You did the test. You know your threshold, your FTP is current, the plan is going exactly as written. Then you look at your watch and it says "Unproductive". Or "Strained". Or you finish an hour of easy recovery spinning and the watch insists you just spent sixty minutes in zone 5.
The question is always the same: am I overtraining?
Almost certainly not. What is wrong is not your fitness — it is the numbers the watch is doing its arithmetic with.
The watch is guessing
A Garmin out of the box knows nothing about you. To give you feedback from day one it uses generic formulas — the famous one being 220 minus your age for max heart rate — plus algorithms that "detect" your thresholds on their own.
It works surprisingly well for someone starting out. It stops working the moment you train seriously.
Take a concrete example. Your real threshold, measured in a field test, is 170 bpm. The watch guessed 155. From there, everything it calculates is shifted:
- Every comfortable run reads as a threshold session.
- Every threshold session reads as a maximal effort.
- Your acute load inflates week after week.
- And because the load looks enormous, the watch concludes the only thing it can: you are overtraining.
The watch is not broken. It is doing flawless arithmetic with the wrong input.
The fix: give it your numbers, then take the wheel away
There are two parts, and almost everyone skips the second.
First, enter your real zones — measured in a test, not estimated. And enter them per sport: your cycling threshold is normally lower than your running one, so a single shared profile guarantees that one of the two sports always reads wrong. In Garmin Connect that lives under User Profile → Heart Rate & Power Zones, and it is worth switching the basis from %Max HR to %LTHR.
Second, and this is the important one: turn off auto-detection. Leave it on and the watch will re-estimate your thresholds on its own and overwrite the numbers you just entered. It does not tell you. A few weeks later you are simply back where you started with no idea why.
Have not measured your zones? That is step zero and there is no shortcut. The training zones calculator tells you which test to do for your sport and turns the result into your pace, heart rate and power zones. It is free and there is no sign-up.
When you have fixed the zones and the watch still says zone 5
If everything is entered correctly and an easy session still shows a sky-high heart rate, what you are most likely seeing is cadence lock.
The optical sensor on your wrist does not measure beats: it measures changes in blood flow by shining green light through your skin. The problem is that running and pedalling are rhythmic, and that regular vibration can fool the sensor — instead of reading your pulse, it latches onto your cadence. Take 170 steps a minute and the watch reports 170 bpm.
Se reconoce fácil una vez que sabés qué buscar:
- The number looks suspiciously like your cadence.
- It jumps up and stays pinned, instead of drifting up and down the way a real heart rate does.
- The effort feels like a 3 out of 10 and the watch says 170. When feel and data disagree that hard, the data is what is wrong.
It is more common on the bike than running — a wrist flexed over the bars plus road vibration is the perfect combination to confuse the sensor — and it gets worse in the cold, because blood flow to the skin drops.
For interval work and for the bike, a chest strap solves the problem entirely. An optical arm band is a good middle ground: considerably more reliable than the wrist and considerably more comfortable than the chest. For steady easy sessions the wrist is perfectly fine — you do not need to buy anything for those.
Training Readiness and HRV: what they are actually measuring
Newer Garmins show a Training Readiness score from 0 to 100 and an HRV Status. When they drop, the usual reaction is alarm. Two things help you read them:
Broken zones break the score too. Training Readiness combines sleep, HRV and your recent load. If your zones were wrong, the watch believes your load was enormous, and the score sinks for a reason that has nothing to do with you. Watch for this: after fixing the zones, the score takes a few weeks to normalise, because it is still carrying the miscalculated load from the days before.
And low HRV is not an alarm, it is a description. Heart rate variability reflects the state of your autonomic nervous system, and a hard session or a long block suppresses it for 24 to 72 hours. That is not a problem: it is exactly what should happen when you train seriously. HRV dropping and Readiness sitting in "recovering" in the middle of a loading block is normal, not the exception. What is worth watching is the trend across weeks, not this morning's number.
If you do not use Garmin
None of this is Garmin-specific. Polar, Coros, Suunto and Wahoo all do the same thing — they estimate your zones so they can give you feedback from minute zero, and several of them also re-adjust those zones on their own over time. What changes is where the menu lives, not the problem:
- Polar Flow: per-sport profile settings, with heart rate zones configurable per sport and a manual zone option.
- Coros: thresholds live in the athlete profile in the app and can be set by hand.
- Suunto and Wahoo: zones per sport profile, same as above.
The rule is the same everywhere: enter your measured numbers, and switch off any automatic adjustment that can overwrite them.
The watch records; you do the reading
Garmin makes extraordinary hardware, and its software is built for millions of people who have never done a test. That is exactly the point: the defaults are built for someone who is not you.
When the watch contradicts you — it says strained while you are absorbing the plan comfortably, or logs zone 5 on a session that felt conversational — the answer is almost never to change the training. It is to check where those numbers came from.
A well-configured watch is an excellent tool. A badly configured one is an anxiety generator with a strap.