Children with cerebral palsy (CP) have altered gait patterns as a result of primary and secondary symptoms. Ankle-foot orthoses (AFOs) are frequently used to improve their gait. Despite evidence of AFO-effects on gait kinetics and -kinematics, the effects on muscle activity remain unclear.

This study will investigate the effect of AFOs on the amplitude and timing, as well as the co-activation of lower limb muscle activity in children with spastic CP.

With a prevalence of two to three per 1000 live births, Cerebral Palsy (CP) is the most common motor disability of childhood. Improving disturbed gait in ambulatory children with CP is an important treatment goal because it is associated with functional independence and participation of children in the society. It is a common practice to prescribe ankle-foot orthoses (AFO) for ambulatory children to improve their gait, prevent secondary deformities, provide an improved base of support, and compensate for muscle weakness.

Previous research highlighted that there is a direct effect on the muscle activity of the distal muscles and an indirect effect on the proximal muscles. However, the impact of the AFO on the muscle activity of the plantar and dorsiflexors is clinically relevant since reduced muscle activity may lead to muscle atrophy and altered motor control. Therefore, more research is needed on the effect of AFOs on the medial gastrocnemius and the tibialis anterior, in both unilaterally and bilaterally involved children. Moreover, the impact of the AFO on the muscle activity of the quadriceps, apart from the hamstrings, needs to be further explored as well.

The purpose of the current study is to investigate the effect of the AFO on muscle activity in the distal and proximal leg muscles of children with CP while walking.

On the measurement day, subjects will first receive a standard clinical examination preceding the clinical overground three-dimensional gait analysis (3DGA) that is planned as a routine clinical follow-up at the CMAL (clinical motion analysis laboratory), extended with an additional 3DGA on the treadmill. The treadmill gait laboratory and overground gait laboratory are across the hall from each other, which makes it possible for the subject to walk from one to the other gait laboratory in just a minute. During the 3DGA, kinematic, kinetic and EMG-data will be collected.

Inclusion criteria:

• Gross Motor Function Classification System (GMFCS) level I - III
• CP (bilateral & unilateral)
• Age: 6 - 17 years
• Prescribed AFO by the medical team (as part of the standard care)

Exclusion criteria:

• Severe contractures or spasticity, which makes it impossible to wear a conventional AFO
• Cognitive or visual impairment that hinder them to understand instructions
• Previous surgery on bones and/or muscles of the legs in the last 12 months prior to assessment
• Presence of ataxia or dystonia

Ambulant children with cerebral palsy between 6 and 17 years old with a consistent gait pattern. They have prescribed ankle-foot orthoses by the medical team as part of the standard care.