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.