In a 2011 study in the journal Proceedings of the National Academies of Sciences, the researchers showed that the exercise prevented many of the physiological symptoms of aging as well as premature death in the mice — to the point where they were indistinguishable from non-genetically altered mice.
"We protected not just the muscles — which people conceptually would say, 'Well, yeah, it makes sense that if you run, your muscles will be protected' — but even their cataracts, their kidneys, their gonads," Tarnopolsky says.
Similar results can be seen in humans. For 21 years, researchers at Stanford University have studied the effects of consistent exercise on 284 runners 50 and older. In a 2002 article in the Archives of Internal Medicine, they reported that — 13 years into the study — a control group of 156 similar people who exercised much less on the whole than the runners had a 3.3 times higher death rate than runners as well as higher rates of disabilities.
In a 2008 study in the same journal, they reported that after 19 years, 15% of runners had died, compared with 34% of the control group. After 21 years, runners had significantly lower disability levels than non-runners; their death rates from cardiovascular events, cancer and neurologic disorders were much lower than in non-runners — 65 of the runners had died of cardiovascular, neurologic and cancer events compared with 98 deaths in the control group.
"You're 100 times better … as an athlete training in your 40s and 50s than a sedentary person in your 20s, any way you look at it," Tarnopolsky says.