Some athletes use the more portable option of heart-monitoring chest straps. Like an EKG, they measure electrical activity in the heart using a single sensor that needs to be strapped as close to the heart as possible. Chest straps are generally worn during exercise and the information is generally used to achieve training goals rather than to warn of something wrong.
|Ideal resting HR||50-70 beats per minute (bpm)|
|Normal HR||60-100 bpm|
|Intense exercise HR||70-80% of your max; nearing the threshold of fatigue|
|Max HR||220 minus your age|
Wrist-worn trackers use a different type of sensor called a photoplethysmogram (PPG) that uses light to measure how much blood the heart is pumping under the surface of the skin instead of electrical activity. As the heart beats, blood flow increases and absorbs more light. Between beats, when there’s less blood, more light is reflected back to the sensor. This resulting measurement is your pulse.