Carotid baroreflex function during prolonged exercise

K. H. Norton, K. M. Gallagher, S. A. Smith, R. G. Querry, R. M. Welch-O'Connor, P. B. Raven

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The present investigation was designed to uncouple the hemodynamic physiological effects of thermoregulation from the effects of a progressively increasing central command activation during prolonged exercise. Subjects performed two 1-h bouts of leg cycling exercise with 1) no intervention and 2) continuous infusion of a dextran solution to maintain central venous pressure constant at the 10-min pressure. Volume infusion resulted in a significant reduction in the decrement in mean arterial pressure seen in the control exercise bout (6.7 ± 1.8 vs. 11.6 ± 1.3 mmHg, respectively). However, indexes of central command such as heart rate and ratings of perceived exertion rose to a similar extent during both exercise conditions. In addition, the carotid-cardiac baroreflex stimulus-response relationship, as measured by using the neck pressure-neck suction technique, was reset from rest to 10 min of exercise and was further reset from 10 to 50 min of exercise in both exercise conditions, with the operating point being shifted toward the reflex threshold. We conclude that the progressive resetting of the carotid baroreflex and the shift of the reflex operating point render the carotid-cardiac reflex ineffectual in counteracting the continued decrement in mean arterial pressure that occurs during the prolonged exercise.

Original languageEnglish (US)
Pages (from-to)339-347
Number of pages9
JournalJournal of applied physiology
Volume87
Issue number1
DOIs
StatePublished - Jul 1999

Keywords

  • Central command
  • Operating point
  • Saturation
  • Threshold

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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