1
|
Trappe TA, Minchev K, Perkins RK, Lavin KM, Jemiolo B, Ratchford SM, Claiborne A, Lee GA, Finch WH, Ryder JW, Ploutz-Snyder L, Trappe SW. NASA SPRINT exercise program efficacy for vastus lateralis and soleus skeletal muscle health during 70 days of simulated microgravity. J Appl Physiol (1985) 2024; 136:1015-1039. [PMID: 38328821 DOI: 10.1152/japplphysiol.00489.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 12/21/2023] [Accepted: 02/05/2024] [Indexed: 02/09/2024] Open
Abstract
The efficacy of the NASA SPRINT exercise countermeasures program for quadriceps (vastus lateralis) and triceps surae (soleus) skeletal muscle health was investigated during 70 days of simulated microgravity. Individuals completed 6° head-down-tilt bedrest (BR, n = 9), bedrest with resistance and aerobic exercise (BRE, n = 9), or bedrest with resistance and aerobic exercise and low-dose testosterone (BRE + T, n = 8). All groups were periodically tested for muscle (n = 9 times) and aerobic (n = 4 times) power during bedrest. In BR, surprisingly, the typical bedrest-induced decrements in vastus lateralis myofiber size and power were either blunted (myosin heavy chain, MHC I) or eliminated (MHC IIa), along with no change (P > 0.05) in %MHC distribution and blunted quadriceps atrophy. In BRE, MHC I (vastus lateralis and soleus) and IIa (vastus lateralis) contractile performance was maintained (P > 0.05) or increased (P < 0.05). Vastus lateralis hybrid fiber percentage was reduced (P < 0.05) and energy metabolism enzymes and capillarization were generally maintained (P > 0.05), while not all of these positive responses were observed in the soleus. Exercise offsets 100% of quadriceps and approximately two-thirds of soleus whole muscle mass loss. Testosterone (BRE + T) did not provide any benefit over exercise alone for either muscle and for some myocellular parameters appeared detrimental. In summary, the periodic testing likely provided a partial exercise countermeasure for the quadriceps in the bedrest group, which is a novel finding given the extremely low exercise dose. The SPRINT exercise program appears to be viable for the quadriceps; however, refinement is needed to completely protect triceps surae myocellular and whole muscle health for astronauts on long-duration spaceflights.NEW & NOTEWORTHY This study provides unique exercise countermeasures development information for astronauts on long-duration spaceflights. The NASA SPRINT program was protective for quadriceps myocellular and whole muscle health, whereas the triceps surae (soleus) was only partially protected as has been shown with other programs. The bedrest control group data may provide beneficial information for overall exercise dose and targeting fast-twitch muscle fibers. Other unique approaches for the triceps surae are needed to supplement existing exercise programs.
Collapse
Affiliation(s)
- Todd A Trappe
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Kiril Minchev
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Ryan K Perkins
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Kaleen M Lavin
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Bozena Jemiolo
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Stephen M Ratchford
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Alex Claiborne
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Gary A Lee
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - W Holmes Finch
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| | - Jeffrey W Ryder
- Universities Space Research Association, NASA Johnson Space Center, Houston, Texas, United States
| | - Lori Ploutz-Snyder
- Universities Space Research Association, NASA Johnson Space Center, Houston, Texas, United States
| | - Scott W Trappe
- Human Performance Laboratory, Ball State University, Muncie, Indiana, United States
| |
Collapse
|
2
|
Mastrandrea CJ, Hedge ET, Robertson AD, Heckman GA, Ho J, Granados Unger F, Hughson RL. High-intensity exercise does not protect against orthostatic intolerance following bedrest in 55- to 65-yr-old men and women. Am J Physiol Regul Integr Comp Physiol 2023; 325:R107-R119. [PMID: 37184226 DOI: 10.1152/ajpregu.00315.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/20/2023] [Accepted: 05/09/2023] [Indexed: 05/16/2023]
Abstract
Prolonged bedrest provokes orthostatic hypotension and intolerance of upright posture. Limited data are available on the cardiovascular responses of older adults to head-up tilt following bedrest, with no studies examining the potential benefits of exercise to mitigate intolerance in this age group. This randomized controlled trial of head-down bedrest (HDBR) in 55- to 65-yr-old men and women investigated if exercise could avert post-HDBR orthostatic intolerance. Twenty-two healthy older adults (11 female) underwent a strict 14-day HDBR and were assigned to either an exercise (EX) or control (CON) group. The exercise intervention included high-intensity, aerobic, and resistance exercises. Head-up tilt-testing to a maximum of 15 minutes was performed at baseline (Pre-Bedrest) and immediately after HDBR (R1), as well as 6 days (R6) and 4 weeks (R4wk) later. At Pre-Bedrest, three participants did not complete the full 15 minutes of tilt. At R1, 18 did not finish, with no difference in tilt end time between CON (422 ± 287 s) and EX (409 ± 346 s). No differences between CON and EX were observed at R6 or R4wk. At R1, just 1 participant self-terminated the test with symptoms, while 12 others reported symptoms only after physiological test termination criteria were reached. Finishers on R1 protected arterial pressure with higher total peripheral resistance relative to Pre-Bedrest. Cerebral blood velocity decreased linearly with reductions in arterial pressure, end-tidal CO2, and cardiac output. High-intensity interval exercise did not benefit post-HDBR orthostatic tolerance in older adults. Multiple factors were associated with the reduction in cerebral blood velocity leading to intolerance.
