Exercise and Memory: How Physical Activity Changes Your Brain

Exercise doesn't just make your muscles stronger. It makes your brain bigger.

In a landmark 2011 study, older adults who walked briskly for 40 minutes, three times a week, showed a 2% increase in hippocampal volume after just one year. The control group, who did only stretching, showed the typical 1-2% shrinkage expected with aging. The walkers effectively reversed two years of age-related brain decline.

The hippocampus is the brain region most associated with forming new memories. Its volume correlates with memory performance, and it's one of the first areas affected in Alzheimer's disease. The fact that a simple walking program can actually grow this structure is remarkable.

I can tell you from personal experience that this isn't just a statistic. For years, I lived a mostly sedentary lifestyle: sitting in class, sitting at work, sitting at the computer. Light walking at most. I lifted weights occasionally but avoided cardio. And my memory was poor. My concentration was poor. Studying felt like pushing a boulder uphill.

When I finally committed to regular cardiovascular exercise, the change was dramatic. During weeks when I do my workouts consistently, my thinking is sharper, my focus is clearer, and my ability to remember information improves noticeably. This isn't placebo effect. It's the predictable result of well-understood biological mechanisms.

This page covers what those mechanisms are, what different types of exercise do for your brain, and practical recommendations based on current research. The evidence here is among the strongest in all of brain health science.

The Headline Finding: Exercise Grows Your Hippocampus

The study I mentioned above deserves a closer look because it's foundational to understanding why exercise matters for memory.

Researchers at the University of Pittsburgh randomly assigned 120 older adults (average age 67) to either an aerobic exercise group or a stretching control group. The aerobic group walked on a track, starting at 10 minutes and building to 40 minutes, three times per week. The stretching group did toning and balance exercises for the same amount of time.

After one year, MRI scans revealed that the aerobic group's anterior hippocampus had grown by approximately 2%. The stretching group's hippocampus had shrunk by about 1.4%, which is the normal trajectory of aging. The difference was striking: the walking group had effectively reversed one to two years of typical age-related decline.

Crucially, the volume changes correlated with changes in blood levels of BDNF (brain-derived neurotrophic factor), a protein essential for the growth and survival of neurons. And the larger hippocampal volumes correlated with better performance on spatial memory tests.

This wasn't intense training. It was walking. Moderate-intensity walking, done consistently, for a year. If that sounds achievable, it should. The intervention was deliberately designed to be realistic for older adults.

How Exercise Changes Your Brain: Five Mechanisms

The hippocampus growth in the walking study isn't magic. It's the visible result of several interacting biological processes that exercise triggers. Understanding these helps explain why exercise has such broad cognitive benefits.

1. Increased Cerebral Blood Flow

When you exercise, your heart pumps harder, increasing blood flow throughout your body, including to your brain. Research confirms that regular aerobic exercise improves cerebral blood flow, particularly to the hippocampus and prefrontal cortex.

This matters because your brain depends entirely on oxygen and glucose delivered through the blood. Better circulation means more fuel for neural activity. It also means more efficient removal of metabolic waste. Over time, regular exercise improves the health and function of the blood vessels that serve your brain.

If you've ever noticed that a brisk walk clears your head and helps you think, this is part of why. The effect is immediate (acute exercise temporarily boosts brain blood flow) and cumulative (regular exercise improves vascular function over time).

2. BDNF: The Brain's Growth Factor

BDNF (brain-derived neurotrophic factor) is one of the most important molecules in understanding how exercise affects the brain. This protein plays a key role in neuronal survival, synaptic plasticity, and the growth of new neurons. It's often called "Miracle-Gro for the brain."

BDNF is highly expressed in the hippocampus, cortex, and amygdala. Lower levels are associated with depression, cognitive decline, and neurodegenerative diseases. Higher levels are associated with better learning, memory, and mood.

Exercise reliably increases BDNF levels. A 2024 meta-analysis confirmed that both aerobic exercise and resistance training elevate BDNF, with moderate-to-high intensity exercise being most effective. The mechanism involves a fascinating cascade: when muscles contract during exercise, they release molecules (including lactate and a protein called irisin) that cross the blood-brain barrier and trigger BDNF production in the hippocampus.

