FOSTER, C., R. A. GAL, S. C. PORT, and D. H. SCHMIDT. Left ventricular ejection fraction during incremental and steady state exercise.Med. Sci. Sports Exerc., Vol. 27, No. 12, pp. 1602–1606, 1995. Despite extensive study of left ventricular (LV) function during incremental exercise (INC), there is little known about LV function during steady state exercise typical of that used during exercise training. In this study we evaluated LV ejection fraction (LVEF) during upright cycle ergometer exercise using first-pass radionuclide angiography (RNA). Healthy volunteers (N= 10) were studied during both INC and steady state. INC studies were performed at rest, at the ventilatory threshold (VT), and at maximal exercise. During steady state studies were performed after 10, 20, and 30 min of exercise at VT. During INC LVEF increased from rest (61% ± 5%) to exercise at the VT (73% ± 5%). There was no further change in LVEF at maximal exercise (73% ± 5%). During steady state, LVEF increased from rest (61% ± 5%), to exercise at VT (73% ± 5%), with further increases after 20 (78% ± 6%) and 30 (79% ± 3%) min of exercise. The results suggest that LVEF is nearly maximal during submaximal exercise at VT. During steady state LVEF continutes to increase with continuation of steady state exercise.