What causes an increase in pulse rate during exercise?

An increase in pulse rate during exercise is primarily caused by the demand for oxygen and energy delivery. When engaging in physical activity, the muscles require more oxygen to sustain higher levels of activity. This increased demand for oxygen necessitates that the heart pumps more blood per minute in order to supply the muscles with the necessary oxygen and nutrients they need for energy production.

As exercise intensity increases, the body’s metabolism accelerates, leading to an uptick in the production of carbon dioxide and other metabolic byproducts. The heart rate increases to facilitate the removal of these waste products while also ensuring a continuous supply of oxygen-rich blood to the tissues.

The other options do not correctly address the primary physiological response to exercise. For instance, while waste removal is important, it is not the direct cause of an increased pulse rate; rather, it is a consequence or secondary need linked to the heightened demand for oxygen. Additionally, a reduction in blood vessel size would generally lead to increased resistance and an increase in blood pressure, but not necessarily an increase in pulse rate. Lastly, an increased resting heart rate does not typically occur immediately during exercise; it is more of a long-term adaptation to consistent training rather than a direct response to temporary exercise activity.