Heart rate pacing: thresholds, wearables and alerts for ME/CFS and Long COVID

Short answer

Heart rate pacing is a way of managing post-exertional malaise (PEM) in ME/CFS and Long COVID by keeping your pulse under a personal ceiling during everyday activity. The usual starting estimate is your seven-day average resting heart rate plus 15 beats per minute — a heuristic, not a measured threshold — and it only works with continuous readings and an alert from a wearable.

Before you blame yourself, check what your body already recorded. If you crashed two days after a day that felt fine, that is not weakness and not a failure of willpower. In PEM the cost of effort typically arrives 12 to 48 hours later, which is exactly why a number on a screen can help where feeling alone cannot.

Note: this article is for education and is not medical advice. Heart rate pacing is a self-management approach, not a treatment, and every threshold here is an estimate to discuss with a clinician — especially if you take medicines that change your heart rate, faint, or have a heart condition.

What is heart rate pacing?

Pacing, in the sense used for ME/CFS and Long COVID, means limiting exertion so that you stay inside the amount of activity your body can currently handle without a delayed crash — what patients call the energy envelope. Heart rate pacing is one way of doing that: instead of judging effort by how you feel in the moment, you use your pulse as an outside reading and stop, sit or lie down when it crosses a ceiling you set in advance.

The logic is borrowed from exercise physiology but turned upside down. An athlete uses heart-rate zones as a target to reach. In heart rate pacing the number is a ceiling you are trying not to break, and the monitor works more like a smoke alarm than a coach. When it goes off, the right response is to rest — not to finish the task first.

It sits alongside other pacing approaches rather than replacing them. Some people count activities, some keep a symptom and activity diary, some pace by how their morning felt, some combine several. Our guide to pacing with chronic illness compares them side by side. Heart rate pacing is the most hardware-dependent of the group: it needs a device that reads your pulse all day and can alert you, which in practice means a chest strap, an armband or a watch.

The UK's national guideline on ME/CFS, NICE NG206 (2021), describes energy management as a self-management strategy led by the person themselves, with support from a healthcare professional, covering "all types of activity (cognitive, physical, emotional and social)". It does not prescribe one tool, but it does tell clinicians to make self-monitoring as easy as possible by using tools a person already has, and it names "an activity tracker, phone heart-rate monitor or diary" as examples. Heart rate pacing is one of the ways people put that advice into practice.

The short version: heart rate pacing turns an invisible threshold into a visible one. It does not make the threshold higher, and it does not tell you everything about your load. It gives you one objective reading at the moment you most need it.

Why does heart rate pacing work for post-exertional malaise?

Two features of post-exertional malaise make ordinary self-regulation unreliable. The first is delay: NICE describes symptoms that typically worsen 12 to 48 hours after activity and last for days or even weeks. The second is mismatch: the activity that triggers the crash can be small, and the crash is out of proportion to it. Put together, the feedback most people use — "I'll stop when I feel tired" — arrives too late to be useful.

Heart rate pacing leans on a line of research from the Workwell Foundation group in California and others using the two-day cardiopulmonary exercise test (CPET). In a healthy person, two maximal exercise tests done a day apart give almost identical results. In a 2014 study of 22 people with ME/CFS who did two CPETs 24 hours apart, oxygen use at the ventilatory threshold fell by 15.8% on the second day and the workload they could manage at that threshold fell by 21.3%; peak heart rate dropped by about 9 bpm. The ventilatory (or anaerobic) threshold is roughly the point where the body leans more heavily on less efficient, anaerobic energy production. The finding that it shifts downward after exertion is one of the most specific objective signatures of PEM.

The practical idea follows from that: if activity above the threshold is what the body pays for later, then keeping everyday activity below it is meant to lower what you pay. Heart rate is used because it is the easiest continuous proxy for how hard you are working.

