The authors examined by Doppler echocardiography 30 subjects aged 21-30 years, exposed during examination to an isometric load by using a manual balloon dynamometer. The authors investigated different indicators of left ventricular filling during diastole and their indexes which evaluate indirectly the left ventricular diastolic function. The assessed correlations of some indicators with the quantitative expression of the isometric load (double product) were as follows: peak speed E - r = 0.3671 (p < 0.05), peak speed A - r = 0.6098 (p < 0.001), index of rations of peak speeds E/A - r = 0.6098 (p < 0.0001, sum of speed--time integrals TVIE + TVIA - r = 0.6469 (p < 0.001) and the time of retardation of the early filling phase of the left ventricle related to the heart rate DCT/TF - r = 0.7249 (p < 0.001). A statistically significant increase during the load was recorded in the peak speed A and a reduction of the E/A ratio (p < 0.01). The time speed integral TVIE increased (p < 0.01), both indexes TVI E + A and TVI E/A declined (p < 0.05). The time of retardation of the early filling stage to the early filling time DCT/DFT increased (p < 0.05) and DCT in relation to the heart rate DCT/TF declined significantly (p < 0.01). There was an insignificant decline of the peak speed of early filling E and its time-speed integral, TVI E. The sum of time-speed integrals TVIE + A did not change significantly.(ABSTRACT TRUNCATED AT 250 WORDS)