How do modern estimates of heart output compare with William Harvey’s estimates?

William Harvey’s estimates of heart output were significantly lower than modern measurements, as he intentionally used conservative values to demonstrate that the body could not possibly produce or consume blood at the rate required by traditional theories.1

Harvey estimated that the heart pumped between 0.5 and 1 litre of blood per minute. In contrast, modern physiological measurements indicate that a healthy human adult at rest has a cardiac output averaging slightly more than 5 litres per minute. During periods of vigorous exercise, this output can increase significantly, reaching up to 25 litres per minute.12

While Harvey’s quantification was approximate and designed to support his hypothesis of blood circulation, his work successfully established that the volume of blood passing through the heart was far too great to be accounted for by the prevailing belief that blood was consumed by the body as quickly as it was produced.1