Muscle fatigue during a short walking exercise in children with cerebral palsy who walk in a crouch gait.

Parent, Audrey; Pouliot-Laforte, Annie; Dal Maso, Fabien; Cherni, Yosra; Marois, Pierre; Ballaz, Laurent

BACKGROUND A deterioration of crouch gait was found in a group of children with cerebral palsy (CP) after a short walking exercise. The increased knee flexion reported after a continuous walk could be related with muscle fatigue and muscle strength. AIM Does muscle fatigue appears at the end of a walking exercise in children with CP who walk in a crouch gait? METHODS Eleven children with cerebral palsy (GMFCS I to III) who walk in a crouch gait were included. Isometric muscle strength was assessed using a handheld dynamometer. Children were asked to walk for 6 min at comfortable speed. Spatio-temporal, kinematic and electromyographic (EMG) measurements were recorded at the first and the last minute of the 6-minute walking exercise. Muscle fatigue was evaluated using the shift of EMG signals median frequency. RESULTS There was no significant difference in walking speed, cadence, and step length at the end of the 6mwe. Maximal and mean anterior pelvic tilt decreased and knee flexion increased (p < 0.05). Rectus femoris EMG median frequency decreased (p < 0.05). The median frequency in other muscles did not decrease significantly. Greater hip extensor strength was associated with lesser knee flexion at the end of the 6-minute walking exercise (p < 0.05). SIGNIFICANCE The increase in knee flexion at the end of the 6-minute walking exercise can be explained by muscle fatigue found in rectus femoris. Hip extensor strength can limit the deterioration of crouch gait after a 6-minute walking exercise representative of daily activities.