The Leadville 100 — why do they do it?

You don’t have to be interested in mountain bike racing to enjoy the thrilling and beautifully shot documentary, “Race Across the Sky,” about last summer’s Leadville 100 competition in Colorado.

This grueling 100-mile race takes place in some of the most beautiful scenery in the country and the filmmakers clearly designed the movie so that non-sports fans can enjoy it as much as those who have taken part in such races (or dream of doing it one day).

As a longtime armchair enthusiast of skiing and surfing films, I was immediately taken by the high quality of the cinematography and the editing of “Race Across the Sky.” It’s a smart, action-packed look at an annual event somewhat like the New York Marathon, in that it draws a large group of competitiors who range from ordinary people who simply want to finish the course to pros and semi-pros who race bikes for a living and are desperate to win.

The movie was broadcast to theaters around the country last October as a one-night only event, but the Community Theatre in Fairfield is screening it Friday night at 7:30 as part of a benefit for the Connecticut Challenge Bike Race’s cancer survivorship programs.

The annual Connecticut Challenge has been held every summer since 2005 when it was set up by Jeff Keith and John Ragland, to raise money for the first survivorship clinic in the state. Keith is a pediatric cancer survivor, athlete, and long-time fundraiser for cancer research. Ragland is a cyclist and business entrepreneur.

“Race Across the Sky” shows us how the depressed one-time mining town of Leadville, Colorado, created the race 25 years ago to spur tourism. The event has gotten large each year with more than 1,200 men and women taking part in 2009.

Citizen Pictures — which produced the movie — falls into some of the same hokey traps as other sports films. The music is — most of the time — a bombastic embarrassment with jacked-up choral chanting that sounds like it was borrowed from the soundtrack of “The Omen.”

But the race itself makes for great footage of competitors working their way up incredible vertical climbs and going through numerous weather patterns — from hail to torrential downpours to heat.

And the rivalry between the six-time Lakeville champion Dave Wiens (below right) and international biking superstar Lance Armstrong (above) makes for some high drama (the nice-guy local vs. the somewhat distant outsider).

“Race Across the Sky” is a good movie for a good cause. For more information on tomorrow night’s screening in Fairfield, go to www.ctchallenge.org.