I apologize for long post... if you decide it's too long to read I will understand! I am mildly affected: on average I walk 4500 steps per day and am able to do computer work 6 hrs per day as long as I don't do much else in life. No cooking, minimal dish washing, no other cleaning. In August I started meticulously tracking everything I did in a day and how I felt - OK, tired, very tired etc. From this I calculated an activity score (how much I did in a day) and fatigue score (high score = high fatigue) for each day. What I got was this graph: blue = activity score (the higher, the more active I was) red = fatigue score (the higher, the more tired I was) As you can see, sometimes I do a lot (for me) and don't feel as much fatigue and sometimes I rest all day and am very fatigued. Well, usually I rest all day because of the fatigue Also I had 9 very good days with relatively little fatigue in the middle of the graph. In that time I was taking a recovery mix for bodybuilders and will definitely be trying it again! But what happens if I move fatigue two days to the left? That is, what if I compare how active I was to how much fatigue I felt 2 days later? blue = activity score (the higher, the more active I was) yellow = fatigue score two days later (the higher, the more tired I was two days later) To me it looks like in this graph the yellow line moves more in sync with blue (fatigue moves with activity) than the red line did in in the previous graph. When blue line goes up, yellow line tends to go up as well and vice versa. At least much more often than the red line. My fatigue feels so random to me, I never know if I'm going to feel OK or terrible the next day. But in the above graph I think I see a PEM delayed by 2 days. Well, mostly. Sometimes I am tired, but still have things that need to get done so on those days activity and same-day-fatigue (red line) would both be high and the peak in yellow line would precede the peak in blue line by 2 days. What do you think? Does it look like my fatigue is delayed by 2 days or not? If you think there's no correlation, please tell me so Edited to add: The reason for logging activity and fatigue was mainly because how I feel fluctuates so much that it's hard to know whether a new supplement is doing anything (unless it would have a major effect). Also, I wanted to be able to compare how I feel now to how I felt six months ago and I didn't really get a good feeling for it by reading my symptom diary. I guess I'm more of a numbers person. It was not to asses PEM, I just thought once I had the data, let's see whether my fatigue is less random than I thought.