In the 2011 hippocampus study, the walkers' increased hippocampal volume was directly correlated with their increased serum BDNF levels. This provides strong evidence that BDNF mediates at least part of exercise's brain benefits.

3. Neurogenesis: Growing New Brain Cells

For most of the 20th century, scientists believed that adults couldn't grow new brain cells. We now know this is wrong. The hippocampus continues to produce new neurons throughout life, a process called neurogenesis. And exercise is one of the most reliable ways to stimulate it.

Animal studies consistently show that exercise increases neurogenesis in the dentate gyrus, a subregion of the hippocampus critical for memory formation. The new neurons integrate into existing circuits and appear to contribute to learning and pattern separation (the ability to distinguish between similar experiences).

Proving neurogenesis in living humans is technically difficult, but indirect evidence strongly suggests it occurs. The volume increases seen in imaging studies, combined with the memory improvements, are consistent with new neuron growth.

4. Reduced Inflammation

Chronic low-grade inflammation is increasingly recognized as a driver of cognitive decline. As we age, inflammatory markers tend to rise, and this "inflammaging" is associated with worse memory and higher dementia risk.

Regular exercise has anti-inflammatory effects. It reduces circulating inflammatory markers like C-reactive protein and interleukin-6. Research indicates that these anti-inflammatory effects contribute to exercise's protective effects on the brain, particularly for people who are overweight or have metabolic dysfunction.

5. Improved Insulin Sensitivity

Your brain runs on glucose, and insulin helps regulate how well your cells can use it. Insulin resistance, common in obesity and type 2 diabetes, impairs the brain's ability to fuel itself. Some researchers have called Alzheimer's "Type 3 diabetes" because of the strong links between metabolic dysfunction and cognitive decline.

Exercise improves insulin sensitivity throughout the body, including in the brain. This means better glucose uptake, better energy production, and better cognitive function. The metabolic benefits of exercise may be particularly important for the growing population with prediabetes or metabolic syndrome.

What Type of Exercise Works Best?

Different types of exercise affect the brain differently. Here's what the research shows about each major category.

Aerobic Exercise: Strongest Evidence for Memory

Aerobic (cardiovascular) exercise has the most robust evidence for improving memory specifically. Walking, running, cycling, swimming, dancing: anything that gets your heart rate elevated for a sustained period falls into this category.

A 2025 network meta-analysis that compared different exercise types found that aerobic exercise had the strongest effect on memory function. The hippocampus growth seen in the landmark 2011 study came from aerobic exercise (walking), not from stretching or resistance training.

The mechanisms make sense: aerobic exercise is particularly good at increasing cerebral blood flow and BDNF production. The sustained cardiovascular demand seems to be what drives the strongest hippocampal benefits.

Practical note: Intensity matters. Leisurely walking is better than sitting, but moderate-intensity exercise (where you're breathing harder but can still talk) appears more effective than very light activity. The 2011 study used walking at 60-75% of maximum heart rate.

Resistance Training: Strongest for Executive Function

Weight training, resistance bands, and bodyweight exercises have traditionally received less attention in brain health research than aerobic exercise. That's changing. Recent studies show that resistance training has significant cognitive benefits, particularly for executive function.

A 2025 systematic review and meta-analysis of 17 randomized controlled trials found that resistance training significantly improved overall cognition, working memory, verbal learning and memory, and spatial memory in older adults. The network meta-analysis found that resistance training had the strongest effect on overall cognitive improvement and inhibitory control (the ability to filter out distractions and resist impulses).

The mechanisms differ somewhat from aerobic exercise. Resistance training appears to work partly through increased IGF-1 (insulin-like growth factor), muscle-derived myokines, and improvements in cortical thickness in vulnerable brain regions. A 2025 randomized trial showed that just 12 weeks of resistance training increased cortical thickness in the hippocampus and prefrontal cortex.

Practical note: Current evidence suggests 2-3 sessions per week, with 45-60 minutes per session, produces meaningful cognitive benefits. Progressive overload (gradually increasing difficulty) matters for both muscle and brain adaptation.

Combined Training: The Best of Both?

