From G tolerance to physiological state monitoring: mechanisms and adaptive protection.

G-induced loss of consciousness (G-LOC) remains a challenge in high-performance aviation because it can rapidly impair pilot functional capacity and compromise aircraft control. Traditional approaches have largely treated G-LOC as a physiological tolerance or threshold problem, emphasizing maximum +Gz tolerance, centrifuge-based assessment, and post hoc identification of loss of consciousness. However, operational G-LOC risk is more dynamic and depends on the interaction among +Gz magnitude, rate of onset, exposure duration, individual physiological reserve, and anti-G straining maneuver effectiveness. This review reframes G-LOC as a time-dependent physiological decompensation process rather than a discrete terminal endpoint. We synthesize evidence on the progression from compensated cardiovascular regulation to potential loss of consciousness, with particular attention to early functional degradation, including visual, cognitive, behavioral, and performance-related changes. We further discuss how mechanism-informed physiological monitoring may support adaptive protection strategies. This framework shifts G-LOC research from static tolerance assessment toward dynamic physiological state monitoring and individualized protection in high-performance aviation.