Four years ago I wrote a tip about the American history class I took my Freshman year in college.
The short version: it was a required course, I wasn’t a fan of history at the time, and the professor spent every session doing exactly what his title suggested. He stood behind the lectern and professed. No notes. No props. No handouts. Not even the occasional joke to give twenty-five students something to hang a memory on.
A week before each exam we’d get a single sheet of paper with ten questions on it. Three would show up on the test, and we’d answer two of them in a bluebook. So for a week before every exam, my free time went to reading and re-reading a few hundred pages of a textbook, hoping enough of it would still be in my head on test day.
I was up late during those weeks. And the last thing I felt I had time for was training.
But I went anyway. Around 8 PM each night I’d walk over to the university fitness center, put in an hour, and head back to the dorm lounge to read for a few more hours before bed. And every single time I sat back down, the pile of work I had left seemed smaller than it had before I trained.
I called that tip When In Doubt, Move Your Body, and the point I made was that movement made the work feel more manageable. Which it did.
But it turns out that I only had half the story when I originally wrote that tip.
What I didn’t know at the time—because I hadn’t come across the research yet—is that the training probably wasn’t only changing how the work felt. It was likely changing how my brain processed the material.
What that hour was actually doing
Exercise puts you into a state of autonomic arousal. Your heart rate and breathing climb, and your adrenal glands release adrenaline (among other effects).
Adrenaline acts on receptors on the vagus nerve, which then carries the signal upward—where norepinephrine takes over and raises activity across the regions of the brain responsible for alertness and attention. So that “switched-on” feeling you’ve probably experienced after a hard training session isn’t your imagination—it’s a real effect that occurs through a specific mechanism.
Not every movement drives that response equally, though. The brain areas that control your core musculature and that are required by compound, multi-joint movements call on the adrenals most strongly—meaning that squats, deadlifts, presses, pull-ups, and get-ups do far more here than isolated work like curls or leg extensions. (Conveniently, except for get-ups, the former list of exercises is most of what I did those nights in the university weight room.)
In any case, that mental state of arousal turns out to be useful for learning.
In a study from 2007, researchers had 27 healthy adults learn a set of novel vocabulary words under three different conditions: immediately after two sprints of less than three minutes each, immediately after 40 minutes of easy running, or after sitting still. Short-term learning occurred about 20% faster following the sprints compared to the other two conditions—meaning that intensity seemed to be the more important variable than duration.
While this study didn’t find any difference in long-term retention between the groups, timing of the exercise may have been the culprit.
In another study published in 2016, 72 people learned 90 picture-location pairs. After a baseline recall test, some of the participants exercised immediately, some waited four hours before exercising, and some didn’t exercise at all. Re-tested two days later, the group that waited four hours remembered more and showed more hippocampal activity when they recalled correctly. (The hippocampus is the brain structure most responsible for forming new memories.) The group that exercised immediately did no better than the group that didn’t exercise at all.
Looking back at my study sessions, the hours of reading that came before and after training probably benefited in slightly different ways. The reading I’d done earlier in the afternoon—several hours before I trained—may have stuck with me longer than it otherwise would have. The pages I read right before heading out probably didn’t get much additional benefit. And the reading I did after training may have happened a little quicker, which could also be why it felt less monumental than before I trained. (I did end up doing fine in that class, for whatever that’s worth.)
I’d like to claim that I had planned at least some of that—but I didn’t. I just didn’t want to skip a workout.
Putting it into practice
If you’re already training consistently: don’t add anything. But consider when you train relative to the work that demands the most from your head—the reading, writing, studying, or decision-making. Putting a relatively vigorous session right before it may help the material go in faster or be easier to decipher.
If there’s something specific you’re trying to retain—a course, a certification, a language, a presentation you’d rather not read off a card—train after you study it, and train hard. The research disagrees on the ideal gap: the study above found four hours worked while training immediately didn’t, while a 2014 study found two hard sets of knee extensions right after learning improved recall two days later. What they agree on is intensity, not the type of exercise.
And if you’re stuck right now: a few minutes of compound movement—squats, swings, get-ups, a brisk walk up the stairwell—when the work has stalled just might help get you un-stuck.
That was the homework in the 2022 tip—and I still use it to this day, including when I wrote this one.