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Selective voluntary motor control influences knee joint torque, work and power in children with spastic cerebral
Eileen G Fowler1, Andy Vuong2, Loretta A Staudt2
1Center for Cerebral Palsy at UCLA/Orthopaedic Institute for Children, Department of Orthopaedic Surgery, 22-70 Rehab Center, David Geffen School of Medicine, University of California at Los Angeles, 1000 Veteran Ave, Los Angeles, CA 90095-1795, USA; Tarjan Center at UCLA, USA.
Insights
Selective motor control (SMC) significantly impacts knee joint biomechanics in children with spastic cerebral palsy (CP). Impairments in SMC correlate with reduced torque, work, and power, especially at higher movement velocities.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Pediatric Physical Therapy
Background:
- Children with spastic cerebral palsy (CP) exhibit corticospinal tract damage affecting selective motor control (SMC).
- Corticospinal tract (CST) function is crucial for regulating joint movement force, velocity, and timing, essential for skilled motor actions.
Purpose of the Study:
- To investigate the relationship between selective motor control (SMC) and knee joint biomechanics in children with spastic cerebral palsy (CP).
Main Methods:
- A prospective study involving 23 children with spastic CP assessed SMC using the Selective Control Assessment of the Lower Extremity (SCALE).
- Knee joint biomechanics, including peak torque, total work, and average power, were measured across velocities from 0-300 deg/s using an isokinetic dynamometer.
- Logistic and linear regression models analyzed the association between SCALE scores and biomechanical parameters.
Main Results:
- Knee torque production decreased with increasing velocity in both low (0-4 SCALE points) and high (5-10 SCALE points) score groups.
- The high SCALE group demonstrated greater knee extension torque at 300 deg/s and flexion torque across multiple velocities compared to the low SCALE group.
- Positive correlations were observed between SCALE scores and knee torque, work, and power at specific velocities (0-120 deg/s), particularly for the high SCALE group.
Conclusions:
- Biomechanical deficits associated with low SMC in children with CP are significant, impacting high-velocity movements crucial for daily activities like gait, play, and sports.
- Individualized assessments and interventions for CP should consider variations in SMC to address specific biomechanical impairments effectively.
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 (0-300 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 300 deg/s (p < 0.05) and flexion torque at 30, 90,180, 240 and 300 deg/s (p < 0.05). The ability to produce torque markedly decreased above 180 deg/s for Low group flexion. For knees that produced torque, significant positive correlations between SCALE limb scores and joint torque (0 and 120 deg/s), work (120 deg/s) and power (120 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 120 deg/s (p < 0.05). Few Low group participants generated knee flexor torque above 120 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.
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