The time course of muscle sympathetic and cardiovascular responses to physical and mental stressors in males and females

  • Khadigeh El Sayed

Western Sydney University thesis: Doctoral thesis

Abstract

Elevated blood pressure (BP) responses to stressors in young people have been associated with greater risk of hypertension later in life. The aim of this project was to determine what drives BP responses to stress in healthy young males and females. The time course of muscle sympathetic nerve activity (MSNA), BP and heart rate (HR) responses to mental stressors (Stroop colour-word test and mental arithmetic) and physical stressors (cold pressor test (CPT), static handgrip exercise, and post-exercise ischemia) were recorded in 21 healthy young males and in 19 healthy young females. Individuals who experienced a rise in MSNA during stress were classified as positive responders, and those who experienced a fall in MSNA during stress were classified as negative responders. In Study 1 it was hypothesised that negative responders to mental stress experience a more rapid rise in BP at the onset of the task than positive responders. It was also hypothesised that parallel increases in BP and MSNA occur during physical stressors and these are consistent between participants. The results indicate that that negative responders to mental stress exhibit a more rapid rise in diastolic pressure at the onset of the stressor (1.3 ± 0.5 mmHg/s), suggesting a baroreflex-mediated suppression of MSNA. In positive responders there is a more sluggish rise in BP during mental stress (0.4 ± 0.1 mmHg/s), which appears to be MSNA-driven. The physical stressors elicited large and consistent increases in BP and MSNA amongst participants. In Study 2, the effects of sex on the early BP response to stress were examined in both positive and negative responders. The peak changes, time of peak, and rate of changes in BP were compared between males and females and between positive and negative responders. Consistent with the findings in the males, the female negative responders experienced a greater rate of rise in diastolic BP (1.1 ± 0.6 mmHg/s) compared to the positive responders (0.2 ± 0.1 mmHg/s). Cardiovascular and sympathetic responses to stressors were generally consistent between males and females. However, changes in total MSNA during mental arithmetic were greater in males and changes in HR during handgrip were also greater in males (P
Date of Award2016
Original languageEnglish

Keywords

  • stress (psychology)
  • blood pressure
  • hypertension
  • young women
  • young men

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