Another incentive: Regular exercise keeps cells young

It was striking, recalls Dr Christian Werner,an internal-medicine resident at Saarland University Clinic in Homburg,to see in our study that many of the middle-aged athletes looked much younger than sedentary control subjects of the same age.

Even more striking was what was going on beneath those deceptively youthful surfaces. When scientists examined white blood cells from each of their subjects,they found that the cells in both the active and slothful young adults had similar-size telomeres. Telomeres are tiny caps on the end of DNA strands the discovery of their function won several scientists the 2009 Nobel Prize in medicine.

When cells divide and replicate these long strands of DNA,the telomere cap is snipped a process that is believed to protect the rest of the DNA but leaves an increasingly abbreviated telomere. Eventually,if a cells telomeres become too short,the cell either dies or enters a kind of suspended state, says Stephen Roth,an associate professor of kinesiology at the University of Maryland who is studying exercise and telomeres. Most researchers now accept telomere length as a reliable marker of cell age. In general,the shorter the telomere,the functionally older and more tired the cell is.

Its not surprising then that the young subjects telomeres were about the same length,whether they ran exhaustively or sat around all day. None of them had been on earth long enough for multiple cell divisions to have snipped away at their telomeres.

When researchers measured telomeres in the middle-aged subjects,however,the situation was quite different. The sedentary older subjects had telomeres that were on average 40 percent shorter than in the sedentary young subjects,suggesting that the older subjects cells were aging. The runners,on the other hand,had remarkably youthful telomeres,a bit shorter than those in the young runners,but only by about 10 per cent. In general,telomere loss was reduced by approximately 75 per cent in the aging runners.

Or,to put it more succinctly,exercise,at the molecular level,has an anti-aging effect, Dr Werner says.

There are plenty of reasons to exercise,but the effect that regular activity may have on cellular aging could turn out to be the most profound.

Its pretty exciting, says Thomas LaRocca,a PhD. candidate in the department of integrative physiology at the University of Colorado in Boulder,who has just completed a new study echoing Werners findings. In LaRoccas work ,people were tested both for their V02max or maximum aerobic capacity,a widely accepted measure of physical fitness and their white blood cells telomere length.

In subjects 55 to 72,a higher V02max correlated closely with longer telomeres. The fitter a person was in middle age or onward,the younger his or her cells.

There are countless unanswered questions about how and why activity affects the DNA. For instance,Dr Werner found that his older runners had more activity in their telomerase,a cellular enzyme thought to aid in lengthening and protecting telomeres. Exercise possibly affects telomerase activity and not telomeres directly. In addition,Stephen Roth measured telomeres and telomerase activity in a wide variety of tissues in mice and found,as he says,the protective effects from exercise only in some tissues.

Another question is whether we must run 50 miles a week to benefit. The answer can only be speculative at the moment, Dr Werner says adding: One could speculate that any form of intense exercise that is regularly performed over a long period of time will improve telomere biology meaning that with enough activity,each of us could outpace the passing years.