Cyclists who participate in 2,100-mile Tour de France are the top athletes in the world, one U.S. researcher says. Phil Gallagher, director of the Applied Physiology Laboratory at the University of Kansas in Lawrence, Kan., says it takes exceptional human physiological processes for these select cyclists to ride for 21 days and push their bodies to extremes. \"These guys have been training their entire lives,\" Gallagher says in a statement. \"As a result, elite cyclists have larger hearts than the typical person, so they\'re able to push out more blood per beat. They\'re able to extract more oxygen from their blood than an untrained individual would.\" Gallagher, who qualified several times for the U.S. Olympic trials as a cross-country skier, measured the output of cyclists with a power meter. Gauging cyclists\' productivity in watts, Gallagher found that average cyclists generate less than half the power of the elite athletes who compete in the Tour de France. \"For example, I just went out and cycled around 45 miles this weekend, and averaged around 200 to 225 watts,\" Gallagher says. \"These tour riders average double that and they\'re riding double that distance each day. They\'ll put out 450 watts average power. They\'re basically the top athletes in the world.\" To maintain this energy production, the cyclists hone their bodies through extreme training to produce more oxygen-transporting red blood cells than the average person, Gallagher says. No comparisons were provided for elite athletes in other sports.