To the Moon, Mars and beyond: recommending exercise countermeasures against musculoskeletal and cardiovascular deconditioning during microgravity exposure, for future spacecraft applications

Laws, Jonathan Michael (2021) To the Moon, Mars and beyond: recommending exercise countermeasures against musculoskeletal and cardiovascular deconditioning during microgravity exposure, for future spacecraft applications. Doctoral thesis, Northumbria University.

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Abstract

Exposure to the microgravity environment during spaceflight can lead to the deconditioning of physiological systems that are concerned with mechanical loading, the musculoskeletal and cardiovascular systems. Deconditioning of the musculoskeletal and cardiovascular systems can impact astronaut health and operational performance both during and after spaceflight. Physical exercise is a common countermeasure that has been implemented to reduce or eliminate these negative physiological outcomes. The Orion Multi Purpose Crew Vehicle (MPCV) is the next generation of exploration capsular spacecraft intended for use during crewed missions beyond low Earth orbit, however, it is constrained by technical limitations that might prevent the use of the exercise countermeasures currently used on-board the International Space Station. To prepare for future spaceflight using the MPCV, it is necessary to investigate the constraints of the MPCV and recommend new exercise countermeasures against musculoskeletal and cardiovascular deconditioning that are effective within these constraints.

To achieve this, the thesis identified the technical constraints of the Orion MPCV and transferable capsular spacecraft that prevent the use of current ISS exercise countermeasures using a qualitative systematic review. Next, a mixed-methods systematic review investigating the musculoskeletal and cardiovascular outcomes of greatest relevance to astronaut health and operational success was conducted to enable selection of exercise recommendations based on the highest priority space medical needs. Having identified both the technical constraints of the Orion MPCV and the most important outcomes, it was then possible to identify the most effective exercise countermeasures that may work within the constraints of the MPCV for space medicine priority outcomes using a quantitative systematic review and meta-analysis. Self-reported outcomes from astronauts on their preferences for an exercise device during spaceflight were collected via a qualitative survey and analysed to provide additional context and input to help inform final exercise recommendations.

The findings indicate that a flywheel device may be the most effective exercise countermeasure for use during spaceflight to reduce musculoskeletal and cardiovascular deconditioning for missions of up to 30 days. Any potential countermeasure, including flywheel, must be assessed against the technical constraints of the Orion MPCV identified within this thesis to ensure its suitability. For missions of longer than 30 days, astronauts indicated a single countermeasure alone might not be sufficient as limited options may induce boredom, reducing adherence to exercise prescriptions and risking their health and the chance of operational mission success. Missions of longer than 30 days should consider implementing a larger spacecraft or deep-space habitat for use alongside the Orion MPCV in which the volume and mass constraints preventing the use of only a single exercise device can be negated. Considerations should be made for the entertainment of astronauts during exercise (such as access to podcasts) to prevent boredom and increase adherence to exercise. Additional social considerations, including the implementation of team exercises, or exercise that utilises the spaceflight environment might also be useful in increasing adherence to exercise.

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