Anyone who buys a chest strap or a ring to measure heart rate variability is usually after a simple answer: can I push today, or do I need to recover? Heart rate variability, or HRV, is the way the interval between one beat and the next keeps lengthening and shortening, and the apps turn it into a morning number that is supposed to tell you how well you have recovered.
For an archer, research gives that number a narrower use than the apps promise, and its limits are worth knowing before it decides a training session. The index to look at is RMSSD, but the rule comes from general psychophysiology and nobody has tested it in archers. The same archer's heart rate changes from one session to the next, so a single morning reading carries little weight and what counts is the weekly average, compared with your own and never with a teammate's. The use many archers buy the device for, working out whether the training load is right, comes from endurance sport. In competition, finally, heart rate rises above resting levels, often past a hundred beats per minute, while HRV as a measure of tension has produced results that do not agree.
What heart rate variability measures
Even at rest the heart does not beat like a metronome: the interval between beats shifts slightly, partly in step with breathing, and much of this fluctuation depends on the vagus nerve, the branch of the autonomic nervous system that slows the heart. This is why heart rate variability is used as a window on vagal tone, the activity of the system that dominates when the body is calm.
The idea that high variability is a good sign is what the apps are built on, and its basis is narrower than it is usually made out to be. In general physiology higher heart rate variability goes with better aerobic fitness, and people with low variability tend to be older and less aerobically fit. The reference methodological recommendations add a caution: higher resting vagal tone is usually a favourable sign, but not always, because there are conditions in which it is high for reasons that have nothing to do with fitness. Nobody has set archers' variability against their aerobic capacity, and the registry treats this reading as transferred from other populations.
Which index to use: RMSSD
Apps and studies express variability through different indices, which fall into two families. Time-domain indices are calculated directly from the intervals, and the most widely used is RMSSD, the root mean square of successive differences between beats. Frequency-domain indices split the signal into bands, a low one and a high one, and for years the ratio between them was read as the balance between the sympathetic and parasympathetic systems.
A 2017 methodological review sorted the two out. RMSSD estimates vagal tone, is little affected by breathing and needs only a couple of minutes to be calculated properly; the band ratio, on the other hand, does not measure that balance, even though about two papers in three still use it, and the high band works as a measure of vagal tone only when breathing falls between 9 and 24 breaths a minute. Hence the rule that to measure an archer's heart rate variability you need RMSSD, not the ratio between the bands. The registry rates it as transferred, because nobody has compared the indices against each other in archers: it holds as a methodological rule taken from other fields.
The same review sets two conditions that determine how to take the measurement. The first is that vagal tone cannot be read while the body is moving: in twenty-two beginners, RMSSD during shooting rose by 10% over rest while heart rate went up, a sign that with a bow in hand the number cannot be interpreted as it would be at rest. The second is that two readings are comparable only if taken at the same time of day, after similar sleep, with no coffee or hard training beforehand. The reading that matters, then, is the morning one, lying down or seated, before anything else.
Even when it is done properly, the measure varies a great deal from person to person. In eighteen elite Turkish archers measured for five minutes seated, resting RMSSD averaged 82.8 milliseconds, with a standard deviation of 52.9, almost two thirds of the mean. So comparing your number with that of the archer next to you on the shooting line tells you little about which of you is in better shape.
Why a single morning reading carries little weight
The first premise of any HRV rule is that an archer's heart rate does not stay put from one session to the next. Two studies indicate that the same archer's heart rate changes from one session to the next: in four elite Australian archers measured in sessions between one and just over three months apart, resting heart rate changed significantly from one session to another, and in 2025 thirty-two Indian archers who shot two identical sessions had a lower heart rate on average in the second and the same score, 279.4 against 279.5 out of 300, although the authors did not test the difference in heart rate. Both studies are small and were designed for something else, and nobody has measured how much an archer's heart rate fluctuates with a method built for the purpose, so the registry rates the claim as reported. They are enough, though, to stop anyone reading a single morning as a verdict.
