Satellite SOS on Wearables: How Emergency Messaging Works Without Cell Service
Some watches can now reach emergency help by satellite when there is no cell signal. Here is how it works and its limits.
Features Explained
Crash Detection on Smartwatches: How It Works and When It Calls for Help
Some smartwatches can sense a severe car crash and call for help if you cannot. Here is what the sensors look for and what to set up.
Fall Detection Explained: How Smartwatches Know You’ve Taken a Hard Fall
Your watch can tell a hard fall from dropping onto the couch most of the time. Here is how the sensors and software decide, and where they still fall short.
Stress Tracking on Wearables: What the Numbers Are Really Measuring
Wearable stress scores track how your nervous system reacts, mostly through HRV. Here is what the numbers measure, what fools them and how to use them in daily life.
Readiness and Recovery Scores Explained: How Your Watch Decides You Need Rest
Readiness scores blend sleep, HRV, resting heart rate and recent training into one number. Here is how they are built and how to use them without letting them run your week.
VO2 Max Estimates on Smartwatches: How They Work and How Accurate They Are
Your watch estimates VO2 max from heart rate and pace during outdoor runs or walks. Here is how the number is made, how close it gets, and how to read the trend.
Skin Temperature Sensing on Wearables: What the Readings Mean
Your ring or watch does not show a thermometer reading. It compares each night to your own baseline. Here is what those small changes mean and what can affect them.
How Wearables Track Sleep Stages Without Wires or Electrodes
Your watch or ring cannot read brain waves, so it estimates light, deep and REM sleep from movement and heart signals. Here is how that works and how far to trust it.
HRV Explained: What Heart Rate Variability Tells You About Recovery
HRV measures tiny changes in the time between heartbeats, and it is one of the best recovery signals your wearable tracks. Here is how to read it.
Blood Oxygen (SpO2) Tracking Explained: How Wearables Measure It
Wearables estimate blood oxygen with red and infrared light. Here is how SpO2 tracking works, what typical readings look like and why it is not a medical device.