Gym workout is passé. CrossFit is in. If you are clueless about what CrossFit stands for, it’s a fitness program started more than a decade ago in USA and is now practiced by millions around the world. CrossFit works on the principle of mixing high intensity exercises to build up stamina and improve one’s preparedness for any physical challenge. Aerobic exercises, weight lifting and gymnastics are all part of a regular CrossFit workout schedule.