Does the global temporal activation differ in triceps surae during standing balance?

One of the most important muscular groups which contribute to maintain standing balance is triceps surae. However, it is unclear whether the postural controllers of triceps surae, medial gastrocnemius (MG) and soleus (SOL), have different temporal patterns of activation during upright stance. This paper aimed at evaluating whether the global temporal activation in triceps surae differ among young subjects during standing balance. Nine male volunteers performed two tasks: standing quietly and with voluntary back and forward sways over their ankle. Electromyograms (EMGs) from soleus medial (MSOL) and lateral (LSOL) regions and from MG were sampled with linear arrays of surface electrodes. The percentage of muscle activation in time (i.e. temporal index) was computed for each muscle during upright standing. The results revealed that the medial portion of soleus muscle (MSOL) was activated continuously compared to the lateral portion of soleus (LSOL) and MG, which were activated intermittently. Therefore, the global temporal activation differed among the postural muscles of triceps surae during standing balance.