Isometric exercise (IME) produces significant hemodynamic changes in the cardiovascular system. We have used IME to study the effect of age on diastolic left ventricular (LV) function in 100 normal volunteers. The E/A ratio (peak velocity of early/atrial filling phases), deceleration time (DT), and isovolumic relaxation time (IVRT) of the transmitral flow were assessed during echocardiography with pulsed-Doppler ultrasound at rest and at peak IME using handgrip. LV mass index (LVMI) and LV ejection fraction (LVEF) were also calculated. Both E/A and IVRT reduced significantly with increasing age. The LVEF decreased (P <.0001), whereas LVMI increased (P <.05) with advancing age. The LVEF was inversely related to LVMI (P <.05). An inverse relationship was noted between E/A and LVMI (P <.01) during IME. The contribution of the atrial contraction to the total diastolic flow increased significantly with advancing age (P <.02) and increased from 0.29 +/- 0.04 at rest to 0.34 +/- 0.08 during IME (P <.0001). It is concluded that with progressing age, the left ventricle becomes stiffer resulting in a reduction in early filling and a compensatory increase in flow due to atrial contraction. A progressive increase in LVMI, which accompanies aging may contribute to stiffening of the left ventricle and deterioration in diastolic function of the left ventricle. This is exaggerated by IME.