Analysis of the repeated one-leg heel-rise test of ankle plantar flexors in manual muscle testing

The purpose of this study was to evaluate the repeated one-leg heel-rise test method of ankle plantar flexors in MMT with kinetic measuring devices and electromyograms (EMG). Seven healthy young males (age, 23 +/- 2 y) with no prior history of fractures or surgery involving the lower limbs participated in this study. The ankle and knee motions from flexible electrogoniometers (EGM), ground reaction forces (GRF) and center of pressure (COP) from one force plate and the root-mean-square (RMS) and mean-power-frequency (MPF) from EMG in the medial head of the gastrocnemius and soleus muscles during the repeated one-leg heel-rise test. Kinetic and kinematic data from EGM, GRF and COP were unchanged during the tests. Although the RMS in both muscles and the MPF in the soleus muscles were unchanged during this test, the MPF in the gastrocnemius muscles decreased with the number of iterations (r=-0.79, p < 0.001). The MPF of the gastrocnemius muscles in the late phase was significantly lower that in the early and middle phases (respectively, p < 0.05, p < 0.05). Our results show that this repeated motion method estimates muscle endurance rather than the muscle power.