Collapse
Affiliation(s)
| | - Eric T Hedge
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
| | - Andrew D Robertson
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
| | - George A Heckman
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
| | - Joanne Ho
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
| | - Federico Granados Unger
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
| | | |
Collapse
|
3
|
Robin A, Wang L, Custaud MA, Liu J, Yuan M, Li Z, Lloret JC, Liu S, Dai X, Zhang J, Lv K, Li W, Gauquelin-Koch G, Wang H, Li K, Li X, Qu L, Navasiolava N, Li Y. Running vs. resistance exercise to counteract deconditioning induced by 90-day head-down bedrest. Front Physiol 2022; 13:902983. [PMID: 36117704 PMCID: PMC9473647 DOI: 10.3389/fphys.2022.902983] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 06/29/2022] [Indexed: 11/13/2022] Open
Abstract
Spaceflight is associated with enhanced inactivity, resulting in muscular and cardiovascular deconditioning. Although physical exercise is commonly used as a countermeasure, separate applications of running and resistive exercise modalities have never been directly compared during long-term bedrest. This study aimed to compare the effectiveness of two exercise countermeasure programs, running and resistance training, applied separately, for counteracting cardiovascular deconditioning induced by 90-day head-down bedrest (HDBR). Maximal oxygen uptake (V˙O2max), orthostatic tolerance, continuous ECG and blood pressure (BP), body composition, and leg circumferences were measured in the control group (CON: n = 8), running exercise group (RUN: n = 7), and resistive exercise group (RES: n = 7). After HDBR, the decrease in V˙O2max was prevented by RUN countermeasure and limited by RES countermeasure (−26% in CON p < 0.05, −15% in RES p < 0.05, and −4% in RUN ns). Subjects demonstrated surprisingly modest orthostatic tolerance decrease for different groups, including controls. Lean mass loss was limited by RES and RUN protocols (−10% in CON vs. −5% to 6% in RES and RUN). Both countermeasures prevented the loss in thigh circumference (−7% in CON p < 0.05, −2% in RES ns, and −0.6% in RUN ns) and limited loss in calf circumference (−10% in CON vs. −7% in RES vs. −5% in RUN). Day–night variations in systolic BP were preserved during HDBR. Decrease in V˙O2max positively correlated with decrease in thigh (r = 0.54 and p = 0.009) and calf (r = 0.52 and p = 0.012) circumferences. During this 90-day strict HDBR, running exercise successfully preserved V˙O2max, and resistance exercise limited its decline. Both countermeasures limited loss in global lean mass and leg circumferences. The V˙O2max reduction seems to be conditioned more by muscular than by cardiovascular parameters.
Collapse
Affiliation(s)
- Adrien Robin
- Univ Angers, CHU Angers, CRC, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Linjie Wang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Marc-Antoine Custaud
- Univ Angers, CHU Angers, CRC, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Jiexin Liu
- Beijing Tiantan Hospital, Medical Capital University, Beijing, China
| | - Min Yuan
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Zhili Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | | | - Shujuan Liu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Xiaoqian Dai
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Jianfeng Zhang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Ke Lv
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Wenjiong Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | | | - Huijuan Wang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Kai Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Xiaotao Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Lina Qu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Nastassia Navasiolava
- Univ Angers, CHU Angers, CRC, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
- *Correspondence: Nastassia Navasiolava, ; Yinghui Li,
| | - Yinghui Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
- *Correspondence: Nastassia Navasiolava, ; Yinghui Li,
| |
Collapse
|
4
|
Hedge ET, Patterson CA, Mastrandrea CJ, Sonjak V, Hajj-Boutros G, Faust A, Morais JA, Hughson RL. Implementation of exercise countermeasures during spaceflight and microgravity analogue studies: Developing countermeasure protocols for bedrest in older adults (BROA). Front Physiol 2022; 13:928313. [PMID: 36017336 PMCID: PMC9395735 DOI: 10.3389/fphys.2022.928313] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/27/2022] [Indexed: 12/18/2022] Open
Abstract
Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts’ bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55–65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.
Collapse
Affiliation(s)
- Eric T. Hedge
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | | | | | - Vita Sonjak
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Guy Hajj-Boutros
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Andréa Faust
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - José A. Morais
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
- Division of Geriatric Medicine, McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Richard L. Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- *Correspondence: Richard L. Hughson,
| |
Collapse
|
5
|
Kramer A, Venegas-Carro M, Zange J, Sies W, Maffiuletti NA, Gruber M, Degens H, Moreno-Villanueva M, Mulder E. Daily 30-min exposure to artificial gravity during 60 days of bed rest does not maintain aerobic exercise capacity but mitigates some deteriorations of muscle function: results from the AGBRESA RCT. Eur J Appl Physiol 2021; 121:2015-2026. [PMID: 33811556 PMCID: PMC8192329 DOI: 10.1007/s00421-021-04673-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 03/28/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE Spaceflight impairs physical capacity. Here we assessed the protective effect of artificial gravity (AG) on aerobic exercise capacity and muscle function during bed rest, a spaceflight analogue. METHODS 24 participants (33 ± 9 years, 175 ± 9 cm, 74 ± 10 kg, 8 women) were randomly allocated to one of three groups: continuous AG (cAG), intermittent AG (iAG) or control (CTRL). All participants were subjected to 60 days of six-degree head-down tilt bed rest, and subjects of the intervention groups completed 30 min of centrifugation per day: cAG continuously and iAG for 6 × 5 min, with an acceleration of 1g at the center of mass. Physical capacity was assessed before and after bed rest via maximal voluntary contractions, cycling spiroergometry, and countermovement jumps. RESULTS AG had no significant effect on aerobic exercise capacity, flexor muscle function and isometric knee extension strength or rate of force development (RFD). However, AG mitigated the effects of bed rest on jumping power (group * time interaction of the rmANOVA p < 0.001; iAG - 25%, cAG - 26%, CTRL - 33%), plantar flexion strength (group * time p = 0.003; iAG - 35%, cAG - 31%, CTRL - 48%) and plantar flexion RFD (group * time p = 0.020; iAG - 28%, cAG - 12%, CTRL - 40%). Women showed more pronounced losses than men in jumping power (p < 0.001) and knee extension strength (p = 0.010). CONCLUSION The AG protocols were not suitable to maintain aerobic exercise capacity, probably due to the very low cardiorespiratory demand of this intervention. However, they mitigated some losses in muscle function, potentially due to the low-intensity muscle contractions during centrifugation used to avoid presyncope.
Collapse
Affiliation(s)
- Andreas Kramer
- Human Performance Research Centre, Department of Sport Science, University of Konstanz, 78457, Konstanz, Germany.
| | - María Venegas-Carro
- Human Performance Research Centre, Department of Sport Science, University of Konstanz, 78457, Konstanz, Germany
| | - Jochen Zange
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Wolfram Sies
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | | | - Markus Gruber
- Human Performance Research Centre, Department of Sport Science, University of Konstanz, 78457, Konstanz, Germany
| | - Hans Degens
- Department of Life Sciences, Manchester Metropolitan University, Manchester, UK.,Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - María Moreno-Villanueva
- Human Performance Research Centre, Department of Sport Science, University of Konstanz, 78457, Konstanz, Germany
| | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| |
Collapse
|
6
|
Sandal PH, Kim D, Fiebig L, Winnard A, Caplan N, Green DA, Weber T. Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning-A Systematic Review. PLoS One 2020; 15:e0234412. [PMID: 32516346 PMCID: PMC7282646 DOI: 10.1371/journal.pone.0234412] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 05/24/2020] [Indexed: 12/13/2022] Open
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.
