Why do cardio machines need two hands to monitor heart rate but smartwatches only need one wrist?

Question

Why do cardio machines need two hands to monitor heart rate but smartwatches only need one wrist?

In: 670

Answer 1

I know that smartwatches use light to capture the changes in light as blood runs under your skin as blood absorbs light differently and the veins pulse blood so you get a pulsing reflection, small but detectable. Watches are situated right on top of yoir wrist, an ideal location.

Cardio machines use metal electrodes to detect the minute electrical activity your heart generates. Electrodes need two points, like positive and negative, and your body completes the circuit, allowing the equipment to measure the pulse.