Keeping fit as you age may help your body protect against infections and disease.
A new study shows doing lots of exercise in your old age can boost your immune system.
Researchers followed more than 100 long-distance cyclists including some who were in their eighties.
They discovered that those older athletes had the immune systems of 20-year-olds.
Experts also believe being physically active in later life will help people respond better to
vaccines and prevent against infections such as the flu.