Open AccessHuman cardiovascular adaptation to hypergravity
Author(s) -
Ola Eiken,
Michail E. Keramidas,
Håkan Sköldefors,
Roger Kölegård
Publication year - 2022
Publication title -
american journal of physiology. regulatory, integrative and comparative physiology/american journal of physiology. regulatory, integrative, and comparative physiology
Language(s) - English
Resource type - Journals
eISSN - 1522-1490
pISSN - 0363-6119
DOI - 10.1152/ajpregu.00043.2022
Subject(s) - hypergravity , blood pressure , medicine , orthostatic vital signs , distension , cardiology , vascular resistance , hydrostatic pressure , heart rate , endocrinology , physics , thermodynamics
Despite decades of experience from high-G exposures in aircraft and centrifuges, information is scarce regarding primary cardiovascular adaptations to +Gz loads in relaxed humans. Thus, effects of G-training are typically evaluated after regimens that are confounded by concomitant use of anti-G straining maneuvers, anti-G suits and pressure breathing. Accordingly, the aim was to evaluate cardiovascular adaptations to repeated +Gz exposures in the relaxed state. Eleven men underwent 5 weeks of centrifuge G training, consisting of 15 × 40 min +Gz exposures at G levels close to their individual relaxed G-level tolerance. Before and after the training regimen, relaxed G-level tolerance was investigated during rapid (ROR) and gradual (GOR) onset-rate G exposures, and cardiovascular responses were investigated during orthostatic provocation and vascular pressure-distension tests. The G training resulted in: (i) a 13% increase in relaxed ROR G tolerance (P < 0.001), but no change in GOR G tolerance, (ii) increased pressure resistance in the arteries and arterioles of the legs (P < 0.001), but not the arms, (iii) a reduced initial drop in arterial pressure upon ROR high G, but no change in arterial pressure under basal resting conditions or during GOR G loading, or orthostatic provocation. The results suggest +Gz adaptation via enhanced pressure resistance in dependent arteries/arterioles. Presumably this reflects local adaptations to high transmural pressures, resulting from the +Gz-induced exaggeration of the intravascular hydrostatic pressure gradients.