One 30-Minute Workout Shielded Memory From a Short Night's Sleep, Study Finds

Cutting sleep nearly in half, from 8.5 hours to 4.5 hours, normally causes a major drop in memory performance, particularly the hippocampus-dependent memory that supports decision-making and emotional health. A study published in the journal SLEEP tested whether a single bout of exercise could act as a buffer, and found that it did. Researchers split 88 healthy young adults into four groups: 8.5 hours of sleep with or without exercise beforehand, and 4.5 hours of sleep with or without exercise beforehand.

Before the sleep portion of the experiment, all participants memorized 80 face-name pairs. They then either rode a stationary bike for 30 minutes, with a 5-minute warm-up and cool-down, or sat quietly in a chair for 40 minutes. After sleeping either from 11 p.m. to 7:30 a.m. or from 2 a.m. to 7:30 a.m., with brainwave and eye-movement electrodes tracking their sleep overnight, participants took a final memory test on 120 face-name pairs, including the 80 they had studied and 40 new ones.

All four groups performed equally well when tested immediately after learning the faces and names. It was only the next morning that a difference emerged: participants who exercised before their short, 4.5-hour night scored statistically as well as those who had a full 8.5-hour night, while those who did not exercise before the short night showed the usual memory decline. The researchers also found that participants with naturally higher amounts of slow-wave sleep, the deepest sleep stage, got an even stronger memory boost from exercising.

Lead author Emmanuel Frimpong and colleagues said the findings suggest an evening bout of moderate exercise could become a recommended tool for buffering the memory-impairing effects of a short night, if the results hold up in larger, more diverse, real-world studies.