While most of us would be grateful to even have a pulse at the age of 100, last weekend, Britain's Fauja Singh showed the world what a centenarian can really do with bit of determination.

The 100-year-old completed the Scotiabank Toronto Waterfront Marathon and set a new record as the world's oldest marathon runner.

Sure, he wasn't fast – it took Singh more than eight hours to finish the 42.2-kilometre race – but just crossing the finish line was a headline-grabbing, record-breaking achievement.

It capped off a week of breaking records. Just three days before, Singh -- who's known as "The Turbaned Tornado" -- set eight world records at Scarborough's Birchmount Stadium track for running distances as short as 100 metres to as long as 5,000 metres.

Judy Chu, who provides fitness instruction to seniors at the Terraces of Baycrest retirement home in Toronto as well as to seniors in the community says it's not unheard of for 100-year-olds to still be active. But running at 100 and completing one the most challenging tests of fitness – the marathon – at 100 is rather unique.

"We have 100-year-old people who take part in our chair exercise program or water exercise program. But they're not runners," she says.

"Running isn't for everyone. It's for the few, like that 100 year-old man, who's probably run all his life."

In fact, Singh's family says the 100-year-old took up competitive running only about 10 years ago, when he was 89 and ran his first marathon. But they say he has always enjoyed running and consistently puts in about 10 to 15 kilometres a day of pavement-pounding.

As inspiring as Singh's achievement is, the reality is that staying a long-distance runner into your 80s, 90s and beyond is demanding. Research shows that with every decade, we lose 10 per cent of our aerobic capacity, no matter how fit we were to begin with. Muscle strength falls off in our later years, and many seniors either develop osteoarthritis or see joint problems caused by regular wear and tear.

But research has also shown that regular running can actually slow the effects of aging. While many might think that seniors who run might have more joint injuries and disabilities than non-runners, a study from the Stanford University School of Medicine a few years ago found the opposite. It found that elderly runners live longer and become disabled about 16 years later than non-runners.

When CTV News ran a news item on that study in 2008, Chu's own father, Gordon, appeared in the broadcast to illustrate the story. Chu's father is now 83 and is still a regular runner.

"Some (seniors) do run. My father is one of them. But he doesn't just run," Chu says.

Instead, he mixes his mile-long run around the track with days when he swims, or with workouts on the weight machines. And in the warmer weather, he also plays tennis.

"He's done that as long as I can remember, ever since he came to Canada over 60 years ago," Chu says.

"So he had done cross-training all his life. He doesn't do one thing, he does many things. So he hasn't taxed his body in any one area and he hasn't been injured."

Chu believes that seniors can take up a sport any age, as long as they are healthy with no joint issues and have the assurance from their doctor that they have no medical conditions that could stop then from exerting themselves.

She doesn't advise seniors start a new sport on their own without seeking the advice of a fitness expert on how to get started, what kind of equipment and footwear to use and how long to rest in between.

"They need expertise for that," Chu says. "Because the last thing a senior needs is an injury. That will just leave them more sedentary."

While Singh's achievement last weekend has likely inspired lots of seniors, Chu says they shouldn't feel that they need to take up running in order to get in shape.

"Running is for the elite senior. That 100-year-old man is that person. Seriously, how many 100-year-old people can run?" she says.

"My point of view is not everybody can run, but a lot of people can walk... Walking is one of the friendliest and most available exercises around," she says.