No. You could be getting a build-up of heat in the deeper tissues of the back. As the temperature rises, it can irritate the pain sensors on the covering of the bone in your spine or ribs. This deep, achy pain is called periostial sensation.
There are no heat sensors in the soft tissues below the skin surface. The periostial sensation may be your only sign that the heat is building up too much in your tissues. So make sure to tell your therapist right away.