The footballer aged 72, the marathon runner in his 90s – what's their secret? Rebecca Armstrong finds out how these senior sportsmen keep running

Anyone who finds doing regular exercise something of a chore could do worse than following Dickie Borthwick's example. Known as Dixie to his friends, Borthwick plays football once a week, eats low GI porridge for energy, takes vitamins every day and gave up smoking to improve his heath. Couch potatoes should also take note that Borthwick is 72 years old and played his first match aged 12. "I don't feel like I'm in my 60th season," he says. "I still feel young at heart and feel like I can go on for a few years yet."

Borthwick isn't the only older athlete putting fitness-phobics half his age to shame. John Starbrook, 76, competed in his first triathlon earlier this year "for a bit of a challenge". This gruelling event would be enough of a challenge to most people, but Starbrook also runs in two marathons every year. "I've done about 40 marathons in total. As I do two marathons a year, I basically train all year round – it's New York in November and London in April," he says. "In between I've started doing triathlons for a bit of fun."

Fauja Singh, 96, from Redbridge, Essex, took up marathon running at the age of 89. "I've always been active and growing up in Beas Pind in India I used to miss school to watch sporting events. I moved to London aged 84 and began running marathons five years later," he explains. "Now I walk or jog eight to 10 miles per week with one proper session with my trainer."

According to NHS guidelines, everyone, regardless of age, should aim to do at least 30 minutes of moderate physical activity five times a week to improve mobility and reduce the risk of heart disease, type 2 diabetes and osteoporosis. But while it can be all too easy to find excuses to avoid starting an exercise routine, Borthwick, Singh and Starbrook prove that age shouldn't stand in the way of fitness.

So what are their secrets? "I attribute my health to simple, stress-free living and humbleness before God," says Singh. "I'm teetotal, vegetarian and don't eat greasy or fast foods. Fresh food is best." And while Borthwick is a fan of supplements – "I have a strict routine with my vitamins every day" – Starbrook eats a normal diet and doesn't hold much truck with pills of any kind. "I don't eat much rubbish food – no burgers or any of that – just good stuff," he says. "I don't take any vitamins or supplements, I don't even like taking an aspirin, but I seem to be alright."

As we age, our bodies start to change. "The first thing is that you tend to get a change in body composition so you get a reduction in muscle mass and strength and an increase in percentage of body fat," says Lorenzo Masci, a sports physician at Pure Sports Medicine. "The second thing is that you get an overall reduction in maximum heart rate and a reduction in your body's ability to take in oxygen."

Masci also warns that as we can expect lower heat tolerance and less flexibility. "People have a reduced capacity to recover from injuries, or recover in general, so they need to be aware of that – they're not like they were when they were 18."

While this might sound depressing, it's not all bad news. "A lot of these changes can be attenuated by exercise," Masci says. "A study of athletes in their 70s shows that these changes can be reduced by 50 per cent or more."

According to Help The Aged, we can't store the benefits of exercise. If you were sporty until your 40s, it won't help in your 70s, except that you may have a higher baseline to lose strength from. But if you had an active background, like Borthwick, Singh and Starbrook, you're more likely to continue to exercise as you get older.

So what tips can they offer? "Running is a natural thing that any able-bodied person can do and it's free," says Singh. "It exercises more than just the legs... I hope my running has given courage to everyone." Starbrook says regular training is the key. "You've just got to put your mind to it. Don't over-train, just do enough. It's either that or do the garden."

But if you're out of condition – whatever your age – it's important to start slowly. The NHS recommends that anyone who has been inactive for a long period of time should try to build up to 30 minutes a day – which can include activities like walking or gardening – over the course of a week, and avoid high impact exercises that involve hard jolts to the body. "It's never too late to start exercising but start slow," says Masci. "I usually tell people to start off by doing a combination of things – a little bit of aerobic exercise like cycling on a stationary bike, walking or swimming – and then some resistance exercise."

However, it's important to speak to your GP before embarking on a fitness kick. "The important thing is to do things that you enjoy – studies have found that people who do activities they enjoy are more likely to stick with them," Masci says.

And just remember – it's never too late to try something new. Just ask Starbrook. "At the moment I'm hoping to try skydiving. I've never done anything like that but I'm just going to go up, shut my eyes and shout 'Geronimo' as I jump out of the plane."