Heart beat rate means the number of heartbeats per unit time, usually expressed as beats per minute (bpm). The human heart pounds to pump oxygen rich blood to the muscles and carry cell waste products away from the tissues. Heartbeat rate can vary according to the demand of the muscles to absorb oxygen and excrete carbon dioxide changes such as during exercise or sleep. It also varies significantly between individuals based on age, fitness and genetics. This means that the heart must beat faster to deliver more oxygen rich blood. During exercise routines, the heartbeat rate gives a strong indication of how effective the exercise is to the body.