What happens to cardiac output (Q) during exercise?

During exercise, cardiac output (Q) increases to meet the heightened demands of the body's tissues for oxygen and nutrients. During physical activity, the muscles require significantly more blood to sustain their function; thus, the heart responds by pumping more blood per minute. This increase in cardiac output is primarily achieved through two mechanisms: an increase in heart rate and an increase in stroke volume (the amount of blood ejected with each heartbeat).

As exercise intensity rises, the heart rate can increase dramatically, often reaching levels that are several times higher than resting rates. Simultaneously, the stroke volume also increases due to enhanced venous return and the stronger contractions of the heart muscle. The combination of these physiological changes results in a substantial increase in overall cardiac output, ensuring that the active muscles receive adequate oxygen and nutrients to perform efficiently.

In summary, the increase in cardiac output during exercise is essential for meeting the metabolic demands placed on the body during physical activity, which is why this response is critical for exercise performance and overall health.