Haven't I read elsewhere that PwME often have an anaerobic threshold below this? Unfortunately, my heart rate frequently goes above even this number.
Normal would just be the 220-age I think. The x .6 is what takes into account our decrepitude
I believe the 220-age is the
very rough estimate of a healthy person's maximum heart rate. It's highly inaccurate for any one given person, but exercise physiologists continue to use it because it's easy.
(220-age) *0.8 supposedly calculates a healthy person's AT. The (220-age)*0.6 is supposed to be closer to accurate for the generic PWME. Again, all these calculations are extremely inaccurate and so should only be used as general guidelines. I suspect the (220-age)*0.6 number is too high for people with moderate to severe ME/CFS.
I had my AT tested twice 5 years apart and got the same number each time. It is low, as is expected in PWME, but closer to the higher end for PWME than the lower. My AT is about 0.7 * (220-age). I cannot function near my AT routinely. For normal activities I have to stay closer to the 0.6*(220-age).
I don't know if this is true for others, but I find that there's a level I can maintain (about 0.6*(220-age)) without my HR continuing to climb. When I start to do more, my HR climbs pretty rapidly to my measured AT and if I don't sit/lie down right away, I'll PEM. So, I find I can gauge my activity by how
rapidly my HR climbs -- too fast = too much.