Collapse
Affiliation(s)
- Peter H. Sandal
- Space Medicine Team, European Astronaut Centre, European Space Agency, Köln, Germany
| | - David Kim
- Space Medicine Team, European Astronaut Centre, European Space Agency, Köln, Germany
- Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Leonie Fiebig
- Space Medicine Team, European Astronaut Centre, European Space Agency, Köln, Germany
- Institute of Biomechanics und Orthopaedics, German Sport University, Cologne, Germany
| | - Andrew Winnard
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Nick Caplan
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - David A. Green
- Space Medicine Team, European Astronaut Centre, European Space Agency, Köln, Germany
- Centre of Human & Applied Physiological Sciences, King’s College London, London, United Kingdom
- KBR GmbH, Köln, Germany
| | - Tobias Weber
- Space Medicine Team, European Astronaut Centre, European Space Agency, Köln, Germany
- KBR GmbH, Köln, Germany
| |
Collapse
|
7
|
Palacios S, Caiani EG, Landreani F, Martínez JP, Pueyo E. Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of T-Wave Vector. Front Physiol 2019; 10:1510. [PMID: 31920714 PMCID: PMC6928004 DOI: 10.3389/fphys.2019.01510] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/29/2019] [Indexed: 11/13/2022] Open
Abstract
Ventricular arrhythmias and sudden cardiac death during long-term space missions are a major concern for space agencies. Long-duration spaceflight and its ground-based analog head-down bed rest (HDBR) have been reported to markedly alter autonomic and cardiac functioning, particularly affecting ventricular repolarization of the electrocardiogram (ECG). In this study, novel methods are developed, departing from previously published methodologies, to quantify the index of Periodic Repolarization Dynamics (PRD), an arrhythmic risk marker that characterizes sympathetically-mediated low-frequency oscillations in the T-wave vector. PRD is evaluated in ECGs from 42 volunteers at rest and during an orthostatic tilt table test recorded before and after 60-day –6° HDBR. Our results indicate that tilt test, on top of enhancing sympathetic regulation of heart rate, notably increases PRD, both before and after HDBR, thus supporting previous evidence on PRD being an indicator of sympathetic modulation of ventricular repolarization. Importantly, long-term microgravity exposure is shown to lead to significant increases in PRD, both when evaluated at rest and, even more notably, in response to tilt test. The extent of microgravity-induced changes in PRD has been associated with arrhythmic risk in prior studies. An exercise-based, but not a nutrition-based, countermeasure is able to partially reverse microgravity-induced effects on PRD. In conclusion, long-term exposure to microgravity conditions leads to elevated low-frequency oscillations of ventricular repolarization, which are potentiated following sympathetic stimulation and are related to increased risk for repolarization instabilities and arrhythmias. Tested countermeasures are only partially effective in counteracting microgravity effects.
Collapse
Affiliation(s)
- Saúl Palacios
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Enrico G Caiani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Federica Landreani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Juan Pablo Martínez
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
| | - Esther Pueyo
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
| |
Collapse
|
8
|
Koschate J, Thieschäfer L, Drescher U, Hoffmann U. Impact of 60 days of 6° head down tilt bed rest on muscular oxygen uptake and heart rate kinetics: efficacy of a reactive sledge jump countermeasure. Eur J Appl Physiol 2018; 118:1885-1901. [PMID: 29946969 DOI: 10.1007/s00421-018-3915-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 06/08/2018] [Indexed: 01/06/2023]
Abstract
PURPOSE The effects of 60 days of head down tilt bed rest (HDBR) with and without the application of a reactive jump countermeasure were investigated, using a method which enables to discriminate between pulmonary ([Formula: see text]O2pulm) and muscular ([Formula: see text]O2musc) oxygen uptake kinetics to control for hemodynamic influences. METHODS 22 subjects were randomly allocated to either a group performing a reactive jumps countermeasure (JUMP; n = 11, male, 29 ± 7 years, 23.9 ± 1.3 kg m- 2) or a control group (CTRL; n = 11, male, 29 ± 6 years, 23.3 ± 2.0 kg m- 2). Heart rate (HR) and [Formula: see text]O2pulm were measured in response to repeated changes in work rate between 30 and 80 W before (BDC-9) and two times after HDBR (R+ 2, R+ 13). Kinetic responses of HR, [Formula: see text]O2pulm, and [Formula: see text]O2musc were assessed applying time series analysis. Higher maxima in cross-correlation functions (CCFmax(x)) between work rate and the respective parameter indicate faster kinetics responses. Statistical analysis was performed applying multifactorial analysis of variance. RESULTS CCFmax([Formula: see text]O2musc) and CCFmax([Formula: see text]O2pulm) were not significantly different before and after HDBR (P > 0.05). CCFmax(HR) decreased following bed rest (JUMP: BDC-9: 0.30 ± 0.09 vs. R+ 2: 0.28 ± 0.06 vs. R+13: 0.28 ± 0.07; CTRL: 0.35 ± 0.09 vs. 0.27 ± 0.06 vs. 0.33 ± 0.07 P = 0.025). No significant differences between the groups were observed (P > 0.05). Significant alterations were found for CCFmax of mean arterial blood pressure (mBP) after HDBR (JUMP: BDC-9: 0.21 ± 0.07 vs. R+ 2: 0.30 ± 0.13 vs. R+ 13: 0.28 ± 0.08; CTRL: 0.25 ± 0.07 vs. 0.38 ± 0.13 vs. 0.28 ± 0.08; P = 0.008). CONCLUSIONS Despite hemodynamic changes, [Formula: see text]O2 kinetics seem to be preserved for a longer period of HDBR, even without the application of a countermeasure.
