Physical Activity for Brain Health

In short

• Regular physical activity is one of the best-supported habits for long-term brain health, at any adult age.
• Exercise raises brain-derived neurotrophic factor (BDNF), a protein that supports the growth and maintenance of brain cells.
• In a year-long trial, older adults who walked three days a week grew their hippocampus, a key memory region, by about 2 percent.
• Aerobic exercise and strength training both help. Each has improved attention and executive function in randomized trials.
• Aim for 150 to 300 minutes of moderate activity a week plus two strength sessions, and start wherever you are.
  

Physical activity supports brain health by changing the brain itself. Regular exercise increases blood flow to memory regions, raises growth factors that help brain cells form and keep connections, and in trials of older adults it has increased the size of the hippocampus and improved attention and executive function. These changes build over months of consistent activity, and they have been shown in people who started exercising late in life.

Here is what the research shows, and how much activity it takes.

What exercise does for the brain over the long term

The short-term effects of a workout, such as a lift in mood and a calmer stress response, are covered in How Does Working Out Reduce Stress?. This post is about what accumulates over months and years.

1. It raises a growth factor the brain depends on

Brain-derived neurotrophic factor (BDNF) is a protein that helps neurons grow, survive and strengthen their connections. It is one of the main molecules behind neuroplasticity, the brain's ability to change with experience. A meta-analysis found that a single session of exercise raises BDNF, and that people who exercise regularly see a larger rise from each session.

2. It increases blood flow to memory regions

In a study of adults who completed three months of aerobic training, blood volume rose in the dentate gyrus, a part of the hippocampus involved in forming new memories. The increase tracked how much each person's fitness improved, and it was linked to better scores on a memory test.

3. It can grow the hippocampus

The hippocampus tends to shrink gradually in later adulthood. In a randomized trial of 120 older adults, one group walked around a track for 40 minutes, three days a week, for a year. A comparison group did stretching and toning. The walking group's hippocampus grew by about 2 percent. The stretching group's shrank by about 1.4 percent. Larger gains in volume went with larger rises in BDNF and better spatial memory.

4. It adds volume in regions behind planning and attention

An earlier trial gave adults aged 60 to 79 six months of aerobic training or a toning program. The aerobic group gained gray matter in prefrontal and temporal regions and white matter in the tracts connecting the two halves of the brain. The toning group showed no such change.

5. It strengthens connections between brain networks

The brain works through networks of regions that need to communicate. In a year-long walking trial, older adults showed stronger connectivity within the default mode network and a frontal executive network, two systems that weaken with age. The gains in connectivity went with gains in executive function.

6. Strength training counts too

Aerobic exercise gets most of the attention, but resistance training has its own evidence. In a 12-month randomized trial of 155 women aged 65 to 75, those who did resistance training once or twice a week improved on a test of selective attention and conflict resolution. The balance-and-toning group did not.

Why the brain responds to movement

One proposed explanation is evolutionary. Researchers have argued that the human brain developed under conditions where physical activity and thinking happened together: tracking, foraging and navigating across long distances while making decisions. In that model, the brain responds most to movement that also asks something of the mind.

It remains a hypothesis, but it suggests a practical idea. Activities that combine movement with attention, such as trail walking, dancing, racket sports or learning a new skill, may give the brain more to adapt to than a treadmill alone.

How much physical activity for brain health

A meta-analysis of exercise trials in adults over 50 found that exercise improved cognitive function regardless of where people started. Aerobic training, resistance training and mixed programs all helped. The benefits appeared at moderate intensity or above, with sessions of 45 to 60 minutes.

The Physical Activity Guidelines for Americans recommend:

• Aerobic activity: 150 to 300 minutes of moderate activity a week, or 75 to 150 minutes of vigorous activity.
• Strength training: muscle-strengthening work on two or more days a week.
• Any amount above zero: the guidelines note that some activity is better than none, and that a single session brings short-term benefits to thinking.
  

A brisk walk counts as moderate activity. So does cycling at a steady pace, swimming, or any activity that raises your breathing enough that talking takes effort but stays possible.

