Leg length inequality, pelvic tilt and lumbar back muscle activity during standing.

The influence of an artificial leg length discrepancy on lateral pelvic tilt and on activity of the intrinsic lumbar back muscles was investigated. An artificial leg length discrepancy of up to 50 mm was created by putting boards of different height under the right foot. Lateral pelvic tilt increased linearly with increasing artificial leg length discrepancies. The rectified and averaged e.m.g. of the intrinsic lumbar back muscles showed a small increase at the longer leg side. It increased non-linearly with an increment in slope above a certain artificial leg length discrepancy (mean 34 mm).