Collapse
Affiliation(s)
- J Koschate
- Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany.
| | - L Thieschäfer
- Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany
| | - U Drescher
- Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany
| | - U Hoffmann
- Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany
| |
Collapse
|
9
|
|
10
|
Zhang LF, Hargens AR. Spaceflight-Induced Intracranial Hypertension and Visual Impairment: Pathophysiology and Countermeasures. Physiol Rev 2017; 98:59-87. [PMID: 29167331 DOI: 10.1152/physrev.00017.2016] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 05/25/2017] [Accepted: 05/26/2017] [Indexed: 12/21/2022] Open
Abstract
Visual impairment intracranial pressure (VIIP) syndrome is considered an unexplained major risk for future long-duration spaceflight. NASA recently redefined this syndrome as Spaceflight-Associated Neuro-ocular Syndrome (SANS). Evidence thus reviewed supports that chronic, mildly elevated intracranial pressure (ICP) in space (as opposed to more variable ICP with posture and activity on Earth) is largely accounted for by loss of hydrostatic pressures and altered hemodynamics in the intracranial circulation and the cerebrospinal fluid system. In space, an elevated pressure gradient across the lamina cribrosa, caused by a chronic but mildly elevated ICP, likely elicits adaptations of multiple structures and fluid systems in the eye which manifest themselves as the VIIP syndrome. A chronic mismatch between ICP and intraocular pressure (IOP) in space may acclimate the optic nerve head, lamina cribrosa, and optic nerve subarachnoid space to a condition that is maladaptive to Earth, all contributing to the pathogenesis of space VIIP syndrome. Relevant findings help to evaluate whether artificial gravity is an appropriate countermeasure to prevent this seemingly adverse effect of long-duration spaceflight.
Collapse
Affiliation(s)
- Li-Fan Zhang
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, China; and Department of Orthopaedic Surgery, University of California, San Diego, California
| | - Alan R Hargens
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, China; and Department of Orthopaedic Surgery, University of California, San Diego, California
| |
Collapse
|
11
|
How to prevent the detrimental effects of two months of bed-rest on muscle, bone and cardiovascular system: an RCT. Sci Rep 2017; 7:13177. [PMID: 29030644 PMCID: PMC5640633 DOI: 10.1038/s41598-017-13659-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/27/2017] [Indexed: 11/22/2022] Open
Abstract
Physical inactivity leads to a deconditioning of the skeletal, neuromuscular and cardiovascular system. It can lead to impaired quality of life, loss of autonomy, falls and fractures. Regular exercise would be a logical remedy, but the generally recommended high-volume endurance and strength training programs require a lot of time and equipment. In this randomized controlled study with 23 healthy participants, we established that a short, intensive jump training program can prevent the large musculoskeletal and cardiovascular deconditioning effects caused by two months of physical inactivity during bed rest, particularly the loss of bone mineral mass and density, lean muscle mass, maximal leg strength and peak oxygen uptake. The jump training group showed no significant changes with respect to these indicators of musculoskeletal and cardiovascular health after 60 days of bed rest, whereas the control group exhibited substantial losses: up to −2.6% in tibial bone mineral content and density, −5% in leg lean mass, −40% in maximal knee extension torque and −29% in peak oxygen uptake. Consequently, we recommend jump training as a very time-efficient and effective type of exercise for astronauts on long-term space missions, the elderly and sedentary populations in general.
Collapse
|
12
|
Goswami N. Falls and Fall-Prevention in Older Persons: Geriatrics Meets Spaceflight! Front Physiol 2017; 8:603. [PMID: 29075195 PMCID: PMC5641583 DOI: 10.3389/fphys.2017.00603] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 08/04/2017] [Indexed: 02/04/2023] Open
Abstract
This paper provides a general overview of key physiological consequences of microgravity experienced during spaceflight and of important parallels and connections to the physiology of aging. Microgravity during spaceflight influences cardiovascular function, cerebral autoregulation, musculoskeletal, and sensorimotor system performance. A great deal of research has been carried out to understand these influences and to provide countermeasures to reduce the observed negative consequences of microgravity on physiological function. Such research can inform and be informed by research related to physiological changes and the deterioration of physiological function due to aging. For example, head-down bedrest is used as a model to study effects of spaceflight deconditioning due to reduced gravity. As hospitalized older persons spend up to 80% of their time in bed, the deconditioning effects of bedrest confinement on physiological functions and parallels with spaceflight deconditioning can be exploited to understand and combat both variations of deconditioning. Deconditioning due to bed confinement in older persons can contribute to a downward spiral of increasing frailty, orthostatic intolerance, falls, and fall-related injury. As astronauts in space spend substantial amounts of time carrying out exercise training to counteract the microgravity-induced deconditioning and to counteract orthostatic intolerance on return to Earth, it is logical to suggest some of these interventions for bed-confined older persons. Synthesizing knowledge regarding deconditioning due to reduced gravitational stress in space and deconditioning during bed confinement allows for a more comprehensive approach that can incorporate aspects such as (mal-) nutrition, muscle strength and function, cardiovascular (de-) conditioning, and cardio-postural interactions. The impact of such integration can provide new insights and lead to methods of value for both space medicine and geriatrics (Geriatrics meets spaceflight!). In particular, such integration can lead to procedures that address the morbidity and the mortality associated with bedrest immobilization and in the rising health care costs associated with an aging population demographic.
