CrossFit is a strength and conditioning method where exercisers perform functional movements (squats, kettlebell swings, and running, to name just a few) at high intensity.
Most workouts are timed, with the goal being to complete a required number of reps as quickly as possible. Created by former gymnast Greg Glassman in his Santa Monica gym, CrossFit has grown rapidly over the past decade, from a handful of “boxes” (CrossFit-affiliated gyms) in 2005 to nearly 8,000 worldwide as of mid-2013. CrossFit combines elements of gymnastics, weightlifting, powerlifting, endurance training, and calisthenics to promote general fitness, but it is also used in some sport-specific training.
Greatist’s Resources on CrossFitA Look Inside the World of CrossFit