Effects of Specific Exercise Training During 120 Days Isolation on Physiological Kinetics and Inhibitory Control

PURPOSE Long-term isolation is known for the detrimental effects of inactivity and decreased external stimuli on physical and cognitive systems, which is relevant for space travel in microgravity but also for pandemic-related isolation periods. Exercise countermeasures are investigated in terrestrial analog settings concerning feasibility, time efficiency, and overall beneficial effects on cardiorespiratory and cognitive fitness (i.e., positive exercise-cognition interaction). In terrestrial settings, interval (INT) and continuous (CON) treadmill exercise showed positive effects on heart rate (HR) and oxygen uptake (V̇O2) capacities and kinetics, but research for space application is still pending. We expected (I) negative effects of isolation on cognitive performance and (II) physical fitness improvements, especially from INT. METHODS Six participants (34±6 years, 3 females) spent 120 days in isolation on a simulated journey to the moon (SIRIUS-19). 8 weeks of CON, followed by 8 weeks of INT aerobic exercise on a treadmill were conducted in a crossover design. Cardiorespiratory capacities, kinetics (HR, V̇O2), and cognitive performance (Flanker task measuring inhibitory control) were assessed with an exercise protocol, including pseudo-random binary sequences (PRBS), constant work-rate phases (Rest, 3, 6, 9 km h-1, recovery), and incremental exercise for Pre, Post, and five times during isolation (ANOVA: time x phase). RESULTS Peak values for HR (P=0.025), V̇O2 (P=0.012), and respiratory exchange ratio (P=0.001) had significant time effects with lower values during isolation. Kinetics of HR and V̇O2 improved during the mission with slightly better effects for INT (both p<0.05). Inhibitory control was not altered by 120 days of isolation. CONCLUSION This study proved the successful implementation of cognitive testing within our endurance exercise test. Positive effects for INT and CON aerobic exercise were confirmed for HR, but not for V̇O2 kinetics during isolation periods. We assume the lack of general physical activity is merely compensated for by the applied exercise countermeasure, at least in 1G contexts. Currently, additional exercise modalities (i.e., strength training, passive treadmill exercise) are investigated during a consecutive 240-day mission (SIRIUS-21).