Resting heart rate for athletes: a training signal

Morning resting heart rate can tell you something about accumulated fatigue, but less than you might hope. In a meta-analysis of competitive athletes, short hard blocks raised resting heart rate by a moderate amount, longer ones didn't change it at all, and the authors concluded the shifts could easily hide inside normal day-to-day variation.¹ Read it against your own recent range, alongside HRV and how training feels, and only act on changes that hold for days.

This page doesn't give a "normal" resting heart rate for athletes, on purpose. Whether a number is normal for your heart is a health question, and it belongs with a clinician. If your resting heart rate changes sharply and you feel unwell, short of breath, dizzy or have chest pain, stop training and get checked.

What the research found#

Bosquet's group pooled studies where competitive athletes went through deliberate overload training, then measured heart rate before and after.¹

Two things in that table are worth sitting with. A short block of hard training nudged resting heart rate up, but a long one didn't move it at all, which is exactly the situation you'd most want a warning for. And the authors' conclusion was that the size of these effects limited their usefulness on their own, because the expected changes could fall within the day-to-day noise of the measurement.¹

Buchheit's review puts numbers on that noise. In his summary table, resting heart rate has a typical day-to-day error of about 10% and a signal-to-noise ratio of about 0.7, meaning the changes you're looking for are smaller than the scatter.² Halson's review warns against using fixed cut-offs, such as "a change of more than 5%".³

Resting HR vs HRV#

HRV usually gets top billing, and there's a reason. In supine measurements, Buchheit cites a signal-to-noise ratio of about 3 for a vagal HRV index against 1.3 for resting heart rate.² But he also says HRV's advantage is "unlikely as large as previously thought". In an often-cited triathlete case study, the trend toward non-functional overreaching was only slightly clearer in HRV than in resting heart rate (0.88 against 0.81, as Buchheit reports it).⁴²

The practical answer is to use both. They come from the same morning, cost nothing extra, and when they move together you can trust the move more than either alone.

What a real spike looks like#

Here's my resting heart rate from late August to late September 2026, from Apple Health, with the usual range for 8 September drawn the way the app draws it: the average of the previous 28 days plus or minus one standard deviation.

Ken's resting heart rate vs his usual range

day (day 1 = 29 Aug 2026)	Resting HR (bpm)	Usual range, top (bpm)	Usual range, bottom (bpm)
1	43	45.6	41.8
2	43
3	42
4	44
5	42
6	44
7	41
8	43
9	45
10	49
11	56
12	48
13	47
14	44
15	44
16	47
17	45
18	45
19	44
20	44
21	48
22	45
23	39	45.6	41.8

Usual range = mean plus or minus 1 SD of the 28 days before 8 Sep (43.7 plus or minus 1.9 bpm), held flat for reference. Source: Ken's own Apple Health data in hybridAF, read from the database on 22 October 2026.

For four mornings, 7 to 10 September, it read 49, 56, 48 and 47 bpm, all above the band, with the peak about 12 beats over my average. My HRV on the same four nights was 49, 25, 34 and 35 ms, far below its own range. By 11 September it was back inside the band.

That's the shape that deserves a response: a multi-day move, well past the noise, with HRV agreeing. Compare the single high mornings later in the month, 47 on day 16 and 48 on day 21, each back near the band the next day. On their own, those are noise until something else agrees. The data can't tell you why any of them happened, and it shouldn't try.

Reading it day to day#

Measure it the same way every time. Buchheit's recommended protocol is a short reading on waking, in the same position each day.² A watch's overnight or all-day low is convenient but isn't the same measurement, so compare it only with itself.

Then judge it against your own band. Your average over recent weeks, plus or minus a standard deviation or so, is a better reference than any population table, and the studies above compare each athlete with themselves, before and after, for this reason.¹²

Wait for several days before you act. One high morning after a late night, a hot room or a hard session is noise until proven otherwise. Two or three in a row, alongside HRV, is information; Buchheit suggests waiting for 2 to 3 consecutive days.²

And check it against what you did. Buchheit's point is that heart rate measures mean little without the training context, and that they work best combined with a training log and simple performance checks.² A week of high resting heart rate during your heaviest training block reads differently from one in a quiet week.

Resting HR and VO2max#

There's a second use for resting heart rate. Uth and colleagues showed in 46 well-trained men that VO2max is roughly proportional to the ratio of maximal to resting heart rate, with a factor of 15.3.⁵ As arithmetic: with a maximum of 190 and a resting rate of 45, that's 15.3 × 190 ÷ 45, about 64.6 ml/kg/min. At a resting rate of 49 it's about 59.3. A 4-beat change moves the estimate by more than 5 points, which tells you how sensitive this is to how resting heart rate is measured.

That's not hypothetical for us. hybridAF computes this ratio from watch data, but doesn't count it toward your Engine Index. When we compared it with exercise-based estimates in the 7 accounts where both existed, the ratio read higher every time, by 6 to 29 ml/kg/min. Our best explanation is that a watch's resting heart rate is the lowest reading of the day, likely lower than a rested measurement taken in a lab, which inflates the ratio. Uth's own paper says the method's use in other groups still needs direct validation.⁵ Until a study validates it on wearable data, it stays visible and uncounted. The full list of what feeds the engine is on the science page.

Related reading#

Resting heart rate is best read next to HRV, which has its own page: HRV for hybrid athletes. If you're wondering whether to change training based on these morning numbers, the trials are in Does HRV-guided training work?. And for the load side, the thing your heart rate is responding to, see session RPE training load. Everything else is in the recovery hub.