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Effectiveness of Exercise Countermeasures for the Prevention of Musculoskeletal Deconditioning in Simulated Hypogravity: A Systematic Review
Abstract:
Background
Exercise countermeasures are the main approach taken to protect astronauts from musculoskeletal deconditioning in microgravity (μg). Future exploration class missions will require astronauts to live on the surface of the Moon (0.16g) and Mars (0.38g) in hypogravity where the level of protection is assumed to be insufficient. However, it is not well understood how much exercise is required to protect the musculoskeletal system against ‘small planet deconditioning’. The purpose of this review was to systematically synthesize evidence regarding the effectiveness of exercise countermeasures for the prevention of musculoskeletal deconditioning in hypogravity.
Method
Databases were searched for relevant literature using appropriate search terms: PubMed, Web of Science, EMBASE, The Cochrane Collaboration Library, SPORTDiscus, The National Aeronautics and Space Administration (NASA) Technical Reports Sever, The NASA Life Science Data Archive and the German Aerospace Centre Elibrary. Two independent reviewers screened hits for relevance in accordance with the a priori PICOS criteria. Studies that included Earth based hypogravity analogues (e.g. head up tilt bed rest), a healthy terrestrial population, an exercise countermeasure and non exercise control group (i.e. randomized/clinical control trial), measuring any musculoskeletal outcome, were eligible for inclusion. Space related research (e.g. Lunar mission data) were not eligible for inclusion.
Results
No studies were identified that met the eligibility criteria established for this review. Of the n = 2,805 articles identified, n = 124 were classified as potentially relevant, however all were excluded following full text examination.
Conclusions
Assumptions regarding the effect of hypogravity on the human musculoskeletal system are yet to be confirmed with long duration data. Future research should aim to fill this gap by investigating the longitudinal effects of simulated hypogravity (and Lunar/Martian habitat environments) on the human musculoskeletal system, to establish whether any deconditioning is of a large enough magnitude to compromise health and performance. If so, thereafter investigating exercise countermeasure strategies to prevent deconditioning in simulated Lunar/Martian settings will help inform evidence-based medical guidelines for planetary exploration. The ecological validity and thus transferability of data from chronic hypogravity analogs are essential to providing accurate and high quality data. Therefore, Lunar/Martian data is extremely valuable to understand whether data collected in analogs can be accurately transferred.
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Citation: Swain, Laws, De Martino, Wotring & Winnard (2021)Effectiveness of Exercise Countermeasures for the prevention of Musculoskeletal Deconditioning in Simulated Hypogravity: A Systematic Review. Acta Astronautica (in press).
The Potential of Fasting and Caloric Restriction to Mitigate Radiation Damage—A Systematic Review
Abstract:
Detrimental health effects from ionizing radiation to living organisms is one of the key concerns identified and addressed by Radiation Protection institutions, nationally and internationally on Earth and for human spaceflight. Thus, new methods for mitigating the adverse effects of ionizing radiation are urgently needed for terrestrial health and deep space exploration. Caloric restriction and (intermittent-) fasting have been reported to elicit a variety of immediate and long-term physiological effects. The rapidly growing body of evidence of research studies investigating the effects of caloric restriction and dietary fasting points toward a multitude of benefits affecting numerous physiological systems. Therefore, a systematic review was performed to evaluate the evidence of caloric restriction and dietary fasting on the physiological response to ionizing radiation in humans and animals. All experimental studies of humans, animals, and eukaryotic cell lines available in PubMed, Cochrane library, and specialized databases were searched comparing irradiation post-caloric restriction or fasting to a non-nutritionally restricted control group on a broad range of outcomes from molecular to clinical responses. The initial search yielded 2,653 records. The final analysis included 11 studies. Most studies investigated survival rate or cancer occurrence in animals. Included studies did not reveal any benefit from pre exposure caloric restriction, except when performed with post radiation caloric restriction. However, the effects of pre-exposure fasting suggest increased resilience to ionizing radiation.
