If you are in the treatable group, good for you. For those with CFS who read this, I would like to propose an explanation of CFS that may lead to an alternative treatment. My idea is that melatonin and DHEA levels determine blood pressure.
Blood pressure is lowest in children and increases thereafter.
Melatonin is highest at night, and blood pressure decreases slightly at night. I suggest melatonin reduces blood pressure by reducing DHEA production. Exercise increases DHEA and blood pressure. The increased blood pressure of exercise, therefore, is temporary. People with CFS exhibit lingering tiredness after exercise.