Collapse
Affiliation(s)
- Nandu Goswami
- Gravitational Physiology, Aging and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria.,Department of Health Sciences, Alma Mater Europea University, Maribor, Slovenia
| |
Collapse
|
13
|
Ried-Larsen M, Aarts HM, Joyner MJ. Effects of strict prolonged bed rest on cardiorespiratory fitness: systematic review and meta-analysis. J Appl Physiol (1985) 2017; 123:790-799. [DOI: 10.1152/japplphysiol.00415.2017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/29/2017] [Accepted: 07/07/2017] [Indexed: 12/29/2022] Open
Abstract
The aim of this systematic review and meta-analysis [International Prospective Register of Systematic Reviews (PROSPERO) CRD42017055619] was to assess the effects of strict prolonged bed rest (without countermeasures) on maximal oxygen uptake (V̇o2max) and to explore sources of variation therein. Since 1949, 80 studies with a total of 949 participants (>90% men) have been published with data on strict bed rest and V̇o2max. The studies were conducted mainly in young participants [median age (interquartile range) 24.5 (22.4–34.0) yr]. The duration of bed rest ranged from 1 to 90 days. V̇o2max declined linearly across bed rest duration. No statistical difference in the decline among studies reporting V̇o2max as l/min (−0.3% per day) compared with studies reporting V̇o2max normalized to body weight (ml·kg−1·min−1; −0.43% per day) was observed. Although both total body weight and lean body mass declined in response to bed rest, we did not see any associations with the decline in V̇o2max. However, 15–26% of the variation in the decline in V̇o2max was explained by the pre-bed-rest V̇o2max levels, independent of the duration of bed rest (i.e., higher pre-bed-rest V̇o2max levels were associated with larger declines in V̇o2max). Furthermore, the systematic review revealed a gap in the knowledge about the cardiovascular response to extreme physical inactivity, particularly in older subjects and women of any age group. In addition to its relevance to spaceflight, this lack of data has significant translational implications because younger women sometimes undergo prolonged periods of bed rest associated with the complications of pregnancy and the incidence of hospitalization including prolonged periods of bed rest increases with age. NEW & NOTEWORTHY Large interindividual responses of maximal oxygen uptake (V̇o2max) to aerobic exercise training exist. However, less is known about the variability in the response of V̇o2max to prolonged bed rest. This systematic review and meta-analysis showed that pre-bed-rest V̇o2max values were inversely associated with the change in V̇o2max independent of the duration of bed rest. Moreover, we identified a large knowledge gap about the causes of decline in V̇o2max, particularly in postmenopausal women, which may have clinical implications.
Collapse
Affiliation(s)
- Mathias Ried-Larsen
- Centre for Physical Activity Research, Rigshospitalet, Copenhagen, Denmark; and
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Hugo M. Aarts
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Michael J. Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| |
Collapse
|
14
|
Heer M, Baecker N, Frings-Meuthen P, Graf S, Zwart SR, Biolo G, Smith SM. Effects of high-protein intake on bone turnover in long-term bed rest in women. Appl Physiol Nutr Metab 2017; 42:537-546. [DOI: 10.1139/apnm-2016-0292] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Bed rest (BR) causes bone loss, even in otherwise healthy subjects. Several studies suggest that ambulatory subjects may benefit from high-protein intake to stimulate protein synthesis and to maintain muscle mass. However, increasing protein intake above the recommended daily intake without adequate calcium and potassium intake may increase bone resorption. We hypothesized that a regimen of high-protein intake (HiPROT), applied in an isocaloric manner during BR, with calcium and potassium intake meeting recommended values, would prevent any effect of BR on bone turnover. After a 20-day ambulatory adaptation to a controlled environment, 16 women participated in a 60-day, 6° head-down-tilt (HDT) BR and were assigned randomly to 1 of 2 groups. Control (CON) subjects (n = 8) received 1 g/(kg body mass·day)−1 dietary protein. HiPROT subjects (n = 8) received 1.45 g protein/(kg body mass·day)−1 plus an additional 0.72 g branched-chain amino acids per day during BR. All subjects received an individually tailored diet (before HDTBR: 1888 ± 98 kcal/day; during HDTBR: 1604 ± 125 kcal/day; after HDTBR: 1900 ± 262 kcal/day), with the CON group’s diet being higher in fat and carbohydrate intake. High-protein intake exacerbated the BR-induced increase in bone resorption marker C-telopeptide (>30%) (p < 0.001) by the end of BR. Bone formation markers were unaffected by BR and high-protein intake. We conclude that high-protein intake in BR might increase bone loss. Further long-duration studies are mandatory to show how the positive effect of protein on muscle mass can be maintained without the risk of reducing bone mineral density.
Collapse
Affiliation(s)
- Martina Heer
- Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, 53115 Bonn, Germany
| | - Natalie Baecker
- Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, 53115 Bonn, Germany
| | - Petra Frings-Meuthen
- German Aerospace Center (DLR), Institute of Aerospace Medicine, 51147 Cologne, Germany
| | - Sonja Graf
- Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, 53115 Bonn, Germany
| | - Sara R. Zwart
- University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Gianni Biolo
- Department of Clinical, Technological and Morphological Sciences, Division of Internal Medicine, University of Trieste, 34127 Trieste, Italy
| | - Scott M. Smith
- Human Health and Performance Directorate, NASA Lyndon B. Johnson Space Center, Houston, TX 77058, USA
| |
Collapse
|
15
|
Schneider SM, Lee SMC, Feiveson AH, Watenpaugh DE, Macias BR, Hargens AR. Treadmill exercise within lower body negative pressure protects leg lean tissue mass and extensor strength and endurance during bed rest. Physiol Rep 2017; 4:4/15/e12892. [PMID: 27495299 PMCID: PMC4985554 DOI: 10.14814/phy2.12892] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 07/19/2016] [Indexed: 01/26/2023] Open
Abstract
Leg muscle mass and strength are decreased during reduced activity and non‐weight‐bearing conditions such as bed rest (BR) and spaceflight. Supine treadmill exercise within lower body negative pressure (LBNPEX) provides full‐body weight loading during BR and may prevent muscle deconditioning. We hypothesized that a 40‐min interval exercise protocol performed against LBNPEX 6 days week−1 would attenuate losses in leg lean mass (LLM), strength, and endurance during 6° head‐down tilt BR, with similar benefits for men and women. Fifteen pairs of healthy monozygous twins (8 male and 7 female pairs) completed 30 days of BR with one sibling of each twin pair assigned randomly as the non‐exercise control (CON) and the other twin as the exercise subject (EX). Before and after BR, LLM and isokinetic leg strength and endurance were measured. Mean knee and ankle extensor and flexor strength and endurance and LLM decreased from pre‐ to post‐BR in the male CON subjects (P < 0.01), but knee extensor strength and endurance, ankle extensor strength, and LLM were maintained in the male EX subjects. In contrast, no pre‐ to post‐BR changes were significant in the female subjects, either CON or EX, likely due to their lower pre‐BR values. Importantly, the LBNPEX countermeasure prevents or attenuates declines in LLM as well as extensor leg strength and endurance. Individuals who are stronger, have higher levels of muscular endurance, and/or have greater LLM are likely to experience greater losses during BR than those who are less fit.
