High sustained +Gz acceleration: physiological adaptation to high-G tolerance.
Since the early 1940s, a significant volume of research has been conducted in an effort to describe the impact of acute exposures to high-G acceleration on cardiovascular mechanisms responsible to maintaining cerebral perfusion and conscious in high performance aircraft pilots during aerial combat maneuvers. The value of understanding hemodynamic characteristics that underlie G-induced loss of consciousness has been instrumental in the evolution of optimal technology development (e.g., G-suits, positive pressure breathing, COMBAT EDGE, etc.) and pilot training (e.g., anti-G straining maneuvers). Although the emphasis of research has been placed on the development of protection against acute high +Gz acceleration effects, recent observations suggest that adaptation of cardiovascular mechanism associated with blood pressure regulation may contribute to a protective 'G-training' effect. Regular training at high G enhances G tolerance in humans, rats, guinea pigs, and dogs while prolonged layoff from exposure in high G profiles (G-layoff) can result in reduced G endurance. It seems probable that adaptations in physiological functions following chronically-repeated high G exposure (G training) or G-layoff could have significant impacts on performance during sustained high-G acceleration since protective technology such as G-suits and anit-G straining maneuvers are applied consistently during these periods of training. The purpose of this paper is to present a review of new data from three experiments that support the notion that repeated exposure on a regular basis to high sustained +Gz acceleration induces significant physiological adaptations which are associated with improved blood pressure regulation and subsequent protection of cerebral perfusion during orthostatic challenges.
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Physiology Research Section, Air Force Research Laboratory, Brooks Air Force Base, TX 78235, USA.
D000054:Acceleration; D000222:Adaptation, Physiological; D000337:Aerospace Medicine; D001359:Aviation / Q000193:education; D017704:Baroreflex / Q000502:physiology; D002346:Carotid Sinus / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D018471:Hypergravity; D007024:Hypotension, Orthostatic / Q000517:prevention & control*; D007318:Inservice Training; D008150:Lower Body Negative Pressure; D008297:Male