Factors influencing a person's heart rate include genetics, age, stress levels, medications, general health, exercise frequency and intensity, and a wide range of external conditions, including temperature, according to Howard LeWine, MD, and Harvard Health Publications chief medical editor. Heart rate even varies depending on the type of exercise a person is engaged in.
According to Polar, maker of heart rate monitors and other fitness devices, running tends to be the activity responsible for the highest heart rate. However, regardless of the type of activity a person is engaged in, heat and humidity generally increase pulse. This is largely due to the fact that heat and humidity limit a person's ability to sweat. Perspiration is the body's way of cooling itself. When body temperature climbs, the heart rate tends to climb as well.
Polar reports that those eating diets too low in carbohydrates sometimes experience elevated heart rates when exercising as the body requires some carbohydrates to burn fat for energy. Once the body runs low on carbohydrates, it is likely to run low on energy, thereby increasing the heart rate.
A 2013 study by the German Research Centre for Environmental Health indicates that noise from road traffic is capable of increasing a person's heart rate. Researchers participating in the study concluded that everyday outside noise is capable of influencing heart rate to a significant degree.