💓 Heart Rate (PPG)
Your watch shines green or red lights into your skin to read blood flow.
Best accuracy when:
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Snug fit
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1 finger above wrist bone
-
Clean skin
🧠 HRV (Heart Rate Variability)
HRV is the time between heartbeats.
Higher HRV = better recovery and lower stress.
Used in:
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Garmin Body Battery
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Fitbit Readiness
-
Samsung Stress score
🫁 Oxygen Level (SpO₂)
Reads how much oxygen is in your blood.
Useful for:
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Sleeping trends
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High altitude
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Breathing awareness
Not for medical diagnosis.
⚡ ECG (Heart Rhythm)
Some watches can record a short ECG to check for irregular heartbeat (AFib).
You place your finger on the crown or buttons.
🆘 Fall & Incident Detection
If your watch detects a hard fall or crash, it can text emergency contacts with your GPS location.
🌡️ Temperature / Skin Sensors
Used for:
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Sleep depth
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Recovery
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Cycle tracking
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Stress trends