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Human beings have known for centuries that physical exercise can remodel muscles. Working muscles to the point of exhaustion and then giving them an opportunity to recover and rebuild makes them larger, stronger, and less vulnerable to fatigue.

Physical Exercise May Whip Lazy Brain Cells Into Shape

Part of the process of making muscles stronger involves increasing the number of mitochondria in muscle cells. The mitochondria are the energy-producing powerhouses of every cell. When a muscle is exercises, the number of mitochondria in the cell increases, giving the muscle more capacity for making energy, and also "soaking up" excess energy sources from the rest of the body. University of South Carolina scientists set out to determine whether a similar process might not also occur in the brain.

Dr. J. Mark Davis, professor of exercise science at the Arnold School of Public Health at the University of South Carolina, led a research team studying the effects of exercise in mice. For eight weeks, the scientists exercised a group of mice every day. They also maintained another group of sedentary mice in the same lab given the same food and the same living conditions as the exercising mice, except for being given opportunities to use tiny treadmills.

Then at the end of two months the researchers forced all the mice to exercise to exhaustion on a treadmill. It was no surprise that the mice that had been exercising every day lasted longer, an average of 126 minutes compared to an average of 74 minutes for the sedentary animals.

What was interesting to the scientists was changes in brain tissue. All of the animals were sacrificed at the end of the experiment, and samples of brain tissue were examined under a microscope. Brain tissue samples from the exercised mice showed formation of new mitochondria, but no similar changes were found in the brains of mice that had not been exercised. Davis and colleagues for the first time showed that physical exercise increases the number of mitochondria in the brain as well as in the muscles.

Profound Implications for Many Health Concerns

The finding that exercise can increase numbers of mitochondria in brain cells has profound implications for many health concerns, especially for some of the most dreaded diseases of aging, such as Alzheimer's disease and Parkinson's disease. Long-distance runners are known to be at lower risk for both conditions. It is possible that exercise triggers the creation of additional mitochondria in the brain, giving neurons a buffer against the effects of tissue destruction. And simply feeling more alert and in control can slow down the effects of deteriorating executive function, the ability to make good life decisions, which declines in both conditions.

Just how much daily exercise is needed to protect the brain?

Dr. Davis believes that the answer to this question is "not much." A 30-minute jog, Davis says, is likely to stimulate increased activity and formation of mitochondria in the human brain, potentially protecting against neurodegenerative diseases of aging. Exercise also helps create new connections in the brain, keeping memories alive and judgment keen.

  • Steiner JL, Murphy EA, McClellan JL, Carmichael MD, Davis JM. Exercise Training Increases Mitochondrial Biogenesis in the Brain. J Appl Physiol. 2011 Aug 4. [Epub ahead of print]
  • Photo courtesy of lwr on Flickr: