CrossFit is a strength and conditioning program consisting mainly of a mix of aerobic exercise, calisthenics (body weight exercises), and Olympic weight lifting. An hour-long CrossFit class will typically include a group warm-up, a skill development and / or strength segment, the high-intensity "workout of the day" (or WOD), and a period of individual or group stretching. The programming changes each and every day, is always completely scalable and is suitable for all ages and abilities.