Effect of Functional Power Training on Calf Muscle Length and Strength in Children With Spastic Paresis

Spastic paresis (SP) is a common motor condition in children and is often caused by cerebral palsy. Skeletal muscles develop differently in children with SP due to brain damage in early development; muscle strength and muscle length are reduced compared to typically developing (TD) children. Especially, the calf muscles are affected, which particularly affects their ability to walk and to run, hindering participation in society. There are several treatments aimed to increase the range of motion of the joint by lengthening the muscle, for example botulinum toxin injections. However, these treatments can have a weakening effect on the muscle due to deconditioning from immobilization and due to paralysis. In rehabilitation centers in the Netherlands functional power training (MegaPower) is offered to children with SP who want to walk and run better. It has been shown that this training improves calf muscle strength and performance during functional walking tests. However, the effect of MegaPower training on muscle morphology (i.a. muscle volume and length) is still unknown. Therefore, the aim of this study is to assess the effect of MegaPower training on the muscle morphology of the medial gastrocnemius in children with SP using 3D ultrasonography. It is expected that MegaPower training results in an increase of muscle volume as well as elongation of the muscle belly. Muscle volume could increase due to hypertrophy of the muscle fibers induced by the training, which could elongate the muscle belly length due to the pennate structure of the medial gastrocnemius. A double-baseline design will be applied for this study with three different measurement times (T0-T1-T2) to compare the training period (12 weeks) with a period (12 weeks) of usual care.