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Citation: Valayer, Kim, Fogtman, Straube, Winnard, Caplan, Green, Van Leeuwen and Weber (2020) The potential of fasting and caloric restriction to mitigate radiation damage - a systematic review Front. Nutr. | doi: 10.3389/fnut.2020.58454
Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning
Abstract:
A systematic review was performed to evaluate the effectiveness of nutrition as a standalone countermeasure to ameliorate the physiological adaptations of the musculoskeletal and cardiopulmonary systems associated with prolonged exposure to microgravity. A search strategy was developed to find all astronaut or human space flight bed rest simulation studies that compared individual nutritional countermeasures with non-intervention control groups. This systematic review followed the guidelines of the Cochrane Handbook for Systematic Reviews and tools created by the Aerospace Medicine Systematic Review Group for data extraction, quality assessment of studies and effect size. To ensure adequate reporting this systematic review followed the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analyses. A structured search was performed to screen for relevant articles. The initial search yielded 4031 studies of which 10 studies were eligible for final inclusion. Overall, the effect of nutritional countermeasure interventions on the investigated outcomes revealed that only one outcome was in favor of the intervention group, whereas six outcomes were in favor of the control group, and 43 outcomes showed no meaningful effect of nutritional countermeasure interventions at all. The main findings of this study were: (1) the heterogeneity of reported outcomes across studies, (2) the inconsistency of the methodology of the included studies (3) an absence of meaningful effects of standalone nutritional countermeasure interventions on musculoskeletal and cardiovascular outcomes, with a tendency towards detrimental effects on specific muscle outcomes associated with power in the lower extremities. This systematic review highlights the limited amount of studies investigating the effect of nutrition as a standalone countermeasure on operationally relevant outcome parameters. Therefore, based on the data available from the included studies in this systematic review, it cannot be expected that nutrition alone will be effective in maintaining musculoskeletal and cardiopulmonary integrity during space flight and bed rest.
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Citation: Sandal, Kim, Fiebig, Winnard, Caplan, Green and Weber (2020) Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning – A Systematic Review. Plos One 15(6)
Systematic review of the technical and physiological constraints of the Orion Multi-Purpose Crew Vehicle that affect the capability of astronauts to exercise effectively during spaceflight.
Abstract:
Background
The constraints of the Orion Multi-Purpose Crew Vehicle present challenges to the use of current exercise countermeasures necessary to prevent severe deconditioning of physiological systems during microgravity exposure beyond Low Earth Orbit. The purpose of this qualitative systematic review was to determine the technical constraints of the Orion Multi-Purpose Crew Vehicle which may hinder astronauts’ capabilities to effectively exercise during long distance spaceflight.
Methods
Databases were searched from the start of their records to December 2018. Included documents were quality assessed with the AMSRG quality scoring tool and Thematic Analysis was used to analyse the included documents to assess technical constraints of the Orion Multi-Purpose Crew Vehicle.
Results
19 studies were included in the final review. All identified constraints, other than data transmission limitations, were found to ultimately be a result of the volume and upload mass constraints of the Orion Multi-Purpose Crew Vehicle. There was a lack of detailed studies and lack of consistency in specifying spacecraft in the literature that limit the conclusions of this review.
Conclusion
Space agencies are advised to ensure that information on relevant spacecraft constraints is readily available to researchers. This information should be made accessible in an official published document as opposed to disparate and grey literature, and include quantitative information rather than qualitative summaries.
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Citation: Laws, J, Caplan, N, Bruce-Martin, C, McGrogan, C, Lindsay, K, Wild, B., Debuse, D, Wotring, V. and Winnard, A (2020) Systematic review of the technical and physiological constraints of the Orion Multi-Purpose Crew Vehicle that affect the capability of astronauts to exercise effectively during spaceflight. Acta Astronautica, 170. pp. 665-677.
Effect of time on human muscle outcomes during simulated microgravity exposure without countermeasures – systematic review.
