Heart rate, a key measure of exercise intensity, is expressed in beats per minute. The abbreviation is bpm, meaning the number of heart contractions counted during 60 seconds. A heart rate of fl 150 bpm therefore means the heart is beating 150 times per minute.
Heart rate changes as the body’s demands change. During exercise, working muscles need more oxygen and produce more carbon dioxide, so the heart usually beats faster to increase blood flow. Stress, illness, medication, temperature, fitness, age, and hydration can also affect the reading.
Heart rate is related to pulse rate, but the two terms are not perfectly interchangeable in every situation. Heart rate is the heart’s actual beating frequency, while pulse is the pressure wave felt in an artery. In healthy people they are usually the same or very close. For adults, a commonly cited resting range is 60–100 beats per minute, although trained athletes may have substantially lower resting values. “Per second” or “per hour” would describe a different time scale, not the standard unit used in exercise science.