Principal Investigator: Carolynn Patten, PhD, PT Project Staff: Kevin C. McGill, PhD; Garry E. Gold, MD; David C. Tong, MD; C. Maria Kim, MSc, PT; Jody M. Dozono, MPT; and Christine A. Dairaghi, BS Project Category: Stroke - 2004 Objective: The long-term goal of this research is to develop efficient and effective therapeutic interventions for rehabilitation of persons with post-stroke hemiparesis. Key to attainment of this goal is demonstration of the physiologic mechanisms mediating adaptation to therapeutic intervention and understanding their effects on functional motor activity. We know of no studies systematically examining simultaneous training-related effects and adaptations in physiologic mechanisms mediating these effects, thus results of this study will provide sound, scientific evidence of physiologic mechanisms responsible for weakness, evidence of the processes involved in neuromuscular adaptation, and will elucidate the relationship between impairment and motor disability in post-stroke hemiparesis. This information will form a basis for prescription of appropriate, focused, timely, and effective clinical interventions. Research Plan and Methods: In this project, we investigate the effects of resistance exercise with eccentric loading on recovery of locomotor function in persons with post-stroke hemiparesis. These effects are compared with subjects who participate in a control intervention of concentric resistance exercise. We are conducting a controlled, randomized, double blind, staged clinical trial of: 1) high-intensity resistance training followed by 2) gait training. Over two years we will study 36 hemiparetic persons in the subacute phase of recovery (6 - 18 months post-stroke). Subjects are evaluated for functional status including: clinical assessments, lower extremity strength, intermuscular coordination patterns, motor activation, and gait function. This full battery of assessments is performed at baseline, following resistance training, following gait training and at six and twelve months post-treatment. Motor unit firing patterns will be studied in a subset of subjects to better understand training-related adaptations in the neuromuscular mechanisms of force regulation. Clinical Relevance to the VA: There is growing evidence that weakness, rather than spasticity, is the predominant impairment following stroke, and recent research has called for more work addressing the role of muscular strength in rehabilitation of persons with post-stroke hemiplegia. Despite little direct evidence, it is broadly speculated that weakness in post-stroke hemiparesis results from impaired neuromuscular activation. Thus it remains a significant question of both clinical and scientific merit whether activation impairment can be significantly reduced in hemiparetic persons, whether such a reduction translates to clinically meaningful improvement in locomotor function and whether such improvement leads to increased activity levels and persists over time. Progress Report and Findings to Date: Twenty-eight subjects have completed the training aspect of the project, to date. We have found that all subjects increase gait speed significantly in response to strength training. Additional gains in gait speed are observed following the gait training portion of the study. We do not yet have an appropriate sample size to determine whether differential effects are present between the concentric and eccentric resistance training groups. We have also observed marked reductions in neuromuscular activation impairment following the therapeutic intervention. Our focus for analysis in the upcoming project year will include identifying the key neuromuscular mechanisms involved in increased strength and how these adaptations contribute to improved locomotor function. Research Plan for the Next Year: Patient recruitment and treatment is projected for completion in May of this year. We will continue to perform follow up studies on all subjects through the third and final year. Data analysis and initial dissemination efforts will be performed this year. We project at least three manuscripts from the baseline cross-section studies will be submitted this year. Funding Source: RR&D Merit Review Funding Status: Active |
