Although the hemodynamic responses to isotonic and isometric exercise are different, few data exist comparing the response of left ventricular (LV) diastolic filling dynamics with these two forms of exertion. Therefore we performed Doppler examination before and at the end of isotonic and isometric exercise in 20 normal volunteers to define the differential responses of LV filling to these two forms of exertion. Transmitral inflow velocity signals from the apical view and phonocardiography were recorded before and at the termination of treadmill exercise (TRD) to 11 METs and handgrip (HG) (50% maximal for 2 minutes). Mean blood pressure (mBP), heart rate (HR), early diastolic (E) and late atrial (A) inflow velocities, mean acceleration rate (ACC) of E wave, time velocity integral of inflow (Ti), and isovolumic relaxation time (IRT) from second heart sound to onset mitral inflow were measured. Absolute changes from baseline were significantly different for the two forms of exertion: TRD versus HG: BP = 11 ± 9 versus 36 ± 10 mm Hg, HR = 37 ± 16 versus 16 ± 9 beats/min, E = 11.6 ± 11.3 versus −7.0 ± 9.4 cm/sec, A = 29.9 ± 14.5 versus 14 ± 12 cm/sec, ACC = 164 ± 151 versus −56 ± 135 cm/sec², Ti = 1.9 ± 3.0 versus −1.7 ± 1.7 cm, and IRT = −12 ± 9 versus 9 ± 10 msec, all p < 0.0001 except for A, p < 0.001). Isotonic treadmill exercise resulted in enhanced early diastolic filling manifested by increases in E and ACC and a decreased in IRT. Conversely, isometric handgrip exercise produced evidence of reduced early filling including decreased E and ACC and slightly increased IRT. Thus the response of LV filling dynamics recorded by Doppler differs for isotonic and isometric exertion and likely reflects the variable pressure and flow alterations induced by these two forms of exertion.