The effect of leg length discrepancy on paraspinal muscles activation using surface electromyography

Abstract

Abstract Objective To assess the effects of leg length discrepancy (LLD) on paraspinal muscle activity and kinematic variables during gait. Design Thirty-nine healthy participants aged 5 to 12 years performed the 10-m walk test using the surface electromyography and G-walk sensor for the following conditions: 1) non-LLD condition (LLD 0 cm) and 2) LLD condition with an insole on the right leg at three different heights (LLD 0.5 cm, 1.0 cm, and 1.5 cm). The root mean square (RMS) was normalized using maximal voluntary contraction and reference voluntary contraction methods (RMS_MVC and RMS_ref) and compared between the sides. Results The mean RMS_MVC of the 12th thoracic erector spinae (EST12) on the right side was significantly higher at an LLD 0.5 cm and 1 cm. Regarding the 3rd lumbar multifidus (MuL3), the mean RMS_MVC on the right side was significantly higher at an LLD 1.5 cm. The mean RMS_ref exhibited similar patterns. Pelvic obliquity and rotation showed asymmetry at an LLD 1.5 cm compared with an LLD 0 cm. Conclusions A small LLD significantly affected the asymmetric hyperactivation of the MuL3 and EST12 muscles during gait. Considering the action of these muscles, asymmetric hyperactivation might result in rotation and bending of the lumbar spine and the bending of the thoracolumbar spine.