Originally written for Heart and Stroke Foundation Center for Stroke Recovery: January 2012 Newsletter
CSR researcher to investigate how exercise helps stroke recovery, study what “dose” of exercise is most effective
Exercise may help stroke survivors avoid a second stroke and accelerate their recovery. “However, we need to know more about why exercise has such a positive effect, and what kinds of exercise are most helpful,” says Dr. Bradley MacIntosh, Neuroimaging Scientist at Sunnybrook Health Sciences Centre.To find out, he and his colleagues are launching an ambitious study called Exercise and the Brain: Neurovascular underpinnings of exercise after stroke.
“Many people don’t realize that exercise is useful in preventing stroke,” says Dr. MacIntosh. “They think of exercise as being good for the heart and for losing weight – not for brain health. But exercise does help protect from stroke. It also reduces stroke survivors’ risk of having subsequent events. So exercise on its own is a preventative ‘drug’ or ‘intervention’ in a sense.”
Exercise also seems to play a role in recovery. Dr. MacIntosh and his colleagues will examine how exercise alters the regulation of genes and whether it stimulates the formation of new blood vessels (a process known as angiogenesis) and new brain cells (neurogenesis) – both vital in stroke recovery.
“Laboratory studies suggest that exercise does increase neurogenesis and angiogenesis,” says Dr. MacIntosh. “However, we are not sure why or how this happens. Our study will allow us to “connect some of the dots” between what we see in the lab and what happens as patients’ brains recover from stroke injuries.”
For their study, Dr. MacIntosh and his team are considering a unit of exercise as a drug and each exercise session as a dose of that drug. They also plan to vary exercise intensity, asking participants to exercise at either low or moderate levels of intensity. A low-intensity exercise session will be considered as one pill and a moderate-intensity session as two pills.
“We need to understand how the brain’s blood supply is altered by exercise,” says Dr. MacIntosh. “To do this, we hope to measure changes in the brain’s blood vessels caused by a single exercise session. At the same time, we are testing whether the imaging techniques we use are sensitive enough to measure the effects of a single session of exercise.”
Dr. MacIntosh will be studying levels of a biochemical (brain-derived neurotrophic factor or BDNF) produced during exercise and linked to the formation of new brain cells. Because BDNF is produced in greater amounts by people with a certain genetic profile, researchers will study the relationship between production of BDNF and individuals’ genes, as well as their environments and other factors.
“We are also going to measure blood flow to the brain,” says Dr. MacIntosh. “We’re doing this at multiple time points to figure out when perfusion response is greatest after exercise. We’ll also be looking at brain function after exercise to learn which areas of the brain are connected to each other. We suspect the areas that are affected by exercise are going to be ‘talking to each other,’ so we’re going to see an increase in the connections between these specific regions of the brain after a dose of exercise. Finally, we will further quantify short-term effects of exercise in stroke survivors.”
Positive results from this experiment will pave the way for new approaches to stroke rehabilitation—that is, application of exercise to enhance brain recovery and reorganization after stroke. The study is now underway, and researchers hope to finish data collection within two years.
“We are hopeful that an exercise training program may result in short-term changes in the selected measures,” concludes Dr. MacIntosh. “These in turn may predict long-term changes in the brain associated with improved recovery.