Running Empty

I cycle commute to work about 38km each way, currently about a 90 minute effort. I ride at for me, "threshold" (above 90% of max heart rate) for 45 minutes of that and remainder at "tempo". No where near "ultra" but I think I'm near my biological maximum.

I too have hit a period where I was feverish for several weeks. Foolishly kept cycling and became ill / fatigued to the point where it was a struggle to get out of bed. The physician I visited didn't find anything conclusive and I was on variants of ibuprofen to control the fever and for pain relief. When I was finally feeling better, I cycle commuted once and that knocked me back into bed for another week.

Likely I was going too hard for the conditions. This occurred when temps during the commute was hovering around 0dC. Low temps make it a challenge body temperature and may have stressed my body too much.

Strava provides a metric to guess how fatigued one is from cycling. I noticed that the point when I fell ill was the same time it was reporting record fatigue levels. I now keep an eye on it but I'm feeling a touch of that "fatigue" these days. Likely to due to $dayjob and cycling...

I wish there was a way to measure all my activities to guide when I should be backing off. I've found my breaking point and crossing the that point means weeks of recovery.

For what it's worth, I'm faster then I ever was... but something is going to break.

OTS is almost certainly the same as chronic fatigue syndrome. The only difference is that in OTS the stressors are usually mostly physical, where in CFS they are (usually) mostly mental. In many cases there is also an apparent flu-like illness at onset, although it isn't clear whether this is an actual illness or just a symptom of the immune system going haywire.

It seems that at some point after prolonged, chronic stress the brain just says "that's enough", and further stressors result in a reduced stress response from the brain, rather than the usual increase in stress response (cortisol, etc.) Essentially it's a form of burnout.