Physiological unloading of cardiopulmonary mechanoreceptors by posture changes does not influence the pressor response to isometric exercise in healthy humans

Ferdinando Iellamo, Jacopo Maria Legramante, Filippo Castrucci, Michele Massaro, Gianfranco Raimondi, Giuseppe Peruzzi, Giuseppe Tallarida

Research output: Contribution to journalArticle

Abstract

In recent studies in humans the role of cardiopulmonary baroreflexes in modulating the cardiovascular responses to isometric exercise (somatic pressor reflex) has been investigated by performing static hand-grip exercise during deactivation of cardiopulmonary receptors produced by low levels of lower body negative pressure; however, findings from these studies have not been consistent. The purpose of this study was to investigate whether a more physiological unloading stimulus of cardiopulmonary baroreceptors, obtained by sequentially changing posture, could influence the pressor response to somatic afferent stimulation induced by isometric, exercise. To accomplish this, ten healthy subjects performed a 2-min isometric handgrip (IHG) at 30% maximal voluntary contraction after 10 min of supine rest and, in rapid sequence, after 10 min of sitting and 10 min of standing, at the time when, owing to their transitory nature, the cardiovascular effects, due to arterial baroreceptor intervention should have been minimal. During IHG arterial pressure (BPa) was continuously and noninvasively measured to quantify accurately the blood pressure response to IHG both in magnitude and time course. Results showed that the pressor response to IHG was not significantly influenced by change in posture, either in magnitude or in time course. The mean arterial pressure increased by 17.4 (SEM 2.5), 18.6 (SEM 1.2) and 17.0 (SEM 1.3) mmHg in supine, sitting and standing [2.3 (SEM 0.3), 2.5 (SEM 0.2) and 2.3 (SEM 0.2) kPa] positions, respectively. Also the heart rate response to IHG was unaffected by change in posture. Most important, the sum of the separate BPa responses induced by supine IHG and by posture change from supine to sitting (summation of reflexes) was not significantly different from the pressor response observed during sitting IHG (interaction of reflexes). Likewise, the sum of the separate BPa. responses induced by sitting IHG and by changing postures from sitting to standing was not significantly different from the pressor response to standing IHG. These data indicate that, under physiological conditions, cardiopulmonary baroreflexes do not exert a significant role in modulating the reflex pressor drive from muscles during isometric exercise in healthy humans.

Original languageEnglish
Pages (from-to)381-387
Number of pages7
JournalEuropean Journal of Applied Physiology and Occupational Physiology
Volume66
Issue number5
DOIs
Publication statusPublished - Sep 1993

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Keywords

  • Exercise pressor reflex
  • Orthostatic stress
  • Reflex interactions
  • Somatic afferent stimulation
  • Vagal afferent stimulation

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Physiology

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