Stroke volume

Stroke volume is the quantity of blood ejected by the left ventricle per heartbeat — approximately 60–100 ml at rest in healthy adults and 150–200 ml or more in elite endurance athletes at peak exertion. With heart rate it determines cardiac output (cardiac output = stroke volume × heart rate), setting the physiological ceiling for VO2max. The primary amplifying mechanism is the Frank-Starling response: increased venous return stretches the ventricular wall during diastole, raises end-diastolic volume, and augments contractile force. Endurance training enhances this through left ventricular eccentric hypertrophy, expanded blood volume, accelerated diastolic filling, and reduced afterload. Gledhill et al. (1994) showed that competitive cyclists — unlike sedentary controls — increase stroke volume progressively to VO2max rather than plateauing early. Vella and Robergs (2005) synthesised four response patterns — plateau, plateau-with-drop, plateau-with-secondary-rise, and progressive increase — shaped by training status, blood volume, age, and sex. Age attenuates stroke volume through reduced diastolic compliance and slower early ventricular filling, contributing to the roughly 10% per-decade VO2max decline after approximately age 25 in sedentary individuals. Higher stroke volume at a given heart rate reflects a more efficient pump and directly supports aerobic capacity — one of the strongest independent predictors of all-cause mortality — making aerobic training and adequate hydration central strategies for cardiovascular healthspan.