Track each client’s HRV as a 7-day average against their own usual range, and read it next to resting heart rate Resting heart rate How many times your heart beats per minute while you are fully at rest. For adults it is usually 60 to 100 beats per minute, and lower in well-trained athletes. More about Resting heart rate and how they feel. Ignore single mornings, comparisons between clients and the exact number on a readiness score Readiness score A single number, often out of 100, that a device builds from your HRV, resting heart rate, sleep and other inputs to suggest how ready you are for the day. The weighting is not published. More about Readiness score .
Used that way, HRV can help you decide when to push and when to hold back. Treated as a daily pass or fail, it mostly creates worry for you and your client.
What the training studies found
Heart rate variability (HRV) is the small change in time from one heartbeat to the next. After a hard session it usually drops for a day or two before coming back. HRV-guided training uses that pattern: a client trains hard when their HRV is in its normal range and goes easy when it has dropped.
An early trial ran in Finland (Kiviniemi and colleagues, 2007). Twenty-six moderately fit men were split into three groups for four weeks. Eight followed a fixed plan with four hard runs a week, while nine trained hard only when their morning HRV had not dropped. For that group, a drop meant a reading below their 10-day average minus one standard deviation, or two days of falling values. The other nine were a control group.
- In the HRV group, peak oxygen uptake rose from 56 to 60 ml/kg/min, while in the fixed-plan group it did not change significantly.
- The gap in oxygen uptake between the two training groups was not significant.
- Top running speed rose in both groups, by 0.9 km/h with HRV guidance and 0.5 km/h on the fixed plan, and that difference was significant.
A 2021 meta-analysis pooled this trial with later ones (Manresa-Rocamora and colleagues, 2021). HRV-guided training raised HRV itself more than fixed plans did. For aerobic fitness and endurance performance, the results leaned towards HRV guidance, but the effects were small (standardised differences of about 0.2 to 0.26) and not statistically significant. The authors concluded that any advantage at group level is likely small, and that HRV guidance may make poor responses less likely.
For a trainer, that is a modest promise. HRV guidance is a sensible way to decide where the hard days go, but it will not turn an average plan into a great one.
Track the weekly average
A single reading moves with sleep, a late meal, a drink, a stressful day or a bad night in a hotel, and the weekly average smooths most of that out.
A study of 10 runners over a 9-week training block tested this directly (Plews and colleagues, 2013). Changes in their HRV on one isolated day had almost no link with changes in their running fitness, measured as estimated maximal aerobic speed (r = -0.06), while changes in the weekly average had a very strong link (r = 0.72).
A second study, in trained triathletes, asked how many readings a week you need (Plews and colleagues, 2014). An average of at least 3 valid readings a week, taken on random days, came close to the result from all 7. With only 1 or 2 readings, the average showed the change much less clearly. So a client who forgets twice a week is still giving you useful data, while one reading a week tells you far less.
Two clients show the difference:
- Sam flew home late on Sunday and slept five hours. Monday’s reading is well below her usual range, but her 7-day average is still inside it. That is one low day with an obvious cause, so keep the plan, perhaps trim the hardest set, and look again tomorrow.
- Tom, a 52-year-old runner, has a 7-day average that has drifted below his usual range for over a week. His resting heart rate is creeping up and his easy runs feel harder. That is a trend, and an easier few days while you look for the cause is a reasonable call.
The lesson on building your HRV baseline shows how to set a usual range, and should I train when my HRV is low? covers the day-to-day decision.
What to track and what to ignore
| Track | Ignore |
|---|---|
| The 7-day average against the client’s own usual range | A single morning reading |
| Resting heart rate, measured the same way | How the client’s HRV compares with a friend’s or yours |
| How the client feels, sleeps and performs | Small daily swings inside the usual range |
| The same device, time and position every day | Readings taken during or soon after a session |
| Life events: travel, illness, alcohol, work stress | The exact number on a readiness score |
Buchheit’s review of heart rate monitoring in athletes makes the same point from the research side (Buchheit, 2014). Short resting recordings taken almost daily are among the most useful heart rate tools. Each change should be judged against the error of the measurement and the training phase. Heart rate measures cannot tell you everything, so Buchheit pairs them with training logs, short questionnaires and simple performance tests such as a jump test.
