Apple Watch now tracks heart rate continuously

Updated September 9, 2026, following Apple’s announcement of continuous heart rate tracking and HRV in Vitals.

Today Apple announced continuous heart rate tracking for Apple Watch. Heart rate is now measured every 5 seconds and HRV is measured every 5 minutes.

The new 4th generation sensor on Apple Watch, announced Sep 9.

I worked on the first continuous heart rate tracking app for Apple Watch and coauthored a JAMA Cardiology study on detecting atrial fibrillation with Apple Watch data. The exciting part of more frequent recording is what we could learn between workouts, throughout the day and night.

There’s a ridiculous amount of signal locked within the humble heart rate sensor: heart rhythm disorders, Long Covid and dysautonomias, HRV, stress, sleep, and fitness.

In fact, here are twenty examples of how continuous heart rate tracking could be useful:

20 examples of what continuous heart rate can tell you, across medical, sleep, stress, and fitness applications.

What changes with continuous heart rate tracking?

Previous Apple Watches captured heart rate roughly every 5 minutes. Increasing the resolution to every 5 seconds enables a surprising number of applications. Here are a few of my favorites.

Heart arrhythmias

Atrial fibrillation (AFib) produces an irregular rhythm. Our JAMA Cardiology study detected AFib from Apple Watch heart rate and step data, performing substantially better in controlled testing than everyday use. Longer recordings could catch intermittent episodes.

Atrial flutter can produce a regular pulse, so algorithms that look for irregularity may miss it. Researchers have studied AFib and flutter detection with wrist optical data, but confirming the rhythm requires an ECG.

Supraventricular tachycardia (SVT) often starts and stops abruptly. Recording when it starts and stops could help a doctor investigate palpitations. A wearable study found poor performance for short SVT episodes, so the algorithm must also respond fast enough to capture them.

Does AFib burden predict stroke risk?

AFib burden is the proportion of monitored time spent in atrial fibrillation. Apple’s existing AFib History estimates burden, but is not a continuous monitor.

A study called KP-RHYTHM showed people who spent more than 11.4% of monitored time in afib had *about three times the rate of stroke and stroke-like events while off anticoagulants. (An example of a stroke-like event is a TIA.)

3x the risk of stroke-like events when you spend more time in atrial fibrillation. Continuous heart rate on Apple Watch could make this type of monitoring cheap and upiquitous. Source: KP-RHYTHM study

An separate analysis linked episodes longer than 24 hours to roughly 3.2 times the adjusted risk of stroke or systemic embolism. Neither study establishes a universal safe threshold or validates a smartwatch’s burden estimate. The randomized REACT-AF trial is testing continuous anticoagulation against 30-day courses following watch-detected AFib lasting more than an hour. An investigational algorithm and supervised protocol will test whether intermittent treatment prevents clots while reducing bleeding. Patients take their prescribed dose during those courses. A low watch-reported burden isn’t a reason to stop prescribed anticoagulation; treatment changes require a clinician’s assessment.

Long Covid, POTS, and other dysautonomias

Dysautonomias disrupt automatic control of heart rate, blood pressure, and other functions. They can develop after Covid, including postural orthostatic tachycardia syndrome (POTS).

One diagnostic criterion is heart rate that rises more than 30bpm after standing, and stays there. Pairing continuous readings with posture and symptoms could capture that difference passively. Evaluating POTS also requires blood pressure measurements, persistent symptoms, and ruling out other causes, as our active stand test guide explains.

In a wearable study, the Long Covid group’s average resting heart rate stayed above its pre-infection baseline for 133 days, versus 71 days without Long Covid. Continuous recording could show which activities accompany a racing heart (though a normal trace doesn’t rule out Long Covid — this is still a condition that’s poorly understood).

How could continuous tracking improve Apple Watch HRV?

Heart rate variability measures changes in the intervals between normal beats. We often decompose heart rate variability into the frequency domain using a Fourier transform:

Real ECG-derived beat intervals from PhysioNet, record nsr001, 00:05–01:05. Red: one hour; tan: its first minute. Logarithmic axes. Data: Phyllis Stein / PhysioNet, ODC-By 1.0; analysis by Empirical Health.

Brief HRV recordings capture short fluctuations, but can’t fully characterize slower changes that unfold over minutes. This very low frequency (VLF) range spans roughly 0.0033–0.04 Hz, or cycles lasting 25 seconds to five minutes.

An HRV reading every 5 minutes could make daily stress and recovery trends easier to follow. But measuring HRV every 5 minutes isn’t the same as measuring beat intervals continuously for 5 minutes. Whether the update enables the longer-window analysis illustrated above depends on the duration of each recording and access to the underlying beat intervals.

High-frequency (HF) variability largely reflects the vagus nerve adjusting heart rate with each breath (parasympathetic activity). Low-frequency (LF) variability includes blood-pressure regulation and mixed autonomic influences; it isn’t a direct sympathetic activity meter. The mechanisms behind very-low-frequency (VLF) variability are less settled; autonomic, hormonal, and temperature regulation may contribute.

HRV analysis must account for motion artifacts and abnormal beats. (Recording length also affects SDNN, the HRV metric Apple uses: overnight and brief daytime measurements aren’t interchangeable.)

Can heart rate show stress and recovery?

Stress and recovery are wellness applications that apply to nearly everyone. While there are some existing stress and recovery apps, they can be much more effective with continuous recording.

In a 2022 study, 197 adults took public-speaking and arithmetic stress tests. From arithmetic to recovery, changes in perceived stress correlated with changes in heart rate and HRV (RMSSD). A separate study of 221 adults with overweight and psychological distress found a similarly modest correlation between perceived stress and an HRV-derived stress index.

Continuous data could show whether heart rate settles after a difficult meeting. Breathing, heat, and movement also affect heart rate and HRV, so interpreting these modest correlations requires context.

What could Apple Watch continuous tracking reveal about sleep and fitness?

A study of 4,098 Finnish employees linked alcohol to higher heart rate and poorer HRV-derived recovery during the first three hours of sleep, with larger changes at higher doses. Continuous tracking could show whether heart rate settles after bedtime or stays elevated for hours.

Apple Watch already records continuously during logged workouts. Continuous background recording could capture an unlogged walk or recovery beyond the workout window. Comparing the same walk over time could show how that response changes.