Exercise during isolation: Daily vs. every second day exercise protocols and their (neuro)psychophysiological effects

INTRODUCTION: Not only astronauts in space, but also our population on Earth is faced with physical and social isolation to an increasing degree. Isolation has been shown to trigger divers psychological and physiological impairments (e.g. mood/affect, cognitive perfor- mance (1,2)) potentially resulting in decreased productivity, health and life quality and increasing health and economical costs. The pre- sent study aimed to compare exercising daily versus every second day in order to examine the effect and amount of exercise needed to counteract isolation-triggered impairments. METHODS: Two groups of sixteen participants each were included in isolation campaign 3 (group C3: 30-day isolation, N=16, aged 36.3 years) and 4 (group C4: 45-day isolation. N=16, aged 39.4 years) of the National Aeronautics and Space Administration (NASA) within the Human Exploration Research Analog (HERA) at Johnsons Space Centre in Houston, Texas. Participants were asked to exercise on a daily basis during C3 and every second day during C4 alternating between bicycle ergometer and stretching and toning exercise. Tests in- cluded a blood draw in the morning (cortisol, brain-derived neurotrophic factor (BDNF)), the Positive And Negative Affect Scale extended (PANAS-X), and a rest-electroencephalography (EEG) recording (16-channel V-Amp system, Brain Products, Munich, Germany) and were performed prior, during, as well as after isolation. A control group (N=18, aged 32.8 years) completed the same protocol of C3, but under non-isolated conditions. RESULTS: The control group did not show any significant changes. Both isolated groups showed a significant elevated cortisol level during isolation compared to pre and post (p= .001), while cortisol of group C3 was higher than group C4 (p=.01). BDNF did not change for group C3, but decreased significantly in C4 towards post isolation (p< .05). Preliminary cortical current density and frequency analyses of EEG revealed no significant changes for both groups. Negative affect differed between groups (p= .01), and slightly increased for group C4 during isolation. Positive affect decreased towards the end of isolation and post isolation for both groups (p= .01). CONCLUSION: Isolation caused stress reflected by increased cortisol levels and decreased positive affect. Daily exercise seems to cause higher cortisol response, while it might prevent from disturbances of BDNF and negative affect. Future studies controlling for multiple stressors of space analogue missions are required to confirm the effects of different exercise protocols on neuro-psychophysiological health under isolated conditions. (1) Cacioppo JT et al. (2015) The neuroendocrinology of social isolation. Annu Rev Psychol 66:733-767. (2) Golden J, et al. (2009) Loneliness, social support networks, mood and wellbeing in community-dwelling elderly. Int J Geriatr Psychiatry 24(7):694-700.