Mechanisms for increasing stroke volume during static exercise with fixed heart rate in humans

Antonio C L Nóbrega, Jon W. Williamson, Jorge A. Garcia, Jere H. Mitchell

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Ten patients with preserved inotropic function having a dual-chamber (right atrium and right ventricle) pacemaker placed for complete heart block were studied. They performed static one-legged knee extension at 20% of their maximal voluntary contraction for 5 min during three conditions: 1) atrioventricular sensing and pacing mode [normal increase in heart rate (HR; DDD)], 2) HR fixed at the resting value (DOO-Rest; 73 ± 3 beats/min), and 3) HR fixed at peak exercise rate (DOO-Ex; 107 ± 4 beats/min). During control exercise (DDD mode), mean arterial pressure (MAP) increased by 25 mmHg with no change in stroke volume (SV) or systemic vascular resistance. During DOO- Rest and DOO-Ex, MAP increased (+25 and +29 mmHg, respectively) because of a SV-dependent increase in cardiac output (+1.3 and +1.8 l/min, respectively). The increase in SV during DOO-Rest utilized a combination of increased contractility and the Frank-Starling mechanism (end-diastolic volume 118-136 ml). However, during DOOEx, a greater left ventricular contractility (end- systolic volume 55-38 ml) mediated the increase in SV.

Original languageEnglish (US)
Pages (from-to)712-717
Number of pages6
JournalJournal of applied physiology
Issue number3
StatePublished - Sep 1997


  • Echocardiography
  • Frank-Starling mechanism
  • Left ventricular volume
  • Myocardial contractility
  • Pacemaker

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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