Dog sledding. I think it is the toughest.
no of corse by alot
dogsled teams of 16 start out running in the race
The Iditarod Trail Sled Dog Race, usually just called the Iditarod, is an annual sled dog race in Alaska, where mushers and teams of typically 16 dogs cover 1,161 miles (1,868 km) in eight to fifteen...
this race is about 10 hours... or tthats whhat a website said to me :) i had to do this for homework too!