Muscle fatigue in a standing heel-rise test.

The fatigue process of the triceps surae was evaluated during a standing heel-rise test, comprising of eccentric and concentric muscle actions. Ten healthy women with a mean age of 24 years participated. The heel-rise test was performed until exhaustion. Work and electromyographic activity expressed as root mean square and mean power frequency of the gastrocnemius and soleus muscles were calculated. The average number of heel-rises performed was 25 +/- 1. Work decreased significantly during the test. Mean power frequency decreased significantly in both phases. During the eccentric phase the decrease was significantly larger in the gastrocnemius than in the soleus muscle. There were no significant changes in root mean square except for a decrease in the soleus muscle during the eccentric phase. The present results, showing different fatigue patterns in the two muscles, could be used as reference when testing the fatigue process in different clinical conditions. Recommendations for standardization of a heel-rise test are given.