Cerebral Palsy (CP) is a non-progressive disorder caused by a lesion in the brain. Spasticity and passive muscle stiffness are common symptoms which lead to joint contractures and functional impairments.

Fascicle length, and muscle- and fascicle excursions were compared between children with CP and typically developing (TD) children. Fascicles were found to be shorter and relative muscle- and fascicle excursions were greater in children with CP compared to TD children. We concluded that short fascicles and great fascicle excursions could be a contributing factor to muscle weakness and joint contractures in children with CP.

Botulinum Toxin Type-A (Botox) is used to reduce spasticity in children with CP, but the effects of Botox on passive muscle stiffness are not clear. We found no difference in passive muscle stiffness before and five days following Botox injection. We concluded that it is important to distinguish between passive stiffness and spasticity before Botox is used to treat children with CP.