Most of us are aware of the many physical benefits of exercise such as strength and fitness, maintaining a healthy weight, and protecting us from chronic diseases like heart disease, cancer and diabetes. But did you know that regular exercise has positive effects on brain function and mental health – reducing risk for dementia, anxiety and depression while improving mood, improving sleep and building resilience to stress.
Research studies have shown that people who exercise regularly are more likely to have better cognitive function (memory, focus, thinking skills) than those who don’t exercise. This has been found for people at middle age and at old age, where regular physical exercise is associated with better cognitive function and less age-related shrinkage of the brain. According to latest research, moderate-intensity exercise can help improve your brain performance in as little as 6 months.
Science has also proven that exercise has positive effects on psychological wellbeing – reducing anxiety, improving mood, improving sleep and protecting against the harmful consequences of stress, building resilience. Researchers have found that those who participate in regular vigorous exercise are 25% less likely to develop depression or an anxiety order over the next five years.
How does it work?
We now know that the brain has the ability to change its structure in response to learning and experience, known as neuroplasticity. Through neuroplasticity new neurons (brain nerve cells) are created and new neural connections or pathways are formed, thereby increasing the volume and changing the structure to the part of the brain affected by the event or experience. Studies have shown that people who engage in regular moderate-intensity physical activity have increased brain volume in regions of the brain associated with memory, learning, concentration and planning. Suggesting that these individuals may have experienced neuroplasticity as a result of regular exercise, allowing their brains to function more effectively. Older adults who are physically active have also been shown to have brain volumes and connectivity typical of younger adults.
Abundant research in the last decade has shown that exercise is one of the strongest promoters of neurogenesis in the human brain, and this has introduced the possibility that proliferating neurons could contribute to the cognitive enhancement observed with exercise. Exercise has also been shown to increase the production of certain growth factors — chemicals that affect the growth of cells and tissues within the body. Brain derived neurotrophic factor (BDNF) is the most prevalent growth factor in the central nervous system and plays a crucial role in the development and plasticity of the brain. BDNF promotes the survival and aids in the regeneration of neurons, enhances synaptic growth, promotes learning and protects against cognitive decline. The finding that exercise increases BDNF levels in the hippocampus – an area vital for memory formation and learning – has provided insight about the possible molecular mechanisms responsible for the positive effects of exercise on cognition. BDNF has also been implicated in mood and anxiety disorders, with decreased BDNF levels found in post-mortem studies of suicide depression patients.
The brain is our most complex organ, requiring constant supplies of oxygen and nutrients in order to function effectively. The supply of oxygen and nutrients is dependent on the health of the blood vessels which transport oxygen and nutrient rich blood to the brain, and remove harmful waste products such as neurotoxins. It has been estimated that nearly every neuron in the human brain has its own capillary (blood vessel), therefore with the formation on new neurons associated with neuroplasticity comes the increased need for adequate blood supply. Cardiovascular diseases and diabetes can damage the blood vessels in the brain thereby compromising brain function. Exercise is protective against these diseases, reduces inflammation and damage in the body, increases blood flow to the brain and promotes healthy blood vessels.
Increased brain blood flow, healthier brain cells and reduced cardiovascular risk may all contribute to the beneficial effects of physical activity on brain performance. Exercise can also boost memory and thinking indirectly by improving mood and sleep, and by reducing stress and anxiety, building resilience. Problems in these areas frequently cause or contribute to cognitive impairment. Studies show that exercise has a positive effect on neurobiological factors of resilience such as:
Exercise increases NPY – A neuropeptide (small protein-like molecule used by brain cells (neurons) to communicate with each other) that inhibits anxiety and protects against stress. Reduced NPY levels are associated with posttraumatic stress disorder (PTSD) while higher levels are associated with better behavioural and stress responses.
Exercise increases serotonin – A neurotransmitter (chemical messenger used to transmit signals within the brain) that affects the regulation of mood, anxiety, happiness and sleep. Reduced serotonin levels are associated with anxiety and depression. Chronic stress and the associated release of cortisol (stress hormone) has been shown to reduce serotonin levels.
Exercise increases HRV – Heart rate variability (HRV) is a measurement we use that looks at the changes in the interval between heartbeats (R-R intervals) over time. HRV reflects the health of the autonomic nervous system (ANS) by measuring the balance of sympathetic (stress response) and parasympathetic (relaxation response) activation, thereby measuring the balance between stress and recovery. A high HRV translates to improved ANS balance resulting in decreased cortisol release, and improved resilience. Low HRV reflects ANS imbalance consisting of sympathetic dominance and diminished parasympathetic stimulation.
Regular exercise significantly elevates HRV robustness, similarly, research has found that aerobically-trained individuals exhibit a high degree of HRV compared to sedentary individuals. This is demonstrated in the evidence from over 100,000 Firstbeat assessments that shows people who exercise regularly have higher HRV, and achieve better quality recovery when compared to inactive people.
Exercise improves sleep – Research has shown that exercise improves not only the quantity of sleep but the quality too with studies indicating that regular exercise increases both total sleep time and slow wave sleep, the deepest and most restorative stages of sleep. Exercise has also been shown to strengthen the circadian rhythm, promoting daytime alertness and vitality, whilst helping to bring on sleepiness at night. Sleep deprivation is often associated with or driven by anxiety, depression and chronic stress. Sleep deprivation has many of the same negative effects as chronic stress and can aggravate the stress response creating a vicious cycle where chronic stress results in sleep deprivation and sleep deprivation results in elevated stress levels.
How much exercise is needed to gain a benefit?
