluntary muscle activation patterns, varying the instantaneous frequency within a train of pulses could be used to improve dynamic muscle performance. These findings provide new insight into the relationship between activation frequency and human skeletal muscle performance.