Tolerability of daily intermittent or continuous short-arm centrifugation during 60-day 6o head down bed rest (AGBRESA study)

Abstract

Artificial gravity through short-arm centrifugation has potential as a multi-system countermeasure for deconditioning and cranial fluid shifts that may underlie ocular issues in microgravity. However, the optimal short-arm centrifugation protocol that is effective whilst remaining tolerable has yet to be determined. Given that exposure to centrifugation is associated with presyncope and syncope and in addition motion sickness an intermittent protocol has been suggested to be more tolerable. Therefore, we assessed cardiovascular loading and subjective tolerability of daily short arm centrifugation with either an intermittent or a continuous protocol during long-term head-down bed rest as model for microgravity exposure in a mixed sex cohort. During the Artificial Gravity Bed Rest with European Space Agency (AGBRESA) 60 day 6˚head down tilt bed rest study we compared the tolerability of daily +1 Gz exposure at the center of mass centrifugation, either performed continuously for 30 minutes, or intermittedly (6 x 5 minutes). Heart rate and blood pressure were assessed daily during centrifugation along with post motion sickness scoring and rate of perceived exertion. During bed rest, 16 subjects (6 women, 10 men), underwent 960 centrifuge runs in total. Ten centrifuge runs had to be terminated prematurely, 8 continuous runs and 2 intermittent runs, mostly due to pre-syncopal symptoms and not motion sickness. All subjects were, however, able to resume centrifuge training on subsequent days. We conclude that both continuous and intermittent short-arm centrifugation protocols providing artificial gravity equivalent to +1 Gz at the center of mass is tolerable in terms of cardiovascular loading and motion sickness during long-term head down tilt bed rest. However, intermittent centrifugation appears marginally better tolerated, albeit differences appear minor.

Optic disc edema and chorioretinal folds develop during strict 6° head‐down tilt bed rest with or without artificial gravity

“…Twenty‐four subjects participated in this study, which was conducted at the :envihab facility at the German Aerospace Center (DLR) in Cologne, Germany (Frett et al, 2020 ). Subjects were recruited by the DLR and eligibility for enrollment was determined according to the International Academy of Astronautics’ guidelines for bed rest studies (Sundblad et al, 2014 ), including a clinical eye examination that confirmed the absence of ocular disease.…”

“…The iAG exposure consisted of 6 periods of AG that lasted 5 min each, with a 3‐min break between each period. The centrifuge arm radius and velocity were adjusted according to each subject's height to achieve 1 g at the center of mass (approximately 2 g at the feet and 0.3 g at the eyes) (Frett et al, 2020 ). All centrifugation sessions were performed in the 0° supine posture, and on testing days, ocular measures were acquired from the cAG and iAG subjects before the centrifugation session.…”

Effects of long‐term immobilisation on endomysium of the soleus muscle in humans

“…More detailed information is set forth in Guidelines for standardisation of bed rest studies in the spaceflight context (Sundblad & Orlov, 2014). Details of the AGBRESA study have been published which specify the daily routines (Frett et al., 2020).…”

Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bed rest

“…AG was produced by rotating the participants on a centrifuge arm with a 3.0-m radius. The rotational speed of the centrifuge was calculated individually based upon each participant's anthropometry to produce 1Gz at the center of mass (22). Participants' cardiorespiratory parameters were continuously monitored by trained medical personnel.…”