Im am just about to graduate from Physical Therapy for my knee reconstruction. My therapist said she was going to give me a workout to stay fit. I have been doing 5 hour workouts,5 days a week for a month so I want to keep going forward. I was surprised to see the program she gave me was Cross Fit . That name rang a bell so I searched here on TT and found quite a few people here really like it. It looks to be a pretty extreme workout but if your serious about staying in shape it may be worth a look. BTW...its free.