Effect of Leg Length Discrepancy on Trunk Muscle Fatigue and Unintended Trunk Movement.

Abstract

Asymmetry, including scoliosis compensatory to leg length difference, is commonly thought to degrade one's performance and to predispose one to injury. We examined differences between persons with and without leg length discrepancy in ability to control motion during fatiguing trunk flexions and extensions. Loss of control was measured by the amount of unintended rotation and lateral flexion during the flexions and extensions. Fifteen subjects with leg length discrepancy and fifteen without flexed and extended their trunks with maximum effort and speed for as long as possible against resistance equal to 70 per cent of maximum isometric flexion. The excursion of flexion and extension did not include the last 15 degrees of the fully available range of motion in either direction. The two groups did not differ in variance of excursion into rotation and lateral flexion or in the number of repetitions completed to fatigue. We interpret this to mean that no difference was detected between subjects with and without leg length discrepancy in degree of neuromuscular control of the trunk during this particular testing procedure.