Posts tagged: Heart Rate

11 posts found

An ECG waveform diagram showing the difference between normal sinus rhythm and the chaotic irregular pattern of atrial fibrillation, illustrating what smart rings try to detect with PPG sensors

Your Smart Ring's AFib Detection Is Not Medical Grade. Here Is What It Actually Measures.

Smart rings use PPG sensors to detect patterns that may suggest atrial fibrillation. But PPG-based AFib detection is not medical-grade diagnosis. Here is how it works, what the accuracy actually looks like, and why the Circular Ring 2 with real ECG is the exception.

James Hoffmann

Jun 26, 2026 1 min read

Prescription medication pills on a dark surface, representing GLP-1 drugs like Ozempic and Wegovy

Heart RateOn Device AiHrv

What GLP-1 Drugs Do to Your Smart Ring's Readings

GLP-1 drugs like Ozempic and Wegovy increase your resting heart rate by 2-5 bpm, lower HRV, and change skin temperature. Here is how that breaks every wearable algorithm and why your recovery score is lying to you.

James Hoffmann

Jun 23, 2026 1 min read

A pregnant woman wearing a smart ring, with abstract biometric data lines flowing around her finger

Heart RateBiometricsAlgorithms

Your Smart Ring Has No Idea You're Pregnant: How Pregnancy Breaks Every Biometric Algorithm

Pregnancy raises your resting heart rate by 10 to 20 bpm, drops your HRV, raises your temperature, and changes your sleep architecture. Every wearable algorithm trained on non-pregnant baselines gets this wrong. Here is what the data actually looks like.

James Hoffmann

Jun 21, 2026 1 min read

An oscilloscope display showing a clean waveform, representing the textbook PPG signal that smart rings almost never actually capture during motion

PpgHeart RateSensors

What Your Smart Ring's Heart Rate Data Looks Like After You Move: Motion Artifacts, Adaptive Filters, and the Signal You Never See

Your smart ring's PPG sensor produces clean heart rate data roughly 40 percent of the time. The other 60 percent is a signal that has been through an adaptive filter, and what comes out is a reconstruction. Here is what actually happens inside the chip when you wave your hand.

James Hoffmann

Jun 18, 2026 1 min read

Closeup of roasted coffee beans scattered on a white surface, representing the source of caffeine that disrupts wearable biometric readings

PpgHeart RateBiometrics

Why Your Morning Coffee Confuses Your Sleep Tracker: Caffeine, Biometrics, and the False Recovery Signal

Caffeine changes your biometrics in ways that look like recovery to a wearable. Higher HRV, elevated resting heart rate, and altered sleep architecture produce a readiness score that says you are rested while your body metabolizes a stimulant. Here is how the blind spot works and what wearables could do about it.

James Hoffmann

Jun 17, 2026 1 min read

A close-up of an ECG monitor screen showing the characteristic electrical waveform of a heartbeat. Smart rings measure something completely different.

PpgHeart RateMedical Devices

Why Smart Rings Can't Do ECG

The Apple Watch measures electrical voltage. Every smart ring measures light bouncing off blood. These are two different physical phenomena, and the ring form factor makes ECG impossible with current technology.

James Hoffmann

Jun 10, 2026 13 min read

A close-up of a green LED and photodiode sensor on a small circuit board, the same components found inside every smart ring that claims to monitor your heart rate continuously

Smart RingsTransparencyHeart Rate

The 'Continuous' Heart Rate Lie: Why Your Ring Samples Your Pulse in Bursts, Not Streams

Smart rings claim 'continuous' heart rate monitoring. The physics of photoplethysmography and a 20 milliamp-hour battery make that impossible. Here is the duty cycle nobody talks about, and why Pulsyn shows the gaps instead of hiding them.

James Hoffmann

Jun 9, 2026 11 min read

A conceptual visualization of stress physiology showing the interconnected nervous system response that wearable devices attempt to measure

StressAlgorithmHrv

What Goes Into Pulsyn's Stress Score

Most wearables compute a stress score by running your heart rate through a black box. Pulsyn does the same thing, but the weights are public, the math is in the repository, and the app tells you exactly how confident it is. Here is the full breakdown.

James Hoffmann

Jun 4, 2026 13 min read

A close-up of a heart rate monitor sensor on a finger, showing the pulse reading in real time

AlgorithmsAccuracyHeart Rate

How Pulsyn Calculates Resting Heart Rate (and Why Your Current Number Is Probably Wrong)

Most wearables report resting heart rate as the lowest heart rate they can find, usually during sleep. The clinical definition is different. Pulsyn measures it during motionless awake periods, and the gap between the two definitions is often 10 to 15 beats per minute.

James Hoffmann

Jun 3, 2026 13 min read