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Insights on health technology, privacy-first design, and the science behind smarter wearables.

LATEST ARTICLES

Close up of tattoo ink on skin, the very layer where PPG optical sensors struggle to read blood flow

Why Tattoos Break Your Smart Ring's PPG Sensor

Tattoo ink sits right where your smart ring's PPG light needs to go. The physics of why Oura, Whoop, and every other wearable struggles with inked skin, and what it means for the next generation of optical sensors.

James Hoffmann

Jun 19, 2026 1 min read

An assortment of prescription medication pills scattered across a surface, representing the medications that alter biometric signals measured by smart rings

BiometricsWearable AccuracyMedication

The Medications That Break Your Smart Ring's Algorithms

Beta-blockers suppress HRV by 30 to 50 percent. SSRIs alter sleep architecture. Antihistamines fragment deep sleep. If you take medication and your smart ring gives you bad scores, the problem might not be your body.

James Hoffmann

Jun 19, 2026 1 min read

A woman in a tech workspace using a laptop, representing the underrepresentation of women in the datasets that train wearable algorithms

Wearable AccuracyAlgorithm BiasWomen Health

Your Smart Ring Was Trained on Men: The Gender Data Gap in Wearable Algorithms

Most wearable algorithms are trained on datasets that are 70 to 80 percent male. Heart rate thresholds, sleep stage classifiers, and stress baselines are systematically less accurate for women. Here is why, and what Pulsyn is doing about it.

James Hoffmann

Jun 18, 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 glass of wine and alcoholic drinks on a bar table, representing the common context of drinking before sleep

PpgAccuracyHrv

What Your Smart Ring Misses After a Night of Drinking: Alcohol and the Anatomy of a Broken Biometric

Alcohol breaks your wearable's data in three compounding ways. HRV goes up (which looks like recovery but is the opposite), deep sleep increases from delta wave activity (low quality), and PPG signal quality degrades from dehydration. Your readiness score may look fine while your body is metabolizing a toxin.

James Hoffmann

Jun 17, 2026 1 min read

A stack of insurance paperwork and documents on a desk, representing the fine print in wearable data sharing agreements

PrivacyData OwnershipConsumer Rights

Your Health Insurance Company Wants Your Wearable Data. Here Is What That Actually Means.

John Hancock, UnitedHealthcare, and Aetna all offer premium discounts for sharing wearable data. The fine print lets them use that same data to raise your rates. Here is how the system works and what you can do about it.

James Hoffmann

Jun 16, 2026 1 min read

A person holding a phone with a health dashboard visible, looking stressed rather than informed

Quantified SelfHealth AnxietyDigital Orthorexia

When Your Health Tracker Makes You Anxious: The Rise of Health Tracking Anxiety

A growing body of research shows that wearables and wellness apps can increase stress and trigger obsessive behaviors. Here is what health tracking anxiety looks like, why the industry does not talk about it, and what Pulsyn does differently.

James Hoffmann

Jun 16, 2026 1 min read

Frost-covered hands in cold weather. The same vasoconstriction that makes your fingers cold also breaks your smart ring optical sensor.

PpgAccuracySpo2

Why Your Smart Ring Fails in Cold Weather: The Vasoconstriction Problem Nobody Mentions

Your smart ring's PPG sensor stops working properly when your fingers get cold. Vasoconstriction reduces blood flow to your extremities, and the data quality drops by 50 percent or more. I spent a winter measuring exactly how much, and the numbers are worse than the industry admits.

James Hoffmann

Jun 15, 2026 1 min read