A second strand of evidence comes from Long COVID. A 2026 observational study continuously recorded heart rate and heart rate variability (HRV) in 121 people with Long COVID and 21 healthy controls, alongside a logbook of daily activities, and measured each person's heart rate at the first ventilatory threshold on an exercise test. Around that threshold, HRV in the patients stayed lower than in controls for 24 hours after exercise, and night-time HRV fell further after more intense and longer exertion. The authors suggested that the risk of PEM rises above the first ventilatory threshold. That is not proof that heart rate pacing prevents crashes, but it is consistent with the reason people use it.

Two honest caveats. The research case for heart-rate-guided pacing is still small: a 2025 randomised feasibility study included 47 people (32 with ME/CFS, 15 with Long COVID) over 8 weeks, which is enough to show the approach can be studied and is acceptable to patients, not enough to settle how well it works. And the threshold idea explains part of PEM, not all of it — cognitive, emotional and sensory load can trigger crashes without much change in pulse, which we come back to below.

How do you find your heart rate pacing threshold?

There are four ways people arrive at a number, and they differ a great deal in accuracy, cost and risk.

Resting heart rate plus 15. This is the number most people meet first. The Workwell Foundation's patient guidance (published April 2024, updated July 2026) says to record your resting heart rate on waking for seven days, average it, and add 15 bpm as "a starting point" for estimating the ventilatory/anaerobic threshold. With a seven-day average of 68 bpm, that gives a ceiling of 83 bpm. Workwell calls this a conservative estimate. Treat it as a heuristic: a sensible place to start, not a measurement of your threshold.

Why the estimate is deliberately low. A 2019 review from the same research group pooled heart-rate responses from maximal exercise tests and found that people with ME/CFS consistently show a smaller-than-expected rise in heart rate as workload increases — a pattern called chronotropic intolerance. If heart rate climbs less than it should for the work being done, a formula built on healthy hearts will tend to place the threshold too high. That is one reason a ceiling close to resting heart rate is used rather than a percentage of maximum.

Age-based formulas. In the 2025 feasibility study, the heart-rate limit was calculated either with the resting +15 method or with a formula based on age; the app used with the study's armband applied a different age-based formula again, (220 − age) × 0.6, as the paper reports. Three methods, three different numbers for the same person — which tells you how approximate all of them are.

Measured thresholds. A CPET measures the heart rate at which your ventilatory threshold actually occurs. It is the best number available, but specialist two-day testing is offered in very few places, and it carries a real risk of provoking a crash. It is not something to ask for simply to prove a point to a sceptical clinician.

Adjusting by symptoms. Whatever you start with, your own record decides whether it holds. If you stayed under the ceiling and still crashed 48 hours later, the ceiling is too high for you right now — or the load that caused the crash was one your pulse did not show. People with more severe illness often end up well below the formula. Moving the number down after a crash is part of the method, not a sign of doing it wrong.

Which device do you need for heart rate pacing?

This is where heart rate pacing differs from most other pacing approaches: it needs continuous heart rate and an alert. A reading taken once in the morning cannot tell you that you crossed your ceiling while carrying laundry up the stairs at 4 pm. So the real choice is between devices that read your pulse all day.

Chest strap versus wrist. In a 2017 study of 50 healthy adults exercising on a treadmill, bike and elliptical, an electrode chest strap agreed with ECG almost perfectly (concordance 0.996), while wrist-worn optical monitors ranged from 0.67 to 0.92 depending on the model; none was accurate on the elliptical with arm levers. A 2020 study of consumer and research-grade wearables found that absolute error during activity was on average 30% higher than at rest, with no significant difference across skin tones, and that devices differed most in how they responded to changes in activity. Workwell's guidance recommends a chest strap for the same reason. For pacing, the moments that matter most are exactly the sudden changes — standing up, climbing stairs, lifting a child — so a wrist device's smoothing is a real limitation, not a technicality.

What people actually use. In a 2023 international survey of 488 people with ME/CFS about pacing with a heart-rate monitor, respondents reported using more than 100 different types of device and listed more than 30 benefits and more than 30 drawbacks. Chest straps can be uncomfortable for all-day wear, particularly with chest-wall pain or sensory sensitivity, and many people alternate: a strap for known heavy tasks, a watch for the rest of the day.

