Differential Adaptations of Muscle Architecture to High-Velocity Versus Traditional Strength Training in Cerebral Palsy

Background. Everyday activities for youth with cerebral palsy (CP) require muscle power, but the velocity component of muscle contraction is neglected with traditional strength training (ST). Objective. To determine whether velocity training (VT), which includes resistance training at increasingly higher velocities, would induce specific muscle adaptations not observed with ST. Methods. Sixteen ambulatory youth with CP were randomized to VT or ST. Participants trained the knee extensors 3 times per week for 24 sessions on a Biodex dynamometer. At each session, 6 sets of 5 concentric repetitions were performed either at 30 deg/s (ST group) or progressively higher velocities from 30 deg/s to 120 deg/s (VT group). Outcomes included muscle architecture, power, strength, walking speed, and functional walking performance. Results. A significant increase in rectus femoris fascicle length was observed after VT with a decrease after ST. Rectus femoris cross-sectional area increased in both groups. Both showed significant increases in isokinetic strength at all tested speeds; however, peak velocity and power improved after VT only. Self-selected and fast walking speed and functional walking performance improved after VT only. Conclusions. Muscle architecture in CP is capable of adapting differentially to the training stimulus. VT was equally effective as traditional ST in improving isokinetic strength of the knee extensors but more effective in improving velocity of movement, muscle power, and walking performance. Differences may be partially attributed to specificity of training effects on muscle architecture, such as the increase in fascicle length after VT. Strengthening interventions involving higher velocity movements should be incorporated into clinical practice.