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What Does Exercise Do to the Brain?

The effects of exercise on cardiovascular health are well documented, but a growing body of evidence suggests that physical activity also improves mental and neurological function throughout all stages of life. Neuroscientists aren't sure why, but the leading theory is that exercise triggers a kind of domino effect -- starting with the release of chemicals that promote increased blood flow, causing the brain to perform more efficiently in various ways.

People who exercise regularly may be at moderate to dramatically reduced risk of contracting serious and disabling brain diseases, research has shown. In a six-year study involving 1,740 adults published in the 2006 issue of "Annals of Internal Medicine," researchers found that those who exercised three or more times a week had a 40 percent lower risk of Alzheimer's disease. Seattle internist Dr. Eric Larson, who led the study, theorized that more exercise contributes to healthier blood vessels and results in greater ability to withstand stress and recover from injury -- especially in the brain's hippocampus region, where Alzheimer's typically starts. Similarly, a nine-year Harvard University study involving 143,325 people published in the January 2008 edition of "Movement Disorders" noted a reduced risk for Parkinson's among physically active participants.

Some studies, including one published in the May 19, 2010, issue of "Neuroscience," suggest that physical activity enhances the ability to learn and remember by triggering the creation of new neurons in the brain. The study's lead author, neuroscientist Carl W. Cotman of the University of California at Irvine, found that cognitive improvements in rats with unlimited access to running wheels lasted for seven days after exercise stopped. Furthermore, improvements in memory and learning ability in animals that exercised on alternate days were the same as in those that exercised every day.

Numerous studies have shown that exercise helps alleviate depression, anxiety and other mood disorders. One study conducted by the Southwestern Medical Center in Dallas and published in the January 2005 issue of the "American Journal of Preventive Medicine" found a reduction of almost 50 percent in symptoms of depression among adults ages 20 to 45 who participated in a 30-minute aerobic workout three to five times a week. The reasons are unclear, but physical activity is known to elevate levels of two brain chemicals with antidepressant properties, nerve growth factor and brain-derived nerve factor.

In addition to protecting against neurological disease, a critical evaluation of cognitive studies published in the October 2008 "British Journal of Sports Medicine" suggested that exercise might even reverse some of the age-related damage to learning and memory associated with aging. Although the claim remains controversial, the study generated worldwide media interest. The lead author, neuroscientist Art Kramer of the Beckman Institute at the University of Illinois, told reporters that "We can safely argue that an active lifestyle with moderate amounts of aerobic activity will likely improve cognitive and brain function, and reverse the neural decay frequently observed in older adults."

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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.