Exercise, under the supervision of a GP, is "invaluable" for older people, Help the Aged said yesterday.
Mike Foster, public relations account manager at Help the Aged, said that an appropriate level of exercise has many health benefits, boosting bone strength, cardiovascular health and the immune system.
He added that keeping fit can help to combat erectile dysfunction, a condition which affects one in ten men.
Mr Foster said: "The best activities of all are new challenges, which not only work your body in different ways but are also shown to help keep your mind alert and fit too.
"Retirement is a time when we can all look forward to relaxing, but it is possible to focus too much on 'putting your feet up', which can be detrimental to one's happiness and relationships as well as one's health."
Help the Aged campaigns for changes in government policy and carries out research into older people's needs, as well as supporting elderly people in the community.