[Study of blood pressure, hemodynamic, ventilatory and metabolic responses to isometric exercise performed during dynamic exercise in health subjects]

The object of this study was to study the blood pressure, haemodynamic, ventilatory and metabolic changes on isometric exercise during a dynamic effort in healthy subjects. Twelve healthy subjects underwent isometric exercise by manual prehension at 40% maximal capacity under these conditions: isolated (A), five minutes after the onset of rectangular dynamic exercise on a cycle at 60% of ventilatory threshold (B) and at the fourth minute of the recovery phase of dynamic exercise (C). The blood pressure, heart rate, stroke volume and cardiac index measured by Doppler echocardiography, systemic arterial resistances, respiratory flow and respiratory rate, were measured before and after each isometric exercise. The results showed blood pressure and heart rate to increase in a similar manner during isometric exercise under all conditions. The cardiac index increased by 29.5% +/- 8.3% (p < 0.01) under condition A and by 38.1% +/- 10% (p < 0.01) under conditions C but did not change significantly under conditions B. On the other hand, the systemic arterial resistances increased by 15.5% +/- 6.5% (p < 0.05) under conditions B, decreased by 8.8% +/- 3.9% (p < 0.05) under conditions C but did not change significantly under conditions A. The respiratory flow increased under all three conditions although the respiratory rate was only increased under conditions B. The authors conclude that, in healthy subjects, the increase in blood pressure during isometric and dynamic exercise is the result of an increase in systemic resistances whereas, during isometric exercise, it is flow-dependant.