Some factors that affect the pulse rate of a person include body size, medication, body position and air temperature. The normal heart rate varies from one person to another, as stated by the American Heart Association.
When the temperature increases, the heart tends to pump more blood thus making the pulse increase. Body positions, such as standing, may also make the pulse rate increase. The body size of a person does not alter his or her heart rate, but people with obesity may have a higher resting pulse. Beta blockers tend to reduce the heart pulse while thyroid medication increases the pulse of a person.