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

A recent study revealed that a brief 20-minute workout can protect memory just as effectively as a 90-minute nap following a night of insufficient sleep. Published in the journal PNAS, the research indicates that while both strategies improve memory to a similar degree, they utilize different internal brain mechanisms to achieve this benefit.

Episodic memory, which allows people to recall past events, including their location and timing, is crucial for daily functioning. However, sleep loss significantly impairs the brain's ability to form these memories. Researchers have been searching for accessible ways to protect the brain from the cognitive effects of sleep deprivation, particularly among shift workers and medical professionals.

Exercise has previously been shown to benefit the brain during normal resting periods. For instance, a 2019 study found that a short session of physical activity before learning significantly improved memory. The current study, led by Madhura S. Lotlikar, directly compared the effects of exercise and a long nap on memory retention after sleep loss.

To investigate this, the researchers recruited 53 healthy young adults and kept them awake for 30 consecutive hours. Participants were then randomly assigned to three groups: one group exercised on a stationary bicycle for 20 minutes at 80% of their maximum heart rate, another group napped for 90 minutes in a quiet, dark room, and a control group sat on a stationary bicycle without pedaling. After their interventions, participants waited 30 minutes before completing a memory task while wearing EEG caps.

The participants viewed 150 distinct images and rated their emotional intensity, ensuring they were attentive. Three days later, they returned for a surprise memory test, where they had to identify 150 original images and 75 new ones. Both the exercise and nap groups successfully identified 56% and 57% of the original images, respectively, compared to the control group's 46%. This represents an average 22% increase in memory performance for those who exercised or napped compared to the control group.

The EEG recordings showed that the two interventions achieved memory preservation through different brain pathways. The napping group experienced reduced markers of neural fatigue and sleep pressure, placing the brain in an optimal state for memory formation. In contrast, the exercise group displayed the same levels of neural fatigue as the control group before the memory task but showed improved efficiency in processing information when presented with new images.

This suggests that exercise primes the brain to efficiently handle new information, even without the restorative effects of sleep.