The dynamics of gait in children with spastic hemiplegic cerebral palsy: Theoretical and clinical implications

previously, we suggested that neurological insults will change the dynamic resources available to an individual, and a pattern will emerge that is spe cified by, and facilitates the use of the available resources [K.G. Holt, J . Obusek, S.T. Fonseca, Human Movement Science, 15 (1996) 177]. Dynamic res ources refer to the sources of energy (e.g., muscular force, elasticity ene rgy return from soft tissues, and pendulum-like transfers) that are availab le to an individual to perform a function. It was hypothesized that in chil dren with spastic hemiplegic cerebral palsy (CP), neurological impairments would result in increases in global body stiffness on the affected side tha t could be quantified using an escapement-driven, damped hybrid pendulum an d spring model. It was also hypothesized that increases in stiffness and an assumed decrease in the forcing capability would result in, respectively, a decreased stance time on the affected side, and smaller angular displacem ent of the body center of mass around the ankle joint. Five children with s pastic hemiplegic CP and five age, height and weight matched non-disabled c hildren walked overground at their preferred speed and at metronome-driven frequencies that were +/-10% acid +/-20% of their preferred. Significantly greater stiffness on the affected limb of CP was found when compared to the non-affected limb, and to the limbs of non-disabled children. Significantl y smaller amplitudes and shorter stance periods on the affected side were a lso observed. Results provide initial support for the claim that gait patte rns and their adaptations reflect the capability of persons with disabiliti es to exploit the dynamic resources available to them. These findings raise two issues for discussion. First, we discuss the clinical implications of the notion that dynamic resources provide a causal link between the neurolo gic and morphologic changes due to upper motor neuron diseases and abnormal kinematics of gait. Second, we discuss the broader implications of biomech anical modeling in the ability to lawfully capture the interplay of the rel evant constraints that contribute to the emergence of specific movement pat terns. (C) 2000 Published by Elsevier Science B.V. All rights reserved. Psy cINFO classification. 2330; 3297; 3380.