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

PurposeThe body behaves as a global system with many interconnected subsystems. While the effects of a gravitational change on body responses have been extensively studied in isolation, we are not aware of any study that hasexamined thesetwo types of body responses concurrently. Here, we examined how the cognitive and cardiovascular systems respond during application of varying gravito-inertial stressors in men and women.MethodsTen men and nine women underwent three 5-min centrifugation sessions (2.4g at the feet, 1.5g at the heart) in which participants rhythmically moved a hand-held object for 20s. Grip force and hemodynamic responses were continuously measured during centrifugation and rest periods.ResultMen optimized the modulation between grip force and the destabilizing load force, but not women. Exposure to artificial gravity induced higher heart rate and mean arterial pressure in both sexes compared to baseline. However, during artificial gravityexposure, only women decreased heart rate across sessions. Interestingly, we found that finishers of the protocol (mostly men) and Non-finishers (mostly women) exhibited divergent patterns of hemodynamic responses.ConclusionWe speculate that the lack of grip force adaptation reported in women could be linked to the challenged hemodynamic responsesduring artificial gravity. By deriving a simple model to predict failure to complete the protocol, we found that mean arterial pressureand not sex of the participantwas the most relevant factor. As artificial gravity is being proposed as a countermeasure in long-term manned missions, the observed effects in grip force adaptation and hemodynamic responses during varying gravito-inertial stressors application areparticularly important.