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Module outside of its headband.

Valentina Palladino

If you want to get a fitness tracker, you have to decide is if you want one that's compatible with a heart-rate monitor. Learning your heart-rate patterns, both during a workout and during daily activity, can show you a lot about your health. According to Harvard's Health blog, your resting heart rate is a key factor to determining your overall current and future health, and monitoring heart-rate changes over time can give you more of the information you need to lead a healthy life.

Chest straps and optical heart-rate monitors are the two most common types of pulse trackers available for modern wearables, and they both use similar methods to measure your pulse. However, their key differences in methodology and design will dictate which device you choose when picking a workout companion.

Chest straps

Heart-rate monitoring chest straps are both loved and hated. Most of them are made of a long, belt-like elastic band that wraps snugly around your chest, a small electrode pad that sits against your skin, and a snap-on transmitter. These heart-rate monitors work differently than the ubiquitous wrist-bound monitors on new wearables because they use electrocardiography to record the electrical activity of your heart. This process requires electrodes, which live in the shiny, flat pad against the skin. That pad needs moisture water or sweat to pick up any electrical signal. When you're working out and sweating, the electrodes pick up the electrical signals given off by your heartbeat, and they send that information to the transmitter.

The transmitter is typically the only part of the chest strap that is detachable. Inside is a microprocessor that records and analyzes heart rate from those electrical signals, as well as a battery and the chips needed for Bluetooth connectivity. Using Bluetooth and a connected smartphone, the transmitter can consistently send heart-rate data to your mobile device, which acts as the receiver. Before people started using mobile apps as their sole receivers, heart-rate chest straps sent their information to old-school fitness watches that showed the data on their displays. With many chest straps, you now have the option to connect them to another wearable or simply use a compatible mobile app to record and save pulse data.

Optical monitors