Why I don’t train (or sometimes even eat) with a fever: learning how to manage personal illness from fitness tracker data and scientific research

It was two months since I had last stepped into a Jiu Jitsu gym. A white belt having started training 6 months ago, spar after painful spar I had been getting absolutely DECIMATED. It was demoralizing. While I had played plenty of sports as a kid, I didn’t have a martial arts or wrestling background except for Tae Kwon Do, briefly, when I was 10. I hadn’t even watched much UFC. But I had always admired martial artists and loved, loved, loved the movies. And I had always wanted to be like that. But until a fellow MD/PhD student, who also happened to be a Brazilian Jiu Jitsu (BJJ) brown belt, started rotating in our lab, I hadn’t known how to start. So when we got to talking about BJJ, I immediately asked him if I could visit his gym with him.

As I said, the learning curve was steep. I didn’t know what a triangle or an arm-bar were. While I came to the gym 2-3X/week to learn, getting tossed around like a ragdoll was humbling. Demoralizing, really. And day after day, it just hurt. Then graduate school started becoming intense.

If I had to cut gym time to 1X/week and would feel like I was stagnating, could there be a better way? Yes: convincing the wife to become my daily training partner. Each and every morning, 7 days per week. I taught her some grip breaks and submissions. She was hooked. So, rather than give up, I bought some mats. I bought a heavy bag to drill on. I bought a Swiss ball for the same purpose. And I started getting serious about kettlebells. Here is the completed project, also known as my bedroom:

(The desk and the chair have since been jettisoned. And before the break, we were drilling on four mats. I also have a few more kettlebells: they’re my babies.)

So when I dropped into the gym two months later, I came to CRUSH. And crush I did. When drilling on my own, the rough outline of the whole game had started to become clear in my mind. Repeatedly I drilled takedowns, submissions, positions, transitions, escapes, sweeps. As the venerable Mr. Miyagi had once said:

I trained everything.

It translated. I was landing submission after submission. Oh, I was still eating my humble pie. But much of the time I wasn’t. Ten pounds heavier, I felt stronger. And more flexible. And comfortable with the basic positions. I was still somewhere at the bottom of the pile, but I wasn’t at the bottom of the bottom. I had become a decent, solid white belt.

This would all be a cool story if it hadn’t come at a price. And come at a price it had. You see, just a few days earlier, my temperature had started slowly increasing…

After smashing and getting smashed, I limped home, my body broken but my spirit victorious, and I went to sleep. And I woke up to this:

And this:

On a good day, I might look something like:

I had never seen a resting heart rate pattern overnight like that before.

So, the next day I ambled about, hardly able to move. I felt my temperature spiking further, and probably not very intelligently, I rode my bike home, burning hot and with a terrible body flu.

I slept. And the next morning, I woke up to see:

Things were really… heating up.

That’s not the worst of it, though. This temperature spike was on the background of an overall trend downward of temperature (probably related to a decline of total calorie intake and expenditure, as I am actively cutting intake in order to lean out). Here is what things look like relative to the trend over the past 30 days, not the past 3 months:

Almost a 4 degree spike over the average of the previous 30 days!

One thing I noticed starting about a week ago: No overt symptoms. But I felt just… dissatisfied. Upset. Not at ease. Somewhat depressed. No other symptoms. Just “under the weather”.

I was feeling the illness mentally that I could only see on my Oura ring, and which I was only to experience a full 5 days later physically.

Did this subclinical illness progress into a full-blown flu by overstressing my body during training? Or did the stress cause another infection to be superimposed on top of the first?

The relationship between exercise and infection has been studied formally. Two reviews (here and here) each suggest that while moderate exercise is immune system-boosting, strenuous exercise is to be avoided. One review even suggested that training through unresolved illness could be a trigger for chronic fatigue syndrome, a notoriously poorly understood illness. Another study suggested that a drop in antibodies–which fight off infections–occurs acutely immediately following exercise. This makes sense, because cortisol also spikes after exercise, and cortisol is a potent immunosuppressant.

Takeaways:

  1. We are sometimes ill and don’t even know it.
  2. If you’re running a fever and feeling run down, laying off the training might be a good idea. Well, duh. But sometimes training makes me feel better. Now I know to think twice: if my temperature looks OK, do it. If I am running high, lay off.

Bonus: What about eating and illness? We have all experienced appetite loss with acute illness. Does this have any adaptive function? We have some preliminary answers to that, though it may depend on what kind of infection one is dealing with. In mice, survival from bacterial infections were shown to be highly responsive to glucose intake. Here is how mice responded when injected with Listeria bacteria:

Basically, they stop eating when infected, consistent with the evolutionarily preserved “sickness syndrome.”

But does this serve any real purpose? What happens when you force-feed the mice who stop eating? As it turns out: they die.

As always consult a medical professional when making treatment decisions. But it may be the case in certain infections where one loses one’s appetite or one feels a little less inclined toward physical activity, it might be a good idea to heed those signals: they might be there for a reason.

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As an MD/PhD student, my passion is for communicating the cutting edge of medical science and fighting misinformation. If this post is of use to you, please consider donating to my Patreon account. Your contribution will make a significant positive impact, and I will be greatly personally appreciative.

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You can find me on Twitter at @kevinnbass.

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