【Objective】

To investigate the role of the back and foot muscles during lateral weight-shifting in the standing position by examining the corresponding muscle activity patterns associated with a postural change.

【Methods】

The subjects were 24 healthy men (age 24.3 ± 2.6 [mean ± SD] years). The following parameters were recorded : center of pressure (COP) ; surface electromyograms of the multifidus, iliocostalis, longissimus (bilateral), peroneus, and foot supinator (on the moving side) muscles ; and video imaging during lateral weight-shifting after 2 seconds in the standing position.

【Results】

Horizontal movement of the pelvis resulted in elevation of the non-moving side from the middle of the COP, with moving side displacement. In the lower limbs, lateral weight shifting resulted in an outward tilt due to foot pronation. Activity of the multifidus, iliocostalis, and longissimus muscles on the non-moving side, and the peroneus and foot supinator muscles on the moving side, tended to increase with displacement of the COP on the moving side.

【Conclusion】

The multifidus, iliocostalis, and longissimus muscles were involved in lateral flexion of the thoracolumbar area and elevation of the pelvis on the non-moving side. Simultaneously, the foot supinator and peroneus muscles were involved in pronation of the grounded foot.