A new study suggests exercise gets better for you the more you do it

“If we become fitter, our brains benefit even more from a single session of exercise.”

About two years ago, I went to see my doctor. Our conversation went like this:  

“Mr. Murphy, you need to lose weight,” the doctor said.  

“I know, I know. How much do you think I need to lose?” I asked.  

“That depends. How long do you want to live?” the doctor replied. 

We have a joking relationship, my doctor and I, but that one landed, and it marked a turning point. Since then, I’ve made health and fitness a genuine priority in ways I hadn’t since at least before the pandemic. Consistent workouts. Much better eating. Less of the stuff I knew wasn’t helping.  

Slowly but surely, it’s added up. One extra dividend I hadn’t even planned on: I’ve had my best ski season since I was a kid. The days on the mountain feel noticeably better than they did when I started. 

I assumed that was just the result of being in better shape overall. A new study suggests, however, something more specific might also be happening in my head. It might give you a new perspective on exercise too. 

What the research found 

Writing in the journal Brain Research this month, researchers from University College London say they found that the brain benefits from exercise don’t just accumulate. They actually compound as you get fitter. 

Led by Flaminia Ronca of UCL’s Institute of Sport, Exercise & Health, the researchers took a group of sedentary, unfit adults and put them through a 12-week cycling program — three sessions per week. At the start, middle, and end of the study, they measured participants’ levels of a protein called BDNF, or brain-derived neurotrophic factor. 

BDNF is sometimes described as the brain’s fertilizer. It supports the growth of new neurons and new connections between brain cells. It helps maintain the ones already there. Exercise is one of the most reliable ways to trigger its release, as little as 15 minutes of moderate to vigorous aerobic activity appears to be enough to get it going. 

The crux of the study: Resting BDNF levels didn’t meaningfully change over the 12 weeks. However, the spike of BDNF that followed a single hard workout got significantly larger as participants got fitter. That increase tracked directly with improvements in aerobic fitness. 

The fitter they became, the bigger the neurological response to each individual session. 

On top of that, higher BDNF responses were linked to measurably better activity in the prefrontal cortex — the region that governs attention, decision-making, and self-control — during cognitive tests. 

“The most exciting finding from our study is that if we become fitter, our brains benefit even more from a single session of exercise, and this can change in only six weeks,” Ronca said in a press statement. 

The compound interest of fitness 

Most conversations about exercise and cognitive performance are vague. It reduces stress, improves sleep, and boosts mood. However, this research points to something more specific. Getting fitter upgrades the brain’s response to each workout, so that you’re not just maintaining a benefit. You’re increasing what each additional session is worth. 

That reframe matters for anyone who’s wrestled with making exercise a consistent priority. People tend to think of a skipped workout as losing one unit of benefit, but this research suggests the math might be less forgiving than that. What you’re also skipping is an opportunity to build the system that makes the next workout pay more. 

Frankly, it also comports with my own experience, and I suspect anyone else who has gone from a “know I should” attitude to a “really hate to miss it” attitude at the gym. 

There are some caveats. Only around 20 participants completed all the required sessions with usable data, which is a small sample. The results show correlation, not proof of causation. No significant memory improvements showed over the 12 weeks, though the researchers suspect a longer window might change that. 

So, treat this as a compelling early signal, not a settled verdict. Larger trials are needed to confirm what these researchers found. 

What it does fit, though, is a broader pattern in the research: The adult brain is more adaptable than most people assume. The habits that support it tend to reward consistency in ways that aren’t always obvious in the short term. 

Next up: a study on whether having a doctor with a deadpan sense of humor motivates people to be healthier. At least it worked for me. 

This post originally appeared at inc.com.

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