I try to keep my training load fairly consistent, whatever the number happens to be that year. Some years it’s close to ten hours a week, in quieter years six to eight, and in the more motivated ones fourteen or more. The number itself isn’t particularly important. Consistency is. In the last decade I’ve rarely had a complete week off, except for a few special occasions, but every now and then I get several nights of bad sleep in a row and the training has to come down whether I planned it or not. I never thought much about sleep debt and training as connected things — until one week made it obvious.

There was one week when I finally understood why this kept happening, mostly because I’d had versions of the same week before without ever putting the pieces together.

The Week That Started Normally

It started quite normally. On Tuesday I was meeting some old friends from university, and on the weekend there was a high school reunion, which also meant a longer trip in the camper. I’d put a hard training session on Monday because the idea was to get the difficult part done and then sleep it off before a long run the next day. That didn’t happen. My legs were done, I slept badly, and the long run was shortened. Then Tuesday’s meeting with the university friends ran much later than I’d expected, well past my usual bedtime. I told myself it was fine. Light training the next day, then something harder later in the week.

That didn’t happen either.

I drove the camper to the high school reunion and spent the weekend going back to places I hadn’t seen for thirty-five years. Some had changed much more than I expected. I hadn’t really thought about the evenings, though. It was hot, noisy, people were staying up late, and I wasn’t sleeping in the same way I do at home. None of it was terrible. It was just enough, night after night, that by the end of the week I’d lost something like ten hours of sleep, maybe more.

And I felt it.

What It Actually Cost

Not just sleepy. Training had become strangely difficult. The volume had dropped because I wasn’t doing everything I’d planned, but even the sessions I did felt wrong. An easy effort needed more concentration than it should. Things that normally felt automatic started feeling like work. I was very happy to have spent the week with old friends, but at the same time I had this stupid feeling that I’d thrown away months of training in seven days.

That was probably the least accurate part of the whole thing.

I got home on Sunday evening and finally slept properly. Not some special recovery technique, just the kind of sleep I had been missing all week. The following week the usual hard session felt almost too easy. I had a couple of PRs on Strava, and on easy sessions my heart rate was surprisingly low for the pace. I remember looking at it and thinking, how can this possibly be the same body?

Why the Rebound Wasn’t Mysterious

At first I thought I’d somehow had one of those rare weeks where everything comes together. Then I looked back at the numbers.

The week before, I’d slept badly and my training load had fallen at the same time. The week after, sleep was back to normal, and I was starting from a much lower accumulated training load than I would normally have had after a week of training. So the rebound wasn’t really mysterious. I hadn’t become fitter in seven days. I had removed some fatigue that had been sitting on top of the fitness I already had.

Sleep was a big part of it. Research on sleep restriction shows endurance performance gets worse when sleep is cut, and longer efforts seem to suffer particularly badly. It also tends to make the same effort feel harder, which was exactly what I had been experiencing. But the interesting thing in my case was that the poor sleep also changed what I did during the day. I wasn’t just recovering badly from normal training. I was doing less training because I was recovering badly.

My week was not a planned recovery week, and I wouldn’t recommend deliberately creating one by sleeping badly. I’ve had proper rest weeks before, of course. Those never seemed particularly interesting because they were planned. You know you’re coming off a harder block, you deliberately do less, and then you’re supposed to feel better. There is no mystery in it. This one was different because I didn’t choose it, and because the thing that forced it was something I normally think about separately from training.

The Pattern, Not the Score

Sleep was sleep. Training was training. I hadn’t connected the two over a whole week.

That’s probably what changed for me afterwards. I stopped looking at sleep tracking as something that tells me whether last night was good or bad. One night doesn’t tell me very much. Even two nights can be explained away. What gets interesting is when several things start moving together over several days: sleep getting shorter, resting heart rate creeping up, HRV going down, easy training becoming harder, motivation disappearing for no obvious reason.

The opposite can be useful too. A few good nights, less training, heart rate coming back down, and suddenly an effort that felt hard a week earlier is easy again.

The watch didn’t discover this for me. I had been wearing one for years. I just hadn’t looked at the information in the right way.

That is probably the bigger lesson. Sleep tracking is rarely very interesting because of one night’s score. I don’t care that much whether my watch says I had 82 or 87 points last night. What I care about is that my sleep has been shorter for four nights, my HRV is drifting down, my resting heart rate is up, and an easy run feels strangely hard. That’s a pattern.

And if the next week goes the other way, I don’t need to invent a new training theory because I suddenly feel great. Sometimes the fitness was there all along. I was just too tired to show it.

The ten hours of sleep I lost weren’t useful. The week that followed wasn’t some magic recovery trick either. I had simply accumulated enough fatigue that a bad week of sleep exposed it, and then forced me to do something I normally find difficult: train less.

The PRs came afterwards, when the fatigue had finally moved out of the way.

Frequently asked questions

Can losing sleep for a week actually hurt training performance?
Yes — research on sleep restriction consistently shows measurable performance declines, and the effect is cumulative, getting worse across several nights rather than staying flat. Endurance and other prolonged efforts tend to be affected more than short, maximal ones.

Why did a bad sleep week lead to a great training week right after?
It’s usually not the bad sleep helping — it’s that lost sleep often forces training volume down for several days, and reduced training load after a hard block is exactly what periodization calls a taper. The following week’s performance reflects fitness that was already there, freed from accumulated fatigue.

Is it healthy to deliberately under-sleep to force a rest week?
No — this pattern is worth recognizing after the fact, not engineering on purpose. Planned recovery through reduced training load, not through poor sleep, is the safer and more reliable way to get the same benefit.

What’s more useful — a single night’s sleep score, or tracking sleep over time?
Multi-day trends are generally far more informative than any single night. A single bad or good score can be noise, but several days of resting heart rate, HRV, and sleep duration moving in the same direction is a much more reliable signal of accumulating fatigue or recovery.