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

¹Department of Health, Nutrition, and Exercise Sciences, University of Delaware, Newark, Delaware; ²Department of Kinesiology, University of New Hampshire, Durham, New Hampshire; and ³Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts

Submitted 18 May 2007 ; accepted in final form 11 December 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 ± 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 ± 3.1 to 11.8 ± 3.4%; dynamic, 5.8 ± 3.0 to 13.3 ± 3.4%; P < 0.05) and further increased during PEI (static, 18.5 ± 3.1%; dynamic, 18.6 ± 2.9%; P < 0.05). Peripheral and central systolic and diastolic pressures increased (P < 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

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