Alerts. An alert is the part that turns heart-rate data into pacing. Many watches and strap-paired apps let you set a high-heart-rate alarm; set it at your ceiling and treat it as an instruction to stop, not a suggestion. Workwell advises avoiding more than about two minutes above the threshold and resting until heart rate is back within 10 bpm of your resting rate.

Where a phone camera fits — and where it does not. A camera reading uses photoplethysmography: a fingertip over the lens and flash, held still for a short reading. It is a single snapshot of heart rate and HRV at rest. It cannot follow your pulse through the day, cannot alert you, and cannot replace continuous heart-rate monitoring or an ECG. What it can do is give you a consistent morning reading without buying a device — useful for knowing your resting heart rate and for the morning HRV check, which is a different tool from heart rate pacing. If you want to know how close a camera reading gets to a chest strap, see how accurate HRV from a phone camera is. For a side-by-side of the pacing apps built around these devices, see our comparison of pacing apps.

What can't heart rate pacing see?

A heart-rate ceiling is a good guard against one kind of overspending. It is a poor guard against several others, and knowing which is which saves a lot of self-blame.

Cognitive and emotional load. NICE is explicit that energy management covers cognitive, emotional and social activity, not just physical effort. A difficult phone call, a spreadsheet, a noisy waiting room or an argument may barely move your pulse and still land you in bed two days later. If you have ever wondered why you crashed when your step count was zero, this is usually why. Heart rate pacing needs a diary beside it for these loads.

Accumulation. Staying under the ceiling all day does not mean the day was light. Twenty short climbs to 80 bpm are not the same as one, and many devices only alert on crossings, not on time spent close to the line. Total upright time and the number of tasks matter too.

A blunted heart-rate response. Because of chronotropic intolerance, some people's heart rate rises very little even when they are working hard. For them a ceiling may rarely fire, and a quiet monitor can give false reassurance.

Medicines. Drugs that slow the heart change what any number means. If you take one, your ceiling needs to be set with your prescriber, not from a formula: a slower pulse does not mean a lighter load.

Readiness scores. Many devices wrap heart rate and HRV into a daily "readiness" or "recovery" number built and validated on healthy people and athletes. In the 2026 Long COVID study above, HRV was lower in patients during everyday activities and sleep, which is one reason such scores do not transfer cleanly. Treat the raw pulse as the useful number and the composite score as a guess made for someone else.

The future. We are not aware of any validated algorithm that can predict an individual crash. Heart rate pacing is a guardrail you set and follow, not a system that knows what is coming.

Why standing still can break your heart rate ceiling

For many people with ME/CFS, Long COVID or POTS, the hardest activity of the day is not walking — it is standing still. When you stand, blood pools in the legs, less returns to the heart, and the heart speeds up to compensate. The difference between your lying and standing heart rate is one of the most useful numbers you can collect at home.

The formal thresholds. The international consensus definition of postural orthostatic tachycardia syndrome (POTS) in adults is a sustained heart-rate rise of at least 30 bpm within 10 minutes of standing, without a significant fall in blood pressure. A rise that comes close to that threshold on several separate mornings is worth bringing to a clinician, who can run a formal test. A 2025 study of 60 people with POTS who did a 10-minute active stand and a tilt-table test on the same day shows why the lower end is sensible at home: 74% met the heart-rate criterion on the active stand against 98% on tilt, and lowering the stand threshold to 27 bpm narrowed the gap to 83% against 98%. A negative home stand test does not rule POTS out.

What it means for your ceiling. If standing alone takes you from 65 to 100 bpm, a ceiling of 80 will fire all day and stop meaning anything. In that case the tool changes shape: rather than "do not cross this line", the rule becomes "break tasks into pieces short enough that the line does not matter" — sit to prepare food, shower seated, rest lying down between parts of a task. Workwell's advice to avoid more than two minutes above threshold is the same idea from the other direction. A measured orthostatic response is also a reason to ask about orthostatic intolerance directly, because it has its own assessment and management.

