Telomeres (highlighted red in the photo to the left) are protective stretches of DNA and the end of a chromosome. Their length has been shown to shorten as a result of both age and stress. Physical activity has been shown to act as a buffer against stress-induced shortening.
In a previous post the affect of stress on telomere length was discussed. As explained in that post, telomeres are stretches of DNA at the end of chromosomes responsible for protecting the chromosome. Every time a cell divides its telomeres are shortened. In some cells an enzyme named telomerase replenishes the lost telomerase, but in other cells the telomeres gets continually shorter. Therefore, telomere length can be a good predictor of aging. Eventually, the telomere protection disappears and unprotected genetic material would get cut with each division. Usually, at this point the cell dies.
Individuals scoring high on a stress test have been shown by many studies to have shorter telomeres. For a more in depth look at the stress-telomere length studies visit this the Stress and Telomere Length post.
In 2010, a study (The Power of Exercise: Buffering the Effect of Chronic Stress on Telomere Length, Puterman E, Lin J, Blackburn E, O'Donovan, Adler N, et al.) found that the negative effect of stress on telomere length disappeared when the subject was deemed to be physically active.
The study broke subjects into groups based on physical activity reported: sedentary and physically active. Each subject completed a Perceived Stress Scale. Subjects categorized as sedentary tended to score higher on the Perceived Stress Scale. Sedentary subjects showed an inverse correlation between stress score and telomere length, confirming results found in previous studies. Surprisingly, subjects categorized as physically active (equal or more than 75 minutes of exercise per week) did not show a decrease in telomere length when stress level was increased. The relationships are shown below. Notice that the sedentary group shows a noticeably negative relationship between telomere length and perceived stress; conversely, the active group shows no relationship.
Interestingly, 75 minutes of exercise per a week is the recommendation of the Center of Disease Control and Preventions. Shorter telomeres have been shown by many studies to correlate with an increased risk of developing chronic illnesses like cancer and heart disease. Therefore, 75 minutes of weekly exercise may decrease risk of developing a chronic illness through telomere length. Although a relationship has been found between exercise and risk of developing many chronic diseases, telomere length has not been established as the pathway for exercise's effect on chronic illness risk.
The authors of the study theorized that the pathway by which exercise buffers against stress-induced telomere shortening is through telomerase activity. As mentioned above, telomerase is an enzyme that lengthens telomeres shortened by cell division. Stress has been shown to inhibit telomerase activity (Accelerated telomere shortening in response to life stress, 2004, Elissa S. Epel, Elizabeth H. Blackburn, et al.). Exercise has been shown to increase telomerase activity in mononuclear cells from rats and human leukocytes ( 2009, Physical Exercise Prevents Cellular Senescence in Circulating Leukocytes and in the Vessel Wall).
In summary, physical activity acts a buffer against the telomere shortening effects of stress. The biological pathway this may occur is through the exercise proliferation of telomerase, an enzyme responsible for extending telomeres.
Please leave any thoughts you have on this study!