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Monday, February 1, 2010

Is Exercise the Fountain of Youth?

For my kick off blog I have chosen discuss exercise. As an avid runner, or so I label myself, I've run 15 to 30 miles a week for over twenty years. I pride myself on remaining injury-free throughout those twenty years and attribute that to a combination of moderation, cross-training and good luck.

The 2008 Physical Activity Guidelines for Americans were developed by the Department of Health and Human Services and are endorsed by the CDC citing the substantial evidence for the health benefits of regular physical activity.

These recommendations suggest the following minimum requirements for adults:

1. Exercise of moderate-intensity (i.e., brisk walking) for 30 minutes on most days of the week for a total of 150 minutes per week.
2. Exercise of vigorous intensity (i.e., running) for shorter duration three to four days a week, for a total of 75 minutes a week.
3. Strength training on two non-consecutive days of the week using all major muscle groups.

Furthermore, there is evidence that more exercise of higher intensity is better, and that some exercise is better than none, particularly in elderly adults with chronic illness who are limited physically. Despite popular trends, stretching has not yet made it into the formal guidelines for physical activity.

Sunday's New York Times Magazine reported an interesting study, finding that middle-aged adults who exercise vigorously (ran 50 miles a week) were youthful at a cellular level. The study looked at telomeres, an intracellular marker for cell age. With age telomeres become shorter, and eventually cell death occurs. Middle-aged exercisers had telomeres that were significantly longer than their sedentary counterparts and only slightly shorter than those of exercising younger study subjects.

The January 25th issue of the Archives of Internal Medicine published several more studies demonstrating the benefits of physical activity in middle-aged and elderly adults. One reported on the cognitive benefits of strength training (compared with balance and tone training) in the elderly. The other reported on a cohort from the Nurse's Health Study demonstrating a positive correlation of exercise in mid-life with "successful" living at age 70 and beyond (defined as being free of chronic illness).

I am heartened to see many vigorous older adults at my local YMCA. They are clearly engaged and having fun. To me, the psychological benefits of physical activity have always been paramount and equal in importance to its physical effects.

Is physical activity the panacea of old age? Is there reason to be skeptical? How much is enough, and what should we be recommending?


  1. I turned up for a routine physical at Emory only to find you were no longer working there. Are you currently practicing somewhere else? If so where?

  2. I'm an exercise freak, and I totally support the idea that exercise can improve and extend our quality of life. However, I have to play skeptic to the science at hand...

    Telomere length is a good gauge of cellular age, but its contribution to our overall age is not well known. We also have many cells (neural, muscular, adipose, gametes) that don't replicate via mitosis, the process that leaves the telomeres slightly trimmed. We see evidence of degeneration of these cells with physical age, but how can this be attributed to shortened telomeres if there's no mitosis? Conversely, if exercise improves muscular, neural, and possibly our sexual functions, how could increased telomerase production be the cause, when the target cells have telomeres that don't require padding?

    I see a big case of "correlation does not imply causation here." A correlation has been made between exercise and younger cellular age in white blood cells only. I'd like to see evidence that exercise can rejuvenate sun-damaged skin cells (for example) that have had their telomeres shortened due to excessive cellular repair. That would be a much more convincing argument that telomere lengthening from exercise can extend/improve our physical age.

  3. novox77 interesting comments. Another possible explanation for the molecular basis of improved health related to physical activity: increased stem cell production. See this paper from Circulation citing increased endothelial stem cell production in physically fit mice: Circulation 2004;109:220-226 Laufs and Nickenig. Don't think health issurance covers telomere measurement yet!