Daily 30-min exposure to artificial gravity during 60 days of bed rest does not maintain aerobic exercise capacity but mitigates some deteriorations of muscle function: results from the AGBRESA RCT

Abstract

Purpose Spaceflight impairs physical capacity. Here we assessed the protective effect of artificial gravity (AG) on aerobic exercise capacity and muscle function during bed rest, a spaceflight analogue. Methods 24 participants (33 ± 9 years, 175 ± 9 cm, 74 ± 10 kg, 8 women) were randomly allocated to one of three groups: continuous AG (cAG), intermittent AG (iAG) or control (CTRL). All participants were subjected to 60 days of six-degree head-down tilt bed rest, and subjects of the intervention groups completed 30 min of centrifugation per day: cAG continuously and iAG for 6 × 5 min, with an acceleration of 1g at the center of mass. Physical capacity was assessed before and after bed rest via maximal voluntary contractions, cycling spiroergometry, and countermovement jumps. Results AG had no significant effect on aerobic exercise capacity, flexor muscle function and isometric knee extension strength or rate of force development (RFD). However, AG mitigated the effects of bed rest on jumping power (group * time interaction of the rmANOVA p < 0.001; iAG − 25%, cAG − 26%, CTRL − 33%), plantar flexion strength (group * time p = 0.003; iAG − 35%, cAG − 31%, CTRL − 48%) and plantar flexion RFD (group * time p = 0.020; iAG − 28%, cAG − 12%, CTRL − 40%). Women showed more pronounced losses than men in jumping power (p < 0.001) and knee extension strength (p = 0.010). Conclusion The AG protocols were not suitable to maintain aerobic exercise capacity, probably due to the very low cardiorespiratory demand of this intervention. However, they mitigated some losses in muscle function, potentially due to the low-intensity muscle contractions during centrifugation used to avoid presyncope.

Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest

“…The present results indicated that the impact of iAG was stronger in the anteroposterior plane, as demonstrated by smaller changes in CoP displacement, velocity, and frequency sway parameters than identified for the control group. Our observations may partially confirm the results of Kramer et al (32), which showed moderate preservation of the function of the plantar flexor muscles in the current HDT bed rest by use of the AG protocols. This is congruent with our results for the anteroposterior direction, as the plantarflexor muscles make the primary contribution to balance control in this direction (21).…”

“…This is congruent with our results for the anteroposterior direction, as the plantarflexor muscles make the primary contribution to balance control in this direction (21). Unlike our data, Kramer et al did not detect any differences between the two AG protocols (32), which suggests plantar flexor muscle strength does not fully explain iAG effects. In our study, iAG mitigated the deleterious effects of HDT bed rest on sway displacement, sway velocity, and sway power spectra, particularly in conditions with eyes closed and standing on an unstable surface (see Table 1 for details).…”

The Effects of Long Duration Spaceflight on Sensorimotor Control and Cognition

“…HDBR studies have examined the effects of artificial gravity applied via centrifugation as a potential countermeasure for spaceflight-associated brain and behavioral changes ( Frett et al, 2020 ). Recent data shows that artificial gravity does not prevent aerobic capacity declines during bed rest, although it does mitigate some muscular function decay ( Kramer et al, 2021 ) and partially counteract upright balance ( De Martino et al, 2021 ).…”

A comparison between left ventricular ejection time measurement methods during physiological changes induced by simulated microgravity

“…Subjects experienced a radial force of 2 g on the foot level and 1 g on the centre of mass. A more detailed description of the countermeasure can be found elsewhere (Kramer et al., 2021 ).…”