Given that aerobic and resistance exercise work through partially different mechanisms, combining them makes intuitive sense. A 2025 meta-analysis of 35 randomized controlled trials found that concurrent aerobic and resistance training had a positive effect on global cognition in healthy older adults.

The analysis found that interventions of medium length (13-26 weeks) were most effective, and that adults aged 65 and older showed greater benefits than younger participants. Both frequency and duration of exercise positively influenced outcomes.

For most people, a program that includes both cardiovascular exercise and some resistance training is probably optimal for both physical and cognitive health. This aligns with general fitness recommendations from organizations like the American College of Sports Medicine.

What About Yoga, Tai Chi, and Stretching?

Mind-body exercises like yoga and tai chi combine physical movement with attention, breathing, and often social interaction. Research suggests these practices can improve aspects of cognition, particularly attention and executive function, though the evidence is less extensive than for traditional aerobic exercise.

Simple stretching, as a control condition in many studies, typically doesn't produce the same brain benefits as aerobic exercise. However, stretching isn't useless: it improves flexibility, reduces injury risk, and may have stress-reduction benefits.

If mobility limitations make traditional aerobic exercise difficult, yoga and tai chi are reasonable alternatives that provide some cognitive benefits along with balance and flexibility improvements.

The 20-Minute Solution: Getting Started

One thing I've learned from my own experience: the hardest part isn't the exercise itself. It's building the habit.

For years I knew exercise was important but didn't do it consistently. My schedule felt too packed. I'd start and stop. The benefits I experienced during active periods would fade during inactive ones.

What finally worked for me was committing to a minimum of 20 minutes of intense cardio at least five days a week. Twenty minutes is short enough to fit into almost any schedule, long enough to provide real benefits. I use interval training: alternating between moderate and higher intensity rather than staying at a steady pace. This makes the time go faster and may provide additional benefits.

Here's a simple approach to get started:

Week 1-2: Walk for 20 minutes, 5 days a week. Just walk. Get in the habit of showing up.

Week 3-4: Add brief intervals. Walk faster for one minute, then return to normal pace. Repeat 3-4 times during your walk.

Week 5+: Gradually increase either duration (up to 30-40 minutes) or intensity (faster intervals, more of them).

The key insight from research is that consistency matters more than any single session being perfect. The brain changes happen over weeks and months of regular activity. Missing one workout doesn't undo your progress, but stopping for weeks does allow your gains to fade.

I've had times when my schedule was so hectic I found myself on the treadmill at midnight just to get my workout in. But as someone once told me, the exercise is almost always worth more than the sleep you'd get instead. Given what we now know about how exercise protects brain function, that advice has more weight than ever.

Practical Recommendations

Based on current evidence, here's what I recommend:

For aerobic exercise: Aim for 150 minutes per week of moderate-intensity activity (brisk walking, cycling, swimming) or 75 minutes of vigorous activity (running, fast cycling). This aligns with general health guidelines and is the threshold associated with meaningful cognitive benefits.

For resistance training: 2-3 sessions per week, working major muscle groups. This can be weight machines, free weights, resistance bands, or bodyweight exercises. Focus on progressive overload: gradually increasing the challenge over time.

For best results: Combine both types. A program that includes aerobic exercise for cardiovascular and hippocampal benefits, plus resistance training for executive function benefits, covers your bases.

For timing: Exercise before learning may provide an acute boost to attention and encoding. But the long-term benefits come from regular practice over months, not from perfectly timing individual sessions.

For those starting from sedentary: Something is better than nothing. Start with whatever you can do consistently. Even modest amounts of walking are better than no activity. You can build from there.

For older adults: The benefits may actually be larger for older adults than for younger ones, and the interventions don't need to be extreme. Walking programs produce measurable brain changes in people in their 60s and 70s.

The Brain-Heart Connection

Exercise benefits your brain partly by benefiting your heart and blood vessels. The cardiovascular system and the brain are intimately connected.

High blood pressure in midlife is associated with increased risk of cognitive impairment and dementia later. The small blood vessels that supply your brain are vulnerable to damage from hypertension, leading to white matter lesions, microbleeds, and impaired blood flow.

Exercise is one of the most effective interventions for blood pressure. It also improves cholesterol profiles, reduces arterial stiffness, and decreases the risk of stroke. All of these vascular benefits translate to brain benefits.

