So, I'm sure many of us are familiar with the idea of establishing an activity baseline, which is where the activity that you are able to manage doesn't trigger PEM. I would argue though that the concept of a baseline is inherently dangerous for PwME as it implies a position that can then be improved on, even if that isn't the intention of anyone suggesting it. And when this language is used in UK's fatigue clinics, it explicitly is something that the therapists, typically physios, then want the patient to progress away from. Far better, I would suggest, to use the concept of an exertion ceiling. This then has the advantage of implying something that shouldn't be gone above, given the potential harm to PwME I think this is extremely valuable. Alternatively I've used the phrase Sustainable Exertion Limit before, which, while being the same concept and more descriptive, doesn't quite roll off the tongue so well. It's still not the perfect description of course, our ceiling can move, both up and down, and for the most severe it's likely they are in PEM constantly, but I think that something that will lessen potential harm in the way that I think this would is important. Thoughts and comments welcome. P.S. @PhysiosforME , you may be interested in this idea.