Cardiac Output and Stroke Volume

Cardiac output is calculated by multiplying stroke volume by heart rate. Stroke volume is the amount of blood one ventricle discharges per heartbeat, while heart rate is the number of beats per minute. For example, a resting male with a stroke volume of 70 mL per beat and heart rate of 75 beats per minute has a cardiac output of 5.25 liters per minute.

Stroke volume is the amount of blood that one ventricle discharges per heartbeat. It is derived from the difference between the end-diastolic volume, which is the amount of blood in the ventricle at the end of filling, and the end-systolic volume, which is the amount remaining after contraction. This difference represents the actual volume of blood ejected with each heartbeat.

Exercise increases both stroke volume and heart rate, which enhances cardiac output and overall cardiovascular health. This increase in exercise and cardiac output allows the heart to pump more blood to meet the body's increased metabolic demands during physical activity.

Cardiac reserve is the difference between maximum cardiac output and resting cardiac output, representing the heart's capacity to handle increased demand. An average individual has a cardiac reserve of four to five times their resting cardiac output, while athletes may achieve seven to eight times. Individuals with severe heart disease may have minimal or no cardiac reserve.

Athletes typically possess a cardiac reserve of seven to eight times their resting cardiac output due to enhanced cardiovascular conditioning. In contrast, individuals with severe heart disease may exhibit little to no cardiac reserve, restricting their ability to perform even simple daily tasks and limiting their physiological adaptability.

The typical cardiac output for an average resting adult male is approximately 5.25 liters per minute. This is calculated from an average heart rate of 75 beats per minute multiplied by a stroke volume of 70 milliliters per beat, representing the volume of blood the ventricles eject into the aorta and pulmonary trunk each minute.