Post-stroke exercise rehabilitation: What we know about retraining the motor system and how it may apply to retraining the heart
ABSTRACT
A plateau in recovery within the first few months of rehabilitative therapy was assumed to be the norm in stroke survivors. Recent studies in our laboratory examined the effect of 6 months of treadmill exercise training in chronically disabled stroke survivors. Treadmill exercise improves fitness and walking ability in patients when initiated 6 months or more following their index stroke. Functional imaging studies show that such exercise also induces subcortical reorganization in these patients. Future investigations will explore the relationship between these functional and structural effects and characterize the therapeutic mechanisms of post-stroke rehabilitation. Nonetheless, treadmill exercise appears to have motor, cardiac, and daily functional benefits in stroke survivors.
DISCUSSION AND CONCLUSIONS
Central control of walking
Control of gait in animals is mediated by the cortex, brainstem/cerebellum,9,10 and spinal cord—the so-called cervical gait and lumbar gait pattern-generating areas of the spinal cord. In humans, cortical and spinal gait pattern areas are thought to be major regulatory centers of ambulation. Whether the cortical areas influence ambulatory recovery mediated by exercise training or whether the recruitment of spinal gait areas is needed to improve motor control after stroke is not known in humans. We will test the hypothesis that the recruitment of cortical and/or subcortical areas is relevant to some or all of the exercise-induced neuroplasticity response to treadmill rehabilitation. If a consistent pattern of brain regional activation is associated with an improvement in walking ability, this finding will suggest potential brain targets for neurally directed rehabilitation interventions. If brain targets for rehabilitation produce viable therapeutic improvement in walking and cardiocirculatory performance (such as VO2), this will be further evidence of heart-brain interactions.
Future research directions
Studies to date demonstrate that long-term treadmill exercise affects both the brain and cardiac physiology. This has holistic implications for the function of the whole person as well. Yet several pressing issues continue to confront researchers in post-stroke rehabilitation. One is the optimal therapeutic target and the intensity of the rehabilitative effort. Is this improvement solely a response of muscle and cardiac tissue to exercise, or is it possible that improved neuromotor control is a critical component to a major recovery of walking function? Furthermore, the most efficacious elements of rehabilitative therapy are not known. Should treadmill training be high- or low-intensity, and should it be accompanied by strength training, agility and flexibility activities, or other elements directed at reacquisition of finer degrees of gait-related motor training and neuropsychological input, as achieved by tai-chi or yoga? Another issue is the proper dose of rehabilitative therapy, which has barely been explored, although recent preliminary work suggests that the response is dose-dependent. Finally, predictors of response have not been established because the mechanisms of therapy and surrogate markers for early response are not well understood.
Our future research plans are to assess whether a better understanding of neural targets for rehabilitative treatment will be a fruitful avenue to improve recovery. Additionally, this plan will assess whether fMRI can serve as a surrogate marker of recovery by offering a noninvasive means to measure response to rehabilitation.
