In the back, neck, shoulder, and limbs, trigger points are the main cause of pain. Associated with palpable nodules in taut bands of muscle fibers, they have extremely constrained sarcomeres. Sarcomeres that are dysfunctional contract so tightly that they cut off their own blood supply. As a result, waste products accumulate. Build-up of waste products irritates the sensory nerve endings, causing further contraction. Metabolic crisis is the result of this vicious cycle. In the theory, the delivered acoustic energy unblocks the calcium pump, which reverses the metabolic crisis in the muscle fibers and releases the trigger points.