Exercise and the Brain: The Neurobiological Case for Moving Your Body
Exercise benefits the ageing brain: in a meta-analysis of randomised trials in adults over 50, exercise improved cognitive function.6 In animal studies, exercise raises BDNF and other growth factors and stimulates the birth of new neurons.1
- In a randomised trial of 120 older adults, aerobic exercise training increased the size of the hippocampus by 2%, effectively reversing 1 to 2 years of age-related shrinkage, and improved spatial memory.5
- Proposed mechanisms include growth factors such as BDNF, better blood flow to the brain and a reduction in peripheral risk factors such as poor metabolic health.4,5
- In the meta-analysis, sessions of 45 to 60 minutes at moderate intensity or higher were associated with benefits to cognition.6
- Strength training helps too: in a 12-month trial in 155 women aged 65 to 75, resistance training once or twice a week improved a test of selective attention and conflict resolution compared with balance and tone exercises.7
- The meta-analysis authors recommend both aerobic and resistance exercise of at least moderate intensity on as many days of the week as feasible.6
The idea that exercise benefits the brain is ancient: mens sana in corpore sano, a healthy mind in a healthy body. Modern research has added mechanisms. In animal studies, voluntary exercise raises levels of BDNF and other growth factors, stimulates neurogenesis, increases resistance to brain injury and improves learning.1 Randomised trials in people now show measurable effects on brain structure and cognition.
Hippocampal Neurogenesis: The Central Discovery
For most of the 20th century, scientists believed that adult brains could not make new neurons. Animal research overturned this for rodents: in a 1999 mouse study, voluntary wheel running doubled the number of surviving newborn cells in the hippocampus, as much as a fully enriched environment did.2 Whether, and how much, adult humans make new hippocampal neurons is still debated.
In people, the closest evidence comes from brain imaging. In the randomised trial of 120 older adults, aerobic exercise training enlarged the anterior hippocampus by 2% while hippocampal volume declined in the control group; the increase was associated with higher blood levels of BDNF, and spatial memory improved.5
Cerebrovascular Effects: Blood Flow and Angiogenesis
Blood flow matters for the brain. In the Rotterdam Study of 1,730 people aged 55 and older, those with greater cerebral blood flow velocity were less likely to have dementia and, if they did not have dementia, had less cognitive decline over the preceding years.3 Physical activity training can increase blood flow to the hippocampus.5
This matters for Alzheimer’s disease, because blood-vessel disease often coexists with Alzheimer’s changes in the brain and can add to cognitive impairment.
Resistance Training: The Cognitive Dimension
Resistance training may work partly through different routes. A leading review identifies growth factors as a key mechanism by which exercise benefits the brain, and notes that exercise also reduces peripheral risk factors;4 better insulin sensitivity is one such factor.
In the 12-month trial by Liu-Ambrose and colleagues, 155 women aged 65 to 75 were assigned to resistance training once or twice a week or to twice-weekly balance and tone exercises. Performance on the Stroop test, a measure of selective attention and conflict resolution, improved by 12.6% and 10.9% in the two resistance groups and worsened by 0.5% in the balance group; unexpectedly, both resistance groups also showed small reductions in whole-brain volume.7 Across 36 trials in adults over 50, aerobic exercise, resistance training, multicomponent training and tai chi all improved cognition.6
Exercise for Specific Neurological Conditions
Exercise is also being tested in neurological disease. In a phase 2 trial in 128 people with newly diagnosed Parkinson’s disease, six months of high-intensity treadmill exercise was followed by almost no worsening of motor symptoms (0.3 points on the standard rating scale) compared with 3.2 points in the control group; the authors called for a larger efficacy trial.8 For depression, exercise is an effective treatment, as our article on depression and longevity explains.9
References
- 1Cotman CW, Berchtold NC. "Exercise: a behavioral intervention to enhance brain health and plasticity." Trends Neurosci. 2002;25(6):295-301. PubMed · DOI
- 2van Praag H, et al. "Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus." Nat Neurosci. 1999;2(3):266-70. PubMed · DOI
- 3Ruitenberg A, et al. "Cerebral hypoperfusion and clinical onset of dementia: the Rotterdam Study." Ann Neurol. 2005;57(6):789-94. PubMed · DOI
- 4Cotman CW, et al. "Exercise builds brain health: key roles of growth factor cascades and inflammation." Trends Neurosci. 2007;30(9):464-72. PubMed · DOI
- 5Erickson KI, et al. "Exercise training increases size of hippocampus and improves memory." Proc Natl Acad Sci U S A. 2011;108(7):3017-22. PubMed · DOI
- 6Northey JM, et al. "Exercise interventions for cognitive function in adults older than 50: a systematic review with meta-analysis." Br J Sports Med. 2018;52(3):154-160. PubMed · DOI
- 7Liu-Ambrose T, et al. "Resistance training and executive functions: a 12-month randomized controlled trial." Arch Intern Med. 2010;170(2):170-8. PubMed · DOI
- 8Schenkman M, et al. "Effect of High-Intensity Treadmill Exercise on Motor Symptoms in Patients With De Novo Parkinson Disease: A Phase 2 Randomized Clinical Trial." JAMA Neurol. 2018;75(2):219-226. PubMed · DOI
- 9Noetel M, et al. "Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials." BMJ. 2024;384:e075847. PubMed · DOI