If you have hypertension, diabetes, or metabolic syndrome, the cognitive benefits of exercise may be even more important for you. Addressing these vascular risk factors through exercise (and medication if needed) is protective for long-term brain health.

When Exercise Isn't Enough

Exercise is powerful, but it's not magic. If you're experiencing concerning memory problems, exercise alone isn't a substitute for medical evaluation.

See a doctor if you notice memory changes that interfere with daily life, confusion about time or place, difficulty completing familiar tasks, or if family members are expressing concern. These could indicate conditions that need medical attention.

That said, exercise remains beneficial even in the context of mild cognitive impairment or early dementia. Research suggests that exercise can slow the rate of decline, even if it can't reverse established disease. It's never too late to start.

The Bottom Line

If there were a pill that could grow your hippocampus, improve your memory, reduce your dementia risk, boost your mood, help you sleep better, and extend your life, everyone would take it. Exercise is that pill.

The evidence is not ambiguous. Regular physical activity, especially aerobic exercise, produces measurable changes in brain structure and function. It increases BDNF, improves blood flow, reduces inflammation, and may stimulate the growth of new neurons. Resistance training adds benefits for executive function and cortical thickness.

You don't need to become a marathon runner. Walking counts. Consistency counts more than intensity. The improvements compound over months of regular activity.

I can tell you from personal experience that the difference between my brain during periods of consistent exercise versus periods of inactivity is night and day. The research explains why. The benefits are real, they're substantial, and they're available to almost everyone who makes the commitment to move.

For more on lifestyle factors that affect memory, see the Brain Health section. For how sleep interacts with exercise and memory, see Sleep and Memory. For techniques to encode information more effectively once your brain is functioning well, see Memory Skills.

Important: This page provides educational information about exercise and brain health. It is not medical advice. If you have health conditions that might affect your ability to exercise, or concerns about cognitive decline, please consult a healthcare professional. See my Medical Disclaimer.

References & Research

I've reviewed these sources and selected them for their relevance to understanding how exercise affects memory and the brain. Here's what each contributes:

1. Erickson, K.I., Voss, M.W., Prakash, R.S., et al. (2011). "Exercise training increases size of hippocampus and improves memory." Proceedings of the National Academy of Sciences, 108(7), 3017-3022. Free full text at PMC
Researcher's Note: This is the landmark study that demonstrated aerobic exercise actually grows the hippocampus. The randomized controlled design with 120 older adults, the use of MRI to measure brain volume changes, and the correlation with BDNF levels make this one of the most important papers in exercise and brain health research. The intervention (walking 40 minutes, 3x/week) was deliberately modest and achievable.

2. Stillman, C.M., Cohen, J., Lehman, M.E., & Erickson, K.I. (2016). "Mediators of Physical Activity on Neurocognitive Function: A Review at Multiple Levels of Analysis." Frontiers in Human Neuroscience, 10, 626. Free full text at PMC
Researcher's Note: This comprehensive review examines the multiple mechanisms through which exercise affects cognition, including cerebral blood flow, neurogenesis, inflammation, and metabolic factors. It provides the scientific framework for understanding why exercise benefits are so broad and consistent.

3. Miranda, M., Morici, J.F., Zanoni, M.B., & Bekinschtein, P. (2019). "Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain." Frontiers in Cellular Neuroscience, 13, 363. Free full text at PMC
Researcher's Note: This review explains BDNF's role in learning, memory, and neuroplasticity. Understanding BDNF is essential for understanding why exercise benefits the brain. The paper covers both normal function and what happens when BDNF is reduced, as in aging and neurodegenerative disease.

4. Dinoff, A., Herrmann, N., Swardfager, W., & Bhagwagar, Z. (2018). "The Effect of Exercise Training on Resting Concentrations of Peripheral Brain-Derived Neurotrophic Factor (BDNF): A Meta-Analysis." PLOS ONE, 12(9), e0163037. See also: Frontiers in Neurology (2024) review on exercise and BDNF. Free full text at PMC
Researcher's Note: This meta-analysis confirmed that exercise training increases resting BDNF levels. The finding that moderate-to-high intensity exercise is more effective than low intensity has practical implications for exercise prescription. Recent 2024 reviews have continued to support these findings.

