Effect of Varying Time at -Gz on Subsequent +Gz Physiological Tolerance (Push-Pull Effect)

摘要

Previous studies have demonstrated decreased +Gz tolerance when preceded by 0 Czor -G2, referred to as the push-pull effect. The purpose of this experiment was to observe the effect of varying time duration at -Gz on the push-pull effect. Methods: During single sessions, six subjects (three men, three women) were subjected to five relaxed exposures to +2.25 Gz on the NAMRL Coriolis Acceleration Platform (CAP). The first and last exposures were control runs that were preceded by +1 Gz. Each experimental run was preceded by -2 Gz for 2, 5, or 15 5. Blood pressure (BP) was monitored using the Finapres at the level of the clavicle. Visual light loss was assessed at +2.25 Gz using a light bar. Results: Mean BP was significantly reduced when the +2.25 Gz exposures were preceded by -2 Gz. Following 15 s of -2 Gz, mean BP decreased more and was slower to recover than for 2 and 5 s of -2 Gz. Reported incidents of visual light loss were: 1 following 2 s, 2 following 5 s, and 4 following 15 sat -2 Gz. There were no reports of visual light loss during control runs. Conclusion: During relaxed conditions, the push-pull effect is augmented by increasing duration of the preceding -Gz.