Left ventricular volumes during graded upright exercise in healthy untrained subjects.

Left ventricular (LV) volume changes were studied by radionuclide cardiography at rest and during graded upright bicycle exercise in seven healthy untrained men aged 21-30 years. The exercise-induced changes in LV volumes were most pronounced during mild exercise: from rest to 25% submaximal exercise stroke volume increased by 26% and LV ejection fraction from 0.60 to 0.69 (both P less than 0.01), whereas further increments of the work load resulted in only small changes of these variables. LV end-diastolic volume increased initially by 10% (P less than 0.05) but returned to baseline values at higher work loads, whilst a rather constant decrease was recorded in LV end-systolic volume during increasing exercise loads. Changes in plasma catecholamine levels were most pronounced at the high work loads, indicating that these hormones are not directly contributing to the LV volume changes.