![]() ![]() baroreceptor reflex to take effect and, in turn, increases arterial pressure which increases G level tolerance. The gradual onset rate (GOR) run allows time for physiological reflexes, i.e. Human tolerance to +Gz acceleration can be assessed in a human centrifuge, both when relaxed and while straining. The body’s primary natural defense against the effects of G stress is cardiovascular baroreceptor reflexes and the neural tissue oxygen reserve, which determine the characteristic shape of the G-time tolerance curve. During exposure to +Gz stress, typically, an individual progresses through a series of visual symptoms, including peripheral light loss (PLL) and central light loss, before progressing to G-LOC. This results in a 22–25 mmHg difference in blood pressure between heart and brain for every 1 +Gz to which the body is exposed. This drop in blood pressure is due to the hydrostatic column, approximately 30 cm, between the heart and the brain. The physiologic effects of high-G stress include decreased head-level blood pressure due to hydrostatic pressure drop and decreased cardiac output due to inadequate venous return, resulting in symptoms of vision loss and finally G-LOC. Pilots of modern fighter aircraft, who are unable to sustain these high-G loads, can get incapacitated due to G-induced loss of consciousness (G-LOC), resulting in mishaps. Modern generation high-performance combat aircraft can expose the aircrew to a peak +Gz acceleration of 9G at an onset rate of 9G/s. Acceleration is one such stressor, to which the fighter pilots are repeatedly exposed while performing Aerial Combat Maneuvers. Males exhibited a statistically significant, higher relaxed +Gz tolerance as compared to females.Īircrew are exposed to various stressors in the flying environment. Conclusion:Īge and height showed no correlation with relaxed +Gz tolerance in both males and females nonaircrew subjects. However, the relaxed +Gz tolerance was found to be higher in males and this difference was statistically different ( P = 0.008). In both males and females, age and height showed no correlation with relaxed +Gz tolerance. The mean age, height, and relaxed +Gz tolerance of males were found to be 30.25 ± 4.3 years, 172.58 ± 6.5 cm, and 4.89 ± 0.67G, respectively, whereas those of females were 27.28 ± 3.36 years, 158.46 ± 6.78 cm, and 4.4 ± 0.85G, respectively. Relaxed +Gz tolerance of men and women was compared using unpaired t-test. ![]() The data were analyzed using Microsoft Office Excel ® to find the correlation between age and height with relaxed +Gz tolerance. The age and height varied from 27 to 38 years and 157 to 187 cm, respectively. Of these, 39 were male and 31 were female. Relevant data from 70 non-aircrew subjects were included for the study. The study involved a retrospective analysis of existing database of the high-performance human centrifuge at the Institute of Aerospace Medicine. ![]() The present study was undertaken to understand the relationship of these variables with relaxed +Gz tolerance. Some of the non-modifiable factors influencing +Gz tolerance are age, gender, and height. Factors affecting +Gz tolerance vary among individuals and are determined by both modifiable and non-modifiable factors. Aircrew are repetitively exposed to positive Gz acceleration in fighter flying. ![]()
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