How good for you is exercise? According to a study of mice by researchers at McMaster’s University in Ontario, it may be the trick to staying young.
The study involved mice that were genetically programmed to age quickly. These mice lacked the ability to properly repair genetic mutations to their mitochondria, the fuel centers of cells; that damage, which accumulates with age, eventually causes the mitochondria to malfunction and die. As reporter Gretchen Reynolds explains for the New York Times:
Many scientists consider the loss of healthy mitochondria to be an important underlying cause of aging in mammals. As resident mitochondria falter, the cells they fuel wither or die. Muscles shrink, brain volume drops, hair falls out or loses its pigmentation, and soon enough we are, in appearance and beneath the surface, old.
That is, unless you exercise (at least if you are a mouse). Researchers led by pediatrics professor Dr. Mark Tarnopolsky had half of the mice exercise regularly starting at 3 months old. The animals ran on a wheel for 45 minutes at a time three times a week; that’s the equivalent of a human running a 55-min. 10K three times a week starting at age 20. The mice kept up their exercise routine for five months. The other half of the mice remained sedentary. Reynolds reports:
At 8 months, when their sedentary lab mates were bald, frail and dying, the running rats remained youthful. They had full pelts of dark fur, no salt-and-pepper shadings. They also had maintained almost all of their muscle mass and brain volume. Their gonads were normal, as were their hearts. They could balance on narrow rods, the showoffs.
But perhaps most remarkable, although they still harbored the mutation that should have affected mitochondrial repair, they had more mitochondria over all and far fewer with mutations than the sedentary mice had. At 1 year, none of the exercising mice had died of natural causes. (Some were sacrificed to compare their cellular health to that of the unexercised mice, all of whom were, by that age, dead.)
So what do the results mean for humans? Dr. Tarnopolsky told the Times that humans probably don’t have to exercise as strenuously as the mice did in the study in order to reap health benefits. Previous studies have shown that moderate exercise, as well as nonaerobic workouts like weightlifting, can improve mitochondrial function in older adults. “Although there is probably a threshold amount of exercise that is necessary to affect physiological aging, Dr. Tarnopolsky said, ‘anything is better than nothing.’ If you haven’t been active in the past, he continued, start walking five minutes a day, then begin to increase your activity level,” Reynolds writes.
Read the full Times story here.