And remember that the people with ME/CFS often achieve these scores when they are not working and generally living reduced lives. So they might say they're "limited a little" for walking a km/mile or half a km/mile (different versions actually use different measurements!) but they might not answer the same way if they try to do 20/30/40 hours a week of work like people of similar age. In my view, actometer readings would be much better to see if people have "normal" functioning rather than the physical functioning subscale. Going out for a short walk once a day/every second day as a lot of their total activity for their day shouldn't really count. It's like those disability assessments - people with ME/CFS may be able to do something once but that doesn't mean they could do it for eight hour shifts or whatever.