Workout Intensity Sparks Memory Chemicals

Two women at a running track looking at a tablet — Photo: Dragana Gordic / Shutterstock

Pushing your workout just a little harder may do more for your memory than simply showing up.

Quick Take

Studies show exercise raises brain-boosting chemicals called BDNF and IGF-1 in the blood.
Higher intensity workouts appear to produce stronger increases in these brain chemicals than easy ones.
Research in adolescents links high-intensity exercise to better working memory scores.
Scientists say the exact best routine still varies by person, age, and workout type.

The Chemicals Behind The Workout High

Two substances drive most of the brain benefits tied to exercise. Brain-derived neurotrophic factor, or BDNF, helps brain cells grow and survive. Insulin-like growth factor 1, or IGF-1, helps build new blood vessels in the brain and supports memory circuits. Both rise in the bloodstream after a workout, and researchers have spent over a decade tracking exactly how.

A 2020 study published through Springer measured these chemicals in older adults before and after exercise. Both strength training and endurance training groups showed a clear jump in BDNF and IGF-1 compared to people who did not exercise. The increase was statistically significant, meaning it was unlikely to be random chance.

Why Intensity Seems To Matter Most

A separate study on adolescents dug deeper into one specific detail: how hard the workout was. Teens placed in a high-intensity exercise group showed bigger jumps in BDNF, IGF-1, and a stress hormone called cortisol compared to teens doing lighter routines. The high-intensity group also scored better on working memory tests, the kind of memory used to hold information in your head while solving a problem.

That finding matters because adolescent brains are still developing, making them especially responsive to outside signals like exercise. Researchers noted that moderate-to-high intensity aerobic exercise appeared to positively affect both BDNF levels and memory performance in this age group, suggesting the harder effort translated into a sharper mental payoff.

Different Workouts, Different Chemical Signals

Not every study points to intensity alone. One paper comparing continuous running against interval running found that steady, continuous running triggered higher IGF-1 levels and better vigilance than stop-and-start interval training. That suggests duration and steadiness can matter just as much as raw effort, depending on which brain chemical you’re trying to boost.

A resistance-training study backed this up from another angle. After lifting weights, participants saw serum IGF-1 jump by 28 percent in one group and 16 percent in another compared to pre-exercise levels. BDNF rose too, though the increase was smaller and less consistent across participants. The type of exercise appears to shape which chemical gets the bigger boost.

What The Broader Science Actually Shows

Reviewers who pooled multiple studies together have been careful not to declare one perfect formula. A systematic review of IGF-1 and cognition looked at seven studies and found three showed IGF-1 increases, three showed stable levels, and one showed a decrease, with cognition improving in some cases and not others. That spread does not undercut the basic finding that exercise affects the brain. It shows the effect depends on the person, the protocol, and what gets measured.

A meta-analysis focused specifically on BDNF reached a more confident conclusion. Pooling data from 14 studies, researchers found that a single exercise session reliably raised BDNF levels with a moderate effect size, and that regular training boosted the effect further over time. Consistency, in other words, compounds the benefit just as intensity can amplify a single session’s payoff.

The Practical Takeaway For Adults Over 40

For readers past 40, the studies point to a simple, encouraging idea: effort counts, but it doesn’t have to mean brutal workouts. Strength training and endurance work both raised BDNF and IGF-1 in older adults, not just young athletes. Adding a bit more intensity to an existing routine, rather than starting an entirely new program, may be the easiest way to nudge these brain chemicals higher without added risk.

Aging brings a natural decline in BDNF and IGF-1 production, one reason memory and mental sharpness can slip with age. Exercise offers one of the few tools shown to counter that decline directly through biology rather than just lifestyle habit. Choosing a slightly harder pace on a walk, adding light resistance work, or pushing one extra rep may be a small change with an outsized return for the brain over time.

None of this requires a total lifestyle overhaul. The evidence across a dozen-plus studies converges on one steady message: moving your body, and pushing that movement a bit harder when you can, keeps the chemical machinery of memory and focus running longer into life.