Reflex excitability and isometric force production in cerebral palsy: The effect of serial casting

Abstract

During passive dorsiflexion, the angle of stretch-reflex onset was earlier in the dorsiflexion range for children with spastic cerebral palsy (CP) (N = 10) compared with controls (P < 0.001) at comparable velocities of stretch. Isometric plantar-flexor force was lower in children with CP (P < 0.0001) and a leftward shift in the length-tension curve reflected that peak forces were produced in greater plantar flexion in children with CP than in controls (P < 0.0001). Seven children with CP underwent 3 weeks of serial casting resulting in increased dorsiflexion at postcasting and at 6 weeks follow-up (P < 0.002). There was no associated loss in plantar-flexor strength (P > 0.32), but increased reflex threshold (P < 0.03) and a decline in restraint to imposed stretch (P < 0.002) were evident. A rightward shift in the length-tension curve illustrated that peak tension was generated in dorsiflexion rather than plantar flexion following casting (P < 0.001). The gains were still evident at follow-up although generally to a lesser extent.