The purpose of this study was to characterize LV diastolic filling and systolic performance during graded arm exercise and to examine the effects of LBPP or concomitant leg exercise as means to enhance LV preload, in aerobically-trained individuals. Subjects were 8 males with a mean age (±SEM) of 26.8 ±1.2 years. Peak exercise testing was first performed for both legs ( VO₂max=4.21 ±0.19 l/min) and arms (2.56±0.16 l/min). On a separate occasion, left ventricular (LV) filling and ejection parameters were acquired using non-imaging scintography using in-vivo RBC labeling with technetium 99^m first during leg exercise performed in succession for 2 minutes at increasing grades to peak effort. Graded arm exercise (at 30, 60, 80 and 100% VO₂peak) was performed during three randomly assigned conditions: control (no intervention), with concurrent leg cycling (at a constant 15% leg VO₂max) or with 60 mmHg of lower body positive pressure using an Anti G suit. Peak leg exercise LV ejection fraction was higher than arm exercise (60.9±1.7% vs. 55.9±2.7%, p<.05), as was peak LV end-diastolic volume (EDV) reported as % of resting value (110.3±4.4% vs. 97±3.7%, p<.05) and peak filling rate (EDV/s; 6.4±0.28 vs. 5.2±0.25%). Concomitant use of either low-intensity leg exercise or LBPP during arm exercise failed to significantly increase LV filling characteristics or ejection parameters. These observations suggest that perturbations in preload fail to overcome the inherent hemodynamic conditions present during arm exercise which attenuate LV performance.