The weekly average rule comes from a 2013 review of elite endurance athletes. In the data it brings together, single-day values were misleading: in one athlete they flagged worrying drops during periods of good training and competition, whereas the weekly average, or the rolling average of the last seven days, fell only when the athlete's training status had genuinely deteriorated. The authors advise using a single index, log-transformed RMSSD, and reading every change against the profile the same athlete builds up over time.
Is the training load right? A rule borrowed from other sports
This is the use many archers buy the device for, and it is also the one whose basis lies furthest from archery. The idea that heart rate variability tells you whether the training load is right rests on the same review, and its answer is two-sided. Both rises and falls in variability have been linked to poor adaptation to training load, and in very well-trained athletes variability can drop precisely as resting heart rate falls with improving fitness, so the same movement in the number lends itself to two opposite readings. Read as an average over several days and against the athlete's own profile, however, in the Olympic and world champion athletes the authors use as examples it tracked fitness and freshness ahead of a major competition, and in the days before a final a drop could go with freshness rather than fatigue.
There is nothing on archers, and the registry rates the claim as transferred. The gap between the two sports is not small: the review deals with athletes whose training places enormous demands on the cardiovascular system, whereas archery asks far less of the heart, and nobody knows whether a block of arrows leaves the same trace on morning variability as a block of endurance training. An archer who sets the week's arrow count by the strap is applying a rule from another sport, a reasonable one that has never been tested in archery.
Heart rate in competition
Anyone who has shot a shoot-off knows that the heart races in competition, and the measurements all point the same way: in competition an archer's heart rate stays well above resting values in every study that has measured it, and none finds the opposite. The weak point is the word "well". When the same archers were also measured at rest, the resting value was almost always taken seated, and the clearest gap runs from 82 to 95 beats per minute, in eleven recurve archers during a simulated competition. Standing up, however, raises heart rate on its own: in fifteen Turkish national team archers, getting up from lying down added around twenty beats before they had even picked up the bow. Nobody has measured how far heart rate rises in an official competition relative to the same archer's standing rest, which is why the claim is rated as reported.
The reference figure that does the rounds, that while shooting, an archer's heart rate sits at around a hundred beats per minute, describes some of the measurements well and not others. Many fall between 95 and 108, in training, indoors at 18 metres or in simulated competitions with little at stake. In an organised 72-arrow competition at 70 metres, however, twenty-four Indian university archers sat between 110 and 116, ten Indonesian university archers in a simulated competition with alternating shooting between 128 and 142, and in kyudo the peak of each shot reaches averages between 138 and 162 in competition. At the other end, seven elite Indian archers shooting indoors stayed between 83 and 98. A hundred beats describes shooting with little at stake, not every competition, and the status is contested.
HRV as a measure of tension has fared much the same. For a long time the idea that heart rate variability shows how tense an archer is in competition rested on a single case, a Japanese Olympic archer recorded between ends in 1987, and in 2025 two studies arrived that pull in different directions. In the eighteen elite Turkish archers, measured before a training session and before the national indoor championship, RMSSD before the competition, 69.6 milliseconds, could not be told apart from RMSSD before training, 82.8, while mean heart rate rose from 68 to 76; reported anxiety did not change either, though, so the competition may simply not have made them any more tense. In six adolescent archers under official competition conditions, by contrast, a wristband reading variability at the wrist classified the moments of high and low stress the athletes reported with an accuracy of between 68% and 82%. The studies on archers do not agree and are all small, so the status is contested: for now HRV is a clue to tension, not a measure to rely on.
The level of arousal at which an archer shoots best is not the same for everyone either. The evidence that the ideal level of arousal for shooting well differs from archer to archer comes mainly from three top Brazilian archers followed over a whole season, whose optimal zones differed from one another, and from the eight Italian Olympians interviewed before Atlanta 1996, who described opposite ideal states; the registry rates it as reported. It is one more reason to distrust a heart rate or variability threshold that supposedly applies to everyone, and arousal is covered in full in the article on optimal arousal.