5. van Praag, H., Shubert, T., Zhao, C., & Gage, F.H. (2005). "Exercise Enhances Learning and Hippocampal Neurogenesis in Aged Mice." Journal of Neuroscience, 25(38), 8680-8685. Free full text at PMC
Researcher's Note: This influential study demonstrated that exercise increases neurogenesis in the hippocampus of aged mice and that these new neurons contribute to learning and memory. While proving neurogenesis in living humans is technically difficult, this and similar animal studies provide strong evidence for the phenomenon.

6. Han, Y., Zhang, Y., Zhang, R., Li, W., & Wu, X. (2025). "Optimal exercise interventions for enhancing cognitive function in older adults: a network meta-analysis." Frontiers in Aging Neuroscience, 17, 1510773. Free full text at PMC
Researcher's Note: This recent network meta-analysis compared different types of exercise for cognitive benefits. The finding that aerobic exercise was strongest for memory while resistance training was strongest for overall cognition and inhibitory control has practical implications for exercise selection. The study included data from trials through January 2024.

7. Zhang, Y., Liu, R., Wang, H., et al. (2025). "A systematic review and meta-analysis of the effects of resistance exercise on cognitive function in older adults." Frontiers in Psychiatry, 16, 1708244. Free full text at Frontiers
Researcher's Note: This 2025 meta-analysis of 17 RCTs (739 participants) found that resistance training significantly improved overall cognition, working memory, verbal learning and memory, and spatial memory. The findings support resistance training as an evidence-based intervention for cognitive health, not just muscle strength.

8. Kušleikienė, S., Ziv, G., Vints, W.A.J., et al. (2025). "Cognitive gains and cortical thickness changes after 12 weeks of resistance training in older adults." Brain Research Bulletin, 222, 111249. ScienceDirect
Researcher's Note: This randomized controlled trial demonstrated that just 12 weeks of resistance training increased cortical thickness in the hippocampus and prefrontal cortex. This provides structural evidence for how resistance training benefits cognition, complementing the functional improvements seen in other studies.

9. Feng, Y., Zhang, Y., Wang, L., et al. (2025). "The regular effects of concurrent aerobic and resistance exercise on global cognition in healthy elderly populations: A systematic review with meta-analysis of randomized trials." Experimental Gerontology. ScienceDirect
Researcher's Note: This 2025 meta-analysis of 35 RCTs (5,734 participants) evaluated combined aerobic and resistance training. The finding that medium-length interventions (13-26 weeks) were most effective, and that older adults showed greater benefits, provides practical guidance for program design.

10. Gothe, N.P., Khan, I., Hayes, J., Erlenbach, E., & Damoiseaux, J.S. (2019). "Yoga Effects on Brain Health: A Systematic Review of the Current Literature." Brain Plasticity, 5(1), 105-122. Free full text at PMC
Researcher's Note: This systematic review examines the cognitive effects of yoga and similar mind-body practices. While the evidence base is smaller than for traditional exercise, the findings suggest benefits for attention and executive function. Useful for people who may have limitations preventing more vigorous exercise.

11. Livingston, G., Huntley, J., Liu, K.Y., et al. (2024). "Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission." The Lancet, 404(10452), 572-628. The Lancet
Researcher's Note: The Lancet Commission's definitive summary of modifiable dementia risk factors identifies physical inactivity as one of 14 factors that together account for up to 45% of dementia cases worldwide. The report emphasizes that cardiovascular risk factors (including hypertension) are closely linked to brain health.

12. Erickson, K.I., Hillman, C., Stillman, C.M., et al. (2019). "Physical Activity, Cognition, and Brain Outcomes: A Review of the 2018 Physical Activity Guidelines." Medicine & Science in Sports & Exercise, 51(6), 1242-1251. Free full text at PMC
Researcher's Note: This review was conducted for the Physical Activity Guidelines Advisory Committee. The conclusions are authoritative: moderate-to-vigorous physical activity improves cognition across the lifespan, with strong evidence that greater physical activity is associated with reduced risk of cognitive impairment and Alzheimer's disease.

Published: 02/10/2007
Last Updated: 12/30/2025