Michael White, 73

In my mid-20s I thought I was getting a bit fat, so I took up running. Fifty years on, I'm still doing it. Running keeps my stress levels down: when you get out there, you forget everything.

The trick is to vary what you do. Don't always run the same route, and don't get into the habit of always running alone, or always running with others.

I did marathons for many years, but gave them up three or four years ago – I was just too slow. These days, I run at least four times a week, usually between four and six miles. I reckon I could manage 10 but I don't want to injure myself so I try not to push myself too hard.

Carmen O'Neill, 81

When I was younger I did a lot of walking – but in the end I hurt my ankle and had to stop. The temptation is to think, "Well, that's that – I used to exercise but I'm old now." But I was determined to stay as active as possible.

I took up yoga a year ago, and now I do it twice a week. I saw a notice at my doctor's surgery, went along to see what it was like, and loved it – despite being the oldest in the class.

Yoga makes you stretch yourself, just that little bit further than you feel you can go. And that's important when you're older, because it's too easy to do less and less. Now I feel I walk straighter, and taller. I feel I've got more mobility in my joints. And just as importantly – I meet other people, have a good time and chat. It's keeping me young!

Ann Grantham, 72

I took up swimming in my late 30s, because my children liked going to the pool. It's become a passion: these days, I swim at least 15,000 metres a week, usually in five one-hour sessions, swimming 3,000 metres a time. Swimming is a perfect exercise, especially when you're older: the water supports your body, you're less likely to get injured, and it's great for your heart and lungs. It makes you feel so good psychologically. I can honestly say that in more than three decades of swimming I've never once got out of the pool and not thought: that was brilliant, I'm so glad I did that.

So many women think that the menopause will inevitably make them fatter, but I didn't put on an ounce. You've also got the energy and stamina to keep up with the grandchildren.

I'm a bit slower than I used to be, but I still swim competitively – in a senior team – and I love that. Winning gives me a great boost.

Richard Simpson, 68

I got my first bike when I was 12. I've carried on right through my life – I did the Milk Race in the 60s, cycling 1,300 miles in a fortnight. These days I do a ride of between 30 and40 miles on at least five days out of seven. It never feels like a chore: it's a pleasure. I love the countryside so it's a way of feeling close to nature.

In many ways I feel keeping fit is like paying into my pension: it's something you need to do in order to make the most of your later years. I can't imagine ever giving up.