what position to promote blood return to the heart
During exercise, cardiac output can increase, as much as eight-fold in world-class endurance athletes. If exercise is performed in the upright position, returning blood to the heart at this rate is challenging because the pull of gravity provides opposition.
Return of systemic blood to the heart is impeded by the pressure inside the chest. The output of the heart is reduced and stroke volume falls. This occurs from 5 to about 14 seconds in the illustration. The fall in stroke volume reflexively causes blood vessels to constrict with some rise in pressure (15 to 20 seconds).