- 1. Diagnosis of Cerebral Palsy 2. Spasticity at extensor muscle groups of one or both ankles according to the definition of the Task Force on Childhood Motor Disorders, and as evidenced by the presence of a spastic catch or velocity-dependent hypertonia on rapid passive muscle lengthening while the subject attempts to maintain a relaxed state 3. Ambulatory without assistive devices 4. Sufficient ability to follow instructions to be able to comply with the strengthening program and strength testing