RESUMO
BACKGROUND: Children with spastic cerebral palsy (CP) have damage to the corticospinal tracts that are responsible for selective motor control (SMC). Force, velocity and timing of joint movement are related biomechanical features controlled by the corticospinal tracts (CSTs) that are important for skilled movement. RESEARCH QUESTION: Does SMC influence knee joint biomechanics in spastic CP? METHODS: In this prospective study, relationships between SMC and knee biomechanics (peak torque, total work, average power) across a range of velocities (0-300â¯deg/s) were assessed using an isokinetic dynamometer in 23 children with spastic CP. SMC was assessed using Selective Control Assessment of the Lower Extremity (SCALE). Logistic and linear regression models were used to evaluate relationships between SCALE and biomechanical measures. RESULTS: The ability to produce knee torque diminished with increasing velocity for both Low (0-4 points) and High (5-10 points) SCALE limb score groups (p < 0.01). More knees in the High group produced extension torque at 300â¯deg/s (p < 0.05) and flexion torque at 30, 90,180, 240 and 300â¯deg/s (p < 0.05). The ability to produce torque markedly decreased above 180â¯deg/s for Low group flexion. For knees that produced torque, significant positive correlations between SCALE limb scores and joint torque (0 and 120â¯deg/s), work (120â¯deg/s) and power (120â¯deg/s) were found (p < 0.05). Greater knee torque, work and power for the High group was found for the extensors at most velocities and the flexors for up to 120â¯deg/s (p < 0.05). Few Low group participants generated knee flexor torque above 120â¯deg/s limiting comparisons. SIGNIFICANCE: Biomechanical impairments found for children with low SMC are concerning as skilled movements during gait, play and sport activities occur at high velocities. Differences in SMC should be considered when designing individualized assessments and interventions.