Investigator: Carolynn Patten, PhD PT Project Staff: Felix E. Zajac, PhD and Kevin C. McGill, PhD Project Category: Stroke - 2000 The overriding goal of this research is to draw an association between physiological impairment and movement disability in persons with post-stroke hemiplegia. The relationship between impairment and disability is not direct, thus many questions remain regarding the effectiveness of rehabilitative treatments which focus at the impairment level. Similarly, interventions targeted at disability apparently disregard fundamental physiological mechanisms understood as l to movement control. This project is intended to elucidate the contribution of neuromuscular control mechanisms to performance of functional movements. Methods: Needle and fine-wire electrodes are used to investigate the discharge behavior of motor units in the vastus medialis during both isometric and anisometric muscular contractions. All observations are made in persons with post-stroke hemiparesis demonstrating two distinct levels of recovery (CVA-I: Brunnstrom Levels V-VI and CVA-II: Brunnstrom Levels III-IV) and compared against control subjects. Control of functional movements is assessed in all three participant groups. Locomotor activities (gait at self-selected walking speed, and fast gait) are observed using 3-D digital motion analysis (Qualisys) techniques to quantify kinematics and force plate analysis to quantify kinetics. Findings: To date, 21 subjects have been studied: 8 controls, 7 hemiparetic subjects at the CVA-I level and 6 hemiparetic subjects at the CVA-II level. Reduced gait velocity at self-selected pace (SSWS) corresponds with severity of hemiparesis (.93 m/s CVA-I, .68 m/s CVA-II vs 1.44 m/s controls). While all subjects produce significantly increased gait velocity during the fast condition (CVA-I 1.15 m/s, CVA-II 1.0 m/s, Controls 1.94 m/s), hemiparetic subjects fail to reach normal gait velocity observed in control subjects at SSWS. In hemiparetic subjects increased gait velocity is mediated by a significant increase in cadence (19%) while control subjects increase gait velocity through both increased stride length (16%) and increased cadence (12%). The dependence on cadence to increase gait velocity is pronounced in the more impaired CVA-II subjects. Ongoing investigation is examining the association between these parameters of locomotor activity, motor unit firing patterns, contralateral limb influences and indices of relative weakness between the involved and non-involved limbs of hemiparetic persons. Clinical Relevance: Stroke, or cerebrovascular accident (CVA), affects 2.1 million individuals in the United States annually, a third of whom suffer from significant physical disability and impairment of movement function. A prominent sequela of stroke is muscular weakness and disruption of normal force modulation mechanisms. Weakness is significant for its role in the production of purposeful movement such as gait while accurate force modulation is significant with regard to the quality of movement and ability to grade force appropriately within movements. The relationship between impairment and movement disability is not well understood and therefore limits the effectiveness of clinical rehabilitation practice. Findings of this research will improve our ability to determine the rehabilitation potential of persons with post-stroke hemiparesis and further, will improve the efficiency of clinical practice by targeting interventions to address specific impairments affecting movement disability. Funding Source: Foundation for Physical Therapy |
