Time trials pose different problems. Individual riders face the wind and the clock on their own. Individual power and endurance ultimately determine performance. Triathletes are essentially engaging in a time trial during the bicycle leg of their competition. Criterium races are mass start events held on a small, looped course.
Riders perform multiple circuits of the course, with high-speed sharp turns.
Performance is based largely on bike handling skills and sprint speed. Of the three basic forms of bicycle races, the road race is the one most noted for its use of hilly terrain. The ensuing discussion of factors influencing performance on the hills will generally assume that a road race is involved. On modern bicycles with narrow, high pressure tires, rolling resistance is negligible. Going uphill adds gravity to the forces that must be overcome.