Studies of the cardiovascular response to exercise in older subjects have presented conflicting data regarding left ventricular function, the cardiac output – oxygen consumption [Formula: see text] relationship, and the pattern of change in [Formula: see text], stroke volume (SV), and arteriovenous O2 difference. We have examined the cardiovascular response to submaximal and strenuous exercise in 96 men of mean age 63 years during an incremental treadmill test with [Formula: see text] determined by CO2 rebreathing, and in 12 subjects studied during incremental supine exercise with left ventricular volumes evaluated by radionuclide angiocardiography. During treadmill exercise the [Formula: see text] was approximately 10% lower than reported for younger samples, with a lower intercept of the [Formula: see text] relationship. During near-maximal exercise [Formula: see text] was approximately 15 L∙min−1, with SV of 95 mL plateauing or showing a small decline in heavy work. Peak arteriovenous O2 difference (150+ mL∙L−1) approached values of the young. During the supine exercise SV increased from rest to exercise, with a consistent increase in ejection fraction (rest, 66%, to peak exercise, 76%). In contrast to a prior report, the end-diastolic volume was constant, with the increase of SV attributable to a reduced end-systolic volume. Also, in contrast to a number of reports in older subjects, our findings show only small losses in cardiovascular response, and in left ventricular performance during light through strenuous exercise.Key words: ejection fraction, stroke volume, arteriovenous oxygen difference, [Formula: see text]peak, age.
Evaluating cardiac physiology through echocardiography in bottlenose dolphins: using stroke volume and cardiac output to estimate systolic left ventricular function during rest and following exercise