Apple creates a support page explaining how to use the heart rate monitor

Just a couple of days before the **Apple Watch** deliveries **kick off** , the company has decided divulge more details about the heart rate monitor embedded in the wearable. It has created a new support page detailing the heart rate reader that measures a person’s intensity during workouts. Besides the widely known features, the company also talks about the technologies that went into building the product and also some lesser known features. Firstly, it talks about how the wearable measures your heart rate. Going into details, the page explains photoplethysmography that is used by the sensors. The blood absorbs red and reflects green light. So, the Watch uses green LED lights paired with light‑sensitive photodiodes that detects the amount of blood flowing through the wrist every time. “When your heart beats, the blood flow in your wrist — and the green light absorption — is greater. Between beats, it’s less. By flashing its LED lights hundreds of times per second, Apple Watch can calculate the number of times the heart beats each minute — your heart rate,” the page explains There’s the feature called Heart Rate Glance that allows users to check the heart rate any time. The new support page reveals that the Apple Watch is capable of quietly measuring the heart rate every 10 minutes. This data is then stored in the iOS 8 Health app and can be viewed later and integrated with third-party apps. In order to get the best results, the Watch must not be loosely worn. “Your Apple Watch should be snug but comfortable,” the page reads. It further mentions several factors that could affect the performance of the heart rate sensor. For instance, skin perfusion, which means how much blood flows through your skin. “If you’re exercising in the cold, for example, the skin perfusion in your wrist may be too low for the heart rate sensor to get a reading. Motion is another factor. Rhythmic movements, such as running or cycling, give better results compared to irregular movements, like tennis or boxing,” the page further explains.