Readiness scores and raw values
Many apps turn HRV, resting heart rate, sleep and recent activity into one readiness or recovery score. Each brand weighs those inputs in its own way, so two apps can give the same client different scores on the same morning.
The raw HRV value is easier to reason about. Many apps report RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next, in milliseconds. It mainly reflects vagal activity. More about RMSSD , and many sports studies use lnRMSSD lnRMSSD The natural logarithm of RMSSD, with no unit. Taking the log evens out the spread of RMSSD values, which makes day-to-day changes easier to compare and analyse. More about lnRMSSD , its natural log, for statistical reasons. If a client’s app shows the raw number, track that and its weekly average. Use the score as a prompt to look, not as the decision. The HRV by device guide explains what each brand reports.
When a lower HRV is not bad news
In very fit endurance athletes, HRV can fall while resting heart rate also falls. Plews and colleagues call this HRV saturation Parasympathetic saturation When the vagal brake is so strong, usually in very fit people with very slow resting heart rates, that the beat-to-beat swing shrinks. HRV then falls while vagal activity is rising. More about Parasympathetic saturation (Plews and colleagues, 2013). In their review of elite athletes, both rises and drops in HRV were linked with poor adaptation in different studies, and some athletes got fitter while their HRV went down. The authors recommend averaging, and following each athlete over the long term to learn their own pattern.
Most gym clients are not elite athletes, but if you coach a very fit client whose HRV drops while their heart rate is low and their training is going well, do not treat the drop as a warning on its own. See can HRV detect overtraining? for the wider evidence.
The orthostatic test
Some coaches add a standing reading to the morning lying one. This is called an orthostatic test Orthostatic test A short morning test: lie or sit still for 2 minutes, then stand for 2 minutes, recording heart rate and HRV in both positions to see how your body handles standing up. More about Orthostatic test , because it looks at how the heart and nervous system respond to standing up.
A French team used it with 57 elite Nordic skiers, from biathlon, Nordic combined and cross-country skiing, over four years (Schmitt and colleagues, 2013). After 15 minutes of rest, each skier lay still for 8 minutes and then stood for 7 minutes, and HRV was worked out from both parts. A questionnaire flagged when the skiers were fatigued. In the tests taken while fatigued, heart rate was on average about 6 beats a minute higher lying down and about 9 higher standing than in their other tests, and HRV was lower in both positions. HRV also jumped around more from test to test when they were fatigued.
The standing part adds information that the lying reading misses, but the study protocol took about 30 minutes including the rest, and the numbers only mean something against the same person’s earlier tests. It suits a keen athlete more than a busy client.
Go deeper Running a simple orthostatic test with a client
Use the same setup every time: morning, before food, caffeine or training, after a few minutes of quiet rest. Record a few minutes lying still, then stand up and record again while standing still. A chest strap gives the cleanest beat timing for this. Note heart rate and HRV for each position, and compare them only with the client’s own earlier tests. The Schmitt study used 8 minutes lying and 7 minutes standing, and analysed 5 minutes from each.
Keep HRV in its lane
HRV cannot diagnose anything, and it is not a health screen; it tells you how a client is responding to training and life, alongside everything else you see. If a client mentions chest pain, fainting, palpitations, a racing or uneven heartbeat, or breathlessness out of proportion to the effort, stop the session and suggest they see a doctor, whatever their HRV says.
Where to go next on hrv.expert
- HRV for training and recovery, the course lesson on HRV-guided training
- HRV and training, what a workout does to HRV and for how long
- Is wrist HRV as accurate as a chest strap?, for choosing a sensor for clients
- The chest-strap HRV test and the HRV calculator, to record and work out RMSSD from a strap
- All tools, including the camera test and the HRV checker
- HRV for health coaches, for the conversations about stress and sleep around training