Severe sleep loss can make it difficult to concentrate, learn new information and form memories. For overnight workers or anyone facing an occasional stretch without rest, however, getting enough sleep may not always be immediately possible.

A recent study published in Proceedings of the National Academy of Sciences compared two strategies for protecting memory after sleep deprivation. Researchers examined whether aerobic exercise could provide cognitive benefits comparable to those of a nap.

CNN wellness expert Dr. Leana Wen discussed the findings and their practical limits. Wen is an emergency physician and clinical associate professor at George Washington University who previously served as Baltimore’s health commissioner.

The study enrolled 54 healthy adults ages 18 to 35 and kept them awake for 30 hours. Researchers then randomly assigned the participants to an exercise group, a nap group or a control group.

Participants in the exercise group completed 20 minutes of moderate to vigorous cycling while reaching 80% of their maximum heart rate. The nap group received a 90 minute opportunity to sleep, while the control group sat on a stationary bicycle for 20 minutes without exercising.

Afterward, participants viewed 150 images while researchers recorded their brain activity through electroencephalography, also known as EEG. The participants did not know that they would later receive a memory test.

Three days later, after having time to recover from sleep deprivation, participants viewed the original images mixed with new ones. Researchers asked them to identify which images they remembered seeing.

The exercise group correctly recognized 56% of the images, compared with 57% for the nap group and 46% for the control group. Memory performance was about 21% higher after exercise and 23% higher after a nap, with no significant difference between the two interventions.

The experiences of the exercise and nap groups were not identical. Participants who napped reported significantly less fatigue, while those who exercised remained about as tired as people in the control group.

Despite that continued fatigue, the exercise group performed significantly better than the control group on the memory test. EEG recordings suggested that exercise reduced a marker of neural fatigue in regions involved in the task.

Sleep deprivation interferes with the brain’s ability to encode new information, Wen explained. As sleep pressure builds during prolonged wakefulness, the neural processes required to create memories become less efficient.

One possible explanation is that exercise helps a tired brain use its remaining cognitive resources more efficiently. Napping, by comparison, appeared to improve the underlying condition of the sleep deprived brain by reducing fatigue and EEG markers of sleep pressure.

The exercise session also fits broadly within the idea of exercise snacking, although it lasted longer than most such activity. Exercise snacks typically involve 30 seconds to five or 10 minutes of stair climbing, brisk walking, squats or other movements that elevate the heart rate.

Studies cited by Wen suggest that these brief periods of movement may improve cardiorespiratory fitness and reduce the risks of cancer and dementia. Still, the new study addressed a much narrower question involving severe sleep loss and the formation of new memories.

Wen stressed that exercise cannot replace sleep, which supports immune regulation, metabolic processes and many areas of brain function. Regular exercise can help sleep, but a workout lasting 20 minutes cannot provide all the functions of adequate rest.

The findings could have practical relevance for health care workers, transportation workers and others in safety sensitive jobs who experience unavoidable sleep loss. When a nap lasting 90 minutes is not possible, brief aerobic exercise may offer another way to preserve memory.

That does not mean exercise makes driving or other dangerous activities safe after severe sleep deprivation. The study also did not establish that exercise restores attention, reaction time, judgment or the many other abilities affected by insufficient sleep.

The research involved a small group of young, healthy adults who remained awake under laboratory conditions. It did not determine whether the same benefits occur with chronic sleep restriction, among older adults with medical conditions, or after different forms and intensities of exercise.

Wen said sleep should remain the first priority, with adults aiming for at least seven hours regularly. If a nap is impossible, brisk walking, climbing stairs or riding a stationary bicycle could be useful before an activity requiring learning and memory.

Caffeine may temporarily improve alertness and concentration, but it does not reverse sleep deprivation. Wen also recommended balanced meals, hydration and avoiding alcohol, while recognizing that none of these strategies removes the dangers created by severe sleep loss.