[Cardiac effects of exhausting isometric muscular contraction in trained and endurance athletes]

The effect of exhausting isometric contraction (60% of the maximal voluntary contraction) on left ventricular function has been investigated using echocardiography (M and B mode) in 4 groups, each of 8 subjects (27 +/- 5 years; mean +/- SD): weight lifters, 2 years of training; amateur cyclists, 4 years of training; sedentary controls, and hypertensive subjects, 1st WHO class. Heart rate, arterial pressure, ventricular diameters (diastolic and systolic), wall thickness, wall stress and the double product (heart rate x arterial pressure) were determined at rest, at exhaustion and after 30, 90 and 180 s of recovery. Maximal voluntary contraction was 48 +/- 9 kg in weight lifters; 32 +/- 5 kg in amateur cyclists; 32 +/- 4 kg in sedentary control and 36 +/- 7 kg in 1st WHO class. Exhaustion time ranged from 80 s to 120 s. Our results showed that: 1) in all subjects at exhaustion, arterial pressure and heart rate increased significantly and the index of ventricular function was decreased but not significantly; 2) after 180 s of recovery both arterial pressure and heart rate returned to the pre-exercise value; 3) wall stress was significantly lower in weight lifters than in sedentary controls; 4) the double product (index of myocardiac oxygen consumption) resulted lower in amateur cyclists that in sedentary controls. The hypertrophy of the heart could justify the slight increase in wall stress observed in weight lifters during isometric exercise. However, the low index of myocardiac oxygen consumption in amateur cyclists probably reflects the changes in cardiovascular function due to the endurance training. In hypertensive subjects, the isometric contraction causes significant and substantial increase of the wall stress and the double product.