It's not uncommon today for many people to believe that exercise can affect things like their mood, their feelings of happiness, and their ability to take tests and perform other intellectual tasks. What has been missing, though, is evidence that this interrelationship is any more than just that—a belief, without any basis in fact.

New research into the relationship between the mind and the body is revealing the actual physical mechanisms by which the body affects the brain. After more than seven million years of evolution, almost half of the physical structure of the human brain is now devoted to the actions of the body, leaving the other half responsible for perceptions of the outside world.[1] With so much of the brain focused on the physical body, it makes sense that the body, and what we do with it, would have a profound impact on our brains.

The brain dictates every thought and belief we have, every physical action we take, and every decision we make. But what about the opposite: How does the body dictate the functioning of the brain? It should come as no surprise that the way the brain determines these nonphysical parts of life is closely correlated with physical activity.[2]

Exercise: Fertilizer for Your Brain

Our brains function through the activity of networks, each composed of single brain areas and their connections. It was once believed that these complex networks were fixed or static once we entered adulthood. We now know that our brain structures remain "plastic" throughout our lives, capable of being shaped by learning, experience, and—as we now understand—by exercise. This ability of the brain to change its shape is known as neuroplasticity.

Research has shown that physical exercise has both short-term and long-term effects on neuroplasticity, enabling the brain to rewire itself to improve mood and happiness, scholastic performance in children, executive control in adults, and even the speed at which the brain itself processes information.[3]

Physical activity also seems to improve the body's ability to create new brain cells, called neurons. It was previously thought that humans were born with all of the brain cells they would ever have. So if someone suffered an injury or illness that killed neurons, their body would never replace them.

We now know this isn't true. In certain areas of the brain—particularly those involved in motor and cognitive control, learning and memory, and reward—the body is perfectly capable of growing completely new neurons, a process known as neurogenesis. This is due to the effect exercise has on a particular brain hormone, brain-derived neurotropic factor (BDNF).[4,5] BDNF has been likened to fertilizer for the brain. Several studies have clearly demonstrated that exercise significantly increases BDNF production.[6,7] It has been shown in animal models that the more BDNF the brain can create, the greater the capacity to remember, learn new information, improve mood, and improve "inhibitory control."[8]

Inhibitory control, related to self-control, refers to our ability to delay gratification. Exercise improves our inhibitory control, which then improves our ability to change a habit or a learned behavior. This, in turn, enables us to refocus ourselves to complete goals that lead to better long-term outcomes. It may be as simple as developing more willpower to start your day with a workout rather than delaying it until after work, which may not always happen.

The Impact of Various Forms of Exercise on Brain Function

Research has examined the role that four kinds of exercise play in neuroplasticity and neurogenesis. In each case, results underscore new insights that exercise has a very direct—and very physical—impact on the brain itself.

Cardiovascular Exercise: All forms of exercise seem to have a positive impact on the brain, but cardiovascular exercise in particular has a profound impact on blood flow to key areas. A study published in Frontiers in Human Neuroscience found that women with a higher level of fitness (as measured by VO2 max) scored better on measures of executive brain function.[9] In particular, researchers found that these women had more cerebral blood flow to the prefrontal cortex, the area of the brain involved in decision making, future planning, goal-directed behavior, and emotions.

Resistance Training: A study published in the journal Neuroscience Letters suggests that regular resistance training can have a positive impact on brain health in women.[10] Researchers found that women who engaged in strength training at least once per week exhibited significantly greater blood flow to the brain compared to women who did not. Declines in blood flow that occur with normal aging are linked to detriments in both physical and mental health, including fatigue, stroke, depression, and declines in cognitive function.[11-13]

Yoga: A study published in Complementary Therapies in Clinical Practice reviewed multiple studies examining the impact of yoga on brain activity and structural changes.[14] The review concluded that yoga and postural-based exercises significantly increased brain activity. The authors suggested this may improve mood, focus, and overall sense of well-being.

