Physiology Friday #115: Post-workout Nap Enhances Learning and Memory
Exercising before a nap, but not exercise or a nap alone, may enhance encoding processes in the brain that lead to memory consolidation and increased learning.
Happy Physiology Friday!
If you’re a current subscriber who would like to help support this newsletter, please consider becoming a paid subscriber! If you aren’t already subscribed to my Substack, you can do so below to start receiving weekly emails right in your inbox!
Become a subscriber :)
Do you have a big test coming up? Maybe you have to memorize a speech or presentation for a big business meeting. Looking for a way to cement that new language or skill you’re trying to learn?
There are very few reliable ways to improve memory. We know that “cramming” works poorly, and while you can probably find some sort of supplements marketed for “memory improvement”, the evidence for their efficacy is likely non-existent.
There ARE a few things that research has shown to benefit memory — sleep and exercise.
Beyond its well-known effects on lifelong cognitive health and function, exercise is also a potent memory enhancer. A review of exercise and memory finds that acute and chronic exercise have “a favorable effect....on some aspect of memory function.” The effects might be better if you exercise BEFORE or DURING the learning of something, rather than after.
In regards to sleep, it’s absolutely essential in order to facilitate memory and learning. You’ve likely experienced this first-hand — after a short or poor night of sleep, memory the next day is impaired. Interestingly, even short naps might be beneficial to memory. In contrast to exercise, napping AFTER the learning of a task might help to facilitate learning.
Could combining the benefits of exercise and sleep further enhance memory performance? It’s an interesting hypothesis explored in a recent study published in the journal Sleep. The implications could be important for anyone looking for a way to “hack” their memory.
Brief study overview
The purpose of this study was to investigate whether the combined effects of aerobic exercise and sleep would enhance memory to a greater magnitude than either exercise or a nap alone.
The authors hypothesized that: 1) exercising before a learning task (“memory encoding”) would enhance memory recognition after a nap more than exercise or a nap alone and 2) memory performance after a nap would be determined by the intensity of sleep spindles during the post-learning nap (i.e. more sleep spindles = greater memory).
115 young healthy adults (average age 23; males and females) participated in this study. They were free from any medical conditions, were “moderately active”, and had normal sleep habits.
Participants were split up into 4 groups that each completed a different intervention. I’ve described the interventions below, but the study diagram presents a nice outline of the experimental protocol.
Exercise + nap: 40-minutes of cycling, “study session”, 60-minute nap
Exercise + no nap: 40-minutes of cycling, “study session”, no nap (60 minutes of sitting)
No exercise + nap: No exercise, “study session”, 60-minute nap
No exercise + no nap: No exercise, “study session”, no nap
Why 40 minutes of moderate intensity exercise? Literature shows that a 30-40 minute aerobic exercise session at a “moderate” intensity performed >3 hours before sleep benefits memory the most.
During the “study session”, participants were shown 45 different images and told to rate the pictures on how they felt (calm, neutral, or excited). The intent here was to get participants to pay attention to the photos.
The testing sessions were all performed after the nap or the 60-minute “no nap” period. During the test, participants were shown 90 images, 45 of which they had already been exposed to during the study session. Participants were required to state whether the photo was “previously seen” or “not previously seen.”
Their “memory performance” was assessed as the number of photos they accurately identified during the test session.
During the nap, participants were hooked up to a polysomnography device — basically a recording of their brain waves during sleep. This was done to assess certain parameters of sleep like quality, duration, and activity of sleep spindles — bursts of brain activity during sleep.
Neither exercise alone or a nap alone had any effect on memory performance.
Exercise plus a nap enhanced post-nap memory MORE than exercise or a nap alone.
Exercise had no effect on sleep “architecture” or quality — sleep spindle activity was no different during the nap whether participants exercised or not.
Spindle density during the nap was correlated to memory performance improvement in the exercise plus nap group, but NOT the nap only group.
Thoughts and musings
An interesting aspect of this study is what wasn't found. Their observation that exercise alone had no effect on memory performance stands in contrast to some of the literature they cite. Furthermore, taking a nap after learning showed no benefit for memory, which is also contradictory to other research. They also found no evidence that exercise improved the quality of sleep
However, the primary finding that learning and memory are enhanced when a nap is preceded by a single session of exercise is brand-new.
What could explain the memory-enhancing effects of exercise and a nap? The authors list three potential mechanisms:
1. Exercise might enhance the “encoding process” during learning and enhance memory consolidation during sleep.
2. Exercise may enhance sleep architecture and sleep quality — findings of this study do not support this hypothesis, however.
3. Exercise may enhance neuronal activity during sleep to boost memory consolidation — only minorly supported by the findings of this study.
As for the application, I think this could be a useful strategy in times where you need to memorize or learn something “quickly.” Plan your exercise session to occur before you plan on learning a task, skill, or memorize some lines. After you “study”, take a short nap or even better — get a full night of sleep.
This is yet another study to show that the benefits of exercise are seemingly limitless.
Thanks for reading. See you next Friday.