DOES CARDIAC FATIGUE CAUSE A DECREASE IN ARTERIAL-PRESSURE DURING LONG-TERM AEROBIC EXERCISE

Aim of the study: The aim of the study was to investigate whether a de crease in arterial pressure during long-term aerobic exercise is cause d by a fall in cardiac pump function possibly indicating cardiac fatig ue, Patients and method: We studied 13 healthy untrained normotensive volunteers (aged 28 +/- 4 years) during 60 minutes of aerobic ergometr ic exercise, Arterial pressure was measured before, during and after e xercise, Cardiac dimension and function were assessed echocardiographi cally at rest before exercise, and after the 5th and 60th minute of ex ercise at similar heart rates, Results: After an initial increase, art erial pressure decreased continuously from 173 +/- 17/79 +/- 9 (5th mi n) to 143 +/- 13/70 +/- 7 mmHg (60th min) (p < 0.001) despite an incre ase in total peripheral resistance, After 5 minutes of exercise indice s of cardiac pump function (cardiac output, fractional fiber shortenin g, mean velocity of circumferential fiber shortening, contractility in dex) significantly increased, When compared with the values at minute 5, there was a decrease in cardiac output, fractional fiber shortening , mean velocity of circumferential fiber shortening and contractility index after 60 minutes of exercise, Conclusion: We conclude that the g radual decrease in arterial pressure seen with prolonged aerobic exerc ise is the result of a fall in cardiac pump function possibly reflecti ng cardiac fatigue.