Most of the current research linking exercise to improved resilience and reduced stress has focused on aerobic exercise (walking, running, swimming, cycling), and Yoga. Some studies show that exercise can work quickly to elevate mood with as little as 5 minutes of aerobic exercise resulting in anti-anxiety effects. This may be especially relevant when exercising outdoors in a natural environment, also known as green exercise. Research suggests that green exercise results in greater feelings of revitalisation, improved self-esteem and reduced feelings of tension, anger and depression. Being in nature helps reduce stress too with studies showing a fall in stress hormones such as adrenaline, noradrenaline and cortisol, after being within a natural environment. Interestingly, the first five minutes of green exercise appears to have the biggest impact on mood and self-esteem, suggesting an immediate psychological health benefit.
However, physiological changes such as increased HRV and improved sleep seem to require a longer exercise training period. Studies have shown significant increases in HRV after 8 weeks of aerobic and resistance exercise training performed for 1hour, 3 times per week. Researchers have also evidenced significant improvements in sleep in adults with insomnia after 16 weeks of aerobic exercise performed for 30-40 minutes, 3-4 times per week.
Research examining the link between exercise and enhanced brain performance have found the following:
- In a study that followed 1,449 people for over 20 years, those who exercised at least twice a week at midlife were on average 52% less likely to develop dementia in old age (Rovio S, et al. Lancet Neurology, 2005; 4:705-711).
- In another study involving people aged 65 and over, exercising at least 3 times per week was associated with a 38% reduced risk of developing dementia (Larson EB, et al. Ann Intern Med, 2006; 144:73-81).
A study published in the Journal of the American Geriatrics Society suggests that tai chi may enhance cognitive function in older adults, especially with regards to cognitive processes such as planning, working memory, attention, problem solving, and verbal reasoning. This finding could be due to the fact that tai chi involves slow, focused movements, requiring the learning and memorizing of new skills and movement patterns.
Aerobic fitness has also been shown to promote better functioning of the brain, especially in neural networks involved in cognitive control of inhibition and attention. Studies suggest that individuals with higher levels of cardiorespiratory fitness are capable of allocating greater attentional resources toward the environment and are therefore able to process information more quickly, when compared to less active and lower fit individuals. This suggests that engaging in higher intensity exercise that improves your cardiorespiratory fitness level may provide even more benefit to your brain than simply engaging in regular moderate-intensity exercise.
How to get started
Make exercise an essential part of your routine, choose activities that you enjoy and fit easily into your lifestyle, not ones that create more stress. To improve motivation, make your exercise a social activity and exercise with a friend or a group.
Initially aim to exercise at a moderate-intensity — such as brisk walking, swimming or cycling — for a minimum of 150 mins per week (30 mins per day, 5 days per week). If you are new to exercise start with a few minutes a day, and increase the amount by five or 10 mins every week until you feel comfortable to increase the intensity into the moderate range.
For additional health benefits, you should be aiming for 300 mins per week of moderate-intensity exercise (1 hour per day, 5 days per week) OR 150 mins of vigorous-intensity exercise – such as running, fast paced swimming, hill cycling – throughout the week. Exercise should be performed in bouts of at least 10 mins, and muscle-strengthening activities should be done involving major muscle groups (push-ups, squats, lunges) on 2 or more days a week. A stretching programme should also be included on the days of exercise.
Be careful to avoid high intensity exercise too close to bed as this can have a stimulating / alerting effect on the body, reducing your ability to fall asleep and reducing the quality of sleep in the beginning of the sleep period. Research has shown that a poor night sleep can significantly influence exercise duration the next day, so to increase your chances of adherence to your exercise routine ensure you get a good night sleep the night before.
Want to know more?
- Harvard Health Publications, Exercise can boost your memory and thinking skills – http://www.health.harvard.edu/mind-and-mood/exercise-can-boost-your-memory-and-thinking-skills
- Alzheimer’s Australia, Dementia Risk Reduction: A Practical Guide for General Practitioners, 2011.
- Neuron, Volume 57, Issue 2, 24 January 2008, Pages 178–201, Review The Blood-Brain Barrier in Health and Chronic Neurodegenerative Disorders, Berislav V. Zlokovic1.
- Compr Physiol. 2013 Jan; 3(1): 403–428. The Influence of Exercise on Cognitive Abilities
- Trends in Neuroscience, Volume 30. No.9, Exercise builds brain health: key roles of growth factor cascades and inflammation, Carl W. Cotman, Nicole C. Berchtold and Lori-Ann Christie, 2002.
- Front Behav Neurosci. 2013; 7: 10. Published online 2013 Feb 15. Understanding resilience
- Cogn Affect Behav Neurosci. 2001 Dec;1(4):388-93. Correlation between cortisol level and serotonin uptake in patients with chronic stress and depression
- Am J Cardiol 1998; 82: 1236–1241. 15. Effect of endurance exercise training on heart rate variability at rest in healthy young and older men.
- Am Heart J 2004; 147: e21. Eight weeks of moderate-intensity exercise training increases heart rate variability in sedentary postmenopausal women.
- Clin Invest Med 2006; 29: 20–28. Exercise training and heart rate variability in older female subjects.
- Med Sci Sports Exerc. 2014 June ; 46(6): 1057–1066. Exercise Training Improves Heart Rate Variability after Methamphetamine Dependency
- Eur J Cardiovasc Prev Rehabil. 2009 Dec;16(6):705-11. Vigorous physical activity and vagal modulation in young adults.
- Journal of Clinical Sleep Medicine, Vol. 9, No. 8, 2013. Exercise to Improve Sleep in Insomnia: Exploration of the Bidirectional Effects
- Sleep Med. 2010 October; 11(9): 934–940. Aerobic exercise improves self-reported sleep and quality of life in older adults with insomnia