Our primary aim is to determine whether and how muscle architecture of the quadriceps muscles in cerebral palsy (CP) adapts to two separate training programs: traditional strength training (ST) vs. velocity-enhanced training (VT). For the ST group, we hypothesize that muscle size will increase in conjunction with strength. For the VT group, in addition to the above, we hypothesize that fiber length will increase with measures of muscle power. We also hypothesize that walking velocity will improve in both groups but that knee motion and step length will improve only with VT.

Cerebral palsy (CP) is the most common physical disability originating in childhood, occurring in 2-3 per 1,000 live births. Although the primary deficit in CP is injury to the brain, secondary impairments affecting muscle function such as weakness, contractures, and spasticity are often far more debilitating and lead to worsening disability throughout the lifespan. Some have suggested that these muscle changes in CP may be irreversible; however, it is now known that muscles are one of the most 'plastic' tissues in the body. In fact, recent evidence suggests that gross muscle hypertrophy and architectural changes within muscle fibers can occur as early as 3-5 weeks after resistance training in healthy adults. It is also unknown how effectively muscles in CP can adapt to training stimuli that target specific muscle architectural parameters, such as fascicle length and cross-sectional area. These parameters have been observed to be decreased in CP, suggesting loss of sarcomeres in-series (fiber shortening) and in-parallel (muscle atrophy). We propose here that specific training-induced muscle architectural adaptations can occur in CP, leading to improved motor function.

Inclusion Criteria:

• Diagnosis of cerebral palsy
• Gross motor function classification system levels I, II, or III
• Ages 7 to 17

Exclusion Criteria:

• Orthopedic or neurosurgery within the past year
• Botulinum toxin injections within the 4 months prior to the study