≈Heart Rate Variability

Consistency beats device accuracy. Measure at the same time each day (first thing in the morning, before caffeine, after emptying your bladder) in the same posture, for the same length, breathing naturally. Avoid readings right after exercise, alcohol or a rough night if you want a clean baseline. A chest strap gives the truest beat-to-beat data, then rings, then wrist optical sensors, which struggle with motion. And never judge a single morning: HRV is noisy day to day, so read the 7–14 day trend instead.