Brief Exercise or a Nap May Protect Memory After Sleep Loss

A brief bout of exercise or a 90-minute nap helped preserve memory in healthy young adults after 30 hours without sleep, according to a McGill University-led study published in Proceedings of the National Academy of Sciences.

The study included 54 participants who remained awake under laboratory supervision for 30 consecutive hours. They were then assigned to one of three conditions: 20 minutes of cycling, a 90-minute nap, or a control condition involving 20 minutes sitting on a stationary bike without exercising. After the intervention, participants viewed images and later completed a recognition-memory test.

Those who exercised or napped performed about 22% better on the memory test than participants in the control group. The researchers assessed memory three days after the sleep-deprivation session, with the study involving three laboratory visits over roughly a week and a half.

Although the two approaches produced similar memory benefits, EEG recordings indicated that they did not work in the same way. Napping appeared to help restore the brain’s ability to take in and retain new information. Exercise, in contrast, appeared to help participants use their remaining cognitive resources more efficiently, without making them feel more tired.

The findings may be relevant to fatigue-management research in settings where sleep loss is common and mistakes can carry serious consequences, including health care, transportation and emergency response. Senior author Marc Roig said a short period of exercise could help preserve cognitive ability when people cannot immediately obtain more sleep. First author Madhura Lotlikar described exercise as accessible and inexpensive compared with taking a nap during a work shift.

The researchers emphasized that exercise is not a substitute for sleep. The study tested a specific group—healthy young adults—in a controlled laboratory setting, so the results do not establish whether the same effects would occur in other populations or during typical real-world sleep restriction. Its findings concern short-term memory performance after acute sleep deprivation, rather than longer-term effects on health, cognition or sleep.