Signs of overtraining: how to tell, and why you probably are not

"Am I overtraining?" is one of the most searched questions in endurance sport, and almost everyone asking it is not. What most people have is functional overreaching, which is the thing training is supposed to do. Knowing which one you have determines whether you need a week or a season.

What is the difference between overreaching and overtraining?

The ECSS and ACSM joint consensus statement separates them cleanly.

Functional overreaching is short-term performance decline from a deliberate hard block. You feel flat, you recover in days to a couple of weeks, and you come back fitter. This is the mechanism. It is not a problem.

Non-functional overreaching is the same decline without the rebound: stagnation or decline lasting weeks to months, usually with hormonal and psychological signs. You get back to where you were, but you paid weeks for nothing.

Overtraining syndrome is prolonged maladaptation across biological, neurochemical and hormonal systems, taking months to resolve and diagnosed largely by excluding everything else — anaemia, thyroid disease, infection, depression, under-eating. It is genuinely rare outside elite sport.

The consensus statement is blunt about the diagnostic problem: there is no single marker that identifies overtraining syndrome. Anyone selling you one is selling you something.

What are the signs of overtraining worth watching?

Because no single marker works, what matters is a cluster of them moving together, and moving away from your normal.

Performance that will not respond to rest. The definitional sign. If a genuine easy week does not bring you back, that is the one that counts.

Resting heart rate drifting up, HRV drifting down, both for weeks. Not one bad morning. A trend across two to three weeks, measured in the same conditions each day. What a normal HRV swing looks like, so you do not mistake noise for a trend, is in what is a good HRV for my age.

Effort that no longer matches pace. Your usual easy pace costing you zone three. This one is often the earliest, and it is only visible if you know your zones; finding your zones without a lab covers that.

Sleep getting worse while training gets harder. Counterintuitive and telling: fragmented sleep and early waking despite heavy fatigue.

Mood, motivation and appetite. The consensus statement takes these seriously, and so should you. Loss of drive to train is data.

Notice what is missing: being tired after a hard week, being sore, having one low HRV reading. Those are training.

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What is normal fatigue, and what is not?

Normal: heavy legs for two days after a long run, a low HRV the morning after intervals, feeling flat in the third week of a block, soreness after a new exercise. All of these resolve on their own within days and none of them stops you executing the next easy session.

Not normal: the easy session feeling hard for a week, waking at four for no reason, a resting heart rate five beats above usual for ten days, dreading training you used to want. The distinction is duration and direction. Normal fatigue is a dip that recovers. The warning signs are a slope.

Why does overtraining happen to recreational athletes?

Rarely from training alone. The usual recipe is a training block that climbs too fast, stacked on short sleep, under-eating, work stress and no down weeks, with nobody counting the total. Load that looks moderate in each app is a spike in aggregate; how much training load is too much explains why the ratio to your own recent average matters more than the absolute volume.

Sleep is the other common thread. Short nights blunt recovery and amplify every other sign on the list, and sleep that deteriorates as training climbs is itself a warning; sleep as a training variable goes into the evidence.

Can a wearable detect overtraining?

Not on its own, and any device that claims to is overstating what one sensor can see. What a wearable can do well is track two of the cluster, resting heart rate and HRV, consistently enough that a three-week drift becomes visible where a human memory would have lost it. It can also log sleep and total load. What it cannot see is performance relative to effort, mood, appetite or whether you have eaten enough, and those are half of the signs that count.

The useful setup is a wearable for the trends plus a short weekly note on how training felt and how much you wanted to do it. When the sensor trends and the notes point the same way for two or three weeks, that is a cluster. When only one of them moves, it is probably noise or a cold.

The test that settles it

Take a real down week. Not a slightly easier week — cut volume by roughly half, remove all intensity, keep eating normally, and sleep as much as you can.

If you come back sharper within one to two weeks, you were functionally overreached and you have just completed the block correctly. If two weeks of genuine rest leaves you flat, stop guessing and see a doctor: the differential includes iron deficiency, thyroid dysfunction, undiagnosed infection, chronic under-fuelling and depression, all of which are more likely than overtraining syndrome and all of which are treatable.

How do you recover from overreaching?

1. Cut volume by about half for a week; remove every hard session.
2. Keep moving. Easy walks and very easy runs speed recovery more than complete rest for most people.
3. Eat to your training, not to your guilt. Under-fuelling is a common hidden cause and the first thing to fix.
4. Sleep: earlier bedtime, same wake time, no alcohol for the week.
5. Retest with one familiar session at the end of the week. If it feels like it used to, rebuild with a gentler ramp and a down week every third or fourth week.

If step five fails twice, that is the point at which more rest is no longer the answer and bloodwork is.

What PeakU does with this

The reason this is hard to self-diagnose is that it requires holding weeks of several different signals in your head at once, from apps that do not talk to each other. PeakU tracks resting heart rate, HRV against your 30-day baseline, sleep, and acute-to-chronic load on one timeline, and the Peak Score is what those look like folded together.

It flags the pattern rather than the day: load climbing while HRV trends down and resting heart rate trends up, over weeks. The plan then proposes the down week before you have dug the hole, which is the only version of this that is actually useful — a warning after three bad months is a post-mortem.

Hen Eytan · Founder, UPeak

Builds the UPeak apps and writes up the research behind them.