A 20-minute workout protects memory after sleep loss just as well as a 90-minute nap

Experiencing a sleepless night often makes it difficult to absorb and retain new information. A recent study suggests that engaging in a short bout of physical activity or taking a long nap can both protect the brain’s ability to form fresh memories after heavy sleep loss. The findings, published in PNAS, indicate that while these two strategies help memory in similar amounts, they rely on entirely different internal brain mechanisms to achieve that benefit.

Episodic memory allows people to consciously recall past events along with the specific time and place they occurred. This type of memory is essential for daily life, helping people navigate their environment, learn from past experiences, and make informed decisions about the future. When people do not get enough sleep, their capacity to record these episodic memories drops noticeably. In fact, a 2017 review explained how missing sleep directly disrupts the specific brain networks required to absorb and file away new information.

Because sleep loss is common among shift workers and medical professionals, scientists have been looking for accessible ways to shield the brain from its cognitive toll. At the same time, researchers have documented that movement benefits the brain under normal resting conditions. For instance, a 2019 meta-analysis demonstrated that a single short session of physical activity just before learning strongly improves memory performance.

Building on these separate lines of evidence, the authors of a 2021 review advanced the theory that exercise might act as a buffer to counteract the specific memory deficits caused by sleep deprivation. The current research, led by Madhura S. Lotlikar, was designed to test this idea directly by comparing the effects of exercise against the effects of a long nap. To understand what happens beneath the surface, the research team used electroencephalography, or EEG, a technique that involves placing small sensors on the scalp to measure the brain’s electrical waves.

To conduct the study, the researchers recruited 53 healthy young adults and kept them awake in a laboratory for 30 consecutive hours. After the sleep deprivation period, the participants were randomly split into three groups to undergo a specific intervention. One group exercised for 20 minutes on a stationary bicycle at a moderately intense pace, reaching 80 percent of their maximum heart rate. A second group was given a 90-minute opportunity to nap in a quiet, dark room. A third group, acting as a control, sat on a stationary bicycle for 20 minutes without pedaling.

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Following their respective interventions, all participants waited for about 30 minutes. This interval ensured that the napping group had time to shake off any grogginess from waking up. Next, the participants completed a memory task while wearing EEG caps. They viewed 150 distinct images on a screen and rated the emotional intensity of each picture to ensure they were paying attention. Three days later, the participants returned for a surprise memory test where they were shown a mix of the original 150 images and 75 new ones, and they had to indicate whether they recognized each picture.

The results showed that both exercise and napping protected the participants’ memory capacities. The exercise and nap groups successfully identified 56 percent and 57 percent of the original images, respectively, compared to a base rate of 46 percent in the control group. This amounts to an average relative increase of 22 percent in memory performance for those who exercised or rested compared to those who did nothing. The researchers noted that these improvements were not due to participants simply guessing “yes” more often, but reflected a genuine boost in their ability to remember the specific items.

The EEG recordings indicated that the two interventions achieved this memory preservation through distinct brain pathways. For the napping group, sleeping successfully reduced markers of neural fatigue and sleep pressure in the brain before the memory task even began. By downscaling these exhausted neural networks, the nap placed the brain into an optimal state to receive and hold onto new information. In this group, the baseline state of the brain was the strongest predictor of how well a person would perform on the memory test three days later.

The exercise group displayed a different internal response. Before the memory task, their EEG markers showed the same high levels of neural fatigue and sleep pressure as the control group. However, exercise appeared to prime the brain to process information more efficiently once a new image appeared. When a picture was shown, the brains of the exercising participants successfully engaged specific electrical rhythms associated with active learning and attention allocation. This allowed the participants to mobilize their available mental resources without needing to exert extra compensatory effort.

In contrast, the sleep-deprived control group struggled to encode the memories. Their brainwaves indicated high levels of fatigue, and when they tried to process the new images, their brains showed signs of elevated effort. Unlike in the exercise group, this extra mental strain did not translate to better memory performance, suggesting that the sleep-deprived brain was attempting to compensate for its exhaustion but failing to store the new information effectively.

The new findings are in line with a study covered by PsyPost in 2025, which found that a two-hour nighttime nap during a 24-hour shift improved nurses’ visual and verbal memory performance and restored disrupted resting brain connectivity. The results also align with another study covered by PsyPost, which found that engaging in moderate physical activity is associated with better episodic memory performance the following day, though that study tracked everyday activity in middle-aged adults rather than testing an acute workout as a buffer against total sleep deprivation.

As with all research, there are a few caveats to consider. First, the laboratory setting involved a single bout of extreme sleep deprivation, which might not fully mirror the ongoing sleep loss that many shift workers experience in the real world. Additionally, the durations of the two interventions did not match, with exercise lasting 20 minutes and the nap lasting 90 minutes. The researchers intentionally designed it this way to mimic practical real-world options, as exercising for 90 minutes would be physically exhausting and napping for only 20 minutes might not provide enough deep sleep to restore brain function.

Future research could look into how these interventions affect occupation-specific tasks, such as medication administration for nurses or lane tracking for truck drivers. Scientists are also interested in whether combining these strategies, such as taking a nap and then exercising, might offer even greater benefits for the exhausted brain.

The study, “Protecting episodic memory after sleep loss: Similar benefits of exercise and naps via distinct neural contributions,” was authored by Madhura S. Lotlikar, Beatrice Ayotte, Amy Choi, Freddie Seo, Edwin M. Robertson, Fabien Dal Maso, and Marc Roig.