For the seventh year in a row, Texan Lance Armstrong triumphantly rode down the Champs-Elysees as the winner of the Tour de France. This race, he says, will be his last. Many already wonder what the famed bike race will be like without him. There are other talented riders such as German Jan Ullrich, who for four years finished just behind Mr. Armstrong. But, according to medical experts, there may not be another rider like Lance Armstrong.

In the Journal of Applied Physiology, Dr. Edward Coyle, an exercise physiologist at the University of Texas who studied Mr. Armstrong in his human performance lab, writes with awe about the cyclist he called a phenomenon of genetic natural selection and “a person who is truly inspired.” Over the seven years that he has won the Tour de France, the cyclist improved his muscular efficiency by a “remarkable” 18 percent, Dr. Coyle wrote last month.

This is even more astonishing because Mr. Armstrong was diagnosed with testicular cancer in 1996. The cancer spread to his lungs and brain and it was uncertain that he would live. Three months after chemotherapy, he was riding for up to five hours a day, five days a week. He won his first Tour de France in 1999 and has won every one since then.

Dr. Coyle says there are probably only 20 people in the world with Mr. Armstrong’s power and stamina. Ten of them, he says, are bike racers who have ridden in the Tour de France.

Mr. Armstrong can maintain a power output of about 6.8 watts per kilogram of body weight for 20 minutes. A good recreational rider can generate about 4 watts, which means they can travel at about 20 miles per hour on a flat road. Lance Armstrong would be going 34 miles an hour on the same road. His body is also super efficient at carrying oxygen.

Mr. Armstrong’s physical ability is coupled with a strong mental desire to win. Starting last, the cyclist, wearing the yellow jersey marking him as the leader of the tour, stormed through Saturday’s time trial, the last competitive race of the 21-day tour. He won. “As a sportsman, I wanted to go out on top,” Mr. Armstrong said simply of his fast pace despite his comfortable lead in the overall tour.

With his unprecedented seven tour wins, there is no doubt that Lance Armstrong is going out on top.