Electromechanical delay and reflex response in spastic cerebral palsy

Objective: Electromechanical delay (EMD) and reflex response in patients wi th spastic cerebral palsy (CP) were quantified and compared with those in n ormally developing individuals. It was hypothesized that the increased musc le stiffness associated with spasticity must make EMD shorter than the EMD of normally functioning muscles. Design: Electromechanical reflex behavior was assessed in a case-control st udy. Setting: Motion Analysis and Motor Performance Laboratory, University of Vi rginia, a tertiary clinical referral center and research facility. Participants: A volunteer sample of 12 children diagnosed with spastic CP a nd 12 age-matched, normally developing children recruited from the local co mmunity and clinical services. Results: EMD in the patients with spasticity was significantly shorter than in the normally developing subjects, 40.5 msec and 54.7 msec, respectively . The spastic group also had greater reflex activity, rate of force develop ment, and antagonistic muscle activation. Knee flexion angle did not influe nce EMD in either group. Conclusions: Increased biomechanical stiffness in spastic muscle results in abnormally reduced EMD. Reciprocal excitation of antagonistic cocontractio n was uniquely observed in the spastic group, but did not explain the reduc ed EMD.