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 ...

As your exercise session becomes more intense and more work is done, your heart beats faster and faster. This relationship means you can use heart rate as a surrogate measure for the intensity of ...

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A marathon pushes the human body close to its limits. Legs tire, lungs burn and the heart works hard for hours on end. For years, that strain has raised an uncomfortable question: does running 26 ...