How does stroke volume (SV) change with increased workload during exercise?

In the context of exercise physiology, stroke volume refers to the amount of blood the heart pumps with each beat. As exercise intensity increases, stroke volume typically increases up to a certain point. Specifically, during moderate-intensity exercise, stroke volume increases effectively up to approximately 40% to 60% of an individual's VO2max, which represents the maximal volume of oxygen the body can utilize during intense exercise.

This increase in stroke volume occurs due to several factors, including enhanced venous return (more blood returning to the heart), increased contractility of the cardiac muscle, and improved myocardial efficiency. Within this range of exercise intensity, the heart is able to pump more blood with each beat, which is crucial for meeting the increased metabolic demands of the working muscles.

However, beyond this moderate-intensity range—as intensity approaches maximal levels—further increases in stroke volume may not occur. Instead, the increase in cardiac output during more intense exercise relies more on an increased heart rate rather than stroke volume. Thus, the correct understanding of stroke volume dynamics during increasing workloads reflects this pattern of increase leading up to a plateau near 40% to 60% of VO2max.