Female exposure to high G: Chronic adaptations of cardiovascular functions

Victor A. Convertino, Lloyd D. Tripp, David Ludwig, Juano Duff, Tamara L. Chelette

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Introduction: Exposure to microgravity is associated with increased leg venous compliance and reductions in cardiac output, baroreflex functions, and tolerance to orthostatism. However, the effects of chronic exposure to high- G environments are unknown. In addition, there is evidence that females have lower orthostatic tolerance than males, although the underlying mechanisms are unclear. Therefore, we tested the hypotheses that high-G training will enhance baroreflex and orthostatic functions and that females will demonstrate similar adaptations compared with males. Methods: Calf venous compliance, baroreflex function, and orthostatic performance were measured in six men and seven women before and after repeated exposures on the centrifuge (G-training) for 4 wk, 3 times/wk, with gradual levels of G starting with +3 Gz without G-suit protection during week I and advancing to +9 Gz with G- suit protection by the end of week 4. Calf venous compliance was measured by occlusion plethysmography using impedance rheographic recordings of volume change. Baroreflex function was assessed from beat-by-beat changes in heart rate (HR) and mean arterial pressure (MAP) that were measured before, during, and after a Valsalva maneuver strain at 30 mmHg expiratory pressure. The orthostatic performance of reflex responses was assessed from beat-by-beat changes in HR, MAP, stroke volume (SV), cardiac output (Q; by impedance plethysmography), and systemic peripheral resistance during the last 10 cardiac beats of a 4-min squat position and during the initial 10 cardiac beats in a standing position. Results: G-training increased calf compliance in both men and women. SV and Q were increased during the squat-to-stand test in the males, but not in the females, following G-training and provided protection against the development of acute hypotension in the men. Conclusions: G-training caused adaptations in orthostatic functions opposite to those observed following exposure to microgravity environments. However, adaptations to G-training were limited in females, a finding that may provide a physiological basis for their lower simulated combat tracking performance during simulated aerial combat maneuvers compared with males.

Original languageEnglish
Pages (from-to)875-882
Number of pages8
JournalAviation Space and Environmental Medicine
Volume69
Issue number9
StatePublished - Sep 1 1998
Externally publishedYes

Fingerprint

Baroreflex
Compliance
Impedance Plethysmography
Weightlessness
Plethysmography
Cardiac Output
Stroke Volume
Microgravity
Arterial Pressure
Heart Rate
Valsalva Maneuver
Posture
Vascular Resistance
Hypotension
Reflex
Centrifuges
Leg
Pressure
Antennas

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Pollution
  • Medicine(all)

Cite this

Convertino, V. A., Tripp, L. D., Ludwig, D., Duff, J., & Chelette, T. L. (1998). Female exposure to high G: Chronic adaptations of cardiovascular functions. Aviation Space and Environmental Medicine, 69(9), 875-882.

Female exposure to high G : Chronic adaptations of cardiovascular functions. / Convertino, Victor A.; Tripp, Lloyd D.; Ludwig, David; Duff, Juano; Chelette, Tamara L.

In: Aviation Space and Environmental Medicine, Vol. 69, No. 9, 01.09.1998, p. 875-882.

Research output: Contribution to journalArticle

Convertino, VA, Tripp, LD, Ludwig, D, Duff, J & Chelette, TL 1998, 'Female exposure to high G: Chronic adaptations of cardiovascular functions', Aviation Space and Environmental Medicine, vol. 69, no. 9, pp. 875-882.
Convertino VA, Tripp LD, Ludwig D, Duff J, Chelette TL. Female exposure to high G: Chronic adaptations of cardiovascular functions. Aviation Space and Environmental Medicine. 1998 Sep 1;69(9):875-882.
Convertino, Victor A. ; Tripp, Lloyd D. ; Ludwig, David ; Duff, Juano ; Chelette, Tamara L. / Female exposure to high G : Chronic adaptations of cardiovascular functions. In: Aviation Space and Environmental Medicine. 1998 ; Vol. 69, No. 9. pp. 875-882.
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