Physical, Functional and Neural Effects of Two Lower Extremity Exercise Protocols in Children With Cerebral Palsy

Background: * Many people who have cerebral palsy (CP) have spastic diplegia, which affects the legs and causes difficulty with leg movement and walking. Research has shown that exercise can help those with CP learn to move their arms better, but more research is needed to determine whether exercise programs can improve leg movements in people with CP. * Walking on a treadmill with the help of a physical therapist has improved the treatment outcomes of some individuals with spinal cord injuries. Many children with CP already have physical therapy but still have trouble with walking and leg coordination. Two other kinds of exercise machines, a stationary bicycle and an elliptical machine, used in the home, may be able to help children with CP walk better and move their legs better. Objectives: * To see how children with cerebral palsy (CP) move their legs differently from children without CP. * To see if an exercise program can improve leg coordination in children with CP. Eligibility: \- Children between 5 and 17 years of age who either have spastic diplegia CP or are healthy volunteers. Design: * Children who are able and willing will have magnetic resonance imaging (MRI) scans at the start and the end of the study. * During Part I of the study, participants will demonstrate their leg and muscle function with the following tests: * Measurement of leg size and movement * Combined camera motion study and electrical impulse evaluation to assess how well the participant walks (with or without an assistive device, as needed) * Leg movement tests on an exercise bicycle and elliptical machine * Tests of leg muscle strength, stiffness, and effectiveness * Ultrasound scans of leg muscle * Parents of participants will complete computer-based questionnaires about their child s motor abilities. * A smaller group of participants will continue to Part II of the study, which involves regular exercise of 20 minutes a day, 5 days a week, for 3 months, on a stationary bicycle