Background: Space Agencies are planning human missions beyond Low Earth Orbit. Consideration of how physiological system adaptation with microgravity (μG) will be managed during these mission scenarios is required. Exercise countermeasures (CM) could be used more sparingly to decrease limited resource costs, including periods of no exercise. This study provides a complete overview of the current evidence, making recommendations on the length of time humans exposed to simulated μG might safely perform no exercise considering muscles only.
Methods: Electronic databases were searched for astronaut or space simulation bed rest studies, as the most valid terrestrial simulation, from start of records to July 2017. Studies were assessed with the Quality in Prognostic Studies and bed rest analog studies assessed for transferability to astronauts using the Aerospace Medicine Systematic Review Group Tool for Assessing Bed Rest Methods. Effect sizes, based on no CM groups, were used to assess muscle outcomes over time. Outcomes included were contractile work capacity, muscle cross sectional area, muscle activity, muscle thickness, muscle volume, maximal voluntary contraction force during one repetition maximum, peak power, performance based outcomes, power, and torque/strength.
Results: Seventy-five bed rest μG simulation studies were included, many with high risk of confounding factors and participation bias. Most muscle outcomes deteriorated over time with no countermeasures. Moderate effects were apparent by 7–15 days and large by 28–56 days. Moderate effects (>0.6) became apparent in the following order, power and MVC during one repetition maximum (7 days), followed by volume, cross sectional area, torques and strengths, contractile work capacity, thickness and endurance (14 days), then muscle activity (15 days). Large effects (>1.2) became apparent in the following order, volume, cross sectional area (28 days) torques and strengths, thickness (35 days) and peak power (56 days).
Conclusions: Moderate effects on a range of muscle parameters may occur within 7–14 days of unloading, with large effects within 35 days. Combined with muscle performance requirements for mission tasks, these data, may support the design of CM programmes to maximize efficiency without compromising crew safety and mission success when incorporated with data from additional physiological systems that also need consideration.
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Citation: Winnard, Andrew, Scott, J., Waters, Nathan, Vance, M. and Caplan, Nick (2019) Effect of time on human muscle outcomes during simulated microgravity exposure without countermeasures – systematic review. Frontiers in Physiology. ISSN 1664-042X 10, 1046
Comparison of Exercise Interventions from Bed Rest Studies for the Prevention of Musculoskeletal Loss.
Musculoskeletal loss in actual or simulated microgravity occurs at a high rate. Bed rest studies are a reliable ground-based spaceflight analogue that allow for direct comparison of intervention and control participants. The aim of this review was to investigate the impact of exercise compared to no intervention on bone mineral density (BMD) and muscle cross-sectional area (muscle CSA) in bed rest studies relative to other terrestrial models. Eligible bed rest studies with healthy participants had an intervention arm with an exercise countermeasure and a control arm. A search strategy was implemented for MEDLINE. After screening, eight studies were identified for inclusion. Interventions included resistive exercise (RE), resistive vibration exercise (RVE), flywheel resistive exercise, treadmill exercise with lower body negative pressure (LBNP) and a zero-gravity locomotion simulator (ZLS). Lower limb skeletal sites had the most significant BMD losses, particularly at the hip which reduced in density by 4.59% (p < 0.05) and the tibial epiphysis by 6% (p < 0.05). Exercise attenuated bone loss at the hip and distal tibia compared to controls (p < 0.05). Muscle CSA changes indicated that the calf and quadriceps were most affected by bed rest. Exercise interventions significantly attenuated loss of muscle mass. ZLS, LBNP treadmill and RE significantly attenuated bone and muscle loss at the hip compared to baseline and controls. Despite exercise intervention, high rates of bone loss were still observed. Future studies should consider adding bisphosphonates and pharmacological/nutrition-based interventions for consideration of longer-duration missions. These findings correlate to terrestrial bed rest settings, for example, stroke or spinal-injury patients.