Doing it safely. The stand test is a load in itself. In the 2025 feasibility study, the five participants with ME/CFS who could not complete the ten-minute stand test reported PEM immediately afterwards as well as delayed symptoms. Do it only near a bed or sofa, with someone nearby if you tend to faint, lie down at once if your vision greys or you feel yourself going, and stop early if you need to — the minute you stopped is data too. Our step-by-step guide to a stand test at home covers the protocol.

What the days before a crash can look like in your heart-rate data

People who pace with a heart-rate monitor often go back through their data after a crash and find something: a morning resting heart rate a few beats higher than usual, a day with far more time near the ceiling than they realised, a night when heart rate stayed higher than normal. That is worth doing. It is also worth being precise about what it is.

It is hindsight, and hindsight is useful. Looking at what your data looked like before a crash helps you find loads you did not count — the standing queue, the long call, the second errand — and adjust your ceiling or your plan. The 2026 Long COVID study found HRV staying lower for 24 hours after exertion around the threshold, with night-time HRV falling further after harder and longer efforts. A personal version of that pattern, seen across several of your own crashes, is exactly the kind of information that improves pacing.

It is not a warning system. Most days with a higher resting heart rate are not followed by a crash, and some crashes follow days that looked ordinary in every number. Illness, poor sleep, heat, alcohol, the menstrual cycle and medicines all move the same signals. No study has shown a wearable metric that tells an individual in advance that a crash is coming.

How to read it well. Compare yourself with yourself, not with a population range. Look at trends across several days, not single mornings. Write the lagged column in your diary — how you felt 24 and 48 hours after each heavier day — because that column is what connects the heart-rate record to the crash. And when the numbers and your body disagree, believe your body: a green score on a morning you can barely stand is the score being wrong.

A two-week way to start heart rate pacing

This is a starting routine, not a prescription. If you are already under a specialist team, agree changes with them first.

Days 1–7: measure, change nothing. Each morning, before getting up, record your resting heart rate — from your wearable, a strap, or a still, seated phone-camera reading taken the same way each day. Rate how you feel from 1 to 10 against your own yesterday, not anyone else's scale. Through the day, jot down blocks of activity with body position ("20 minutes at the laptop, sitting", "10 minutes standing at the stove"). In the evening, note how you feel compared with 24 and 48 hours ago.

Day 8: set the ceiling. Average the seven morning readings and add 15 bpm. Set a high-heart-rate alert at that number on the device you wear all day. If you have a medicine that slows your heart, or a strong orthostatic response, talk to your clinician before relying on the number.

Days 8–14: follow the alarm. When it goes off, stop and sit or lie down until your heart rate settles back near your resting rate — Workwell uses within 10 bpm. Do not finish the task first. Where the alarm fires on standing alone, break the task into shorter pieces and do more of it seated.

Day 15: look back. Circle the days that were not followed by delayed worsening. If crashes still followed days you stayed under the ceiling, lower the ceiling by a few beats, look for cognitive and emotional loads the monitor missed, and keep going. If the fortnight was stable, hold it there. Stability that feels almost boring is the goal, not a waste of time.

A caution that runs through all of this: heart rate pacing is about staying under a limit, not training to raise it. For ME/CFS, NICE advises against graded exercise therapy — fixed incremental increases in activity — and any exercise programme should be personalised, start below your baseline and be overseen by a physiotherapist in an ME/CFS specialist team. World Physiotherapy's 2021 briefing on Long COVID says the same for people with post-exertional symptom exacerbation: graded exercise therapy or fixed activity prescription should not be used.

None of this is obvious on your own, and most people work it out alone. Welltory runs a paid community, Energy Lab, where women living with energy-limiting conditions learn to read their own tracked data together — education and peer support, not medical care.

Living with heart rate pacing: the questions people ask next

Is heart rate pacing for Long COVID the same as for ME/CFS?

The method is the same where Long COVID includes post-exertional symptoms, and that is common. In an international survey of 3,762 people with Long COVID from 56 countries, 85.9% reported relapses, mainly triggered by exercise, physical or mental activity, and stress. The 2026 study of 121 people with Long COVID found HRV recovering slowly after exertion around the ventilatory threshold. What differs is the surrounding advice: some people with Long COVID have no post-exertional symptoms and can follow ordinary rehabilitation. Heart rate pacing for Long COVID makes sense when effort is followed by delayed worsening; that is the question to settle with your clinician first.