Collapse
Affiliation(s)
| | - Stuart M C Lee
- Wyle Science, Technology, and Engineering Group, Houston, Texas
| | | | | | | | | |
Collapse
|
16
|
Ploutz-Snyder LL, Downs M, Ryder J, Hackney K, Scott J, Buxton R, Goetchius E, Crowell B. Integrated resistance and aerobic exercise protects fitness during bed rest. Med Sci Sports Exerc 2017; 46:358-68. [PMID: 24441215 DOI: 10.1249/mss.0b013e3182a62f85] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION The current exercise countermeasures have not fully protected astronauts' preflight aerobic and muscular fitness levels during International Space Station (ISS) missions, prompting a need to optimize the exercise prescription to improve or maintain astronauts' ability to perform critical tasks and eventually extend the duration of missions. PURPOSE To test the hypothesis that an integrated resistance and aerobic exercise prescription performed with exercise equipment similar to that on the ISS can be tolerated and maintain cardiovascular and muscular fitness during 14 d of exposure to a model of microgravity. METHODS Subjects (n = 9) participated in 14-21 d of pre-bed rest training and familiarization, 14 d of bed rest + iRAT exercise, and 7 d of ambulatory recovery. Peak aerobic capacity (V˙O2peak), ventilatory threshold (VT), and isokinetic and leg press tests were performed before and after bed rest to evaluate cardiovascular and muscle functions. Muscle cross-sectional area (CSA) was determined before, during, and after bed rest using magnetic resonance imaging (MRI). RESULTS Improvements from before to after bed rest were observed in V˙O2peak (2.8 ± 0.2 to 3.2 ± 0.2 L·min(-1)), VT (1.9 ± 0.2 to 2.1 ± 0.2 L·min(-1)), leg muscle power (1582 ± 317 to 1740 ± 359 W), and muscle CSA of the grouped vastus lateralis, vastus intermedius, and vastus medialis muscles (67.5 ± 8.4 to 68.9 ± 8.3 cm). Muscle strength and total CSA of the upper and lower legs were not different from before to after bed rest. CONCLUSIONS This is the first report of exercise being completely effective for the prevention of cardiovascular and skeletal muscle deconditioning during strict bed rest using exercise equipment similar to that on the ISS. This was accomplished with high subject compliance.
Collapse
Affiliation(s)
- Lori L Ploutz-Snyder
- 1Universities Space Research Association, Houston, TX; 2University of Houston, Houston TX; and 3Wyle Science, Technology and Engineering Group, Houston, TX
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Bosutti A, Salanova M, Blottner D, Buehlmeier J, Mulder E, Rittweger J, Yap MH, Ganse B, Degens H. Whey protein with potassium bicarbonate supplement attenuates the reduction in muscle oxidative capacity during 19 days of bed rest. J Appl Physiol (1985) 2016; 121:838-848. [DOI: 10.1152/japplphysiol.00936.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 08/02/2016] [Indexed: 12/29/2022] Open
Abstract
The effectiveness of whey protein plus potassium bicarbonate-enriched diet (WP+KHCO3) in mitigating disuse-induced changes in muscle fiber oxidative capacity and capillarization was investigated in a 21-day crossover design bed rest study. Ten healthy men (31 ± 6 yr) once received WP+KHCO3 and once received a standardized isocaloric diet. Muscle biopsies were taken 2 days before and during the 19th day of bed rest (BR) from the soleus (SOL) and vastus lateralis (VL) muscle. Whole-body aerobic power (V̇o2 max), muscle fatigue, and isometric strength of knee extensor and plantar flexor muscles were monitored. Muscle fiber types and capillaries were identified by immunohistochemistry. Fiber oxidative capacity was determined as the optical density (OD) at 660 nm of succinate dehydrogenase (SDH)-stained sections. The product of fiber cross-sectional area and SDH-OD (integrated SDH) indicated the maximal oxygen consumption of that fiber. The maximal oxygen consumption supported by a capillary was calculated as the integrated SDH in its supply area. BR reduced isometric strength of knee extensor muscles ( P < 0.05), and the fiber oxidative capacity ( P < 0.001) and V̇o2 max ( P = 0.042), but had no significant impact on muscle capillarization or fatigue resistance of thigh muscles. The maximal oxygen consumption supported by a capillary was reduced by 24% in SOL and 16% in VL ( P < 0.001). WP+KHCO3 attenuated the disuse-induced reduction in fiber oxidative capacity in both muscles ( P < 0.01). In conclusion, following 19 days of bed rest, the decrement in fiber oxidative capacity is proportionally larger than the loss of capillaries. WP+KHCO3 appears to attenuate disuse-induced reductions in fiber oxidative capacity.
