Scientists have long known that happiness and stress are two sides of the same coin: the less stressed you are, the happier you’ll be. They’ve also known that exercise lifts mood by releasing feel-good chemicals like endorphins and dopamine into the brain. But last spring, researchers at Princeton University made a startling discovery—the mood-enhancing benefits of exercise aren’t temporary. Exercise, they found, actually rewires your mind.
The finding came out of the researchers’ bid to reconcile a perplexing paradox. Exercise triggers the creation of highly excitable neurons in the hippocampus, the region of the brain associated with memory, learning, and emotional responses. This speeds up overall brain function, but because of the new neurons’ excitability, it should also make the brain more susceptible to anxiety. Yet it doesn’t.
To find out why, the Princeton team split lab mice into two groups. One group had access to a running wheel (with the mice averaging an impressive 2.5 miles per night), and the other did not. After six weeks, the researchers intentionally freaked out all the mice by dunking them in cold water, then looked at their brains with an fMRI machine. Almost immediately, they noticed that the two groups reacted differently. The brain cells of the inactive mice became agitated and leaped into a frenzy, while those of the active mice did not. The reason: the active mice were able to produce and release more of the neurotransmitter GABA, which helps sedate jumpy neurons.
The discovery, published in May in The Journal of Neuroscience, marked a breakthrough in understanding how exercise helps the brain regulate anxiety. In essence, exercise creates new, faster neurons, but it also reinforces the physiological mechanism that prevents those uppity brain cells from firing during times of stress.
“When you exercise, you change 20 things at the same time,” says Dr. Emrah Düzel, director of the Institute of Cognitive Neurology and Dementia Research at Germany’s University Hospital Magdeburg. “There’s no medication that can achieve that.”
“You have to improve cardiovascular function in order to see the effects,” says Düzel. Cardio-vascular function means getting up to 50 percent of your max heart rate, which causes oxygenated blood to circulate more rapidly through the brain, forming new neural connections.
Make Every Minute Count
Just four to six minutes of regular exercise makes a big difference. A Brazilian study found that aging rats that ran for that amount daily for five weeks reversed age-related memory impairment and increased neurotrophic factor, a substance essential for the growth and survival of neurons.
Push Longer and Harder
In a 2012 survey, Penn State researchers found that physically active students who pushed themselves during workouts were more likely to report overall life satisfaction. The reason may be simple: exercise burns off the stress hormone cortisol.
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