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The biological life span of any species is roughly six times the stretch between birth and maturity. Using this formula, the human life span is about 120 years, which is borne out in the record books. The oldest people who have ever lived all topped out at about 120.
Within that 120-year life span, however, the quantity and the quality of life can vary enormously. About one-tenth to one-quarter of that variance is genetically determined; the majority is the result of your lifestyle and environment. New research just released by the University of California at San Francisco highlights one way you can leverage your lifestyle choices to maximize your longevity: exercise.
Researchers at UCSF found that exercise keeps stress from shortening the length of telomeres (pronounced TEEL-oh-meers). Telomeres are tiny pieces of DNA known to promote genetic stability and act as protective sheaths by keeping chromosomes from unraveling, much like plastic tips at the ends of shoelaces. A growing body of research suggests that short telomeres are associated with a range of health problems, including coronary heart disease and diabetes, as well as early death.
"Telomere length is increasingly considered a biological marker of the accumulated wear and tear of living, integrating genetic influences, lifestyle behaviors and stress," says Dr. Elissa Epel, one of the lead investigators and an associate professor in the UCSF Department of Psychiatry. "Even a moderate amount of vigorous exercise appears to provide a critical amount of protection for the telomeres."
Research on telomeres, and the enzyme that makes them, was pioneered by a group that included UCSF molecular biologist Dr. Elizabeth Blackburn, who co-discovered the telomerase enzyme in 1985. Blackburn and two of her colleagues received the Nobel Prize in Physiology or Medicine in 2009. Blackburn also co-authored the most recent study.
"We are at the tip of the iceberg in our understanding of which lifestyle factors affect telomere maintenance and how," says Blackburn.
The new study, which teased out the protective effect of physical activity on telomere length, looked at 62 post-menopausal women (many of whom were caring for spouses or parents with dementia) whose exercise amounted to as little as 42 minutes of vigorous activity spread over three days -- an amount very similar to federally recommended levels. Vigorous activity in the study was defined as "increased heart rate and/or sweating."
Participants were divided into groups -- an inactive group, and an active group whose members met federal recommendations for 75 minutes of weekly physical activity. At the end of each day over three days, the subjects reported their vigorous physical activity in minutes for that day. Separately, they also rated levels of psychological stress they had experienced during the prior month. Immune cells, taken from blood samples, were then examined for telomere length.
The telomeres of those who were under great stress but did not exercise had shortened, while the telomeres of those who were under equally great stress but did exercise had remained long. In other words, stress caused predictable corrosion of the telomeres in the sedentary group, but such corrosion did not occur in the active group.
These findings build on previous studies showing that chronic psychological stress takes a significant toll on the human body. The exact mechanisms have remained elusive, but a 2004 UCSF study found that stress caused damage deep within human cells, and that the damage was linked to reduced longevity.
This is the first research to show that exercise can prevent the shortening of telomeres due to stress and buffer the effects of stress-induced cell aging. It also showed that exercise is linked to longer telomeres.
Eric Heiden, M.D., a five-time Olympic gold medalist speed skater, is now an orthopedic surgeon in Utah. He co-authored "Faster, Better, Stronger: Your Fitness Bible" (HarperCollins) with exercise performance physician Max Testa, M.D., and DeAnne Musolf. Visit www.fasterbetterstronger.com.
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