The world's toughest wheelchair and handcycle race got a little easier Friday when the Sadler's Alaska Challenge conceded ground to Mother Nature.

Citing safety concerns in the face of continued rain and two mild cases of hypothermia during Thursday's race in Cordova, race officials lopped almost 30 miles off Friday's scheduled 55-mile road race.

Racers were left with a marathon-length ride from Valdez to the top of Thompson Pass, a muscle-straining climb that begins at sea level and ends at 2,771 feet.

The shortened course covered 26.2 miles, which, race co-director Ian Lawless of the U.S. Handcycling Federation said in a press release, "sets up Stage 6 as the toughest marathon in the world."

"The only thing it changes," Lawless said, "is the strategy of some of the competitors, now with a mountain top finish instead of a finish on a descent."

After an early morning ferry ride from Cordova, racers left Valdez in mid-afternoon for their fifth straight day of racing and the sixth of eight stages in the week-long Alaska Challenge.

A light rain fell as racers gathered at the Dayville Road starting line, a familiar scene for the record field of 36 racers. It's been raining since competition began Monday with a pair of races in Seward.

Because Friday offered no break from the rain and chill, and because of "hypothermia-related concerns from Stage 5, we decided to put the health and safety of the competitors first," co-director Heather Plucinski of Challenge Alaska said in a press release.

With the reduced mileage, racers will have traveled 223 miles when the event ends Sunday at the top of Hatcher Pass, the third of three mountain passes in the race.