One sleepless night can blur the brain, but just 20 minutes of exercise or a well-timed nap may help new memories survive for days.
In a McGill University-led study, participants who exercised for 20 minutes or slept for 90 minutes after prolonged wakefulness performed about 22 percent better on a delayed memory test than those who did neither. The findings, published in Proceedings of the National Academy of Sciences (PNAS), suggest that two very different interventions can partially protect memory when adequate sleep is temporarily out of reach.
“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, a 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.”
Testing Memory After 30 Hours Awake
Researchers recruited 54 healthy young adults and kept them awake for 30 consecutive hours under laboratory supervision. The participants then completed one of three interventions: 20 minutes of moderate-to-vigorous cycling, a 90-minute nap, or a control condition without either activity.
Immediately afterward, they viewed a collection of images. When their memory was tested three days later, the exercise and nap groups recalled significantly more images than the control group. Measuring memory after several days allowed the researchers to examine whether the interventions influenced the formation of lasting memories, rather than merely producing a brief improvement in alertness.
Exercise and napping delivered nearly identical memory benefits, but recordings of brain activity indicated that they reached that outcome through different processes.
Two Routes to Stronger Memory
Sleep plays an important role in preparing the brain to absorb information and in stabilizing newly formed memories. In the study, the nap appeared to replenish the brain’s ability to encode and retain new material after extended wakefulness.
Exercise produced a different pattern. Instead of restoring the brain in the same way as sleep, cycling appeared to help participants use their remaining mental resources more efficiently. Importantly, the workout did not make them feel more fatigued.
A short workout may be especially practical during demanding shifts, when there is not enough time or a suitable place to nap.
A Possible Tool for Sleep-Deprived Workers
The results could eventually contribute to fatigue management in health care, transportation, emergency response, and other fields where employees may work while short on sleep and a lapse in memory can have serious consequences.
“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 caution that a workout cannot replace the broad physical and mental benefits of sleep. Still, when sufficient rest is temporarily impossible, a short period of exercise may offer a practical way to help the sleep-deprived brain preserve new information.
Reference: “Protecting episodic memory after sleep loss: Similar benefits of exercise and naps via distinct neural contributions” by Madhura S. Lotlikar, Beatrice Ayotte, Amy Choi, Freddie Seo, Edwin M. Robertson, Fabien Dal Maso and Marc Roig, 7 August 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2528246123
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