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Exercise builds new brain cells. Until recently it was believed that the brain cells we’re born with were all we were ever going to have. If brain cells died or were damaged, that was it. However a process called neurogenesis was recently discovered that demonstrated that new brain cells are continuously being made and stored. Scientists at the Karolinska Institute in Stockholm, Sweden found that one-third of the neurons in the hippocampus, the area of the brain involved in forming, organizing, and storing memories, are regularly renewed throughout life. They calculated that roughly 1,400 new neurons were added per day with rates declining modestly with age.1

Other studies indicated that experiences and learning strengthened these new neurons, causing them to branch out and make new connections. As the neurons were utilized, they developed even more connections and became stronger. The connections that were seldom used became weaker and died. Our brains are made up of billions of connections and the more neurons we have the bigger our brains and the better our cognitive functioning.

Exercise contributes to the growing of new neurons. Here’s how it works. As glucose, the body’s fuel derived from our food is digested and moved into the blood stream, it needs to be converted into energy. Within each cell are thousands of smaller molecules called mitochondria. The mitochondria are the cells’ energy factories. They turn the glucose into a substance called adenosine triphosphate (ATP). ATP is a high-energy compound that powers every one of our cells. The work that goes on within each of the 100 trillion human cells is because of the one billion ATP molecules in each cell. The origin of the ATP is the food we eat. To create ATP, glucose needs oxygen. Our breathing or respiration combines oxygen with glucose to create ATP. Exercise, the intake of oxygen through respiration, increases the production of ATP.2

Exercise also produces proteins that travel through the blood steam and in the brain, playing a critical role in our highest thought processes. The protein, insulin-like growth facto, is essential for the development and function of the brain and other organs. It plays a roll in neurogenesis and dendritic branching. Exercise also produces brain-derived neurotrophic factor in the hippocampus.3 BDNF builds and maintains the infrastructure of the brain, aids in neurogenesis and in repairing synapses.

Our bodies are designed to move and as we move hormones are released. Different movements send different messages to our brains to release specific hormones, which then tell the cells to burn fat or sugar, repair or build muscles, make new blood vessels, increase of decrease heart rate, or increase the levels of serotonin, norepinephrine, or dopamine. As we exercise, we amp up these functions and move them from maintenance and survival mode to creation and building mode.

An example of the benefits of exercise include a reduction of risk for Alzheimer’s disease and other forms of dementia for more physically active individuals. Larson et al. assessed 1740 adults over the age of 65 on the frequency of participation in a variety of physical activities (e.g. walking, hiking, bicycling and swimming). After an average follow-up of 6.2 years, 158 of the original participants had developed dementia. After adjusting for age, sex and medical conditions, individuals who exercised more than three times per week during initial assessment were found to be 34 percent less likely to be diagnosed with dementia than those who exercised fewer than three times per week.4

Sitting for long periods of time does more than keep us inactive. It causes fat to accumulate in the liver, heart and brain. Studies from NASA indicated that the astronauts muscles, bones and overall health was weakened by weightlessness, suggesting that weight bearing exercises are necessary for maintaining fitness.5 A study published in the journal Stroke found that walking at least three hours per week reduced the risk of stroke in women better than inactivity, and walking was more effective than high intensity cardiovascular exercise or moderate to heavy exercise.6 The same was not true for men. An article in the journal Neurology found that high intensity exercise in men reduced stroke risk and helped them recover from a stroke better and faster.7

As people age, some areas of the brain naturally shrink. For example, studies show that the hippocampus shrinks one to two percent annually in people without dementia, resulting in an increased risk for a decline in cognitive functioning. A study from the University of Illinois at Urbana-Champaign found that fitness however can change the aging brain and even people who haven’t exercised on a regular basis can improve their brain function later in life. Researchers divided a group of healthy, sedentary adults, ages 55 to 80, to participate in a yearlong exercise program. One group walked for 40 minutes three times per week and the other group performed a variety of strength and balance exercises. The group that walked increased the size of their hippocampus by two percent on average. The participants that completed the yearlong balance and strength-training program experienced a one percent decrease in the volume of the hippocampus. Both groups improved on the natural progression of brain aging.8

Another study involving women ages 70 to 80 with mild cognitive impairment participated in a six month, twice weekly program of aerobic training, resistance training, or balancing and toning. Researchers found women who participated in aerobic training significantly increased hippocampal volume. The others did not.9

Exercise has many other benefits as well. It helps control weight and lowers the risk of heart disease, stroke and some types of cancer. It helps improve sleep, memory, and concentration. It increases the brain’s plasticity and reduces possible damage and shrinkage of the brain by controlling blood sugar levels and type-2 diabetes. Higher levels of fitness relate directly to positive mood and lower levels of anxiety and stress.

Decades of research demonstrate that engaging in regular exercise leads to increased brain volume and improved cognitive functioning among many other benefits. Exercise is good at any age but it’s never too late to start.


  1. Ernst, A., Alkass, K., Bernard, S. et al. (February 20, 2014). Neurogenesis in the Striatum of the Adult Human Brain. Cell online. oi:10.1016/j. cell. 2014.01.044
  2. Alberts B, Johnson A, Lewis J, et al. (2002). Molecular Biology of the Cell. 4th edition. New York: Garland Science. Retrieved from:
  3. Di Salvo, D. (October 13, 2013). How exercise makes your brain grow. Retrieved from
  4. Larson, E.B., Wang, l., Bowen, J.D. et al. (2006, January 17). Exercise Is Associated with Reduced Risk for Incident Dementia among Persons 65 Years of Age and Older. Annals of Internal Medicine;144(2):73–81. doi:10.7326/0003-4819-144-2-200601170-00004
  5. Vernikos, J. (2011). Sitting Kills, Moving Heals: How Everyday Movement Will Prevent Pain, Illness, and Early Death And Exercise Alone Won’t. Fresno, CA: Quill Driver Books, Linden Publishing Inc.
  6. Walking reduces stroke risk among women. (Jan 7, 2013). Medical News Today. Retrieved from php
  7. Willey, J.Z., Moon, Y.P., Paik, M.C. et al. (2009, November, 24). Physical activity and risk of ischemic stroke in the Northern Manhattan Study. Neurology. (73)21, 1774–9. doi: 10.1212/WNL.0b013e3181c34b58
  8. Society for Neuroscience. (2013, August 28). Physical Exercise Beefs Up the Brain Retrieved from: Lifespan/Diet-and-Exercise/Articles/2013/Physical-Exercise-Beefs-upthe-Brain
  9. Weuve, J., Kang, J.H., Manson, J. S. et al. (2004). Physical activity, including walking, and cognitive function in older women. Journal of the American Medical Association. 292(12), 1454–61. doi:10.1001/

Karen V. Unger

Karen V. Unger is the author of the new book “Brain Health for Life, Beyond Pills Politics and Popular Diets.” Dr. Unger has a Master’s Degree in Social Work from Arizona State University, a Master’s Degree in Psychology from Chapman College and a Doctorate in Education from Boston University. She has written a previous book, book chapters, peer-reviewed articles, federal policy papers and an evidence-based practice kit for the Substance Abuse and Mental Health Services Administration of the U.S. Department of Health and Human Services. At Boston University she was a senior staff person at the Center for Psychiatric Rehabilitation and an adjunct professor at Sargent College of Allied Health Professions. She has also been a research associate professor at the Community Rehabilitation Division, Arizona State University in Tucson and is currently a research associate professor at the Graduate School of Education at Portland State University. Dr. Unger is president of Rehabilitation Through Education.