What is a dangerous heart rate?

According to the Mayo Clinic, a normal resting heart rate for an adult is usually between 60 and 100 beats per minute; therefore, a rate exceeding 100 while at rest could provide cause for concern. A lower range implies that the heart is more efficient at pumping blood.

Furthermore, WebMD explains that athletic training can lower an individual's resting heart rate by 10 to 20 beats per minute. Monitoring heart rate is important if one has heart disease and wishes to engage in exercise. Maximum heart rate, despite any amount of physical training, lowers with age by about seven beats per minute every decade.