Deficits in eccentric versus concentric torque in children with spastic cerebral palsy

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.

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).

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.

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.