This past year has been a remarkable year in terms of new studies examining the effects of exercise on your brain.
Everyone knows, of course, that exercise is good for you. But these studies together provide compelling evidence that exercise (and inactivity) profoundly change the structure and function of your brain.
One set of studies has shown that exercise profoundly affects your genes.
It used to be thought that your biologic makeup was determined entirely by the genes you inherited. But a set of studies over the past decade have demonstrated that your biology is also affected by the way your body turns on or turns off your genes. The most important process that changes which genes are active involves methylation of the DNA.
DNA methylation involves the addition of a methyl group to the cytosine or adenine DNA nucleotides (these are the building blocks of DNA). DNA methylation stably alters the expression of genes in cells.
It turns out that one of the things that most profoundly affects this gene regulation is exercise.
In essence, the genes that are turned on if you exercise regularly are very different from the genes that are activated when you are inactive.
More recently, Gretchen Reynolds, in a New York Times blog post in January 2014, summarizes data showing how inactivity changes the structure of the brain and increases vulnerability to stress.
In a study recently published in The Journal of Comparative Neurology, scientists at Wayne State University School of Medicine looked at how exercise or inactivity affected the brain in rats (obviously this study couldn’t be done in humans). They focused on changes in a particular part of the brain, the rostral ventrolateral medulla, which governs your body’s unconscious responses to stress.
After three months, there were significant changes in this area of the brain in the animals who were not allowed to exercise (rats, unlike some humans, like running, and will do so if they have a chance). In those animals, there were new connections between the neurons (brain cells) and these changes appeared to correlate with a much more reactive sympathetic nervous system.
The sympathetic nervous system is the part of the brain that governs our “fight or flight” response to stressful or frightening situations.
If your sympathetic nervous system is hyperactive, you have trouble calming down when you are dealing with moderately stressful situations (you are overly sensitive to stress, and your reactions to stress last longer than they should).
As a result you have a higher risk of heart attacks, hypertension, stroke, and anxiety and depression.
This brain change could explain why exercising is so good at reducing the risk of these conditions.
A number of studies suggest that you can get a lot of benefit from a little exercise – just 30 minutes of activity that raises your heart rate per day (walking, vigorous vacuum cleaning, etcetera).
It seems like a small price to pay for a health brain and body.