Posts tagged: How It Works

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A fitness tracker dashboard showing multiple rings and metrics. The interface design that turns physiological complexity into a single digestible number, and the psychological cost of that simplification

Wearables · How It Works · Recovery

Recovery, Readiness, and Strain: Why Your Wearable Gives You Three Scores for the Same Inputs

Oura calls it Readiness. Whoop calls it Recovery. Garmin calls it Body Battery. They all pull from the same three inputs. The names are different because the marketing departments are different. The math is nearly identical because the sensors are identical.

James Hoffmann

Jun 11, 2026 16 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

Wearables · How It Works · Hrv

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 blood pressure monitor cuff on a desk, the exact device smart rings would need to replace to measure blood pressure accurately

Wearables · How It Works · Hrv

Why Smart Rings Can't Measure Blood Pressure Yet

Blood pressure is a force measurement, not a volume measurement. A PPG sensor in a smart ring tracks blood volume, not pressure. Here is why that gap cannot be closed with machine learning alone, and why Pulsyn will not ship a blood pressure estimate until the physics actually works.

James Hoffmann

Jun 9, 2026 14 min read

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

Stress · On Device Ai · How It Works

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 neon-lit circuit board representing the internal hardware of wearable devices that users are reverse engineering to reclaim their health data

Wearables · How It Works

Why People Are Cracking Their Oura Rings

A Reddit post called Cracked Oura hit 769 upvotes by showing how to bypass Oura's mandatory subscription using raw BLE data. The thread turned into a product support forum for a product Oura refused to build.

James Hoffmann

Jun 2, 2026 14 min read