Australasian Science: Australia's authority on science since 1938

Exercise Helps Brain Repair

By Stephen Luntz

Gentle exercise improves the capacity of the brain to rewire itself, including the ability to restore functions unrelated to the exercise. However, it is important not to overdo things, as strenuous exercise can interfere with brain redevelopment.

Dr Michelle McDonnell of the University of South Australia’s Division of Health Sciences asked 25 healthy adults to spend 30 minutes riding an exercise bike before and after using transcranial magnetic stimulation to create a current within the brain that causes hand muscles to contract.

When using an inhibitory signal designed to reduce the hand’s response, McDonnell found responses were 20% smaller after exercise, indicating that the inhibitory signal was more effective then. “Some of the group were not affected without exercise,” McDonnell says, but experienced an effect when they cycled. “This suggests exercise does something even if you are resistant to the changes in brain wiring,” McDonnell says.

The explanation is likely to lie in chemicals released in the brain during exercise. However, McDonnell says the chemical she considered the most likely agent, based on its effect in animals, decreased in the bloodstreams of the subjects even as their neuroplasticity increased.

“Does this mean measuring the blood levels is a bad way to do it?” she asks. “Or is there another chemical involved? We don’t know, but a team at Harvard has found a new brain chemical that seems to have a role in rodents after exercise, and we don’t yet know if it even exists in humans.”

Whatever the chemicals involved, McDonnell thinks the greater neuroplasticity after exercise is related to the reduced cognitive decline seen in elderly people who exercise. “Exercise on its own will not protect your brain, but in combination with intellectual stimulation it is important,” she says.

McDonnell’s work has been published in the Journal of Applied Physiology.

Other research has indicated that intense exercise reduces the capacity to build memory immediately afterwards, so McDonnell is focusing on gentle exercise. She chose stationary bikes because stroke patients can use them when one leg is not working well enough to walk far.

She hopes to do further research on people who have had a stroke at least 6 months earlier, most of whom will not longer be in formal rehab.