Athletics: Linford Christie may defend his Olympic title, Carl Lewis is nearly back to his best and Tessa Sanderson aims to compete in her sixth Games. How do they defy the years?

When Baron de Coubertin founded the modern Olympics, he called upon the youth of the world to congregate every four years.

One hundred years on, however, the congregation preparing for Atlanta contains a significant number of athletes who hardly qualify for the term "youthful" - and not just in the endurance events, but in the explosive disciplines of sprinting and throwing, traditionally the domain of the twenty-somethings.

Four years after becoming the oldest man to win the Olympic 100 metres gold medal, Linford Christie - now 36 - is still to announce whether he will defend his title. But most of his likely rivals believe that he will be there, and if he does go he will make it difficult for anyone to beat him.

Christie is notoriously wary of talking about his age. He seems to view acknowledgement of the passing years as Superman might regard kryptonite. But his approach, patently, works.

At 35, the American sprinter and long jumper Carl Lewis is seeking to add to the eight Olympic gold medals he already has in his possession. His 100m in 9.94sec at last month's Atlanta grand prix, only marginally wind-assisted, offers statistical evidence that his aspirations are not outlandish. "I don't know what a 35-year-old feels like, so I don't make any concession to age," Lewis said. "I don't know what age is doing to me unless I feel it."

The position was put even more succinctly by Britain's javelin thrower Tessa Sanderson. Her achievement of the Olympic qualifying mark of 60 metres three weeks ago after coming out of a three-year retirement has given her the prospect this summer of equalling the all-time record of six Olympic appearances by a woman athlete. "I'm 40," Sanderson said. "So what?"

If we are surprised at such prowess so late in life, we should not be, according to Professor Bruce Davies, the physiologist who has been director of the British Olympic Medical Centre for the last two years. We are simply confusing chronological time with biological time.

"Age is an appalling benchmark to judge whether someone can perform in society," Davies said. "We all know people who are 20 years old going on 50, or 50 years old going on 20.

"Biological age and chronological age vary so much. People age at different rates - some people are simply genetically programmed to live a lot longer. To be able to perform for a long time in athletics, you have to choose your parents well."

Davies, who has fitness-tested hundreds of international sportsmen and women in the last 20 years, is convinced that athletic longevity is crucially a matter of genetics - even to the extent of being suitable for training. He points to research work carried out recently in Canada by Professor Claude Bouchard of the University of Montreal, which claims there is a gene which allows some people to gain more from training than others.

The bottom line in sprinting is that most top performers are between 19 and 26. It is at this age that there is the maximum ability to move one's legs fast. "Leg cadence is one of the only things you can't improve with training," Davies said.

But the current trend of lengthened athletic careers involves more than genetic determinism or youthful neurological capacity. Davies lists a number of factors which make it easier for today's international athlete to maintain their position.

Recent advances in sports medicine have had a profoundly beneficial effect. Athletes nowadays have access to preventative physiotherapy and information about diet and sensible training. They run in shoes which have been designed to prevent athletes developing injuries which, 10 years ago, might have ended their careers.

Also, if athletes do succumb to injury, sophisticated surgery techniques have been developed which can mend injuries which would have meant retirement 15 years ago. But, as much as anything else, continuing at the top is about having the dedication to maintain specific fitness for a chosen event.

"People like Christie have a tremendous advantage over younger competitors in terms of experience and strength of mind," Davies said. "We are getting a change of attitude. People are beginning to realise that athletes are not over the hill at 25. In the past we have put athletes on the shelf because of the mind-lock we have, particularly in this country. There is something to be said for the idea that you are as young as you feel."

There is, too, an element of solidarity among the thirty-somethings. Merlene Ottey, Jamaica's 36-year-old world 200 metres champion, drew inspiration from Christie's world indoor 200m record last year. "It gave me a real boost," she said. "It made me think, he's the same age, running better than ever, so why not me?"

Finally, there is a very persuasive incentive for the long-distance competitor. The total award money on offer this year in the International Amateur Athletic Federation's grand prix series is $3,338,000 (pounds 2,225,000) - and that's not including the shoe deals.

Linford Christie

Great Britain

Age 36

Reigning Olympic 100 metres champion and 1993 world 100m champion. Won his first major titles - European indoor 200m, European outdoor 100m - in 1986 at the relatively advanced age of 26. Recently extended his unbeaten run of victories in the European Cup to 15. Said last May: "I honestly believe I could go on for another three or four years."

Carl Lewis

United States

Age 34

Will be 35 on 1 July. Won four gold medals at his first Olympic Games in 1984. Has subsequently added four more and is seeking to break Ray Ewry's all-time record of 10 in Atlanta this year. Winner of the last three Olympic long jump competitions. Ran his best 100m in five years last month in a time of 9.94sec. "I feel like my old self again," he said.

Merlene Ottey

Jamaica

Age 36

Won four Olympic and five world championship bronze medals at 100 and 200 metres before winning world title outright at 200 in 1993 to huge acclaim. Competed at the 1980 Olympics. Trains with Christie. Appointed a roving ambassador for Jamaica in 1993. "The young ones are still afraid of me," she said. "They think of me as the grandmother, but that's all right."

Tessa Sanderson

Great Britain

Age 40

First international appearance in 1973. Recently came out of retirement after break of four years and gained Olympic javelin qualifying mark at first attempt. Due to equal all-time record of six Olympic appearances by a woman athlete when she takes to the field in Atlanta. Olympic champion in 1984, three times Commonwealth champion.

Judy Oakes

Great Britain

Age 38

Came out of a second retirement in 1994 to secure her second Commonwealth title and her fifth Commonwealth medal in five attempts. Record international appearances for Britain. Has also won several world powerlifting titles. Recently came second behind world champion Astrid Kumbernuss in the European Cup. Seeking to improve this year on her fourth place at the 1984 Olympics.

Mike Conley

United States

Age 33

Due to defend his Olympic triple jump title in Atlanta. Jumped 17.50m or more every year from 1984 to 1994 - he had an ankle injury in 1995. Last month he improved his long jump best to 8.46, further than he achieved to win 1983 world bronze. Deputy sheriff for Washington County in Arkansas, and professional trainer of police and attack dogs, including Rottweilers named after Olympic stars.