HIIT Training: Additionally, emerging research suggests that short bursts of vigorous activity, known as high-intensity interval training (HIIT), may improve blood flow in the brain, which can provide more nourishment to neurons, resulting in improved brain activity.[15]

Many of the studies cited above are preliminary and come from a relatively new field of brain research. Even so, researchers are now discovering many of the very real, very tangible physical changes that take place on a cellular level within our brains when we engage in physical activity. While more research needs to be done, what was once thought to be no more than a belief is becoming accepted science.

References

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2. Erickson, K. I., Hillman, C. H., & Kramer, A. F. (2015). Physical activity, brain, and cognition. Current Opinion in Behavioral Sciences, 4, 27-32.
3. Konopka, L. M. (2015). How exercise influences the brain: a neuroscience perspective. Croatian Medical Journal, 56(2), 169.
4. Van Praag, H. (2008). Neurogenesis and exercise: past and future directions. Neuromolecular Medicine, 10(2), 128-140.
5. Pang, T. Y., Stam, N. C., Nithianantharajah, J., Howard, M. L., & Hannan, A. J. (2006). Differential effects of voluntary physical exercise on behavioral and brain-derived neurotrophic factor expression deficits in Huntington's disease transgenic mice. Neuroscience, 141, 569–584.
6. Chang, Y. K., Labban, J. D., Gapin, J. I., & Etnier, J. L. (2012). The effects of acute exercise on cognitive performance: a meta-analysis. Brain Research, 1453, 87-101.
7. Smith, P. J., Blumenthal, J. A., Hoffman, B. M., Cooper, H., Strauman, T. A., Welsh-Bohmer, K., ... & Sherwood, A. (2010). Aerobic exercise and neurocognitive performance: a meta-analytic review of randomized controlled trials. Psychosomatic medicine, 72(3), 239.
8. Gómez-Pinilla, F., Ying, Z., Roy, R. R., Molteni, R., & Edgerton, V. R. (2002). Voluntary exercise induces a BDNF-mediated mechanism that promotes neuroplasticity. Journal of Neurophysiology, 88(5), 2187-2195.
9. Dupuy, O., Gauthier, C. J., Fraser, S. A., Desjardins-Crèpeau, L., Desjardins, M., Mekary, S., ... & Bherer, L. (2015). Higher levels of cardiovascular fitness are associated with better executive function and prefrontal oxygenation in younger and older women. Frontiers in Human Neuroscience, 9, 66.
10. Xu, X., Jerskey, B. A., Cote, D. M., Walsh, E. G., Hassenstab, J. J., Ladino, M. E., ... & Cohen, R. A. (2014). Cerebrovascular perfusion among older adults is moderated by strength training and gender. Neuroscience Letters, 560, 26-30.
11. Biswal, B., Kunwar, P., & Natelson, B. H. (2011). Cerebral blood flow is reduced in chronic fatigue syndrome as assessed by arterial spin labeling. Journal of the Neurological Sciences, 301(1), 9-11.
12. Kataoka, K., Hashimoto, H., Kawabe, J., Higashiyama, S., Akiyama, H., Shimada, A., ... & Kiriike, N. (2010). Frontal hypoperfusion in depressed patients with dementia of Alzheimer type demonstrated on 3DSRT. Psychiatry and Clinical Neurosciences, 64(3), 293-298.
13. Bangen, K. J., Restom, K., Liu, T. T., Jak, A. J., Wierenga, C. E., Salmon, D. P., & Bondi, M. W. (2009). Differential age effects on cerebral blood flow and BOLD response to encoding: associations with cognition and stroke risk. Neurobiology of Aging, 30(8), 1276-1287.
14. Desai, R., Tailor, A., & Bhatt, T. (2015). Effects of yoga on brain waves and structural activation: A review. Complementary Therapies in Clinical Practice, 21(2), 112-118.
15. Lucas, S. J., Cotter, J. D., Brassard, P., & Bailey, D. M. (2015). High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence. Journal of Cerebral Blood Flow & Metabolism, 35.