Patterns of Lower Limb Muscle Activity in Young Boys during a One Foot Static Balance Task

Activity patterns of four major muscles were studied in the support leg during a standard one foot balance test. Electromyographic (EMG) activity of the tibialis anterior (TA), peroneus longus (PL), gluteus medius (GM), and adductor magnus (AM) was recorded from 10 boys (aged 7-9 yr) during 30 s balance trials. Rectified, low-pass filtered EMG data, converted to percentages of maximum contractions, were used to establish muscle activation patterns. The results showed that lateral shifts in balance were primarily mediated by the ankle musculature, while the hip muscles appeared to stabilize the pelvis. Immediately prior to lateral shifts of the center of pressure (COP), the activity of each ankle muscle was similar to the activity of the following pose. The hip muscles, however, were not consistently linked to ankle activity. Thus, the control of one-legged lateral balance does not rely on fixed hip-ankle synergies.