Your heart is made up of muscles, when you exercise, your muscles demand more oxygen to perform the physical activity, which increases your heart rate.
The sympathetic nervous system is activated during exercise, which triggers an increase in heart rate to meet the increased oxygen demands of your muscles. [Source: National Library of Medicine]
Hormones such as adrenaline and noradrenaline are released during exercise, increases heart rate by stimulating the sympathetic nervous system.
During exercise, your blood flow increases to deliver oxygen and nutrients to your muscles, which results in an increased heart rate.
As you age, your heart rate response to exercise might change, and you might experience a variation in heart rate during physical activity.
Certain medical conditions or medications might affect your heart rate and result in increasing your heart rate during exercise.
The type and intensity of exercise also affect your heart rate. High-intensity activities, such as running or weightlifting, will result in a higher heart rate compared to low-intensity activities, such as yoga or stretching.