Mystery of Post-Exertional Sickness

Something definitely has changed since July: I'm no longer sleeping well. I walked 2.4 miles yesterday and ended up with less than 5 hours of sleep.  I'm now actually sleeping worse on the days that I walked. Are my days of sleeping like baby coming to an end? Sleeping well with even minimal exercise was the only silver lining in these 8 years of sickness.

I should decrease the distance and see if I can sleep well again. It seems paradoxical that I should sleep worse when I walk more. But I used to have the same problem when I was healthy -- I had to occasionally take sleeping pills on days I practiced judo. (The practice time didn't matter whether it was in the evening or afternoon). And maybe I'm having the same problem now. Anyway, the whole purpose of walking for me is to sleep and feel better, so it's no good if walking makes feel worse. If decreasing the distance restores the sleep, then that's the way it will be.

Now, to today's topic of post-exertional sickness. MS fatigue doesn't have it. The cancer fatigue doesn't have it. Only CFS fatigue has it. The post-exertional sickness is  the unique symptom of CFS that distinguishes it from all other fatigue. Hence, any self-respecting CFS theory must at least explain the post-exertional sickness.

I used to suspect Delayed Onset of Muscular Soreness (DOMS) as the source of post-exertional sickness. DOMS accompanies inflammation and is delayed by the 24 to 48 hours and lasts 3 to 5 days. That fits post-exertional sickness perfectly. And the fact that the walking speed or a few squats can precisely trigger the post-exertional sickness  seems to jibe with DOMS as the source. But there was a paper that did the biopsy of muscle of CFS patients after exercise and did not find micro-tear of the muscle. (I can't locate that paper at the moment, Googling does not turn it up for some reason). Also, inflammation from DOMS are supposed to be local only to the damaged muscle. Though it's still possible that the micro-tear is so minute or few that the investigator simply missed them, and the local inflammation still could affect the central nerve through signaling, it seems reasonable to conclude that DOMS is not likely the source of the post-exertional sickness, at least until there is an evidence for it.

The Journal of Strength and Conditioning Research recently published an article on exercise intensity and recovery. This article must be purchased for you to read, but you can read the summary here. Basically they found:

• Muscle strength is reduced shortly after the exercise and the reduction lasts 12-24 hours.
• The muscle damage marker is present for up to 48 hours.
• Neutrophil, the debris removing immune cells, appear 3 hours after and lasts up to 24 hours
• Lymphocytes, another immune cells, appear 12 hours after and last 3 days

The lymphocyte response roughly corresponds to the post exertional-sickness, except for the 12 hour delay instead of 24 hours, and 3 days instead of 4 days. This study was done with trained athletes, so it's possible that the lymphocyte response is delayed longer and lasts longer for non-athletes. In any case, it's clear that the immune response to an exercise lasts about twice as long as the muscular recovery period. (And this could also explain accumulation effect of exertions over 4 day window.)

The lymphocyte response accompany inflammation. And the post-exertional sickness could be the sickness behavior caused by this inflammation. A recent paper from Norway that claims that knocking out B-cell lymphocytes with Rituximab brought improvements to CFS patients lends some credibility to the lymphocytes as the source as the post-exertional sickness. Lymphocytes are implicated in chronic inflammation as well.