Journal of Applied Physiology, Vol 57, Issue 6 1662-1667, Copyright © 1984 by American Physiological Society
Effect of central hypervolemia on cardiac performance during exercise
L. M. Sheldahl, L. S. Wann, P. S. Clifford, F. E. Tristani, L. G. Wolf and J. H. Kalbfleisch
To investigate the effect of different levels of central blood volume on
cardiac performance during exercise, M-mode echocardiography was utilized
to determine left ventricular size and performance during cycling exercise
in the upright posture (UP), supine posture (SP), and head-out water
immersion (WI). At submaximal work loads requiring a mean O2 consumption
(Vo2) of 1.2 1/min and 1.5 1/min, mean left ventricular end-diastolic and
end-systolic dimensions were significantly greater (P less than 0.05) with
WI than UP. In the SP during exercise, left ventricular dimensions were
intermediate between UP and WI. Heart rate did not differ significantly
among the three conditions at rest and at submaximal exercise up to a mean
Vo2 of 1.8 1/min. However, at a mean Vo2 of 2.4 1/min, heart rate in the UP
was significantly greater than WI (P less than 0.01) and the SP (P less
than 0.05). Maximal Vo2 did not differ statistically in the three
conditions. These data indicate that a change in central blood volume
results in alterations in left ventricular end-diastolic and end-systolic
dimensions during moderate levels of exercise and a change in heart rate at
heavy levels of exercise.
