Muscle-Tendon Unit Function During Continuous And Maximal Hopping

The purpose of the current study was to determine the amount of power contributed by the triceps surae muscle complex and Achilles tendon individually during low-force, continuous hopping in comparison to a maximal hop to determine the amount of power restored to the system by the tendon via stored strain energy. Five male subjects were fitted with an ultrasound probe on the triceps surae muscle complex of their right leg for muscle fascicle imaging. Three-dimensional motion analysis was performed by using the VICON motion analysis system. Participants were placed on a customized sled at a ten-degree angle with all work isolated to the right ankle joint and asked to complete a maximal counter-movement hop followed by submaximal continuous hopping where data were collected after five minutes. The muscle-tendon unit (MTU) and tendon were both found to have significantly different negative and net power (p<0.05) between hops where net power was found to be significantly lower during the continuous hop. The results suggest that subjects used active muscle contractility during both the continuous and maximal hops however, energy restoration was not from stored elastic energy of the tendon as hypothesized and was restored by the muscles during the continuous hop.