1. Increase in heart rate: Generally the resting heart rate of an adult remains at 72 beats per minute. The elite endurance athletes usually have 28 to 40 beats per minute. Even before the beginning of exercise the heart rate increases in anticipation. It is known as anticipatory response. When an individual starts exercise his heart rate increases as per the internsity and duration of the exercise.
2. Increase in stroke volume: Stroke volume is the amount of blood ejected per beat from the left ventricle. It is measured in ml/beat. Stroke volume increases proportionally with exercise intensity. In untrained individuals the stroke volume at rest remains at 50 to 70 ml/beat. It increases up to 110 to 130 ml/beat during intense exercise. The stroke volume of experienced athletes at rest remains at 90 to 110 ml/beat. It increases up to 15 to 22 ml/beat during intense exercise.
3. Increase in cardiac output: Cardiac output is the amount of blood pumped by the heart in one minute. It is measured in litre/minute. Cardiac output is a product of stroke volume and heart rate. If either heart rate or stroke volume increases or both, the cardiac output increases also.
