The instructors provide the motivation I need to push myself. There is no way I would challenge myself at home. I can increase my speed and weights as I get stronger, so the workout changes as I improve my fitness.
I like circuit training. I feel that by incorporating cardio, weights, aerobics, and floor exercises, I am truly getting a full body work out. I also like the competitive nature of the workout and that I am able to see a measurement of my success the entire time.
Simple, easy to follow, and judging by my soreness it works. Also love the orange and red zones so I know exactly how hard I'm pushing myself instead of judging off of people around me who may be at different levels like I do in other structures.