At Suunto we use advanced sensors and algorithms to generate metrics that we believe may help you in your activities and adventures. However, none of the data our products and services collect is perfectly reliable, nor are the metrics they generate absolutely precise. Heart rate readings may vary based on an individual's physiology, age, and other factors. Some people, because of their physiology, cannot get stable, accurate heart rate readings. Your level of activity may also adversely affect your heart rate reading. Calories, heart rate, location, movement detection, shot recognition, physical stress indicators and other measurements may not match the real world. Suunto products and services are intended for recreational use only and are not meant for medical purposes of any kind.