Changes of central haemodynamic parameters during mental stress and acute bouts of static and dynamic exercise

Abstract

Chronic dynamic (aerobic) exercise decreases central arterial stiffness, whereas chronic resistance exercise evokes the opposite effect. Nevertheless, there is little information available on the effects of acute bouts of exercise. Also, there is limited data showing an increase of central arterial stiffness during acute mental stress. This study aimed to determine the effect of acute mental and physical (static and dynamic exercise) stress on indices of central arterial stiffness. Fifteen young healthy volunteers were studied. The following paradigms were performed: (1) 2 min of mental arithmetic, (2) short bouts (20 s) of static handgrip at 20 and 70% of maximal voluntary contraction (MVC), (3) fatiguing handgrip at 40% MVC and (4) incremental dynamic knee extensor exercise. Central aortic waveforms were assessed using SphygmoCor software. As compared to baseline, pulse wave transit time decreased significantly for all four interventions indicating that central arterial stiffness increased. During fatiguing handgrip there was a fall in the ratio of peripheral to central pulse pressure from 1.69 ± 0.02 at baseline to 1.56±0.05 (Po0.05). In the knee extensor protocol a nonsignificant trend for the opposite effect was noted. The augmentation index increased significantly during the arithmetic, short static and fatiguing handgrip protocols, whereas there was no change in the knee extensor protocol. We conclude that (1) during all types of acute stress tested in this study (including dynamic exercise) estimated central stiffness increased, (2) during static exercise the workload posed on the left ventricle (expressed as change in central pulse pressure) is relatively higher than that posed during dynamic exercise (given the same pulse pressure change in the periphery).

The impact of exercise on derived measures of central pressure and augmentation index obtained from the SphygmoCor device

“…The reasons for this are not entirely clear but are in line with some previous studies that have reported increases in AIx during forearm exercise (3,5,10), probably due to increased sympathetic activity. This contrasts with other studies of whole body exercise, which have typically reported decreased AIx during exercise (7,12,13).…”

Radial pulse transit time is an index of arterial stiffness

“…The studies described by Lydakis et al 10 and McEniery et al 18 have demonstrated the proof of the concept that PTT could be estimated from the measurement of a single aortic pulse wave. They showed that the inflection point could be identified by waveform analysis of the aortic pressure pulse.…”

“…PTT has also been estimated from the time of the inflection point in the aorta. 10 For aortic pressure pulses are estimated from radial tonometry pulses with the use of a generalized transfer function, 7,11,12 it raises the possibility that PTT could be derived directly from radial arterial pulses and provided equivalent information to aortic PTT. The study of Millasseau et al 13 suggested that similar information on the aortic pressure wave could be obtained directly from the radial pulse.…”

Location of a Reflection Site Is Elusive

“…10,11 The travel time has also been estimated from the time of the inflection point, ie, the start of pressure augmentation, in proximal aortic pressure. 8,[12][13][14] This time of return, derived from aortic or carotid pressure has been used to estimate aortic pulse wave velocity (PWV) 10,11,[13][14][15] as a measure of aortic stiffness. Assuming that the major refection site is located at the lower abdominal aorta, twice this length (2L) divided by the time of return of the reflected wave (⌬t), ie, 2L/⌬t, has been taken equal to aortic PWV.…”