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Wrist temperature during sleep: what Apple Watch is actually tracking
Apple Watch reports a nightly wrist-temperature deviation from your own baseline, not your body temperature. What that signal reflects — cycle, sleep, feeling unwell — and what it doesn't.
HRV explained: what heart rate variability is and why it matters
What heart rate variability actually measures, what makes it rise and fall, how accurately a wearable like Apple Watch estimates it, and why your own trend matters more than any single number.