Background: A sudden increase (overshoot) in the left
ventricular ejection fraction during the recovery from maximal exercise
has been reported in patients with coronary artery disease, but its
mechanism has not been fully clarified. We investigated whether this
phenomenon may occur in normal subjects, and whether it depends on the
intensity of exercise.
Methods: Thirteen normal
subjects (mean [± SD] age, 59 ± 8 years old) performed
two levels (25 W and 50 W) of mild-intensity, constant-work-rate
exercise for 6 min on a cycle ergometer. Left ventricular function was
monitored continuously during the recovery from exercise using a
computerized cadmium telluride detector.
overshoot was observed in the ejection fraction during the first minute
of recovery compared with the end-exercise value. The overshoot in the
ejection fraction during recovery after the 50-W exercise was greater
than that seen after the 25-W exercise. An overshoot phenomenon in
stroke volume was also observed during the recovery from 50-W
Conclusions: The overshoot in cardiac
function observed during the early phase of recovery, which was caused
mainly by an immediate decrease in end-systolic volume, occurred even
after exercise of mild intensity. This phenomenon appears to suggest
the existence of a transient mismatch between cardiac contractility and
afterload reduction during the recovery from mild-intensity exercise,
even in normal subjects.