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Richter C, Braunstein B, Winnard A, Nasser M, Weber T. Human Biomechanical and Cardiopulmonary Responses to Partial Gravity - A Systematic Review. Front Physiol 2017; 8:583. [PMID: 28860998 PMCID: PMC5559498 DOI: 10.3389/fphys.2017.00583] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 07/28/2017] [Indexed: 11/30/2022] Open
Abstract
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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Affiliation(s)
- Charlotte Richter
- Space Medicine Office (HRE-AM), European Astronaut Centre Department (HRE-A)Cologne, Germany
- Institute of Biomechanics und Orthopaedics, German Sport UniversityCologne, Germany
| | - Bjoern Braunstein
- Institute of Biomechanics und Orthopaedics, German Sport UniversityCologne, Germany
- Centre for Health and Integrative Physiology in SpaceCologne, Germany
- German Research Centre for Elite SportCologne, Germany
| | - Andrew Winnard
- Faculty of Health and Life Sciences, Northumbria UniversityNewcastle upon Tyne, United Kingdom
| | - Mona Nasser
- Peninsula Dental School, Plymouth UniversityPlymouth, United Kingdom
| | - Tobias Weber
- Space Medicine Office (HRE-AM), European Astronaut Centre Department (HRE-A)Cologne, Germany
- KBRwyle, Wyle Laboratories GmbH, Science, Technology and Engineering GroupCologne, Germany
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Grenon SM, Sheynberg N, Hurwitz S, Xiao G, Ramsdell CD, Ehrman MD, Mai CL, Kristjansson SR, Sundby GH, Cohen RJ, Williams GH. Renal, Endocrine, and Cardiovascular Responses to Bed Rest in Male Subjects on a Constant Diet. J Investig Med 2004. [DOI: 10.1177/108155890405200221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
Background Exposure to actual and simulated microgravity induces cardiovascular deconditioning through a variety of factors. Although the mechanisms involved remain uncertain, one involves alterations in volume-regulating systems—the hypothesis being tested in this study. To maximize our ability to detect subtle changes in the volume-regulating systems, subjects were studied on a high-average salt intake to maximally suppress these systems basally. Methods Fourteen healthy male subjects underwent 14-day head-down tilt bed rest (HDTB) during which a constant 200 mEq sodium, 100 mEq potassium diet was maintained. Daily 24-hour urine collection was performed; plasma renin activity, serum aldosterone, plethysmography, and cardiovascular system identification were performed during a control period (pre-HDTB) and at the end of HDTB (end HDTB). Results Sodium excretion increased initially (pre-HDTB = 182.8 ± 10.4 mEq/total volume; early HDTB = 236.4 ± 13.0; p = .002) and then returned to baseline values. Potassium excretion increased 4 days after the initiation of HDTB and remained elevated thereafter (pre-HDTB = 82.2 ± 2.4/total volume; mid- to late HDTB = 89.4 ± 2.1; p = .02). Plasma renin activity increased significantly with HDTB (pre-HDTB = 1.28 ± 0.21 ng/mL/h; end HDTB = 1.69 ± 0.18; p = .01), but serum aldosterone did not change. A significant decrease in autonomic responsiveness and an increase in leg compliance were observed. Conclusions We conclude that even in the presence of a high-average salt intake diet, simulated microgravity leads to renal, cardioendocrine, and cardiovascular system alterations that likely contribute to cardiovascular deconditioning.
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Affiliation(s)
- S. Marlene Grenon
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA
| | - Natalie Sheynberg
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | - Shelley Hurwitz
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | - Grace Xiao
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA
| | - Craig D. Ramsdell
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | - Michael D. Ehrman
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | - C. Lan Mai
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | | | - Grete H. Sundby
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
| | - Richard J. Cohen
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA
| | - Gordon H. Williams
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Boston, MA
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Choukèr A, Thiel M, Baranov V, Meshkov D, Kotov A, Peter K, Messmer K, Christ F. Simulated microgravity, psychic stress, and immune cells in men: observations during 120-day 6 degrees HDT. J Appl Physiol (1985) 2001; 90:1736-43. [PMID: 11299263 DOI: 10.1152/jappl.2001.90.5.1736] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Because 6 degrees head-down tilt (HDT) is an established method to mimic low gravity on earth, the aim of the present study was to determine the effects of 120-day HDT on psychic stress and peripheral blood immune cells in six healthy male volunteers. Psychological state was assessed by a current stress test, and cortisol was measured in saliva. During HDT, all volunteers developed psychic stress, and the diurnal rhythm of cortisol secretion was significantly altered. In addition, urine excretion of dopamine and norepinephrine increased. The innate part of the immune response was activated, as evidenced by the increase in the expression of beta(2)-integrins on polymorphonuclear leukocytes and a rise in the number of circulating natural killer (NK) cell lymphocytes. The ratio of T-helper to T-cytotoxic and T-suppressor cells decreased, whereas no changes in T and B lymphocytes were observed. Plasma levels of interleukin-6 increased significantly and returned to basal levels after the end of the HDT period. Thus 6 degrees HDT appears to be a valid model to induce psychic stress and neuroendocrine-related changes in the immune system, changes that might also be encountered by astronauts and cosmonauts during long-duration spaceflights.
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Affiliation(s)
- A Choukèr
- Clinic of Anaesthesiology, University of Munich, 81366 Munich, Germany
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