Thread by @JeffLubell_C19

A question for people with #MECFS or #LongCOVID: in your experience, is post-exertional malaise a single phenomenon? Or is it possible there are distinct phenomena that are not being adequately distinguished, impeding understanding? #NEISvoid

With my daughter -- who has #hEDS, #MECFS, #POTS, etc. -- we have observed at least 2 and possibly 3 separate phenomena that all seem to fit the description of #PEM. Let's call them (a) "major crash," (b) "day to day PEM" and (3) "cumulative exertion PEM"

She has had 2 major crashes. These were biphasic events that appear to have caused severe damage lasting years. First major crash (2017) was what made us aware of her illness. She felt very hot in the morning. Then, some time after a long hike, she had whole-body chills/shaking.

She had troubled walking after the crash and within a month, had widespread pain and fatigue, couldn't go to school, etc. Had some sympotmatic improvement thereafter, but never recovered to baseline. Second crash (2020) was even worse. In first phase she was hot and red all over

In 2nd phase, she had whole body chills/shaking plus electric zaps down her arms and what felt like fluid waves (blood or lymph?) that moved up her body. Afterwards, it felt like her body was poisoned. Over past 21 months, she has made very slow but significant progress, but

she's still not back to the baseline pre-second-crash. Day-to-day PEM is a distinct phenomenon. Basically, after most kinds of physical or mental exertion, she feels worse. If we don't treat, feeling gets worse over time and it starts to feel like her tissues are not getting

enough oxygen. It can take a few days for her to feel better after day-to-day PEM, though since we started daily lymphatic drainage, recovery is much faster. We are not sure whether "cumulative exertion PEM" is a truly distinct phenomenon or just an extension of day-to-day PEM.

Cumulative exertion PEM is what happens when you don't listen to your body and engage in more exertion than your body can handle. It can come from a single act of exertion -- say, going out to eat -- or, if you don't rest adequately between exertion sessions, it can come

from a series of smaller exertions that collectively push past the threshold. This is probably the one that most people are more familiar with, and leads to feeling of lactic acid build-up and extreme fatigue, etc. Can take several days or longer to recover.

My hypothesis is that major crashes causes vascular damage and/or endothelial dysfunction and that day-to-day PEM are the result of that damage -- leakages from microangiopathic blood vessels that flood tissues, leading to hypoxic conditions if not addressed.

There may also be some dysfunction in the lymphatic system that inhibits the take-up of the interstitial fluid. I do not know whether the cumulative exertion PEM is a distinct phenomenon resulting from pushing past your aerobic threshold, as suggested by the literature,

or just a more extreme version of day-to-day PEM that results from anaerobic respiration taking place in cells that are flooded with interstitial fluid. I'd love to hear about others' experiences. Perhaps we can crowd source some conceptual progress in understanding PEM?