Torque, work and EMG development in a heel-rise test

OBJECTIVE: To study the fatigue process in the calf muscle during a standing heel-rise test. DESIGN: Heel-rises were performed on a force plate measuring development of torque in the ankle joint. BACKGROUND: The heel-rise test is a commonly employed clinical test to evaluate the function of the calf muscle by counting the number of heel-rises before exhaustion. Development of fatigue during other eccentric-concentric actions has earlier been studied as decreases in force, work and EMG. METHODS: Ten healthy males (mean age 25 yr) participated in the study. Torque and work were calculated using measurements from a force plate. Mean power frequency and root-mean-square of the EMG in the triceps surae were evaluated separately in the eccentric and concentric phases. RESULTS: Increases of mean torque during both the eccentric and concentric phases were found. Work performed decreased during the concentric phases due to decreased range of motion. No changes in root-mean-square and decreases in mean power frequency during the concentric phases indicated development of muscular fatigue, whereas decreases in both root-mean-square and mean power frequency during the eccentric phases indicated decreasing muscular activity. CONCLUSIONS: Accordingly, the limiting factor for the heel-rise test was not loss of muscle force at the range of motion used, but rather a failure to maintain the initial range of motion owing to muscle fatigue. RELEVANCE: This method of calculating torque development in the ankle joint provides an opportunity to study the fatigue process in terms of performance. The results show that the heel-rise test reflects muscle endurance rather than strength of the calf muscle.