If you ask wellness experts to name the single most important test for brain longevity, you'd probably hear answers ranging from cognitive assessments, to genetic panels, to brain scans. But neurologist Majid Fotuhi, M.D., Ph.D., offered a different answer entirely in his conversation with mindbodygreen co-founder Jason Wachob at the 2026 Revitalize summit.
And you might be surprised to learn that it's not a brain test at all. It's a fitness metric.
"I think the most important test for brain longevity is VO2 max, which is a measure of your physical endurance," Fotuhi said. "If you increase your physical endurance, your brain will be healthier."
It's a bold claim, but the science backs it up. Here's why your cardio fitness might be the best investment you can make in your cognitive future.
What is VO2 max, exactly
VO2 max measures how efficiently your body uses oxygen during intense exercise. It's essentially a marker of your cardiovascular and aerobic fitness that measures how well your heart, lungs, and muscles work together when you're pushing yourself.
While athletes have long tracked this metric to optimize performance, researchers are now recognizing VO2 max as a powerful predictor of overall health and longevity. And as Fotuhi points out, that includes your brain.
The connection makes sense when you consider that your brain is an energy-hungry organ. It requires a constant supply of oxygen and nutrients delivered via blood flow. The fitter your cardiovascular system, the better equipped it is to nourish your brain.
The hippocampus connection
To understand why exercise matters so much for brain health, you need to know about the hippocampus. It's a small, seahorse-shaped region deep in your brain that's essential for memory formation and spatial navigation.
The hippocampus tends to shrink as we age. And according to Fotuhi, this shrinkage is directly linked to cognitive decline.
"People who have a small hippocampus develop Alzheimer's disease," he explained. "But guess what? You can increase the size of the hippocampus with exercise."
Research confirms this. A 2020 study found that exercise increased hippocampal volume1 in younger adults and prevented age-related volume decline in older adults. All participants were enrolled in a 16 week progressive aerobic exercise program, after which researchers observed a beneficial effect on mental health, in addition to positive changes to hippocampal volume.
What happens in your brain when you exercise
When you work out, you're not just strengthening your muscles, you're changing your brain structure. Fotuhi broke down the mechanism.
"When you exercise, you increase the number of mitochondria, which are the energy-producing organelles inside the cell," he explained. "You increase the number of neurons, brain cells, in your hippocampus."
In other words, exercise can actually help grow new brain cells in the very region that shrinks with Alzheimer's disease.
Studies also show the brain benefits of movement. According to a 2025 review on physical activity and cognitive decline2, the benefits of aerobic exercise include increased cerebral blood flow, enhanced neurogenesis (the birth of new neurons), reduced oxidative stress and inflammation, and positive hormonal changes. All of these physiological changes contribute to better memory, executive function, and mood.
How to improve your VO2 max for brain health
To truly boost your VO2 max, you need to start getting into higher heart rates with higher intensity cardio workouts. You begin stimulating the systems that power VO2 max when you get into zones 4 and 5, which is 80 to 100% of your max heart rate. This is when your cardiac output, capillary density, and mitochondrial function will increase, and better your VO2 max.
You don't need to be a marathon runner to reap these benefits, but you do need to find a way to consistently get your heart pumping. Effective options include:
- Running or jogging — A classic VO2 max booster.
- Cycling — Great for those who prefer lower impact on joints.
- Swimming — Full-body cardio that's easy on the body.
- HIIT workouts — Short bursts of intense effort followed by rest periods can efficiently improve aerobic capacity.
- Dance or aerobics classes — Fun ways to get your heart pumping.
Research suggests that regular aerobic exercise, not just occasional bursts, is what drives meaningful changes in brain structure. Start where you are, and gradually increase duration and intensity over time. Once you're able to consistently get into those higher rate zones, you will see an improvement in VO2 max. those higher
The takeaway
If you're looking for one thing you can do today to protect your brain for the decades ahead, Fotuhi's advice is clear: focus on your physical fitness.
"Exercise is a no brainer," he said.
And unlike many interventions that require expensive tests or complicated protocols, this one is remarkably simple. Move your body and challenge your heart. Your brain will thank you.