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Citation: Konda, Nagarjun, Karri, Rama, Winnard, Andrew, Nasser, Mona, Evetts, Simon, Boudreau, Eilis, Caplan, Nick, Gradwell, David and Velho, Rochelle (2019) A Comparison of Exercise Interventions from Bed Rest Studies for the Prevention of Musculoskeletal Loss. npj Microgravity, 5. ISSN 2373-8065
Human Biomechanical and Cardiopulmonary Responses to Partial Gravity - A Systematic Review.
The European Space Agency has recently announced to progress from low Earth orbit missions on the International Space Station to other mission scenarios such as exploration of the Moon or Mars. Therefore, the Moon is considered to be the next likely target for European human space explorations. Compared to microgravity (μg), only very little is known about the physiological effects of exposure to partial gravity (μg < partial gravity <1 g). However, previous research studies and experiences made during the Apollo missions comprise a valuable source of information that should be taken into account when planning human space explorations to reduced gravity environments. This systematic review summarizes the different effects of partial gravity (0.1-0.4 g) on the human musculoskeletal, cardiovascular and respiratory systems using data collected during the Apollo missions as well as outcomes from terrestrial models of reduced gravity with either 1 g or microgravity as a control. The evidence-based findings seek to facilitate decision making concerning the best medical and exercise support to maintain astronauts' health during future missions in partial gravity. The initial search generated 1,323 publication hits. Out of these 1,323 publications, 43 studies were included into the present analysis and relevant data were extracted. None of the 43 included studies investigated long-term effects. Studies investigating the immediate effects of partial gravity exposure reveal that cardiopulmonary parameters such as heart rate, oxygen consumption, metabolic rate, and cost of transport are reduced compared to 1 g, whereas stroke volume seems to increase with decreasing gravity levels. Biomechanical studies reveal that ground reaction forces, mechanical work, stance phase duration, stride frequency, duty factor and preferred walk-to-run transition speed are reduced compared to 1 g. Partial gravity exposure below 0.4 g seems to be insufficient to maintain musculoskeletal and cardiopulmonary properties in the long-term. To compensate for the anticipated lack of mechanical and metabolic stimuli some form of exercise countermeasure appears to be necessary in order to maintain reasonable astronauts' health, and thus ensure both sufficient work performance and mission safety.
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Citation: Richter, C., Braunstein, B., Winnard, A., Nasser M. & Weber, T. (2017). Human Biomechanical and Cardiopulmonary Responses to Partial Gravity - A Systematic Review. Frontiers in Physiology, 8, 583
Systematic review of countermeasures and rehabilitation interventions to minimise physiological changes and risk of injury to the lumbopelvic area following long-term microgravity.
Background
No studies have been published on an astronaut population to assess the effectiveness of countermeasures for limiting physiological changes in the lumbopelvic region caused by microgravity exposure during spaceflight. However, several studies in this area have been done using spaceflight simulation via bed-rest. The purpose of this systematic review was to evaluate the effectiveness of countermeasures designed to limit physiological changes to the lumbopelvic region caused by spaceflight simulation by means of bed-rest.
Methods
Electronic databases were searched from the start of their records to November 2014. Studies were assessed with PEDro, Cochrane Risk of Bias and a bed-rest study quality tool. Magnitude based inferences were used to assess countermeasure effectiveness.
Results
Seven studies were included. There was a lack of consistency across studies in reporting of outcome measures. Some countermeasures were found to be successful in preventing some lumbopelvic musculoskeletal changes, but not others. For example, resistive vibration exercise prevented muscle changes, but showed the potential to worsen loss of lumbar lordosis and intervertebral disc height.
Conclusion
Future studies investigating countermeasures should report consistent outcomes, and also use an actual microgravity environment. Additional research with patient reported quality of life and functional outcome measures is advocated.
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Citation: Winnard, A., Nasser M., Debuse, D., Stokes, M., Evetts, S., Wilkinson, M., Hides, J. & Caplan, N. (2017). Systematic review of countermeasures and rehabilitation interventions to minimise physiological changes and risk of injury to the lumbopelvic area following long-term microgravity. Musculoskeletal Science and Practice, 27 (suppl. 1), S5-S14.
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