Effects of an artificial gravity countermeasure on orthostatic tolerance, blood volumes and aerobic power after short-term bed rest (BR-AG1)

Abstract

Exposure to artificial gravity (AG) in a short-arm centrifuge has potential benefits for maintaining human performance during long-term space missions. Eleven subjects were investigated during three campaigns of 5 days head-down bed rest: 1) bed rest without countermeasures (control), 2) bed rest and 30 min of AG (AG1) daily, and 3) bed rest and six periods of 5 min AG (AG2) daily. During centrifugation, the supine subjects were exposed to AG in the head-to-feet direction with 1 G at the center of mass. Subjects participated in the three campaigns in random order. The cardiovascular effects of bed rest and countermeasures were determined from changes in tolerance to a head-up tilt test with superimposed lower body negative pressure (HUT), from changes in plasma volume (PV) and from changes in maximum aerobic power (V̇o2 peak) during upright work on a cycle ergometer. Complete data sets were obtained in eight subjects. After bed rest, HUT tolerance times were 36, 64, and 78% of pre-bed rest baseline during control, AG1 and AG2, respectively, with a significant difference between AG2 and control. PV and V̇o2 peak decreased to 85 and 95% of pre-bed rest baseline, respectively, with no differences between the treatments. It was concluded that the AG2 countermeasure should be further investigated during future long-term bed rest studies, especially as it was better tolerated than AG1. The superior effect of AG2 on orthostatic tolerance could not be related to concomitant changes in PV or aerobic power.

Reliability and validity of non‐invasive determined haemoglobin mass and blood volumes

“…In this study, we performed two CO rebreathing tests on the same day in order to limit day-to-day variations. Indeed, interventions leading to only small changes in Hb mass and BVs are often applied in scientific studies (Prommer et al, 2008;Schumacher et al, 2008;Lundby & Robach, 2010;Mørkeberg et al, 2011;Hughson et al, 2012;Robach et al, 2012Robach et al, , 2014Siebenmann et al, 2012;Austin et al, 2014;Linnarsson et al, 2015;Wehrlin et al, 2016). The % TE when using the Rad-57 was, however, around 6%.…”

“…The results demonstrate that non-invasive determination of Hb mass and BV should not be applied to scientific settings where small differences may be of interest. Indeed, interventions leading to only small changes in Hb mass and BVs are often applied in scientific studies (Prommer et al, 2008;Schumacher et al, 2008;Lundby & Robach, 2010;Mørkeberg et al, 2011;Hughson et al, 2012;Robach et al, 2012Robach et al, , 2014Siebenmann et al, 2012;Austin et al, 2014;Linnarsson et al, 2015;Wehrlin et al, 2016). Thus, whilst noninvasive determination of Hb mass and BVs is of limited use in most scientific settings, it is noteworthy that for clinical purposes the precision could be adequate, since in clinical settings Hb mass and BVs may show greater variations; for instance, a single dialysis procedure may remove 2-3 l of PV in just 4 h (Thijssen et al, 2013).…”

Haemoglobin mass alterations in healthy humans following four‐day head‐down tilt bed rest

“…; Linnarrsson et al . ), and we are the first to have measured Hbmass/RCV in the upright, seated position and after graded exercise testing following HDTBR. This unique aspect of our study design leaves open the possibility that the return to orthostasis and graded exercise testing prior to assessment of Hbmass might have influenced our finding of a transient increase in Hbmass.…”

Artificial gravity as a countermeasure for mitigating physiological deconditioning during long-duration space missions

“…The results of these studies showed that intermittent centrifugation with and without concurrent aerobic exercise during otherwise continuous bed rest: (a) attenuated plasma volume loss (Lee et al, 1997; Iwasaki et al, 1998, 2001, 2005); (b) maintained exercise capacity (Katayama et al, 2004); (c) improved post-bed rest orthostatic tolerance time (Schneider et al, 2002; Iwase, 2005; Watenpaugh et al, 2007; Guinet et al, 2009; Shibata et al, 2010; Linnarsson et al, 2015); and (d) reduced the exaggerated responses to head-up tilt after bed rest, such as elevated heart rate and increased muscle sympathetic nerve activity (Iwasaki et al, 2005). …”