Obstacle Course Racing (OCR) is a sport in which a competitor, traveling on foot running on road or trail, must overcome various physical challenges in the form of obstacles. Races vary from mostly obstacles such as Spartan Race, Desert Warrior Challenge and Tough Mudder, to track races, to urban and cross country events. In cross country events, mud and trail runs are often combined and the races are designed to result in mental and physical collapse. Obstacles may include climbing over walls, carrying heavy objects, traversing bodies of water, crawling under barbed wire, and jumping through fire. Many obstacles are similar to those used in military training, while others are unique to obstacle racing and are employed throughout the course to test endurance, strength, and speed.