Collapse
Affiliation(s)
- Alessandra Bosutti
- Department of Medicine, Surgery and Health Sciences, University of Trieste, Cattinara Hospital, Trieste, Italy
- School of Healthcare Science, Manchester Metropolitan University, Manchester, United Kingdom
| | | | - Dieter Blottner
- Center for Space Medicine Berlin (ZWMB), Berlin, Germany
- Charité Universitätsmedizin Berlin, Vegetative Anatomy, Berlin, Germany
| | - Judith Buehlmeier
- University of Bonn, Department of Nutrition and Food Science, Bonn, Germany
- Institute of Aerospace Medicine, German Aerospace Center DLR, Cologne, Germany; and
| | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center DLR, Cologne, Germany; and
| | - Jörn Rittweger
- Institute of Aerospace Medicine, German Aerospace Center DLR, Cologne, Germany; and
| | - Moi Hoon Yap
- School of Healthcare Science, Manchester Metropolitan University, Manchester, United Kingdom
| | - Bergita Ganse
- Institute of Aerospace Medicine, German Aerospace Center DLR, Cologne, Germany; and
| | - Hans Degens
- School of Healthcare Science, Manchester Metropolitan University, Manchester, United Kingdom
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| |
Collapse
|
18
|
Holt JA, Macias BR, Schneider SM, Watenpaugh DE, Lee SMC, Chang DG, Hargens AR. WISE 2005: Aerobic and resistive countermeasures prevent paraspinal muscle deconditioning during 60-day bed rest in women. J Appl Physiol (1985) 2016; 120:1215-22. [DOI: 10.1152/japplphysiol.00532.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 02/16/2016] [Indexed: 11/22/2022] Open
Abstract
Microgravity-induced lumbar paraspinal muscle deconditioning may contribute to back pain commonly experienced by astronauts and may increase the risk of postflight injury. We hypothesized that a combined resistive and aerobic exercise countermeasure protocol that included spinal loading would mitigate lumbar paraspinal muscle deconditioning during 60 days of bed rest in women. Sixteen women underwent 60-day, 6° head-down-tilt bed rest (BR) and were randomized into control and exercise groups. During bed rest the control group performed no exercise. The exercise group performed supine treadmill exercise within lower body negative pressure (LBNP) for 3-4 days/wk and flywheel resistive exercise for 2–3 days/wk. Paraspinal muscle cross-sectional area (CSA) was measured using a lumbar spine MRI sequence before and after BR. In addition, isokinetic spinal flexion and extension strengths were measured before and after BR. Data are presented as means ± SD. Total lumbar paraspinal muscle CSA decreased significantly more in controls (10.9 ± 3.4%) than in exercisers (4.3 ± 3.4%; P < 0.05). The erector spinae was the primary contributor (76%) to total lumbar paraspinal muscle loss. Moreover, exercise attenuated isokinetic spinal extension loss (−4.3 ± 4.5%), compared with controls (−16.6 ± 11.2%; P < 0.05). In conclusion, LBNP treadmill and flywheel resistive exercises during simulated microgravity mitigate decrements in lumbar paraspinal muscle structure and spine function. Therefore spaceflight exercise countermeasures that attempt to reproduce spinal loads experienced on Earth may mitigate spinal deconditioning during long-duration space travel.
Collapse
Affiliation(s)
- Jacquelyn A. Holt
- Department of Orthopaedic Surgery, University of California, San Diego, California
| | - Brandon R. Macias
- Department of Orthopaedic Surgery, University of California, San Diego, California
| | | | - Donald E. Watenpaugh
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas; and
| | | | - Douglas G. Chang
- Department of Orthopaedic Surgery, University of California, San Diego, California
| | - Alan R. Hargens
- Department of Orthopaedic Surgery, University of California, San Diego, California
| |
Collapse
|
19
|
Hargens AR, Vico L. Long-duration bed rest as an analog to microgravity. J Appl Physiol (1985) 2016; 120:891-903. [PMID: 26893033 DOI: 10.1152/japplphysiol.00935.2015] [Citation(s) in RCA: 174] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 02/12/2016] [Indexed: 11/22/2022] Open
Abstract
Long-duration bed rest is widely employed to simulate the effects of microgravity on various physiological systems, especially for studies of bone, muscle, and the cardiovascular system. This microgravity analog is also extensively used to develop and test countermeasures to microgravity-altered adaptations to Earth gravity. Initial investigations of bone loss used horizontal bed rest with the view that this model represented the closest approximation to inactivity and minimization of hydrostatic effects, but all Earth-based analogs must contend with the constant force of gravity by adjustment of the G vector. Later concerns about the lack of similarity between headward fluid shifts in space and those with horizontal bed rest encouraged the use of 6 degree head-down tilt (HDT) bed rest as pioneered by Russian investigators. Headward fluid shifts in space may redistribute bone from the legs to the head. At present, HDT bed rest with normal volunteers is the most common analog for microgravity simulation and to test countermeasures for bone loss, muscle and cardiac atrophy, orthostatic intolerance, and reduced muscle strength/exercise capacity. Also, current physiologic countermeasures are focused on long-duration missions such as Mars, so in this review we emphasize HDT bed rest studies with durations of 30 days and longer. However, recent results suggest that the HDT bed rest analog is less representative as an analog for other important physiological problems of long-duration space flight such as fluid shifts, spinal dysfunction and radiation hazards.
Collapse
Affiliation(s)
- Alan R Hargens
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California; and Institut National de la Santé et de la Recherche Médicale Unité 1059, University of Lyon, St-Etienne, France
| | - Laurence Vico
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California; and Institut National de la Santé et de la Recherche Médicale Unité 1059, University of Lyon, St-Etienne, France
| |
Collapse
|
20
|
Moore AD, Downs ME, Lee SMC, Feiveson AH, Knudsen P, Ploutz-Snyder L. Peak exercise oxygen uptake during and following long-duration spaceflight. J Appl Physiol (1985) 2014; 117:231-8. [DOI: 10.1152/japplphysiol.01251.2013] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This investigation was designed to measure aerobic capacity (V̇o2peak) during and after long-duration International Space Station (ISS) missions. Astronauts (9 males, 5 females: 49 ± 5 yr, 77.2 ± 15.1 kg, 40.6 ± 6.4 ml·kg−1·min−1 [mean ± SD]) performed peak cycle tests ∼90 days before flight, 15 days after launch, every ∼30 days in-flight, and on recovery days 1 (R + 1), R + 10, and R + 30. Expired metabolic gas fractions, ventilation, and heart rate (HR) were measured. Data were analyzed using mixed-model linear regression. The main findings of this study were that V̇o2peak decreased early in-flight (∼17%) then gradually increased during flight but never returned to preflight levels. V̇o2peak was lower on R + 1 and R + 10 than preflight but recovered by R + 30. Peak HR was not different from preflight at any time during or following flight. A sustained decrease in V̇o2peak during and/or early postflight was not a universal finding in this study, since seven astronauts were able to attain their preflight V̇o2peak levels either at some time during flight or on R + 1. Four of these astronauts performed in-flight exercise at higher intensities compared with those who experienced a decline in V̇o2peak, and three had low aerobic capacities before flight. These data indicate that, while V̇o2peak may be difficult to maintain during long-duration ISS missions, aerobic deconditioning is not an inevitable consequence of long-duration spaceflight.
