Relation between postural stability and plantar flexors muscle volume in young males

Purpose: It has been generally assumed that muscle volume is not a limiting factor of balance for young populations. To verify this assumption, this study investigated the relationship between postural stability and muscle volume of the plantar flexors, which have been regarded as the major agonist muscles for postural control, of healthy young male individuals. Methods: Forty-five healthy young males were requested to maintain quiet standing on a force platform for 60 s in eyes-open and eyes-closed conditions. Various time and frequency domain measures of the center of pressure were calculated. Muscle volume of the plantar flexors was estimated from muscle thickness in the lateral gastrocnemius and soleus muscles measured by ultrasonography and was divided by body mass to yield the normalized muscle volume. Results: Many time domain center of pressure measures such as mean distance, root mean square, and mean velocity were negatively correlated to normalized muscle volume (P < 0.05). Conclusions: It is suggested that, even among the young males, the muscle volume of their plantar flexors can act as a limiting factor for postural stability.