The exercise evolution: an introduction to the science behind exercise

We all know exercise is good for us. Regular exercise can boost energy and increase physical fitness as well as prevent and treat heart disease, diabetes and obesity. Moving our bodies can help us combat mental illness, stave off age-related mental and physical decline, and improve our ability to think, solve problems, learn, remember, regulate emotions, and cope with stress. We also now know that sitting around for most of our lives can lead to poor health. Simply put, scientists studying the biology of exercise have increasingly shown that we need to exercise in order to be our best, healthiest, happiest selves. Ever wonder why nature molded us in this way? Why is every facet of our physiology seemingly programmed to benefit from exercise? We may be able to shed light on these questions by studying the evolution of our early human ancestors.

Preceding the 2012 Olympics, Nature published a thought provoking commentary explaining why exercise evolved to be a vital component of human health¹. The authors describe that over millions of years, environmental changes required early humans to undergo physical transformations to promote greater aerobic capacity and endurance so that they could hunt down food and survive. Dense forests turned into flat, open savannahs and early human ancestors underwent adaptations that allowed them to evolve from tree dwellers into runners, physiologically equipped to outlast their prey.

Over time, exercise transformed our minds as well as our bodies. Our skeletons changed so we could support running, and our bodies grew more able to take up and use oxygen. Exercise also helped evolve our brain centers for reasoning, cognition, social behavior and complex emotions, with the help of exercise-induced increases in brain-derived neurotrophic factor (BDNF). BDNF is a protein that is released in the brain and body in response to exercise. Within the brain, BDNF plays a vital role in strengthening connections between brain cells and promoting their growth and survival. The release of this protein during exercise helped sculpt brain regions involved in higher learning and complex behaviors as early humans evolved into a more intelligent, creative species¹.

Flash forward a few millennia. Though the majority of us no longer have to chase down our dinners, we still need to exercise in order to live long, healthy lives. The authors of this Nature paper have placed knowledge concerning the health benefits of exercise into an evolutionary context, and argue that exercise is an indispensable part of our basic biology. It’s a bit of a different take on why we should engage in regular exercise: not only is exercise beneficial, but we as humans are evolutionarily predisposed to require it for optimal health.

Indeed, scientists attribute our modern, sedentary lifestyles as a major causal factor for heart disease, stroke and diabetes–some of our nation’s top killers². A recent paper even demonstrated that prolonged periods of inactivity are associated with chronic disease, cancer and premature death³. Yikes. These results support the notion that we weren’t meant to spend the majority of our time sitting.

If we were to make exercise a predominant part of our daily routine, would we live healthier lives, and be free of modern disease burdens? A large body of research suggests that increasing physical activity can indeed prevent and significantly improve many diseases of the body and mind. Physically active individuals are less likely to suffer from joint pain, cardiovascular and metabolic disease, and even certain cancers².

Exercise can also have far reaching effects on the brain, beyond the increases in BDNF discussed in the Nature piece. The effects of exercise on mental and emotional health are well documented, and demonstrate that active individuals are less prone to develop some of the most prevalent mental disorders including anxiety, depression and age-related cognitive decline^4,5. Starting an exercise program can also improve symptoms for people already diagnosed with these disorders^6,7.

We also may be able to gain some insight on this topic by looking to the Tarahumara people, a tribe of Native Americans inhabiting the Sierra Madre Occidental Mountains in northwestern Mexico. The Tarahumarans are known for their incredible athletic capabilities, and are some of best distance runners in the world. Exercise is still very much a part of their daily lives for sport and out of necessity; running is a means of transportation, hunting and obtaining food, as well as a welcome pastime. As one might predict, Tarahumarans exhibit exceptional endurance and cardiorespiratory fitness, low blood pressure, and aren’t plagued by hypertension, obesity, and high cholesterol⁸.

So far, science has provided a pretty convincing argument for why exercise is nature’s most powerful medicine and possibly the cheapest therapist any of us will ever find. It turns out we may even require it to live our best lives. Further study of the effects of exercise on health is important from a basic and applied research standpoint; understanding how exercise affects our physiology can help us better understand ourselves, while studying exercise as a form of treatment can help us figure out the causes and consequences of various diseases.

At CU, there are several exceptional basic and applied researchers interested in the mechanisms by which exercise affects our physiology, and how exercise can improve health and prevent disease. This group of scientists approach these questions from an interdisciplinary perspective, and are interested in the role of exercise in maintaining physical fitness as well cardiovascular, metabolic, mental and emotional health. In future segments, I plan to share with you the data and ideas put forth by this group of scientists, in hopes to spread word of this energetic science and perhaps entice you to pick up your running shoes.

By Aggie Mika

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1. Noakes T, Spedding M. Olympics: Run for your life. Nature. 2012;487: 295-296.
2. Bamman MM, Cooper DM, et al. Exercise biology and medicine: innovative research to improve global health. Mayo Clin Proc. 2014;89: 148-153.
3. Biswas A, Oh PI, et al. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med. 2015;162: 123-132.
4. Larun L, Nordheim LV, et al. Exercise in prevention and treatment of anxiety and depression among children and young people. Cochrane Database Syst Rev. 2006: CD004691.
5. Hamer M, Stamatakis E. Prospective study of sedentary behavior, risk of depression, and cognitive impairment. Med Sci Sports Exerc. 2014;46: 718-723.
6. Carek PJ, Laibstain SE, et al. Exercise for the treatment of depression and anxiety. Int J Psychiatry Med. 2011;41: 15-28.
7. Mason JO, Powell KE. Physical activity, behavioral epidemiology, and public health. Public Health Rep. 1985;100: 113-115.
8. Connor WE, Cerqueira MT, et al. The plasma lipids, lipoproteins, and diet of the Tarahumara indians of Mexico. Am J Clin Nutr. 1978;31: 1131-1142.