Cerebral palsy is a common neuro-developmental disorder. Among other signs of upper motor neuron syndrome, walking pathologies and muscle weakness are leading signs of disability in children with cerebral palsy. Moreover, the gradual decline in muscle strength is part of the aging process and can be particularly devastating for people with motor disabilities. Therefore muscle-strengthening programs are indicated for children with cerebral palsy. There is evidence that lower extremity muscle strength can be increased by Progressive Resistance Training (PRT) in children with cerebral palsy. However, PRT is time consuming and therefore not always feasible for children with neurologic disorders. Moreover, it does not influence the anaerobic capacity needed for everyday activities in children. High Intensity Interval Training (HIIT) is a time efficient method, which increases both aerobic and anaerobic capacities. The aim of this randomized, stratified, single-blinded study is to compare two home based strength-training protocols (HIIT and PRT) and their effects on muscle strength, gait and aerobic and anaerobic capacity in children with cerebral palsy.