Can I still exercise if I use heart rate pacing?

Heart rate pacing is not an exercise plan, and for people with PEM it should not become one. For ME/CFS, NICE (2021) says not to offer programmes with fixed incremental increases, such as graded exercise therapy, and describes a personalised approach instead: find a baseline that does not worsen symptoms, first reduce activity below it, hold that level, and adjust up or down flexibly under a physiotherapist from an ME/CFS specialist team. In practice, many people who use heart rate pacing count gentle movement, stretching or a short walk as part of the budget, below the ceiling, rather than as training.

Does heart rate pacing work at a desk job?

Heart rate pacing helps with the physical and postural parts of work — the commute, standing in meetings, stairs — but it misses most mental effort. Concentration, video calls and difficult conversations can cost a lot while your pulse barely moves, and NICE counts cognitive, emotional and social activity as part of energy management. For desk work, heart rate pacing works best alongside planned breaks, lying down between tasks where possible, and a diary of the day's cognitive load. If you are negotiating adjustments at work, a two-week record of alarms and delayed symptoms is more persuasive than a description.

What if my heart rate goes over my limit in the shower?

Showers combine standing still with warm water and effort, and in orthostatic intolerance standing alone can raise heart rate sharply — so for many people heart rate pacing alarms fire most reliably in the bathroom. The answer is to change the task rather than ignore the alarm: sit on a shower stool, keep the water lukewarm, wash hair and body as separate steps with a rest between, dry and dress sitting down. Workwell's two-minute limit above threshold is a useful guide to how long each piece should be. If showers regularly leave you close to fainting, raise it with your clinician as part of an orthostatic assessment.

Should my heart rate pacing ceiling change over time?

Yes — the heart rate pacing ceiling is meant to move with you. Workwell bases it on a seven-day average of waking resting heart rate, so recalculating from a fresh week of readings every so often keeps it current. It should also move down after a crash or during a flare: for a flare-up, NICE advises temporarily reducing activity and not returning to usual levels until it has resolved, and for a relapse, reassessing energy limits to stabilise symptoms. Raising the ceiling is a different matter; it should follow weeks of stability, not a single good day, because the good day is often the one that books the next crash.

Does heart rate pacing work if I take a beta-blocker or have POTS?

Heart rate pacing becomes harder to read in both situations. Medicines that slow the heart lower the numbers without necessarily lowering the load, so a formula ceiling can be misleading; the ceiling needs to be set with your prescriber. With POTS, standing alone can push heart rate past the ceiling, as the 30 bpm consensus threshold shows. Many people with POTS and PEM use heart rate pacing as a prompt to break tasks into short, seated pieces rather than as a strict line. If you have POTS without post-exertional symptoms, your clinician may recommend a different, exercise-based approach — that decision depends on whether PEM is present.

Does heart rate pacing help in the long run?

The honest answer is that heart rate pacing has promising but small evidence. The 2025 randomised feasibility study of 47 people found the approach acceptable: 89% of the intervention group planned to continue straight after the 8 weeks, and at six months 66% of all interviewees planned to, with no serious adverse events. In a separate six-week study of 31 people with post-COVID syndrome using a structured pacing protocol based on perceived exertion, weekly episodes of post-exertional symptoms fell from 3.4 to 1.1 on average, with no control group. NICE is clear that ME/CFS symptoms can be managed but there is currently no cure.

How to bring this up with your doctor

Most clinicians have heard of pacing; far fewer have seen a patient arrive with numbers. A short, specific summary changes the conversation.

Say what you are doing and why. "I have delayed crashes 24 to 48 hours after activity. I'm pacing with a heart-rate ceiling at my resting rate plus 15, and I'd like to check that's safe for me." That sentence names post-exertional malaise, shows you are limiting rather than pushing, and invites a review of the number.

