Cyclocross is a cross between road racing and mountain biking. Competitors race laps around a course featuring a variety of surfaces (pavement, grass, sand, gravel, dirt, etc.) while negotiating a number of obstacles that may require them to dismount and remount their bicycle. Beginning in the fall and running through the winter months, cyclocross used to be mostly popular for off-season training, but has become a very popular sport in its own right. Races are very exciting to watch because they consist of adrenalin-filled laps around short courses–typically less than two miles in length.