Posts tagged: Heart Health & HRV

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Thermal imaging of a human hand showing heat distribution. The kind of raw signal most smart rings average away

Sleep · On Device Ai · Wearables

What Skin Temperature Actually Tells You (And Why Most Rings Get It Wrong)

Skin temperature is a proxy for blood flow, circadian phase, and autonomic tone. Most smart rings average it into a single nightly number. We do not.

James Hoffmann

May 28, 2026 14 min read

A medical pulse oximeter clipped to a fingertip, using transmissive light technology that consumer smart rings cannot replicate

Research, Explained · Wearables · Hrv

Why Your Smart Ring SpO2 Reading Is Probably a Guess

Consumer wearables run reflective PPG on body parts never designed for it. The FDA has scrutinized these monitors since 2022 for systematic bias. Smart rings compound the problem with clamp pressure and unvalidated algorithms.

James Hoffmann

May 28, 2026 11 min read

An abstract visualization of the human nervous system and stress response, representing the complex physiology behind fabricated wearable stress scores

Stress · On Device Ai · Wearables

Why Stress Scores Are the Most Fabricated Metric in Wearables

Every major wearable gives you a stress score between 0 and 100. That number is not a measurement. It is a proprietary blend of heart rate variability and secret sauce with no clinical definition. Pulsyn shows you the raw HRV and the context instead.

James Hoffmann

May 26, 2026 13 min read

A medical electrocardiogram monitor showing heart rhythm data, representing the raw physiological signal behind HRV analysis

Research, Explained · Wearables · Recovery

What HRV Actually Measures and Why Your Recovery Score Is a Marketing Invention

HRV is not a score. It is a noisy physiological signal that consumer wearables clean, compress, and repackage as a recovery percentage with no medical validation. This post explains how the sausage is made, why the math does not support the marketing, and what Pulsyn does instead.

James Hoffmann

May 26, 2026 12 min read