Mechanism of overshoot in cardiac function during recovery from submaximalexercise in man

Background: A sudden increase (overshoot) in the left ventricular ejection fraction during the recovery from maximal exercise has been reported in pat ients with coronary artery disease, but its mechanism has not been fully cl arified. We investigated whether this phenomenon may occur in normal subjec ts, and whether it depends on the intensity of exercise. Methods: Thirteen normal subjects (mean [+/- SD] age, 59 +/- 8 years old) p erformed two levels (25 W and 50 W) of mild-intensity, constant-work-rate e xercise for 6 min on a cycle ergometer, Left ventricular function was monit ored continuously during the recovery from exercise using a computerized ca dmium telluride detector. Results: An overshoot was observed in the ejection fraction during the firs t minute of recovery compared with the end-exercise value. The overshoot in the ejection fraction during recovery after the 50-W exercise was gl eater than that seen after the 25-W exercise, An overshoot phenomenon in stroke volume was also observed during the recovery from 50-W exercise. Conclusions: The overshoot in cardiac function observed during the early ph ase of recovery, which was caused mainly by an immediate decrease in end-sy stolic volume, occurred even after exercise of mild intensity. This phenome non appears to suggest the existence of a transient mismatch between cardia c contractility and afterload reduction during the recovery from mild-inten sity exercise, even in normal subjects.