I came across this old Cycling News story from last December, something that might be worth noting in the coming weeks.
From Boonen's trainer:
Boonen's maximum heart rate is 195 bpm. "That doesn't mean much," said Hespel. "That could also be the case with you and I. But the heart of a top athlete like Boonen can pump much more blood per beat, so-called a sports heart. The average resting heartrate of a typical person is 60 to 80 beats per minute. Tom Boonen's is just above 40. That's also normal. The average rider has a resting heartrate of around 45 beats per minute.
Hespel explained further that Boonen wasn't born with his heart, but the potential was always there to train it. "Tom Boonen's father was never a top rider, but if he trained in the same way, he maybe could have been as big a champion. Maybe, because for the same money that's not the case. He may have had the heart of his mother."
Boonen's lung capacity of 6.5 to 7 litres is also typical for a top athlete, according to Hespel. But it's not the capacity itself that's important. "What's exceptional is that Tom can breathe 200 litres per minute at maximum effort. That's one of the highest values that we've ever measured. Most athletes can breathe a maximum of 170 or 180 litres per minute."
Power output is all-important for cyclists, and Boonen is impressive in this department. "We give all our riders the same test," said Hespel. "They start to pedal at 100 Watts, which is easy for them. Every eight minutes, it increases by 40 Watts. Tom can do it up to 460 Watts after an hour and a half. That means that he has ridden for eight minutes at 420 Watts before that, and eight minutes at 380 Watts before that. You should try that one time on your home trainer. We've never seen that here. Museeuw was a fantastic athlete, but on a pure physical level, Tom is a bigger talent."
When Boonen gives it full gas in a sprint, he can put out 1600 Watts at 110 rpm. That's typical of a top road sprinter, of which there are very few in the world. "That's huge. Because of that, he has broken several frames. Remember the stage in the Tour de France where his chain came off his cog? That's not magic."
Last, but not least, is Boonen's mental aspect. Imbued with self-confidence without too much arrogance, Boonen has the ideal mentality for a champion. "He puts realistic objectives before him but also says to all the press that he can be World Champion. To say that is one thing, but he still does it, because he is so realistic.
"He has a huge amount of race knowledge. He knew in the Ronde van Vlaanderen that he had to attack at the right moment. He'll need that more and more, because if he is there in a break, there will always be coalitions formed against him. On the other hand, he is well supported. If you have guys like Nick Nuyens and Paolo Bettini riding for you in the finale, you can't complain."
Boonen has already shown he can win bunch sprints and the most prestigious one day races. But the question on many people's lips is: can he win the Tour de France, however bizarre it might sound for a rider of his mass? Hespel believes it's possible. "If he concentrated on climbing in place of explosiveness, like Lance Armstrong, then there's a chance that he could win the Tour de France in three or four years. With his body, that is possible, but you never know for sure. The only thing we have to ask is whether that's the right choice."