I hate workouts like these.....These types of workouts are so challenging to the knee, that if one has weak knees, as many women do, it is nearly impossible to complete the challenge very well. For me, with issues with my ankles that precludes jumping, this workout is just one extremely long modification. I don't feel as though I come even close to the calorie burn or the heart rate increase that the excercise, if done as shown, gives. However, by the end, I have gone from general achiness to soreness or pain, and cannot face the extra credit challenge (which includes lunges, squats, etc all challenging to weak knees!). Oh!! To have a program that addresses this issue!!! 😕**^^sigh^^**