Effects of Individualized Centrifugation Training on Orthostatic Tolerance in Men and Women

Abstract

AimsExposure to artificial gravity (AG) at different G loads and durations on human centrifuges has been shown to improve orthostatic tolerance in men. However, the effects on women and of an individual-specific AG training protocol on tolerance are not known.MethodsWe examined the effects of 90 minutes of AG vs. 90 minutes of supine rest on the orthostatic tolerance limit (OTL), using head up tilt and lower body negative pressure until presyncope of 7 men and 5 women. Subjects were placed in the centrifuge nacelle while instrumented and after one-hour they underwent either: 1) AG exposure (90 minutes) in supine position [protocol 1, artificial gravity exposure], or 2) lay supine on the centrifuge for 90 minutes in supine position without AG exposure [protocol 2, control]. The AG training protocol was individualized, by first determining each subject’s maximum tolerable G load, and then exposing them to 45 minutes of ramp training at sub-presyncopal levels.ResultsBoth sexes had improved OTL (14 minutes vs 11 minutes, p < 0.0019) following AG exposure. When cardiovascular (CV) variables at presyncope in the control test were compared with the CV variables at the same tilt-test time (isotime) during post-centrifuge, higher blood pressure, stroke volume and cardiac output and similar heart rates and peripheral resistance were found post-centrifuge.ConclusionsThese data suggest a better-maintained central circulating blood volume post-centrifugation across gender and provide an integrated insight into mechanisms of blood pressure regulation and the possible implementation of in-flight AG countermeasure profiles during spaceflights.

Comparison of Autonomic Control of Blood Pressure During Standing and Artificial Gravity Induced via Short-Arm Human Centrifuge

“…Furthermore, due to small sample size, the gender effect on blood pressure regulation and alteration in the dynamics of such behavior under artificial hypergravity remains to be understood. Female astronauts account for approximately 22% of total astronaut population ( Harm et al, 2001 ), and studies have demonstrated significant gender difference in autonomic mechanisms leading to stable stance and in response to countermeasures designed to mitigate deleterious effect of spaceflight deconditioning ( Arzeno et al, 2013 ; Goswami et al, 2015b ; Hughson et al, 2016 ; Macaulay et al, 2016 ). Therefore, generalization of gender effect would further improve our understanding regarding the potential of SAHC as a training tool toward evoking blood pressure regulatory controls analogous to standing.…”

Effect of postural changes on cardiovascular parameters across gender

“…If any subject developed presyncope the experiment was terminated immediately. Presyncope was defined as [ 26 , 27 ] : blood pressure dropping below 80 mm Hg or by ≥20 mm Hg/minute; diastolic by ≥10 mm Hg/minute; and/or HR decreasing by ≥15 bpm. Additionally subjects were instructed to avoid any unnecessary movements, remain as still as possible and breathe normally at all times.…”

The effects of varying gravito-inertial stressors on grip strength and hemodynamic responses in men and women

“…Current evidence from studies of ambulatory and deconditioned men and women indicate that 90 min of an individualized short-arm centrifuge AG profile significantly increases participants’ orthostatic tolerance limits via increased blood pressure and cerebral blood flow (Goswami et al 2015a, b; Evans et al 2015). However, men and women respond differently to these stressors (Harm et al 2001).…”