How to build physical activity into your week

1. Start with walking. It is the exercise used in the hippocampus and connectivity trials, and it needs no equipment.
2. Add two strength sessions. Bodyweight exercises, resistance bands or weights all count.
3. Make some of it demanding for the mind. Choose routes you do not know, sports with rules and tactics, or classes where you learn a sequence.
4. Keep going for months. The brain changes in these trials appeared after six months to a year. Consistency is what the evidence rewards.
   

Training the brain directly

Exercise builds the conditions for change in the brain. Growth factors rise, blood flow improves, and networks become more connected. Training can then direct that capacity toward specific functions such as attention and processing speed, because the brain keeps adapting throughout life. That adaptability is called neuroplasticity.

The Sens.ai at-home system combines brain stimulation, neurofeedback training and an objective assessment of brain function. Neurofeedback shows your brain its own activity in real-time through sound and images, so it can learn to self-regulate.

The Sharp Mind Mission is the protocol the app recommends to people who report brain fog that has crept in with age. In the Sharp Mind whitepaper, 42 participants were measured on an event-related potential (ERP) task before and after the Mission:

• Measured (quantitative): processing speed improved 10.2%, with 84% of users improving. Reaction time improved 7%, with 95% of users improving. Errors fell 40.6%. The 70-person comparison group showed no improvement.
• Self-reported (qualitative): after one month, 73% of users said their mental clarity and memory had improved.
  

The protocol is fifteen minutes a session, three to five times a week, with impact observed and measured after weeks of use. The full results are in the Sharp Mind whitepaper on our results page.

The assessment is never a rerun of the training. You are not tested on the exercise you practiced, so an improvement reflects a change in how your brain is working rather than a better score at a game.

Questions people ask

See what your brain can do

Sens.ai measures, stimulates and trains your brain in one at-home system, so you can see what is changing instead of guessing.

References

1. Szuhany KL, Bugatti M, Otto MW. A meta-analytic review of the effects of exercise on brain-derived neurotrophic factor. Journal of Psychiatric Research. 2015;60:56-64. PMID 25455510.
2. Pereira AC, Huddleston DE, Brickman AM, et al. An in vivo correlate of exercise-induced neurogenesis in the adult dentate gyrus. Proceedings of the National Academy of Sciences. 2007;104(13):5638-5643. PMID 17374720.
3. Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences. 2011;108(7):3017-3022. PMID 21282661.
4. Colcombe SJ, Erickson KI, Scalf PE, et al. Aerobic exercise training increases brain volume in aging humans. Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 2006;61(11):1166-1170. PMID 17167157.
5. Voss MW, Prakash RS, Erickson KI, et al. Plasticity of brain networks in a randomized intervention trial of exercise training in older adults. Frontiers in Aging Neuroscience. 2010;2:32. PMID 20890449.
6. Liu-Ambrose T, Nagamatsu LS, Graf P, et al. Resistance training and executive functions: a 12-month randomized controlled trial. Archives of Internal Medicine. 2010;170(2):170-178. PMID 20101012.
7. Raichlen DA, Alexander GE. Adaptive capacity: an evolutionary neuroscience model linking exercise, cognition, and brain health. Trends in Neurosciences. 2017;40(7):408-421. PMID 28610948.
8. Northey JM, Cherbuin N, Pumpa KL, Smee DJ, Rattray B. Exercise interventions for cognitive function in adults older than 50: a systematic review with meta-analysis. British Journal of Sports Medicine. 2018;52(3):154-160. PMID 28438770.
9. Piercy KL, Troiano RP, Ballard RM, et al. The Physical Activity Guidelines for Americans. JAMA. 2018;320(19):2020-2028. PMID 30418471.
10. Hillman CH, Erickson KI, Kramer AF. Be smart, exercise your heart: exercise effects on brain and cognition. Nature Reviews Neuroscience. 2008;9(1):58-65. PMID 18094706.
11. Sens.ai Sharp Mind whitepaper, results page.