Cycling or running at full speed may sound like the shortest route to fitness. But varying the intensity of your workout could be much better for your brain, say experts from the University of South Australia.

The researchers found that sustained, strenuous exercise raises levels of cortisol, which is often called the ‘stress’ hormone. And when cortisol is raised it blocks the positive effects of exercise on the brain, they claim.

Writing in the Journal of Science and Medicine in Sport, the researchers reviewed a number of studies involving male and female volunteers aged between 18 and 65. The exercise – either cycling or running on a treadmill – ranged from low-intensity continuous exercise to high-intensity interval exercise. As part of the experiments the volunteers had their brains monitored using transcranial magnetic stimulation (TMS) after they’d been exercising.

What the researchers found was that the greatest changes in neuroplasticity – which is the brain’s ability to rewire or modify its neural connections – happened within 20 minutes of interval training or 25 minutes of continuous moderate aerobic exercise. But continuous high-intensity exercise was associated with high cortisol levels, which the researchers say block neuroplastic responses.

The idea of neuroplasticity has been around since the 1960s when scientists suggested the human brain doesn’t have a set number of brain cells, as was previously thought. Neuroplasticity is triggered by the neural connections that your brain makes when you learn or experience something new or memorise new information. Exercise boosts neuroplasticity too – but if this latest study is anything to go by, the way you exercise could be just as – or perhaps more – important than how much or how often you work out.

Other ways to boost neuroplasticity include meditation, brain training games, developing new skills, exploring new places and having new experiences.


Photo by Coen van den Broek on Unsplash