A short workout or a nap can help protect memory after a sleepless night, a McGill University-led study has found.

Researchers found people who either completed 20 minutes of moderate-to-vigorous exercise or took a 90-minute nap performed about 22 per cent better on memory tests after 30 hours without sleep than those who did neither. The findings, published in Proceedings of the National Academy of Sciences (PNAS), point to practical ways to counter the effects of sleep deprivation.

“Sleep loss affects nearly every aspect of how we think and function, but many people can't simply stop what they're doing and get more sleep,” said senior author Marc Roig, Professor in McGill's School of Physical and Occupational Therapy. “Our findings show that even a brief bout of exercise may help preserve one of our most important cognitive abilities.”

The study involved 54 healthy young adults who stayed awake for 30 consecutive hours under lab supervision. Participants were then assigned to one of three groups: a 20-minute cycling session, a 90-minute nap or a control condition. Three days later, researchers tested their memory for images they had viewed immediately after the intervention. Those who exercised or napped remembered significantly more images than participants who did neither.

While the memory benefits were nearly identical, brain recordings revealed that exercise and napping helped in different ways.

Napping appeared to help the brain recharge, making it easier to take in and remember new information. Exercise, by contrast, helped the brain use its remaining resources more efficiently, without making participants feel more tired.

The findings could eventually inform fatigue-management strategies in workplaces where sleep loss is common and mistakes can have serious consequences, such as health care, transportation and emergency response.

“A nap isn't always possible in the middle of a shift,” said first author Madhura Lotlikar, a doctoral candidate in McGill's Department of Neurology and Neurosurgery. “Exercise is accessible, inexpensive and easy to implement. That makes it a promising tool to help people stay cognitively sharp when sleep is limited.”

The researchers emphasize that exercise cannot replace sleep, but it may help people function better when getting enough rest isn't possible.

“Protecting episodic memory after sleep loss: Similar benefits of exercise and naps via distinct neural contributions” by Madhura Lotlikar and Marc Roig et al., was published in Proceedings of the National Academy of Sciences of the United States of America.