So Keizo Yamada is giving up racing marathons. Japan's Iron Man is conceding that he's not up to the training anymore.

He made the decision after running three marathons this year, including his 19th trip to Boston a race he won in 1953. He ran the marathon for Japan the year before at the Olympics in Helsinki.

Yamada's 81. A pretty fit octogenarian.

He told Sports Hochi newspaper "I'm not getting any younger so I won't run any more 42-kilometre races."

"I will carry on running for fun to stay in shape," he added.

His "running for fun" is a daily 20-kilometre jaunt. That's more exercise than the vast majority of even the most active people get. If it's not fun, it's pretty tough to be motivated to enjoy that much exercise.

Researchers have spent a lot of time and effort trying to figure out the most effective ways of getting people motivated to get active enough to stay healthy and ward off obesity.

Two years ago, the Canadian Obesity Network warned that without action Canada would face an obesity epidemic that would be a bigger drain on the health-care system than smoking. The network estimates that 11 million Canadians about a third of the population are overweight and a million of them are so obese they need treatment.

Last week, an Australian study found that spending money on public campaigns can make a difference in getting people active. The study found that encouraging the use of pedometers was more effective than having doctors refer patients to an exercise physiologist.

Pedometers give you instant feedback. They'll tell you how many steps you've taken, how far you've gone and how many calories you've burned.

Feedback's good. You can use those numbers as a base to build on. That can help develop motivation far better than a piece of paper that will get you in to see a specialist a piece of paper that you might ignore.

The findings of the Australian study were similar to one published in the July 2008 edition of the journal Medicine & Science in Sports and Exercise. Among its conclusions was that it's more effective to encourage people to walk at a moderate pace than to prescribe high-intensity walking.

That's right: exercise doesn't have to be this high-intensity medicine that you have to force yourself to swallow every day.

Casting a wide net with mass campaigns might get more people moving, like the ParticipACTION ads did when it was first launched back in the 1970s. But information and encouragement won't be much help in keeping you motivated, especially after you figure out that getting in shape is not the end goal. You don't go back to your old sedentary ways once you hit that target weight or complete your first five-kilometre race.

Getting in shape and staying there is the payoff for being a little more active, for the rest of your life.

Keizo Yamada may be through with marathons, but he's not done testing his limits. He says he could still be coaxed into racing the odd half marathon.