Workouts may protect your immune system from some age-related decline as well.

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For a small study published at the beginning of March in the journal Aging Cell, researchers looked at 125 amateur male and female cyclists aged 55 to 79. They compared those individuals with 75 people of a similar age who rarely or never exercised.

The cyclists were found to have more muscle mass and strength, and lower levels of body fat and cholesterol than the sedentary adults. The athletic adults also appeared to have healthier and younger-looking immune systems, at least when it came to a key organ called the thymus.

The thymus is responsible for generating key immune cells called T cells. In healthy people, it begins to shrink starting around age 20, and T cell production also starts to drop off around that time.

The study found that the thymus glands of the older cyclists looked like they belonged to younger people — their bodies were producing just as many T cells as would be expected from the thymus of a young person.

"We now have strong evidence that encouraging people to commit to regular exercise throughout their lives is a viable solution to the problem that we are living longer but not healthier," Janet Lord, the director of the Institute of Inflammation and Aging at the UK's University of Birmingham, said in a statement.