Readiness is a trend, not a verdict. HRV, resting heart rate and sleep are useful when you compare today with your own recent baseline — not against anyone else, and not against a single number. Two or three signals pointing the same way is a signal. One is noise.
What the three common signals mean
Heart-rate variability (HRV) reflects the balance of your autonomic nervous system. It swings a lot day to day, which is why a single reading is close to meaningless and a seven-day average is useful.
Resting heart rate is slower to move and easier to trust. A rise of several beats over your own baseline, sustained for more than a day, tends to mean something.
Sleep is the one most riders under-weight. Duration matters, but so does consistency — going to bed at wildly different times costs you more than most people expect.
None of these is a fitness score, and none of them says anything about your health. They describe how your body is coping with the load you have been putting on it.
Why you compare yourself with yourself
Absolute HRV values vary enormously between people — by age, genetics, measurement method and time of day. A number that would be alarming for one rider is entirely normal for another.
What is informative is deviation from your own recent baseline, measured the same way at the same time of day. Which is also the practical catch: a measurement taken at a different hour, or after a different evening, is not comparable to yesterday's.
Does steering training by these signals actually work?
It is a fair question, and it has been tested. Thirty recreational runners were split into a predefined training group and an individualized group. In the individualized group, the training load was raised, held or lowered twice a week based on nocturnal heart-rate variability, perceived recovery and a heart-rate-to-speed index. Both groups did the same fifteen-week structure: three preparatory weeks, six volume weeks, six interval weeks (Med Sci Sports Exerc, 2022).
Both groups improved. The difference was in how much: 10-kilometre time improved by 6.2% ± 2.8 in the individualized group against 2.9% ± 2.4 in the predefined group (p = 0.002). Look at the spread of individual responses in that 10-kilometre test: 81% of the individualized group were high responders, against 23% of the predefined group — and while 8% of the predefined group ended up moderately worse than they started, none of the individualized group did.
That last figure is the useful one. Adjusting to the signals did not only raise the average; it reduced the number of people the plan simply did not work for.
🔴 The limits: thirty runners, not cyclists, at recreational level, in a single study. The principle transfers more comfortably than the numbers do.
The honest counterweight
If that were the whole picture, everyone would already train this way. It is not. A systematic review with meta-analysis pooled the trials that compared heart-rate-variability-guided training against predefined training, and the result is far more modest (Int J Environ Res Public Health, 2021).
- Guided training was clearly better at improving the vagal-related HRV measures themselves (SMD 0.50, 95% CI 0.09–0.91) — but not resting heart rate (SMD 0.04).
- For the things you care about, the advantages were small and not statistically significant: maximal aerobic capacity SMD 0.20 (95% CI −0.07 to 0.47), capacity at the second ventilatory threshold 0.26, endurance performance 0.20.
The authors' own summary is the sentence to keep: if guided training is better than predefined training for group-level fitness and performance, current data suggest it is only by a small margin — though with less likelihood of negative responses. They also note that the basics are unsettled, including which HRV index to use, what position to measure in, and whether to compare against a fixed or a rolling baseline.
Put the two together and you get something honest rather than exciting: reading your own signals is unlikely to transform your season, and is a reasonable way to avoid the weeks that wreck one.
The signs that beat any score
Before you look at a number, check three things you already know:
- Motivation. Not wanting to ride once is normal. Not wanting to ride for several days when you normally do is information.
- Power at a given feel. If the effort that usually sits at a comfortable pace now costs you noticeably more, your body is telling you something the watch has not caught up with yet.
- Mood and irritability. The least measurable and often the earliest.
When these disagree with a green score on a screen, trust these.
What to do when the signals point down
The choice is rarely train or do not train. Usually it is: keep the session and reduce the intensity, keep the intensity and cut the volume, or swap the hard day with an easy one later in the week.
Moving a hard session by a day costs you almost nothing. Completing it badly costs you the session and the two days after it. That trade is not close.
And if the pattern persists for more than a week or two, or comes with symptoms that feel like more than training fatigue, that is a conversation for a qualified professional rather than an app.
Your numbers, explained the moment you ask.
The awkward part is that reading these signals well takes a coach's judgement, and most riders are reading them alone at 6 a.m. with a number on a screen and no idea what to do about it.
Peakfy computes readiness from your HRV, resting heart rate and sleep, and then — the part that actually helps — changes today's session to match, and tells you in plain language why it changed. When it says ease off, you can ask what it saw. It is a sport-science training tool, not a medical device, and it does not diagnose anything.
Questions riders ask
Keep reading
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- Can you trust your readiness score? What the research says
- Cycling training over 40: what changes, and what to do with it