White Coat, Black Art·DR. BRIAN'S BLOG

Aerobic exercise helps your brain too, says study

Aerobic exercise is good for your heart. A study shows how regular exercise rebuilds brain tissue and plausibly may help stave off dementia.
Parts of the brain most affected by exercise in a recent study were those engaged in cognition or thinking. (Nicholas Kamm/AFP/Getty)

I run 10 kilometres three times a week. I do it as much to keep my mind sharp as to strengthen my heart and my body.

The beneficial effect on your heart of jogging, cycling or swimming is well-known. A study published last week in the journal Mayo Clinic Proceedings concludes that regular exercise is also good for your brain.  

Katharina Wittfeld and colleagues from the German Center for Neurodegenerative Disease studied 2,103 adults ages 21 to 84 years between 2008 and 2012. They evaluated aerobic fitness by measuring the peak oxygen uptake. They also tested the research subjects' maximal power output while exercising on a bicycle ergometer. Those measures were designed to test that participants were doing enough aerobic exercise to make certain it was having a beneficial effect on the heart.

The researchers did MRI scans to assess the impact on the brain. The researchers found that increases in peak oxygen uptake were associated with increased volume of grey matter (brain tissue) as seen on MRI scans.

The most striking finding is that the parts of the brain most affected by exercise were those engaged in cognition or thinking rather than, say, movement. The other good thing about the findings is that exercise benefited research subjects of all ages, especially those over the age of 45.

The researchers say there are several potential mechanisms that might explain the findings. Studies have shown that physical activity increases the release of natural anti-inflammatory factors. Scientists have long believed that inflammation of brain tissue causes memory loss. Exercise also increases blood flow in the brain. Studies also show that aerobic exercise may also boost the body's production of chemicals such as brain-derived neurotrophic factor. That might help the brain grow new cells and make new connections following injury and slow cognitive decline associated with aging.

Maximum power output, which was measured in the study, refers to exhausting activities that require intense working of the muscles. As the study by Wittfeld suggested, intense physical activities release chemicals from the muscles that in turn get the liver and other vital organs to produce chemicals that increase brain-derived neurotrophic factor in the brain.

Another possible explanation is that exercise doesn't increase higher brain function but that higher brain function motivates people to exercise more. 

Several of the regions of the brain that were apparently affected by exercise may be relevant for cognitive changes in seniors. (Cathy Alex/CBC )

Other studies have concluded in general terms that exercise is good for brain health. At more than 2,100 participants, this study is one of the largest ever done looking at the benefits of exercise. This study is important because until now, few if any studies have indicated precisely what kinds of exercise might be of benefit. As well, this is the first study to show that cardio-respiratory fitness increases grey matter in the parts of the brain that are needed for memory, executive function and the ability to navigate. 

Currently, more than half a million Canadians have dementia, and current trends show the number is rising sharply. That makes me wonder just how much hope this study provides to people with dementia. Several of the regions of the brain that were apparently affected by exercise may be relevant for cognitive changes in seniors. These include the hippocampus, parahippocampal gyrus, temporal gyrus, fusiform gyrus, cingulate, and orbitofrontal cortices.

These findings correlate with some of the regions of the brain that researchers believe are affected in older people with cognitive impairment. Some of the regions of the brain with increased grey matter as described in this study line up with similar areas that are depleted in patients with Alzheimer's disease.

Start moving

Still, the authors of an editorial that was published alongside the study said one must be careful not to suggest at this point that exercise will have any impact on people with Alzheimer's disease. They did, however, say the research is "interesting."

The take-home message is that moderate and regular exercise is good for your heart and likely good for your brain.

The standard recommendation is half an hour of moderate physical activity most days of the week, or 150 minutes a week. If you don't already do that much, start with a few minutes a day, and increase gradually until you reach 30 minutes per session.

The best and most accessible activity is walking, but other moderate-intensity exercises like swimming, dancing, or racquet sports will do nicely. Household chores like raking leaves and shoveling snow are good provided they make you sweat and provided you do them in a way that does not put extra strain on the heart.

Other things you can do include eating healthy, losing weight as well as getting blood pressure, cholesterol and blood sugar under control.  

The study gives me lots of encouragement to keep on running. There is no better time than a new year to start moving.

About the Author

Dr. Brian Goldman is a veteran ER physician and an award-winning medical reporter. As host of CBC Radio’s White Coat, Black Art, he uses his proven knack for making sense of medical bafflegab to show listeners what really goes on at hospitals and clinics. He is the author of The Night Shift and The Power of Kindness: Why Empathy is Essential in Everyday Life.

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