The trick is in the range of motion, not in the number of repetitions, that will lead to more strength and greater muscle mass. “When doing quads, for example, you should go down as low as possible while keeping your back without arching. If you’re not doing this then it’s not a proper squat, ”says Bryant. The same goes for all exercises. If what you want is to activate all the muscles then you must reach the correct range in shape and time, especially in shape in order to have tension in the muscles. When you can no longer do a repetition correctly, it is time to rest.