Exercise as potential countermeasure for the effects of 70 days of bed rest on cognitive and sensorimotor performance

Abstract

Background: Spaceflight has been associated with changes in gait and balance; it is unclear whether it affects cognition. Head down tilt bed rest (HDBR) is a microgravity analog that mimics cephalad fluid shifts and body unloading. In consideration of astronaut’s health and mission success, we investigated the effects of HDBR on cognition and sensorimotor function. Furthermore, we investigated if exercise mitigates any cognitive and sensorimotor sequelae of spaceflight.Method: We conducted a 70-day six-degree HDBR study in 10 male subjects who were randomly assigned to a HDBR supine exercise or a HDBR control group. Cognitive measures (i.e., processing speed, manual dexterity, psychomotor speed, visual dependency, and 2D and 3D mental rotation) and sensorimotor performance (functional mobility (FMT) and balance performance) were collected at 12 and 8 days pre-HDBR, at 7, 50, and 70 days in HDBR, and at 8 and 12 days post-HDBR. Exercise comprised resistance training, and continuous and high-intensity interval aerobic exercise. We also repeatedly assessed an outside-of-bed rest control group to examine metric stability.Results: Small practice effects were observed in the control group for some tasks; these were taken into account when analyzing effects of HDBR. No significant effects of HDBR on cognition were observed, although visual dependency during HDBR remained stable in HDBR controls whereas it decreased in HDBR exercise subjects. Furthermore, HDBR was associated with loss of FMT and standing balance performance, which were almost fully recovered 12 days post-HDBR. Aerobic and resistance exercise partially mitigated the effects of HDBR on FMT and accelerated the recovery time course post-HDBR.Discussion: HDBR did not significantly affect cognitive performance but did adversely affect FMT and standing balance performance. Exercise had some protective effects on the deterioration and recovery of FMT.

Vestibular brain changes within 70 days of head down bed rest

“…HDBR-related declines in FMT and SOT have been documented in our previous publication in a larger sample (Koppelmans et al, 2015). Functional mobility and standing balance performance declined following HDBR, in comparison with the pre-HDBR level, as has been reported in previous studies (Mulder et al, 2014;Reschke et al, 2009).…”

“…Our previous publication has documented that the HDBR‐induced declines in mobility can be partially mitigated by exercise (Koppelmans et al, ). Considering the observed association between HDBR‐related changes in FMT and brain activation, we speculate that appropriate exercise would be able to alleviate HDBR‐associated changes in brain activation for vestibular stimulation.…”

“…All the HDBR and control subjects performed a series of cognitive and sensorimotor tests. The effects of HDBR on cognitive and sensorimotor performance have been previously published from this sample (Koppelmans et al, ). In this study, we were particularly interested in the Functional Mobility Test (FMT) and Sensory Organization Test 5 (SOT‐5 and SOT‐5M) as potential correlates of vestibular brain activity (tests described below).…”

“…The effects of HDBR on cognitive and sensorimotor performance have been previously published from this sample (Koppelmans et al, 2015).…”

Brain structural plasticity with spaceflight

“…39,40 No statistical tests were run because of differences in pre-to-post intervals, scan sequence and parameters, and demographic differences. Figure 3 presents the mean and standard deviation of pre- to post-intervention changes for both long duration head down tilt bed rest and spaceflight.…”