Wave reflection and central aortic pressure are increased in response to static and dynamic muscle contraction at comparable workloads

Abstract

Edwards DG, Mastin CR, Kenefick RW. Wave reflection and central aortic pressure are increased in response to static and dynamic muscle contraction at comparable workloads. J Appl Physiol 104: 439-445, 2008. First published December 13, 2007 doi:10.1152/japplphysiol.00541.2007.-We determined the effects of static and dynamic muscle contraction at equivalent workloads on central aortic pressure and wave reflection. At random, 14 healthy men and women (23 Ϯ 5 yr of age) performed a static handgrip forearm contraction [90 s at 30% of maximal voluntary contraction (MVC)], dynamic handgrip contractions (1 contraction/s for 180 s at 30% MVC), and a control trial. During static and dynamic trials, tension-time index was controlled by holding peak tension constant. Measurements of brachial artery blood pressure and the synthesis of a central aortic pressure waveform (by radial artery applanation tonometry and generalized transfer function) were conducted at baseline, during each trial, and during 1 min of postexercise ischemia (PEI). Aortic augmentation index (AI), an index of wave reflection, was calculated from the aortic pressure waveform. AI increased during both static and dynamic trials (static, 5.2 Ϯ 3.1 to 11.8 Ϯ 3.4%; dynamic, 5.8 Ϯ 3.0 to 13.3 Ϯ 3.4%; P Ͻ 0.05) and further increased during PEI (static, 18.5 Ϯ 3.1%; dynamic, 18.6 Ϯ 2.9%; P Ͻ 0.05). Peripheral and central systolic and diastolic pressures increased (P Ͻ 0.05) during both static and dynamic trials and remained elevated during PEI. AI and pressure responses did not differ between static and dynamic trials. Peripheral and central pressures increased similarly during static and dynamic contraction; however, the rise in central systolic pressure during both conditions was augmented by increased wave reflection. The present data suggest that wave reflection is an important determinant of the central blood pressure response during forearm muscle contractions. tension-time index; exercise pressor reflex; blood pressure THE PRESSOR RESPONSE to exercise had been thought to be greater as a result of static muscle contraction compared with dynamic muscle contraction; however, initial studies were not performed on the same muscle groups or at equivalent workloads (4, 42). When static and dynamic muscle contractions are performed at equivalent workloads by controlling for the tension-time index [TTI; a measure of muscular force produced over time (2, 35)] by equating peak tension and altering duration, the pressor response has been shown to be the same during static and dynamic contractions (11,35). Further, measurement of blood pressure during postexercise ischemia (PEI) indicated no difference in metaboreceptor activation of the pressor reflex between conditions (35). Thus it appears that the pressor response to static and dynamic muscle contraction is similar when muscle mass, peak tension, and TTI are held constant. However, to date, studies of the exercise pressor reflex have not assessed central blood pressure, which may provide important information as ...

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).…”

Wave reflection augments central systolic and pulse pressures during facial cooling

“…Given the statistical relationship between MAP and AI in the present study, we speculate that the primary mechanism of increased wave reflection during facial cooling is alteration in the amplitude and site of wave reflections as a result of sympathetic activation. Previous observations of increased wave reflection during handgrip exercise (12) or CPT (17) may be due to the same mechanism.…”

Acute effects of supramaximal exercise on carotid artery compliance and pulse pressure in young men and women

“…During both high-intensity dynamic (Sharman et al 2005;Studinger et al 2003) and static exercise (Edwards et al 2008;Lydakis et al 2008a, b;Reid and Conway 2006), there are increases in central artery stiffness. Following acute dynamic exercise, there is a reduction in central artery stiffness with lower intensity exercise (Heffernan et al 2007a) but no change in central artery stiffness with maximal dynamic exercise (Heffernan et al 2007b, c).…”