I know the program is for the diehard but then again you only get out of the program what you put into it. Im sure you can downplay your intensity to just "stay in shape" but I am going to tell you what is going to happen.
After about 3 weeks you are going to start feeling GREAT and getting compliments about how you look. Suddenly you start to work a bit harder each workout and before you know it Men's Fitness is calling you up for a photo shoot.
Good luck in whatever you find.
Not at age 51, they're Not