I have never found any info about this and I am wondering. As we know, the aerobic process doesn't function well with ME, so it's best to use the anaerobic process as much as possible. Heart rate beyond a certain point and more than 2 minutes of exercise are said to bring on the aerobic process. So it's relatively easy to avoid getting there, at least when you don't have POTS or other forms of orthostatic intolerance. But what about lactic acid ? Where does it fit between the aerobic and anaerobic energy paths ? Does it happen in the aerobic pathway too ? And what does it mean when we get lactic acid build-up ? I think it's a by-product of the anaerobic pathway, but how is it possible to avoid it ? If figure if I had a clear answer for that, I could maybe avoid lactic acid build-up. Somedays I don't feel it much, and some days I feel it a lot, even when chewing my food. I have no idea why this is. Am I causing over-exerting if I keep doing something when there is a build-up ? Does it have an effect on my overall fatigue ? Many questions, I know, but I have a feeling that's all related.