One dial on your workout, intensity, appears to matter more for your brain than how long you sweat or which machine you pick.
Quick Take
- Studies show exercise raises brain chemicals called BDNF and IGF-1, which support memory and brain cell growth.
- Higher-intensity workouts produced bigger jumps in these brain chemicals than lighter sessions in several studies.
- Both strength training and endurance exercise triggered measurable increases in these markers after just one session.
- Results vary by person, workout type, and age, so no single routine works the same for everyone.
The Brain Chemicals Behind The Buzz
Two proteins keep showing up in exercise research: brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1). BDNF helps brain cells grow, survive, and connect to each other. IGF-1 supports blood vessel growth in the brain and helps activate BDNF itself. Together, researchers say they form a big part of why moving your body seems to sharpen your mind over time.
A 2020 study published in a Springer journal tested strength training against endurance training in older adults. Both groups showed significant jumps in serum BDNF and IGF-1 right after exercising, compared to a group that did not exercise at all. The takeaway was not which method won. It was that movement itself, regardless of style, kicked these brain-support chemicals into gear.
Why Intensity Seems To Be The Key Lever
A separate study on teenagers found something sharper. Researchers split young people into exercise groups of different intensities and measured their blood afterward. The high-intensity group showed significantly bigger increases in BDNF, IGF-1, and even working memory scores compared to lower-intensity groups. Moderate-to-high intensity aerobic work seemed to matter most for boosting these markers in developing brains.
Another study looked at how you run, not just how hard. Continuous running triggered higher IGF-1 levels and better vigilance than the same distance broken into intervals. That suggests steady effort over time, not just peak exertion, plays its own role in how much benefit your brain soaks up from a workout.
Resistance Training Tells A Similar Story
Weightlifting has its own evidence trail. One study found that after resistance exercise, serum IGF-1 rose significantly, by 28 percent in one group and 16 percent in another, compared to levels before exercise. That is a notable jump from lifting alone, without a treadmill in sight. It reinforces the idea that effort intensity, not just cardio duration, drives these chemical shifts.
A large network analysis comparing exercise types ranked resistance training above high-intensity interval training, combined training, and steady aerobic work for boosting BDNF in both healthy and unhealthy people. That ranking does not mean lifting is the only answer. It means harder, more demanding effort across different formats tends to outperform easy, low-effort movement when the goal is brain chemistry.
The Honest Caveat Researchers Keep Repeating
Not every study agrees on the size or shape of these effects. A systematic review of IGF-1 and cognition found three studies showing increases, three showing stable levels, and one showing an actual decrease, with mixed cognitive results across all of them. That spread does not undercut the bigger pattern. It shows the benefit is real on average but depends on the person, the workout, and how it gets measured.
Other reviews echo that nuance. One analysis found aerobic training raised BDNF in some studies and left it unchanged in others, while resistance training showed a similar split for IGF-1. The consistent thread through nearly all of this research is that moderate-to-vigorous effort, sustained regularly, gives your brain the best odds of getting a measurable lift.
What This Means For Anyone Over 40
For readers past midlife, this research lands as encouragement rather than pressure. You do not need to train like a college athlete. You need to occasionally push past a comfortable stroll, whether that means brisk walking intervals, heavier weights, or a harder bike ride once or twice a week. The brain does not seem to care much which sport you choose. It responds to genuine effort.
A hard workout clears the head and sharpens focus. Now the blood tests back it up. Brain-derived neurotrophic factor and insulin-like growth factor 1 rise most reliably when the effort is real, not token. That single detail, intensity, may be the difference between a workout that just burns calories and one that actually builds a sharper mind for the decades ahead.
Sources:
mindbodygreen.com, link.springer.com, frontiersin.org, pmc.ncbi.nlm.nih.gov, psychiatryonline.org
