CrossFit is a constantly-varied approach to training, that uses functional movements at maximum intensity (relative to the physical and psychological tolerances of the participant), which leads to dramatic gains in fitness. Intensity is essential for results and is measurable as work/time. The more work you do in less time, the more intense the effort.

These functional movements are derived from movements that are traditionally classified as gymnastics, cardiovascular, and weightlifting. These movements include pull-ups, push-ups, running, jumping, deadlifts, kettle bells swings, cleans, and many other movements that are too numerous to list.