CrossFit is a strength and conditioning program consisting mainly of a mix of aerobic exercise, calisthenics, weightlifting. The stated goal of improving fitness, which it defines as work capacity across broad time and modal domains. Hour-long classes at affiliated gyms, or “boxes”, typically include a warm-up, a skill development segment, the high-intensity workout of the day (or WOD), and a period of individual or group stretching. Performance on each WOD is often scored and/or ranked to encourage competition and to track individual progress. CrossFit gyms use equipment from multiple disciplines including barbells, dumbbells, gymnastics rings, rope climbs, pull-up bars, jump ropes, kettlebells, medicine balls, plyo boxes, resistance bands, rowing machines, and various mats. CrossFit programming is decentralized, but its general methodology is used by thousands of private affiliated gyms, fire departments, law enforcement agencies, and military organizations, high-school physical-education teachers, high-school and college sports teams.