A different kind of clue concerns emotions. In 86 Turkish university students who had just finished a fourteen-week archery course, variability recorded for four minutes after ten arrows at 18 metres was higher in those who reported regulating their emotions better, and the difference held when the group was split in half. It is a single study, on beginners, with no measurement before shooting and no arrow scores, so the registry reports that archers who regulate their emotions better have higher heart rate variability after shooting and draws nothing further from it.
Slow breathing and biofeedback
The most direct way to move variability is breathing. A systematic review and two narrative reviews agree that the heart rate oscillations linked to breathing peak at around six breaths a minute, closer to five and a half when inhalation and exhalation are the same length; the exact rate varies from person to person, though, so six breaths is a starting point rather than a target. The registry rates as transferred the claim that breathing at around six breaths a minute brings heart rate variability to its maximum, because nobody has looked for that rate in an archer, let alone with a bow in hand, where the breath is held during the seconds of the shot.
Going from breathing to anxiety is another leap. HRV biofeedback, practising breathing while watching your own heart rate on a screen, raises variability fairly reliably, but anxiety falls only some of the time. In the review that gathers these studies on healthy people, the only favourable case involves dance conservatoire students who had to perform, whereas in young adults and in the staff of an elite sporting environment variability rose while anxiety or emotional regulation stayed where they were. That is why the claim that heart rate variability biofeedback reduces the anxiety of people who have to perform is contradicted, on indirect evidence and without a single archer. Slow breathing between ends remains a habit that costs little, but what you can expect to respond is the heart rate, not necessarily the anxiety.
The heartbeat at the moment of the shot
That leaves the subject that draws many archers to HRV in the first place, the heart during the seconds of aiming, and there too the studies disagree: the slowing of the heart in the seconds before the release is contested, and so is the idea that a lower heart rate at the moment of the shot improves the score. I cover both in detail, together with releasing in diastole, in the article on the heartbeat at the moment of the shot. Here it is enough to keep the two measurements apart: the morning reading concerns recovery, the reading during the aim concerns the shot, and neither can be inferred from the other.
How to use HRV in practice
Putting together what is known, the way of using it that holds up best is also the simplest, and it comes down to four habits.
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The same measurement every time
Every morning on waking, before coffee, in the same position and with the same device, for a couple of minutes. The number to watch is RMSSD; the band ratio that some apps display does not measure the sympathetic and parasympathetic balance it claims to.
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A personal baseline
Before reading any changes you need a period of regular measurements, because the reference is the profile you build up over time, not the averages published in apps or a teammate's value.
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The weekly average
Compare the average of the last seven days with your own baseline, not this morning's value with yesterday's. A single low day says nothing on its own; a drop that persists deserves attention alongside everything else, meaning sleep, how hard the sessions felt and how the shooting is going.
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Caution before competition
In the elite Turkish archers, RMSSD before the championship could not be told apart from RMSSD before training, and in endurance athletes a drop in the days before a major competition could go with freshness. A low number on competition morning is not, as far as we know, a forecast of the result.
It is not equally useful for everyone. For someone who shoots once or twice a week with no pressing competitive goals, variability is unlikely to say anything you can act on, and the risk is adding one more thing to think about to a movement that should stay free. It makes more sense for archers who train almost every day and combine arrows, gym work and competitions, as long as they remember that the rule comes from other sports and that nobody has yet tested it in archers.
Which device to choose
For a couple of minutes' measurement in the morning, the simplest choice is a chest strap, which reads the heart's electrical signal and sends the intervals to an app over Bluetooth; the study of elite Turkish archers used a Polar H10, with Elite HRV and Kubios for the analysis. Rings and watches read the heartbeat with an optical sensor, often overnight: they are convenient, but they give a number taken under different conditions, which should only be compared with readings from the same device. Whichever device you choose, it pays to stick with it, because switching mid-season means rebuilding your baseline from scratch.
The risk of depending on the number
There is one last limitation, and it lies in how the tool is used rather than in the studies. Some athletes reach the point where they cannot train unless the morning reading is what they expected, and end up listening to a screen instead of their own sensations. HRV is there to sharpen your reading of your own state, not to replace it, and when the number starts deciding for the archer it is time to put it back in its place, alongside sleep, fatigue and how the arrows are going.