During exercise, your heart naturally beats faster to supply more oxygen-rich blood to your muscles. The more intensely you exercise, the faster your heart rate, as well as your respiration. You can monitor your heart rate to determine, assess and, if you wish, modify the intensity of your exercise.
A number of factors can affect heart rate when you exercise. For example, fitness influences heart rate at rest, as well as during exercise. People who are more fit typically have a lower resting heart rate. Their hearts are larger, stronger and pump more blood with each beat. At the same exercise intensity, their heart rates do not increase as much as those of people who are less fit.
Gender and Age
Women have smaller hearts that pump less blood, but their muscles are also smaller. Although their hearts tend to beat faster during exercise, it is unclear whether maximum heart rate (MHR), or how fast their hearts are capable of beating, is higher among women or men. Although age does not seem to change resting heart rate, it does affect MHR. Beginning at the age of 20, MHR falls by about one beat every year. Athletes whose hearts can beat faster tend to be fitter than people of the same age whose MHR is lower.
Warmer temperatures increase your heart rate. In addition to pumping more blood to the muscles, your heart also transports more blood to the skin in order to cool it. Increased demand causes your heart to beat faster -- anywhere from 20 to 40 beats per minute higher than normal. Hot weather also makes you sweat, decreasing your blood volume. Fluid intake must be increased to compensate for the loss in order to avoid cardiac problems like an abnormally high heart rate.
Other factors that can raise your heart rate during exercise as well as rest include body temperature, various medications, illness and higher altitude. Regular training strengthens your heart and can reduce resting heart rate by 20 to 30 beats per minute. Many athletes use heart rate monitors to track their progress as they train; they can then adjust their workouts to achieve target heart rates. You don't have to be a professional to benefit from this approach.