Samuel C-K Lee - US grants

DESCRIPTION (provided by applicant): Cerebral palsy (CP) has the highest lifetime economic cost and net cost of medical care compared to the most common birth defects. Reduced muscle strength affects functional abilities in children with CP. Volitional strength training in children with CP can produce substantial gains in force production with concomitant gains in function. Volitional strength training, however, may not be optimal for producing strength gains in this population due to reduced voluntary muscle activation. Neuromuscular electrical stimulation (NMES) activates a greater number of motor units and produces higher firing rates of the active motor units than can be obtained volitionally. Thus, NMES may offer advantages over volitional exercise programs for producing gains in force production. The proposed research is designed to develop improved rehabilitation techniques for children with CP. This study compares the effects of a 12-week NMES isometric strength-training program to 12 weeks of traditional isometric strength training in children with CP. A no-exercise control group with CP will also be studied. The specific aims are: 1) To compare the force generating, volitional activation, contractile and fatigue characteristics of the quadriceps femoris and triceps surae muscles in typically developing children and children with CP; 2) to assess the ability of NMES strength training to increase quadriceps femoris and triceps surae muscle force-generating ability as compared to volitional strength training and a no-exercise control group in children with CP; 3) to assess the mechanisms underlying improvements in force-generating ability of the quadriceps femoris and triceps surae after strength training in children with CP; and 4) to assess the ability of strength training to improve gross motor function and gait in children with CP. This work will help clinicians design rehabilitation strategies based on the physiologic differences in skeletal muscle and mechanisms for force production between children with CP and children of typical development. Increasing muscle force-generating ability of children with CP can improve a child's function during activities such as sitting, standing and walking.

DESCRIPTION (provided by applicant): Cerebral palsy (CP) is a non-progressive developmental disorder of the brain that results in reduced strength which negatively affects functional abilities and limits levels of activity. Lack of involvement in physical activity is one of the leading health concerns in the US and is associated obesity, cardiovascular disease, diabetes and other chronic diseases. The need for activity and exercise is especially acute for youth with physical disabilities, who participate in less physical activity than their non-CP peers and thus are at more risk for declines in health. The impact of having fewer options for activity is particularly detrimental for children with CP who tend to peak in ability prior to adolescence and then decline through their teenage years into adulthood. One major cause of decline is the disparity that occurs when muscle strength gains due to growth are not commensurate to gains in body size or weight. The disparity is often exacerbated by the interventions used to abate musculoskeletal and soft tissue changes that contribute to deformity, muscle tightness and joint contractures. Thus, children with CP have an overwhelming disadvantage for maintaining and improving strength, fitness and function. Stationary cycling is a proposed method of exercise for individuals that lack the balance, strength and coordination for upright exercise; however, we demonstrate that individuals with CP have impaired biomechanics that limit their cycling output. To enable greater cycling output, we employ functional electrical stimulation (FES) assistance and demonstrate the ability of FES assistance to produce higher heart rates, power output and cadences than children with CP are able to achieve on their own. Additionally, FES assistance enables cycling at a target powers for longer durations with less variance in cadence, however other than our initial investigations; we are unaware of any studies involving FES-assisted cycling in CP. The objective of this project is to improve physical conditioning and general lower extremity muscle strength for adolescents with CP using FES-assisted cycling. A prospective single blind, randomized controlled grouped experimental design will be conducted to investigate the relative effects of recumbent cycling training using volitional effort vs. training with volitional effort augmented by FES assistance compared to non-intervention controls on physical conditioning, muscle strength, and walking ability in adolescents with spastic CP and marginal walking ability. Both central and peripheral mechanisms for improvements in cycling performance will be investigated.