Bring three things on one page. Your seven-day average resting heart rate; your lying and standing heart rate from a stand test, if you did one safely, with any symptoms and the minute they started; and two weeks of the diary showing which days were followed by delayed worsening. Add a CSV or screenshots only if the clinician wants them.

Ask the questions that change the ceiling. Do any of my medicines affect heart rate, and what should my ceiling be with them? Should my standing heart rate be assessed for orthostatic intolerance or POTS? Would a physiotherapist or occupational therapist in an ME/CFS or Long COVID service help me set limits?

Be careful with testing and exercise offers. If a two-day CPET is suggested, ask how the risk of a prolonged crash will be managed — it is a heavy test. If an exercise or rehabilitation plan is offered, ask one question early: does it advance on a fixed schedule, or only after a stable period with no delayed worsening? For people with PEM, NICE advises against programmes built on fixed increments.

Know when not to wait. Chest pain, fainting, a very fast heart rate at rest with breathlessness or dizziness, or a sudden change from your usual pattern need prompt medical attention — call 911 or your local emergency number if symptoms are severe.

How Welltory helps — and what it cannot do

The limits first. Welltory is a general wellness product, not a medical device. It does not diagnose, predict, monitor, prevent, treat or mitigate ME/CFS, Long COVID, POTS, PEM or any other condition. It also does not do heart rate pacing for you: Welltory does not sound a heart-rate alarm during activity. For real-time pacing you need the alert on your chest strap, armband or watch; Welltory is where your morning reading, your wearable's heart-rate data and your notes sit side by side.

A morning reading. Welltory can take a short HRV and heart-rate spot reading with the phone camera — fingertip over the camera and flash, sitting still — or from a compatible Bluetooth chest strap, Apple Watch or Samsung Watch. A spot reading is one snapshot; it is a steady way to track resting heart rate for your seven-day average, not a substitute for continuous monitoring or an ECG. Heart-rate data from other watches can reach Welltory through Apple Health, Health Connect or Samsung Health, or through direct connections such as Garmin and Fitbit.

Log the crash and what came before. On iOS with an Apple Watch or Oura, the Today screen shows stress minutes and stress stretches — elevated heart rate without movement; a phone-camera reading alone does not produce them. When Welltory flags a stress stretch and asks "What happened?", tap a suggested tag, type a few words or just say it: "crash", "PEM", "stood in line", "long call", "shower", "HR alarm", "short night". On any setup you can add a note with the plus icon ("Share your thoughts…"). With an energy-limiting condition, rest can register as stress even while you are lying down; the help center is clear that this does not mean the rest did not count.

Look at the days before. Morning HRV and resting heart rate — plus sleep, stress minutes and Battery if you use the Today screen with a watch or ring — read as personal trends next to how you felt. When they disagree with your body, believe the floor.

My Patterns. On iOS, the tags you add to stress stretches collect in My Patterns; notes without a stretch attached do not count. After roughly two to three weeks of tagging — at least 7 tagged occurrences in the current month, with some history from the month before — it shows which tagged situations appear most often in your stress stretches, tags that don't happen often but hit your body hard, day-of-week trends, heart-rate data during those episodes, and a complete list of every time a tag appeared.

A record for your doctor. Journal shows HRV measurements, tags, mood and how you feel physically, notes, workouts and menstrual cycles synced from Apple Health, Samsung Health or Health Connect. The web app adds a CSV export (Dashboard → choose a chart → Export) to sit alongside your own diary at an appointment.

Patterns are associations to discuss with your doctor, not proof of a trigger and not a warning system.

Where to learn this with other people. Welltory runs Energy Lab, a paid, moderated community for women aged 18 to 65 living with energy-limiting conditions — ME/CFS, Long COVID, fibromyalgia, POTS, MCAS and similar. It runs alongside the app: you keep collecting your own data, and the Lab is where members learn to read it together. Welltory's health educators and medical board answer questions from the group in plain language; there are no one-to-one consultations. It is education and peer support, not medical care, and it does not replace your own clinician.

How we made it

Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.

Data analysis by Jane Smorodnikova, co-founder of Welltory and the person who built the methodology behind how we read physiological data.

Written by Tatsiana Yashyna.

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