| Muscle weakness is one of many impairments that can be present in children with cerebral palsy (CP). Electrical stimulation of skeletal muscle has been used as a treatment modality in children with CP; however it has been largely used as a functional assist during gait, standing, and reaching and no one has reported using high-intensity neuromuscular electrical stimulation (NMES) for muscle strengthening. The overall goal of this dissertation was to identify if NMES was effective at increasing force production of the quadriceps femoris and triceps surae muscles in children with spastic diplegic CP.; In the first study, the voluntary muscle activation, contractile properties, and fatigability of the quadriceps femoris and triceps surae were characterized in children with and without CP. Deficits in force production for knee extension and ankle plantarflexion of the children with CP was, in part, a result of decreased voluntary muscle activation of the quadriceps femoris and triceps surae muscles and increased coactivation of the antagonist semitendinosus and tibialis anterior muscles, respectively. Children with and without CP had similar contractile and relaxation speeds; however, children with CP demonstrated less quadriceps femoris fatigue.; In the second study, NMES and volitional strength training were compared in a group of children with spastic diplegic CP. Each group performed an exercise program that was matched for the number and duration of isometric muscle contractions. The NMES group achieved larger gains in knee extension and ankle plantarflexion force as compared to the volitional group.; In the third study, the mechanisms behind changes in force production in the NMES and volitional groups were examined by measuring voluntary muscle activation of the agonists, coactivation of the antagonists, and the maximum cross-sectional area (CSA) of the quadriceps femoris and triceps surae. Children who strength-trained volitionally showed an increase in voluntary muscle activation of the quadriceps femoris and neither group demonstrated consistent changes in antagonist coactivation. Children in the NMES group; however, demonstrated a greater increase in quadriceps femoris maximum CSA. When treatment and muscle groups were combined, however, only changes voluntary muscle activation of the agonists were related to changes in force production. |
