Doing regular workouts could keep you younger for longer, according to a study which found it has an anti-ageing effect on the body.
New research discovered keeping fit helps reverse muscle damage and has the effect of restoring youthfulness.
The findings, published in the journal Nature Metabolism, could one day potentially lead to a pill that works as a substitute for exercise.
Until that happens, scientists believe keeping moving will trigger our internal muscle stem cells to repair muscle damage.
Dr Thomas Rando, of Stanford School of Medicine, said: "We found that regular exercise restores youthfulness to tissue repair.
"Their muscle stem cells start to look and behave like those of much younger animals."
He continued: "Studies conducted by us and others have shown that tissue regeneration decreases with age, and that this is due to declining function in adult stem cells.
“Many researchers are looking for a way to restore youthfulness."
Dr Rando noted: "Exercise is known to reduce the risk of a wide variety of age-related problems, including cardiovascular disease, cancer and perhaps even Alzheimer's disease.
"There's a lot of interest in understanding how exercise confers these health benefits."
Looking at mice, his team analysed the muscle stem cells in mice of various ages when they ran on an exercise wheel.
Young mice averaged about 10km each night, while the older mice covered approximately 5km - with two other groups of young and old mice given wheels which didn't rotate.
Dr Rando explained: "The animals were exercising at the intensity levels at which they were comfortable, much like what people do for their own health.
“This is a less stressful situation than resistance training or intense endurance exercise, which may themselves affect muscle stem cell function.
“Subsequent analysis showed that the muscle stem cells of the exercising animals remained quiescent, and that the animals did not develop significant numbers of new muscle fibres in response to the exercise.”
After three weeks of nightly aerobics for the active groups, the researchers compared the ability of the different groups to repair muscle damage.
They found that the bodies of older mice were less able to repair damage than those of younger mice.
However, the older animals which had exercised regularly experienced significantly better muscle repair than their counterparts that did not exercise.
Dr Rando suggested: "If we could develop a drug that mimics this effect, we may be able to experience the benefit without having to do months of exercise.”