Children with cerebral palsy (CP) commonly exhibit pathologic gait patterns. Crouch gait, which is
characterized by excessive stance phase knee flexion and may be accompanied by other deficits at the hip
and/or ankle, is a common and debilitating gait disorder in children with CP. Left untreated or inadequately
addressed, children with crouch gait will experience progressive gait deterioration, leading to a loss of
ambulation in a large portion of adolescents with CP. While crouch gait is one of the most frequently observed
gait deviations in children with CP, current intervention approaches including surgical and non-surgical have
not been optimized to effectively address these key gait deficits in many children with CP. Specifically, surgical
interventions, which typically target the hamstrings, remain the dominant interventions but outcomes are
variable across different studies. Similarly, muscle strengthening programs have been developed to improve
crouch gait, but studies showed inconsistent outcomes. Hamstrings botulinum toxin injections have been
shown to modestly improve knee kinematics 2 weeks post injection, but the effects mostly disappeared by ~12
weeks, leading to a repeated injections of botulinum toxin during growth. Robotic assistance has been used to
improve crouch gait in children with CP, although the effect was not retained after the removal of the
assistance force. Thus, there is a clear need for the development of new interventions for improving crouch
gait in children with CP, which requires a thorough examination of the motor learning mechanisms of the
interventions. The overall objective of this study is to determine whether the application of a targeted
resistance torque to the knee joint during overground walking will induce improvements in crouch gait in
children with CP. Our central hypothesis is that increasing errors by applying a targeted perturbation torque to
the knee joint during overground walking will facilitate motor learning and induce improvement in crouch gait in
children with CP. Specifically, in Aim 1, we will determine the effect of error size on motor learning to improve
crouch gait in children with CP. We expect to see a greater improvement in crouch gait in children with CP
after applying a targeted resistance torque to the knee joint during the swing phase of gait in comparison to
assistance torque during walking. In Aim 2, we will determine the effect of error variability on motor learning to
improve crouch gait in children with CP. We expect to see a longer retention of improved crouch gait in
children with CP after applying a varied resistance torque to the knee joint in comparison to a constant
resistance torque during overground walking. Results from this study are expected to demonstrate the effect
of error size and error variability on the motor learning of improved crouch gait in children with CP. The results
of this study are expected to have an important positive impact by providing a strong justification for the
development of an effective intervention for improving crouch gait in children with CP that is more effective
than the best physical interventions currently available.