MARK FOSTER has always been a swimmer. Now he trains as an athlete. The difference in preparation comes through his unique career as an elite sprint swimmer. This will see him, aged almost 38, become the oldest competitor to take part in the world championships, when Manchester stages the short-course event on April 9. As six-times world champion, eight-times world record-holder and four-times an Olympian, Foster is a rare combination of power and experience.

His speciality is the 50m freestyle, the shortest of all the swimming disciplines, where the emphasis is on an explosive start and arm-flailing dash for the finish. In a short course (25m) pool, there is also one turn, at which Foster excels, giving him extra propulsion on the second length. His best time is 21.13sec in 2001 but after eight months of retirement in 2006, Foster returned to competition and recorded 21.56sec, the fourth-fastest time of the year. Then, last November, he qualified for the world championships, the first time Britain has hosted the event.

Foster will sharpen up for these championships by taking part this week in the Olympic trials in Sheffield where his less-intense attitude may help him towards participating in his fifth Games, something no British swimmer has ever achieved. He says: “Because I have had time out of the sport, I’m more relaxed and I get excited about racing. I love racing and the challenge of beating people, but in the past I just about knew to within a split-second where I was going to be. There was no surprise, whereas now there is. The question pops into my mind, ‘What is going to happen today at this race?’ I’m excited about the unknown.”

He has up to five pool sessions a week, often swimming flat out for only nine or 10 seconds. “I don’t do a lot of distance,” he says. “The race is only 21 seconds and therefore you are only swimming (because of the dive and turn) for 18 seconds.” He also spends three days a week in the gym, working like a bodybuilder with exercises on his upper back and triceps. At 6ft 6in, he weighs more than 14st and avoids putting on too much muscle on his chest because it will act as a drag in the water.

He changed his training when he watched athletes, such as hurdler Colin Jackson in the gym in the late 1990s. He adds: “I like the diversity of training now. I am no longer counting tiles on the bottom of the pool, although I loved it at the time. At least in running you can change the route. In swimming you can’t.

“It would be possible to go on sprint swimming into your 40s. It’s down to money. Swimmers used to finish university and then start thinking about getting a job. If they earned the money of footballers many would go on well into their 30s. I’ve been lucky. I have had sponsorship and recently modelling.” He plans to finish competing this year. Would he continue? “I’m not intending to, but never say never.”

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