By Elizabeth Bacharach

Heart thumping, sweat dripping, neurotransmitters surging.

“This is your body on exercise,” according to the findings of a new imaging study.

Your heart and lungs work harder, of course. But the real surprise is how the exercise produces surges of more neurotransmitters that rev up brain function.

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A recent study by University of California Davis Health System researchers found an increase of the common neurotransmitters glutamate and GABA after intense exercise.

“The two of these together conduct 85 percent of the brain’s business in terms of information exchange through chemical messengers,” said Richard Maddock, study lead investigator and professor in the Department of Psychiatry and Behavioral Sciences at UC Davis. The results appear in the Feb. 24 issue of The Journal of Neuroscience.

The team studied 38 healthy, normal-weight men and women, all volunteers. Thirty-two of these participants exercised on a stationary bicycle, reaching about “80 percent of predicted maximum heart rate,” according to study results. The other six subjects sat on a bicycle without pedaling and were part of the control group.

To measure the glutamate and GABA levels, the researchers conducted imaging studies before and after exercise with a magnetic resonance imaging (MRI) scanner that can show the chemical measurement of changes in targeted area of the brain.

For this study, the team focused on two regions of the brain: the primary visual cortex, a sensory region, and the anterior cingulate cortex, a cognitive and emotional region. Before and after each session of vigorous exercise, lasting between eight to 20 minutes, the team measured the glutamate and GABA levels. They found an increase of these neurotransmitters only in the brains of those who pedaled.

While the researchers did not focus on long-term effects, they assessed the level of physical activities of participants leading up to the study.

“We did find that people who had more physical activity in the preceding week had higher glutamate levels than the people who had less physical activity,” even among those who exercised for the study, Maddock said, “So, that suggests that there are some persisting effects of exercise,” he added.

“It’s interesting that they find both the glutamate and GABA are increased because these two…do opposite things in the brain,” said  Lei Wang, an assistant professor of Psychiatry and Behavioral Sciences and Radiology at Northwestern University’s Feinberg School of Medicine. He was not associated with the study.

Wang explained how glutamate is a neurotransmitter that excites neurons and turns up the activity of the next neuron in the chain of communication. GABA is an inhibitory neurotransmitter whose “role is to put a break on the activity in the brain.”

While the brain needs both of these chemicals, those who are clinically depressed have a decrease in the amount of glutamate.

The study findings also suggest that exercise could be used as an “alternative” treatment for mild to moderate depression. If exercise can also increase neurotransmitters in the brains of those who are depressed, then it “might have value in helping them recover,” Maddock said.

“I think this is obviously a great way by which exercise can be used as a way to effect depression,” opposed to “pharmacological means,” said Julius Dewald, chair of the Department of Physical Therapy and Human Movement Sciences at Feinberg.

Yet Wang emphasized that, because of the MRI scanning techniques, the study only focused on two areas of the brain. Findings cannot be “generalized to other brain areas,” Wang said.

“It’s interesting that they find both the glutamate and GABA are increased because these two…do opposite things in the brain.”   Lei Wang, Northwestern University

Dewald noted examples of how exercise can benefit those affected by illness. Studies have found a “positive effect [following exercise] on the movement problems that occur as a result of Parkinson’s disease,” said Dewald, who is also a professor at Northwestern’s McCormick School of Engineering.

Despite the many beneficial effects that have been demonstrated, Daniel Corcos, who studies the effects of exercise on Parkinson’s disease, said more study is needed. There hasn’t been a study like the one at UC Davis to evaluate the chemical basis for why exercise might aid those with Parkinson’s disease.

“I don’t know of any studies conducted on humans that get to metabolic or neurotransmitter changes in Parkinson’s disease,” said Corcos, a professor of Physical Therapy and Human Movement Sciences at Feinberg.

Corcos added that a study like that is “needed” to understand “the biological basis for the therapeutic benefits of Parkinson’s disease.”

Exercise in general, however, is known to make people feel better.

Johnpaul Higgins is both a “habitual” runner and the director of membership and community development at the Chicago Area Runners Association (CARA). For Higgins, running is “almost addictive” because it makes him “feel better mentally, emotionally – more centered, more grounded.”

Wang also finds that running helps him cognitively. “I run to work…every day, rain or shine…So, I know the benefit on the brain because I feel very rejuvenated, able to focus, and concentrate,” he said.

Because of the already recognized benefits of exercise, Dr. Sara Brown, a primary care sports physician practicing in Chicago, said she was not surprised by the study’s results.

Brown, also a member of the CARA Board of Directors, said she has seen a “positive effect” on her patients’ moods when they exercise frequently and a “negative effect” when they get injured and are no longer able to keep up usual activity.

Brown added that the study’s findings will help her when encouraging depressed patients to exercise. “If I can explain to them the chemical reaction that can occur, which will lead them to feeling better, that might support my argument and they might take it more seriously,” Brown said.

Although Maddock said he is “confident in the findings,” he wants to proceed with more research. His team plans to seek funding from the National Institutes of Health to pursue larger studies, specifically ones involving patients with depression.

“Exercise has no side effect. Right? I think people…should be encouraged to [exercise] regardless of whether we uncover the actual mechanism of exercise in neurotransmitter change,” Wang said.