Deficits in eccentric versus concentric torque in children with spastic cerebral palsy
D L Damiano1, T L Martellotta, J M Quinlivan
1Department of Orthopaedics, University of Virginia, Charlottesville, USA. dld6830@bjc.org
Insights
Children with spastic cerebral palsy (CP) exhibit reduced knee and ankle torque, with greater deficits in concentric than eccentric muscle actions. Spasticity impacts voluntary force production, showing a bias toward eccentric torque and greater concentric torque decline across speeds.
Area of Science:
- Neurology
- Pediatrics
- Biomechanics
Background:
- Cerebral palsy (CP) is a common neurodevelopmental disorder affecting motor function.
- Spasticity, a hallmark of CP, influences muscle properties and voluntary force generation.
- Understanding force production deficits is crucial for targeted rehabilitation in ambulatory children with CP.
Purpose of the Study:
- To assess isokinetic eccentric peak torque abnormalities in ambulatory children with spastic CP at the knee and ankle.
- To investigate the impact of spasticity on voluntary force production in this population.
- To compare eccentric and concentric torque deficits across different muscle groups and speeds.
Main Methods:
- Isokinetic testing of knee and ankle muscles (extensors, flexors, dorsiflexors, plantarflexors) in 24 children with spastic CP and 20 typically developing children.
- Measurement of eccentric peak torque at 30°/s and concentric peak torque at 30°/s, 60°/s, and 120°/s using a Biodex dynamometer.
- Normalization of peak torque values by body weight and calculation of eccentric to concentric (E/C) peak torque ratios.
Main Results:
- Children with spastic CP showed significantly decreased eccentric and concentric peak torques in all tested muscle groups.
- The relative deficit in eccentric torque was smaller than in concentric torque.
- Concentric torque decrements across speeds were more pronounced in children with CP, except for ankle dorsiflexors; E/C ratios were higher for knee muscles.
Conclusions:
- Ambulatory children with spastic CP demonstrate diminished eccentric and concentric peak torques at the knee and ankle.
- Spasticity influences voluntary force production, characterized by a tendency towards greater eccentric torque and a more significant decline in concentric torque across increasing speeds.
- These findings highlight the complex neuromuscular adaptations in spastic CP and inform therapeutic strategies focused on improving force generation capacity.
Purpose:
The purposes of this study were to determine whether ambulatory children with spastic cerebral palsy (CP) had abnormal isokinetic eccentric peak torque values at the knee and ankle, and to gain further insights on the influence of spasticity on voluntary force production in this population.
Methods:
Twenty-four children with spastic CP (mean = 11.1+/-2.6 yr) and twenty children of comparable age with no neuromotor pathology (mean = 10.3+/-2.6 yr) participated in an isokinetic testing protocol on a Biodex dynamometer that measured eccentric and concentric peak torques of the knee extensors, knee flexors, ankle dorsiflexors, and ankle plantarflexors. Angular velocity of the eccentric trials was 30 degrees x s(-1) and of the concentric trials was 30 degrees x s(-1), 60 degrees x s(-1), and 120 degrees x s(-1). Peak torque values were normalized by body weight and compared across groups by using ANOVA procedures. Eccentric to concentric (E/C) peak torque ratios at 30 degrees x s(-1) were computed for each muscle and compared across groups. The torque values in CP were also expressed as a percent of the mean normalized value of the comparison group and compared across conditions using repeated measures ANOVA (P < 0.05).
Results:
Children with CP demonstrated decreased eccentric and concentric peak torques for all muscle groups tested. The relative deficit in eccentric torque was less than the concentric torque and the decrement in concentric torque across speeds was greater in CP for all muscle groups except the ankle dorsiflexors. The E/C ratios for the knee extensors and flexors were also greater in CP.
Conclusions:
Children with CP have diminished eccentric as well as concentric peak torques at the knee and ankle. The influence of spasticity on voluntary force production can be inferred from the bias toward greater eccentric torque and the greater decrement in concentric torque across speeds in children with spastic CP.
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