Optimization Of Exercise Countermeasures For Human Space Flight Lessons From Terrestrial Physiology And Operational Implementation

Optimization of Exercise Countermeasures for Human Space Flight – Lessons from Terrestrial Physiology and Operational Implementation

Human spaceflight has required space agencies to study and develop exercise countermeasure (CM) strategies to manage the profound, multi-system adaptation of the human body to prolonged microgravity (μG). Future space exploration will present new challenges in terms of adaptation management that will require the attention of both exercise physiologists and operational experts. In the short to medium-term, all exploration missions will be realised using relatively small vehicles/habitats, with some exploration scenarios including surface operations in low (<1G) gravity conditions. The evolution of CM hardware has allowed modern-day astronauts to return to Earth with, on average, relatively moderate levels μG-induced adaptation of the musculoskeletal (MS) and cardiovascular (CV) systems. However, although the intense use of CM has attenuated many aspects of MS and CV adaptation, on an individual level, there remains wide variation in the magnitude of these changes. Innovations in CM programs have been largely engineering-driven, with new hardware providing capability for new modes of exercise and a wider range of exercise protocols, which, in turn, has facilitated the transfer of traditional, but effective, terrestrial concepts based around high frequency resistance (multiple-set, multiple repetition) and mediumintensity continuous aerobic training. As a result, International Space Station (ISS) CM specialists have focused their efforts in these domains, taking advantage of hardware innovations as and when they became available. However, terrestrial knowledge in human and exercise physiology has expanded rapidly during the lifetime of the ISS and, consequently, there is potential to optimize current approaches by re-examining terrestrial knowledge and identifying opportunities to implement this knowledge into operational practices. Current terrestrial knowledge in exercise physiology is the product of a large number of intervention studies in which the variables that contribute to the effects of physical activity (mode, frequency, duration, intensity, recovery) have been controlled and systematically manipulated. However, due to limited opportunities to perform intervention studies in both spaceflight analogues – head-down bed rest (HDBR) being considered the ‘gold standard’ – and spaceflight itself, it will not be possible to systematically investigate the contribution of these factors to the efficacy of in-flight CM. As such, it will be necessary to draw on terrestrial evidence to identify solutions/strategies that may be best suited to the constraints of exploration and prioritise specific solutions/strategies for evaluation in HDBR and in flight.

Optimization of Exercise Countermeasures for Human Space Flight - Lessons from Terrestrial Physiology and Operational Implementation

Space Countermeasures and Medicine - Implementation into Earth medicine and Rehabilitation

The effects of microgravity on the human organism have been studied for over 60 years. The experience of short- and long-term space flights revealed alterations in multiple physiological systems either in the course of the flight or afterward. Some of these changes represent serious risks for crew health and functional capacity. This fact served as the trigger for multiple countries with space program participants to develop spaceflight countermeasures and medical support systems. These activities are intended to counteract space flight effects such as axial and support unloading, muscle disuse, monotony, fluid redistribution, sensory deficit, etc. Some countermeasures have been adapted from Earth medicine and sports, while others have been created especially for space flights. Many of the observed space flight effects have similarities to conditions seen on Earth, such as: decrease of motor activity in aging people, immobilized patients, and professions associated with forced physical inactivity and isolation. Thus, many space countermeasures and medical support systems can be applied in Earth medicine and rehabilitation. For example, countermeasures like loading suits, lower body negative pressure suits, electromyostimulation of various regimens, water-salt supplements, vestibular training means, etc. have been used in Earth medicine and sports conditioning over the last 20 years.