Aortic baroreflex control of heart rate during hypertensive stimuli: Effect of fitness

X. Shi, J. M. Andresen, J. T. Potts, B. H. Foresman, S. A. Stern, P. B. Raven

Research output: Contribution to journalArticle

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Abstract

We examined the aortic baroreflex control of heart rate (HR) in seven healthy young men of average fitness (AF) and seven of high fitness (HF). The fitness level was determined by maximal oxygen uptake (AF = 42.9 ± 1.1, HF = 62.3 ± 1.8 ml · kg-1 · min-1). Aortic baroreflex control of HR was determined during a steady-state increase of mean arterial pressure (MAP; AF, +15.0 ± 2.1 and HF, +18.3 ± 0.8 mmHg) with phenylephrine (PE) infusion combined with positive neck pressure (NP; AF, 18 ± 2.0 and HF, 20 ± 0.8 mmHg) to counteract the increased carotid sinus pressure and with low levels of lower body negative pressure to counteract the increased central venous pressure. There was no group difference in the increased MAP or NP, nor was there stage difference in MAP within either group during PE infusion. However, the isolated cardiac-aortic baroreflex gains (i.e., ΔHR/ΔMAP) were significantly less in the HF (0.16 ± 0.02 and 0.14 ± 0.03 beats · min-1 · mmHg-1) than in the AF (0.52 ± 0.08 and 0.59 ± 0.07 beats · min-1 · mmHg-1) subjects at PE + NP and PE + NP + lower body negative pressure. We concluded that during steady-state increases in MAP, the sensitivity of aortic baroreflex control of HR was significantly less in the HF than in the AF subjects.

Original languageEnglish
Pages (from-to)1555-1562
Number of pages8
JournalJournal of Applied Physiology
Volume74
Issue number4
DOIs
StatePublished - 1993

Keywords

  • baroreceptor resetting
  • exercise training
  • gain
  • phenylephrine
  • stroke volume

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