Published: July 10, 2009 12:00 am      

Tour de France is rich with drama

This year's Tour de France boasts numerous treats for viewers, not the least of which is the return of American rider Lance Armstrong. Here is a preview of some of the most dramatic parts of the Tour, when the leadership of Astana and the eventual winner of the Tour may be decided _ the mountain stages.

Each year, the Tour de France alternates which direction the riders will cycle through the country. This year, it's clockwise, which means the dramatic stages in the Alps will come last.

There are several things to consider when judging how hard a mountain pass (or "col") is.

First, there's height. The higher the elevation, the thinner the air, which means the quicker the body will resort to anaerobic respiration.

That means a rider eventually operates without enough oxygen pumping through the blood, resulting in the muscles being flushed with lactic acid. That's why riders stock up on food bags (called "musettes") on the flatter parts of the mountain stages _ to top off their glucose levels and make sure they are hydrated.

Often, it is the job of the domestiques to head to the team cars that follow the peloton and bring their teammates water, fruit and energy bars.

Next, consider gradient. A mountain pass can be quite high without being terribly tough. Gradient measures the incline. Anything above 6 percent is intense.

Lastly, don't forget the descents. Many include hairpin turns, potholes and deadly drops.

Professional riders know their "lines" well, meaning they judge the turns and their apexes in such a way that they can follow as straight a line as possible around a bend, using their brakes little if at all and popping their knee out to maintain their center of gravity.

Often, a descending rider will be bent low on his bike, riding either with his body tucked into itself, seated in the saddle or sometimes on the top tube. This is an aerodynamic position that creates a wind tunnel around the body, allowing the rider to gain maximum speed without expending as much energy.

The Tour ranks the mountain passes from categories 5-1, with 1 being the highest. There are some dreaded mountain passes that exceed even the highest category; these are dubbed "HC," which stands for "hors categorie" or "beyond category."

The big mountain stages in this year's Tour will occur during stages 7-9 (today through Sunday) and 15-20 (July 19-25).