Can we unmask features of spasticity during gait in children with cerebral palsy by increasing their walking velocity?

•Spasticity is commonly measured in a passive condition.•Signs of spasticity may be highlighted when increasing walking velocity.•We compare gait parameters at different walking velocities in CP and TD children.•CP children used a different strategy than the TD children to increase their walking velocity.

Background and aimSpasticity is a velocity dependent feature present in most patients with cerebral palsy (CP). It is commonly measured in a passive condition. The aim of this study was to highlight markers of spasticity of gastrocnemius and hamstring muscles during gait by comparing the effect of increased walking velocity of CP and typical developing (TD) children.Methods53 children with spastic CP and 17 TD children were instructed to walk at self-selected speed, faster and as fast as possible without running. Kinematics, kinetics and electromyography (EMG) were collected and muscle length and muscle lengthening velocity (MLV) were calculated. To compare the data of both groups, a linear regression model was created which resulted in two non-dimensional gait velocities. A difference score (DS) was calculated between the high and low velocity values for both groups.Results103 gait parameters were analyzed of which 16 had a statistically significant DS between TD and CP groups. The spastic gastrocnemius muscle presented at high velocity with a higher ankle angular velocity, plantar flexion moment, power absorption and increased EMG signal during loading response. The spastic hamstrings demonstrated at high velocity a delayed maximum knee extension moment at mid-stance and increasing hip extension moment and hip power generation. The hamstrings also presented with a lower MLV during swing phase.ConclusionsA limited number of gait parameters differ between CP and TD children when increasing walking velocity, giving indirect insight on the effect of spasticity on gait.