Lance Armstrong has overcome extraordinary adversity to become one of the world's leading sportsmen. Brought up by a single parent, he has overcome cancer to win the Tour de France - the world's most gruelling sporting contest - five times in a row.

He says he was 'born to ride bikes' - on 18 September 1971. He and his mother lived opposite a bicycle shop in the suburbs of Dallas, Texas, USA, and he got his first bike, 'an ugly yellow and brown contraption', at the age of seven, the start of a 'lifelong attachment'.

He recalls: 'Our first bike is a matter of kerb-jumping, puddle-splashing liberation. It is a merciful release from parental reliance - one's own way to the movies or a friend's house. Its the first chance we have to choose our own direction.'

He rode on successive bikes from the shop around dirt tracks, around the town, and then around the state. His mother encouraged him and nurtured his athleticism, and in 1989 he competed in his first major event, the junior world championships in Moscow.

Two years later he was the US National Amateur Champion. In 1993 he became the youngest ever road-racing World Champion. By 1996 he was the top-ranked cyclist in the world, but that October he was found to have testicular cancer. It had advanced so far that it had spread to his lungs and his brain and he was given a less than 50 per cent chance of survival.

He had to go through a new, and particularly aggressive, form of chemotherapy.

'When I was sick with cancer, I thought constantly about riding,' he remembers. 'I daydreamed about the sensation of riding through the countryside on a bike, the wind against my face. Riding up the Alps seemed like heaven compared with lying in a hospital bed, drugged, parched and burned from the inside out.

'Before I had enjoyed riding and the living it provided me, but I hadn't truly appreciated it. After my near-death experience, when I confronted the possibility of never being able to ride again, my feelings for the sport multiplied.'

He stormed back to beat the world, winning the Tour de France five years in succession from 1999 to 2003, a feat only equalled by Spain's Miguel Indurain. In 2002 he was named Sports Illustrated's 'Sportsman of the Year' and the Associated Press 'Male Athlete of the Year'. He has written two books: It's Not About the Bike, detailing the pain of chemotherapy, and Bicycle: The Noblest Invention, published in 2003.

Within months of his diagnosis he formed the Lance Armstrong Foundation, which concentrates on helping people manage and survive cancer, and now describes the disease as 'the best thing that ever happened to me' because it helped him to 'wake up' and focus on the most important things in life.

Why does he bicycle on? 'I love to ride. To me, riding is living. Each time I ride in the Tour, I prove that I survived cancer. I ride to prove that, in a mechanized era, the human body is still a marvel.'