There is a science behind the obvious thing that cyclists don't need to be as thin as runners to be successful. Power to weight ratio is the magic figure. Its everything. While reading this article, I once again started thinking about what my ideal weight would be as a cyclist. Striking that perfect balance between too lightweight, or flyweight to climb those long hills, and being bulky with huge legs that will haul one on the flats and down hills is not so easy and I guess much of what you know comes from experience. For example, last season, I was pretty good on some climbs in the area but I found my flat road power going down. Next season is the time to bridge those gaps and strike a perfect chord weight wise. I need to put on more muscle.

The Bicycling Paradox: Fit Doesn’t Have to Mean Thin

By GINA KOLATA

Published: July 17, 2007, New York Times

Andy Hampsten, the former pro cyclist, the only American ever to win the Tour of Italy, the first American ever to win the grueling Alpe d’Huez stage of the Tour de France, does his best to discourage casual riders from signing up for the cycling trips he leads in Tuscany.

“All of our trips are designed to satisfy experienced riders,” Mr. Hampsten writes on his Web site. To train, he suggests, “you should ride at least 100 miles a week for at least 6 to 10 weeks” on routes with “as many hills as you can find.”

So I had an image of what our fellow cyclists would look like when my husband, son and I arrived in Castagneto Carducci for a cycling vacation. They would look like Mr. Hampsten, who at age 45 remains boyishly thin and agile, bouncing with energy.

I was wrong. For the most part, our group consisted of ordinary-looking, mostly middle-age men and a few middle-age women.

These were serious cyclists. One of them was Bob Eastaugh, a 63-year-old justice on the Alaska Supreme Court who said he rode mostly to stay in shape for his true passion, downhill ski racing.

And our trip was challenging. The longest hill was 15 miles, the steepest had a 15 percent grade, the longest one-day ride was 90 miles, and the terrain was never, ever flat. It is hard to imagine that a group of middle-age adults could have handled an equivalently difficult 10 days of running. What, I wondered, made bicycling different?

It turns out that others, too, have been struck by the paradox of bicycling fitness.

“When I first got into cycling, I would see cyclists and say, ‘O.K., that’s not what I perceive a cyclist to be,’ ” said Michael Berry, an exercise physiologist at Wake Forest University. Dr. Berry had been a competitive runner, and he thought good cyclists would look like good runners — rail-thin and young.

But, Dr. Berry added, “I quickly learned that when I was riding with someone with a 36-inch waist, I could be looking at the back of their waist when they rode away from me.”

He came to realize, he said, that cycling is a lot more forgiving of body type and age than running. The best cyclists going up hills are those with the best weight-to-strength ratio, which generally means being thin and strong. But heavier cyclists go faster downhill. And being light does not help much on flat roads.

James Hagberg, a kinesiology professor at the University of Maryland, explains that the difference between running on a flat road and cycling on a flat road has to do with the movement of the athlete’s center of gravity.

“In running, when you see someone who is obviously overweight, they will be in trouble,” Dr. Hagberg said. “The more you weigh, the more the center of gravity moves and the more energy it costs. But in cycling, there are different aerodynamics — your center of gravity is not moving up and down.”

The difference between cycling and running is like the difference between moving forward on a pogo stick and rolling along on wheels. And that is why Robert Fitts, an exercise physiologist at Marquette University who was a competitive runner, once said good runners run so smoothly they can almost balance an apple on their heads.

Even Mr. Hampsten has been surprised by the cycling paradox. He recalls a woman from San Diego who went on one of his trips. “She was quite overweight,” he said, and even though she claimed to be an experienced cyclist, he worried that she would have trouble keeping up with the group. He was wrong.

“She rode so well,” Mr. Hampsten said. “Her cadence was very efficient. I was just amazed and delighted.”

As for the effects of aging, serious recreational cyclists do slow down, but they are not penalized as much as runners by the passing of years, Dr. Hagberg said. It’s because cycling, while grueling, is not as demanding as running.

“The best example of that, in a bizarre way, is the Tour de France,” Dr. Hagberg said. “What runner could go out six hours a day for three weeks and not be totally trashed after a day or two? That’s a microcosm of the aging issue.”

Still, even the best serious recreational cyclist is almost a different species from a professional rider. How much faster, our touring group asked Mr. Hampsten, would a professional rider go up that 15 percent grade during a race? About twice as fast as the fastest in our group, he replied.

And how about recovery after racing? Mr. Hampsten used to compete in 100 races a year, including the Tour de France, and he would recover by going for a long, relaxed ride. It sometimes took him three hours of cycling to warm up after a hard race. Then he’d continue for another two hours.

But recovery does become a limiting factor for professional cyclists, Mr. Hampsten said. It’s why most professional riders can no longer win long, multiday races after age 32.

“It’s almost eerie that at 32 years, you stop winning,” Mr. Hampsten said. “The endurance seems to stay, but recuperation doesn’t come around.”

When Mr. Hampsten retired, he was 34, “and I hadn’t won a race in two years.”

Now, he estimates, he is 80 percent as fit as he used to be.

But 80 percent for Andy Hampsten is still impressive. As soon as our cycling tour ended, he headed out on a fast ride that included a long hill to the town of Suvereto, taking a road with 187 switchback turns.

“It is my favorite road to ride,” he said.