Centrifuge training increases presyncopal orthostatic tolerance in ambulatory men

Joyce M. Evans, Michael B. Stenger, Fritz B. Moore, Helmut Hinghofer-Szalkay, Andreas Rössler, Abhijit R. Patwardhan, David R. Brown, Michael G. Ziegler, Charles F. Knapp

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Introduction: Exposure to spaceflight or simulations of microgravity reduce human postflight orthostatic tolerance. Exercise training and volume loading can reduce associated losses of plasma volume and muscle strength, but are not successful in maintaining postflight orthostatic tolerance. A preliminary study (16) indicated that short bouts of artificial gravity (AG) training on a centrifuge could increase orthostatic tolerance in healthy, ambulatory volunteers. We tested the same AG protocol for its tolerance effect on 14 men who underwent a 3-wk exposure to Gz acceleration training on NASA-Ames' (Moffet Field, CA) human-powered centrifuge. Methods: Subjects trained supine (head near the center of rotation) and in pairs (one subject rode passively while the other provided power to operate the 1.9-m centrifuge). The acceleration profile consisted of 7 min at 1 Gz before alternating between 1 and 2.5 Gz at 2-min intervals for 28 min. Each subject's presyncopal orthostatic tolerance limit (to a combination of 70° head-up tilt and increasing lower body negative pressure) was determined before and after training. Results: There were no significant differences between training groups, but presyncopal orthostatic tolerance time was improved 17 ± 10% (p < 0.05) for the combined groups. Mechanisms associated with increased tolerance included: increased cardiac output (p < 0.04), stroke volume (p < 0.01) and low-frequency spectral power of arterial pressure (p < 0.006), and decreased arterial pressure (p < 0.05) and vascular resistance (p < 0.04). Artificial gravity training in this group of men appears to increase orthostatic tolerance through a combination of decreased vascular resistance and enhanced cardiac function.

Original languageEnglish
Pages (from-to)850-858
Number of pages9
JournalAviation Space and Environmental Medicine
Volume75
Issue number10
StatePublished - Oct 2004

Keywords

  • Acceleration
  • Baroreflex
  • Blood pressure
  • Cardiac output
  • Catecholamines
  • Heart rate
  • Plasma proteins
  • Plasma volume
  • Stroke volume
  • Vascular resistance
  • Vasovagal syncope

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

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