Effects of aerobic exercise in confinement on cardiorespiratory kinetics and cognitive functions – Results from the 4-month SIRIUS-19 isolation project

Abstract Introduction Confinement during sojourns in microgravity affects cardiorespiratory fitness, cognitive parameters, and their interaction with influences on mission success, fitness, and overall well-being. The aim of the experiment was to test the efficacy of two endurance exercise countermeasures to maintain aerobic fitness, indicated by cardiorespiratory kinetics, and cognitive performance during 120 days of confinement. Methods Six participants (34 ± 6 years, 3 females) spent 120 days in confinement, conducting eight weeks of either continuous (CON) or interval (INT) aerobic treadmill exercise in a crossover design. Heart rate (HR) and oxygen uptake (VO2) were assessed with an exercise test protocol, including pseudo-random work rate changes to determine the respective kinetics before the start of confinement (pre), five times during confinement (mission day (MD) 9(±1), 29(±1), 57(±1), 87(±1), and 117 (±1)), and after the termination of the mission phase (post). Additionally, constant work rate phases and incremental exercise were part of the protocol. During the constant phases of the exercise protocol, cognitive performance was assessed. Results HR kinetics accelerated, and mean HR values during the work rate protocol decreased as the mission progressed (p < 0.05). CON and INT exercise both seemed to speed HR kinetics during the mission, with slightly better effects for INT. Inhibitory control was not altered by 120 days of confinement. Conclusion Detrimental effects on cardiorespiratory fitness and cognitive performance from the lack of general physical activity during confinement were compensated by the applied exercise countermeasure, with no clear advantage for CON or INT exercise.