Heart or Lungs? Uncovering the Causes of Exercise Intolerance in a Patient with Chronic Cardiopulmonary Disease https://www.atsjournals.org/doi/abs/10.1513/AnnalsATS.201802-073CC Clinical paper about exercise intolerance in cardiopulmonary disease. I don't have a subscription, so don't know if the cause of exercise intolerance turned out to be heart or lungs. Maybe someone has access and can follow up on this. --- A personal note. A few months ago, a family doctor told me that exercise intolerance was already well known in medicine because of cardiopulmonary disease. And that it might be possible to assign ME/CFS patients similar treatment plans. In other words, use existing resources with no need to create a completely new physio treatment plan specific to ME/CFS. I have no idea how that might work out.