in interval training/circuits, what ranges are we trying to hit? When we go for the break between circuits, how do we know that our heart rates are low enough? I find myself getting very winded and not quite at full power when I start a new circuit in most workouts and wondering if that is the way it is supposed to be or if I need a longer break! I figured with the science behind STS and using the 1RM calculations, there must be a target range for the cardio too.! Thanks in advance! I'm loving the workouts.