It is still working. Your muscles ache in response to a different level of exertion on the muscles (from no exercise to exercise, changing type of exercise, level of of intensity), just because they stop aching doesn't mean they are not working, the muscles are just used to that level of work. You may find that when you move up to level 3 that they start to ache again because of an increase in intensity. Muscles can get used to repetitive workouts and movements though which is why 30DS is so good because she mixes it up xx