Quadriceps Muscle Plasticity in Children With Cerebral Palsy

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.

cerebral palsy, muscle strength, muscle architecture, ultrasound, rehabilitation, rectus femoris, quadriceps muscle

Performed 3 x week for 8 weeks on an isokinetic dynamometer (knee extension exercise)at 30 degrees/second; 6 sets of 5 maximum-effort concentric actions

Performed 3 x week for 8 weeks on an isokinetic dynamometer (knee extension exercise). Subjects will perform 2 sets of 5 concentric exertions at 30°/second. The following 4 sets of 5 repetitions will be performed at a faster speed, starting at 60° /second. The velocity will be increased weekly in 15° /second increments up to a maximum of 120°/second.

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

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