Smart rings use overnight temperature to estimate your cycle phase, predict periods and flag a fertile window. We explain how the method works and its limits.
How a ring on your finger estimates light, deep and REM sleep, which sensors it uses, and how its accuracy compares with a proper sleep lab.
A readiness score condenses overnight heart rate, sleep and training signals into a single number. We explain what it really measures and how far to trust it.
SpO2 is the share of your blood carrying oxygen. We look at how accurately a smartwatch or smart ring measures it, and when to trust the reading.
Heart rate variability is the shifting gap between heartbeats. We explain what HRV measures, why wearables track it, and how to read your own numbers.