Stroke volume is the amount of blood pumped by the heart's left ventricle with each heartbeat. It is an important measure of heart function and is influenced by factors such as heart size, contractility, and the volume of blood returning to the heart. A higher stroke volume typically indicates a more efficient heart, as it can deliver more oxygen-rich blood to the body with each contraction. Conversely, a lower stroke volume may suggest heart problems or reduced physical fitness, making it crucial for assessing cardiovascular health and performance during exercise.