TORQUE, WORK AND EMG DEVELOPMENT IN A HEEL-RISE TEST

Objective. To study the fatigue process in the calf muscle during a st anding heel-rise test. Design. Heel-rises were performed on a force pl ate measuring development of torque in the ankle joint. Background. Th e heel-rise test is a commonly employed clinical test to evaluate the function of the calf muscle by counting the number of heel-rises befor e 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 plat e. Mean power frequency and root-mean-square of the EMG in the triceps surae were evaluated separately in the eccentric and concentric phase s. Results. Increases of mean torque during both the eccentric and con centric phases were found. Work performed decreased during the concent ric phases due to decreased range of motion. No changes in root-mean-s quare and decreases in mean power frequency during the concentric phas es indicated development of muscular fatigue, whereas decreases in bot h root-mean-square and mean power frequency during the eccentric phase s indicated decreasing muscular activity. Conclusions. Accordingly, th e 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 init ial range of motion owing to muscle fatigue.