Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

The aim of this investigation was to determine the acute effects of isometric fatiguing handgrip (IFHG) and lower body negative pressure (LBNP) on indices of central arterial stiffness. Thirteen subjects were studied. Renal blood velocity (Duplex Ultrasound) and blood pressure (Finapres) were monitored during IFHG and LBNP at -30 and -50 mmHg. Radial pulse-wave forms were recorded by applanation tonometry. Central aortic waveforms and other hemodynamic parameters were assessed using the Sphygmocor software. Renal vascular resistance index (RVRI; mean BP/renal blood velocity) was used as index of sympathetic nervous system (SNS) engagement. RVRI increased during both IFHG and LBNP indicating that SNS was engaged; however, BP increased only during the IFHG. Pulse-wave analysis showed that during the IFHG protocol the transit time of the pulse wave decreased and the peripheral pulse pressure/ nonaugmented central pulse pressure ratio increased from baseline. Both of these measurements suggest an increase in central large artery stiffness. During LBNP no changes in the indices of central stiffness were noted, in spite of a similar level of sympathetic system engagement. Heart rate increased during both protocols, whereas augmentation index increased during the IFHG protocol and decreased during the LBNP. Our major conclusion was that blood pressure rather than sympathetic activity seems to play the major role in modulating the elastic properties of the central arteries. The decrease in augmentation index during the LBNP protocol can be attributed to the increased heart rate, given that there is a negative correlation between these two parameters.