If you like intense activities and are up for challenge, try CrossFit.
"No, it doesn't ever get any easier. You wouldn't want it to either." This quote by Greg Glassman , founder of CrossFit, says all you need to know about what some consider the most challenging fitness program ever.
Instead of featuring just one activity such as running or weight-lifting, CrossFit tries to integrate gymnastics, track and field skills, and bodybuilding into a short and intense workout. A Workout of the Day (or WOD) may involve doing 20 pushups, followed by ten pull-ups, and then an 800 meter run - then repeating the set as many times as possible in 20 minutes. Because the workouts change every day, the body does not easily adapt and is always challenged. Of course, a danger is that some people go overboard and risk injury or, at the very least, suffer aches and pains for a few days. But for people who like to push the limits of fitness and strength - there are many police officers, firefighters, and military people who follow it - CrossFit is the key.