Blood pressure, haemodynamic, ventilatory and metabolic changes on isometric exercise during dynamic effort in healthy subjects

The object of this study was to study the blood pressure, haemodynamic, ven tilatory and metabolic changes on isometric exercise during a dynamic effor t in healthy subjects. Twelve healthy subjects underwent isometric exercise by manual prehension a t 40% maximal capacity under these conditions: isolated (A), five minutes a fter the onset of rectangular dynamic exercise on a cycle at 60% of ventila tory threshold (B) and at the fourth minute of the recovery phase of dynami c exercise (C). The blood pressure, heart rate, stroke volume and cardiac i ndex measured by Doppler echocardiography, systemic arterial resistances, r espiratory flow and respiratory rate, were measured before and after each i sometric exercise. The results showed blood pressure and heart rate to increase in a similar m anner during isometric exercise under all conditions. The cardiac index inc reased 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 respira tory rate was only increased under conditions B. The authors conclude that, in healthy subjects, the increase in blood press ure during isometric and dynamic exercise is the result of an increase in s ystemic resistances whereas, during isometric exercise, it is flow-dependan t.