Neuropsychological effects of isolation and physical exercise regimen during SIRIUS-19

Physical exercise could reduce the risk of undesired mental impairments during isolation and space missions. This project aimed to clarify beneficial as well as adverse effects of continuous versus interval running exercise on brain health and cognition and underlying neurophysiological mechanisms during a terrestrial simulated space mission.
Six volunteers (aged 33.6 years, 3 females) simulated a 120-day mission to the Moon (SIRIUS-19). Exercise training consisted of treadmill running during a continuous (CON) or an interval (INT) protocol. Each protocol was performed throughout one half (either first or second) of the mission and switched in a cross-over design. Data was collected prior to (BDC-14 to BDC-7), four times during (start and end of each protocol; MD14/16, MD53/54, MD79/80, MD110/112), as well as post isolation (R+6 to R+9), pre- and post- exercise on two separate days respectively. Cognitive performance (Cognition test battery BHP-SM), self-perceived state of mood (MoodMeter©) and affect (PANAS), and electroencephalographic recordings (EEG, 32-channel) were assessed. Morning blood samples were drawn to assess BDNF, IGF-1, and VEGF and saliva samples every 2 hours from 8am to 10pm to assess cortisol levels. Effects of isolation (factor: TIME), exercise (pre vs post exercise), exercise protocol (INT vs CON) and gender were calculated using non-parametric tests. No significant changes from in to post isolation data collections have been observed. Therefore, only BDC was compared to the end of each training protocol in order to reduce alpha error and increase statistical power (α = 0.05, for factor time α = 0.017). As an effect of TIME, lactate decreased at fixed running speed 9km/h (p = 0.03) at the end of both training protocols compared to BDC (p = 0.046). Cortisol level increased as a factor of time (p = 0.011) from BDC to the end of both exercise protocols (p = 0.028) and cognitive performance improved (overall reaction time p = 0.006, score p= 0.016). Positive (p = 0.549) and negative affect (p= 0.717) as well as perceived physical (p= 0.568) and motivational state (p= 0.200) did not change over time. Perceived psychological strain significantly improved comparing BDC to both exercise protocol end-points (p = 0.015). Neither BDNF (p = 0.607), IGF-1 (p = 0.60) nor VEGF (p = 0.846) did change over time, but IGF-1 showed a significant effect of exercise protocol and higher values at the end of CON compared to the end of the INT protocol (p = 0.028). With this exception, no difference between pre and post exercise, exercise protocols and sex were found for all other variables. Reduced broadband power and a flattening of the 1/f spectral slope was found in resting-state EEG during isolation compared to BDC (see Weber et al. Scientific reports (2020)10: 17987).
In conclusion, this exercise training protocol during 120 days of isolation improved physical fitness. Although cortisol level increased and brain cortical activity decreased during isolation, cognitive performance, mood, affect and neurotrophic factors remained stable independent of gender and the exercise protocol (except IGF-1 increased for CON). Longer duration missions with manipulations of the exercise protocol are needed to further optimize training protocols.