Everything you need to know about photoplethysmography (PPG), the technology behind heart rate measurements in fitness watches and smart rings. When you purchase through links on our site, we may earn ...

Heart rate variability (HRV) is the variation in the time between two consecutive heartbeats over a specific period. Doctors may use HRV as an indicator for certain aspects of a person’s health, ...

Anne R. Crecelius does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond ...