THE EFFECT OF VARYING TIME AT -GZ ON SUBSEQUENT - PHYSIOLOGICAL TOLERANCE (PUSH-PULL EFFECT)(GZ )

Introduction: Previous studies have demonstrated decreased +Gz toleran ce when preceded by 0 Gz or -Gz, referred to as the ''push-pull effect .'' The purpose of this experiment was to observe the effect of varyin g time duration at -Gz on the push-pull effect. Methods: During single sessions, six subjects (three men, three women) were subjected to fiv e relaxed exposures to +2.25 Gz on the NAMRL Coriolis Acceleration Pla tform (CAP). The first and last exposures were control runs that were preceded by +1 Ct. Each experimental run was preceded by -2 Gz for 2, 5, or 15 s. Blood pressure (BP) was monitored using the Finapres at th e level of the clavicle. Visual light loss was assessed at +2.25 Gz us ing 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 Ct, mea n 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 s at -2 Gz. There were no reports of visual light loss during control runs. Conclusion: During relaxed con ditions, the push-pull effect is augmented by increasing duration of t he preceding -Gz.