Collapse
Affiliation(s)
- Alan D. Moore
- Wyle Science, Technology & Engineering Group, Houston, Texas
| | | | | | - Alan H. Feiveson
- National Aeronautics and Space Administration Johnson Space Center, Houston, Texas
| | | | | |
Collapse
|
21
|
Hackney KJ, English KL. Protein and Essential Amino Acids to Protect Musculoskeletal Health during Spaceflight: Evidence of a Paradox? Life (Basel) 2014; 4:295-317. [PMID: 25370374 PMCID: PMC4206848 DOI: 10.3390/life4030295] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/19/2014] [Accepted: 06/23/2014] [Indexed: 11/17/2022] Open
Abstract
Long-duration spaceflight results in muscle atrophy and a loss of bone mineral density. In skeletal muscle tissue, acute exercise and protein (e.g., essential amino acids) stimulate anabolic pathways (e.g., muscle protein synthesis) both independently and synergistically to maintain neutral or positive net muscle protein balance. Protein intake in space is recommended to be 12%-15% of total energy intake (≤1.4 g∙kg-1∙day-1) and spaceflight is associated with reduced energy intake (~20%), which enhances muscle catabolism. Increasing protein intake to 1.5-2.0 g∙kg-1∙day-1 may be beneficial for skeletal muscle tissue and could be accomplished with essential amino acid supplementation. However, increased consumption of sulfur-containing amino acids is associated with increased bone resorption, which creates a dilemma for musculoskeletal countermeasures, whereby optimizing skeletal muscle parameters via essential amino acid supplementation may worsen bone outcomes. To protect both muscle and bone health, future unloading studies should evaluate increased protein intake via non-sulfur containing essential amino acids or leucine in combination with exercise countermeasures and the concomitant influence of reduced energy intake.
Collapse
Affiliation(s)
- Kyle J Hackney
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58102, USA.
| | - Kirk L English
- Exercise Physiology and Countermeasures Laboratory, JES Tech, Houston, TX 77058, USA.
| |
Collapse
|
22
|
Lee SMC, Schneider SM, Feiveson AH, Macias BR, Smith SM, Watenpaugh DE, Hargens AR. WISE-2005: Countermeasures to prevent muscle deconditioning during bed rest in women. J Appl Physiol (1985) 2014; 116:654-67. [PMID: 24458754 DOI: 10.1152/japplphysiol.00590.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objectives of this study were to evaluate the efficacy of two separate countermeasures, exercise and protein supplementation, to prevent muscle strength and lean tissue mass losses during 60 days of bed rest (BR) in women and whether countermeasure efficacy was influenced by pre-BR muscular fitness (strength, endurance, tissue mass). Twenty-four women were assigned to an exercise (EX, n = 8), a no-exercise control (CON, n = 8), or a no-exercise protein supplementation group (PROT, n = 8). EX performed supine treadmill exercise within lower body negative pressure 3-4 days/wk and maximal concentric and eccentric supine leg- and calf-press exercises 2-4 days/wk. PROT consumed a diet with elevated protein content compared with CON and EX (1.6 vs. 1.0 g·kg(-1)·day(-1)). Knee and calf isokinetic strength and endurance, isotonic leg-press strength, and leg lean mass were measured before and after BR. Post-BR knee extensor strength and endurance, ankle strength, and leg lean mass were significantly greater and leg-press strength tended to be higher in EX than in CON and PROT. Post-BR measures in PROT were not different than those in CON. Exercise countermeasure efficacy was less, and strength, endurance, and leg lean mass losses in CON and PROT were greater, in subjects who were more fit pre-BR. An exercise protocol combining resistive and aerobic exercise training protects against losses in strength, endurance, and leg lean mass in women during BR, while a nutritional countermeasure without exercise was not effective. Exercise countermeasures may require individualization to protect higher levels of strength and endurance.
Collapse
Affiliation(s)
- Stuart M C Lee
- Wyle Science, Technology, and Engineering Group, Houston, Texas
| | | | | | | | | | | | | |
Collapse
|
23
|
Zhang LF. Region-specific vascular remodeling and its prevention by artificial gravity in weightless environment. Eur J Appl Physiol 2013; 113:2873-95. [DOI: 10.1007/s00421-013-2597-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 01/20/2013] [Indexed: 10/27/2022]
|
24
|
Hargens AR, Bhattacharya R, Schneider SM. Space physiology VI: exercise, artificial gravity, and countermeasure development for prolonged space flight. Eur J Appl Physiol 2012; 113:2183-92. [DOI: 10.1007/s00421-012-2523-5] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 10/05/2012] [Indexed: 01/06/2023]
|
25
|
Macias BR, D'Lima DD, Cutuk A, Patil S, Steklov N, Neuschwander TB, Meuche S, Colwell CW, Hargens AR. Leg intramuscular pressures and in vivo knee forces during lower body positive and negative pressure treadmill exercise. J Appl Physiol (1985) 2012; 113:31-8. [DOI: 10.1152/japplphysiol.01434.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Quantifying muscle and joint forces over a broad range of weight bearing loads during exercise may provide data required to improve prosthetic materials and better protect against muscle and bone loss. Collectively, leg intramuscular pressure (IMP), ground reaction force (GRF), and the instrumented tibial tray force measurements provide a comprehensive assessment of leg muscle and joint biomechanical effects of gravity during exercise. Titration of body weight (BW) by lower body negative pressure (LBNP) and lower body positive pressure (LBPP) can reproducibly modulate IMP within leg muscle compartments. In addition, previous studies document peak tibial forces during various daily activities of 2.2 to 2.5 BW. The study objective was to determine the IMPs of the leg, axial compressive force on the tibia in vivo, vertical GRF, and knee range of motion during altered BW levels using LBPP and LBNP treadmill exercise. We hypothesize that peak GRF, peak tibial forces, and peak IMPs of the leg correlate linearly with percent BW, as generated across a broad range of upright LBPP and supine LBNP exercise. When running at 2.24 m/s the leg IMPs significantly increased over the loading range of 60% to 140% BW with LBPP and LBNP ( P < 0.001); as expected, leg IMPs were significantly higher when running compared with standing ( P < 0.001). During upright LBPP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s ( R2 = 0.90) and 1.34 m/s ( R2 = 0.98). During supine LBNP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s ( R2 = 0.98) and 1.34 m/s ( R2 = 0.91). The present study is the first to measure IMPs and peak tibial forces in vivo during upright LBPP, upright LBNP, and supine LBNP exercise. These data will aid the development of rehabilitation exercise hardware and prescriptions for patients and astronauts.
Collapse
Affiliation(s)
- Brandon R. Macias
- Department of Health and Kinesiology, Texas A&M University, College Station, Texas
| | - Darryl D. D'Lima
- Orthopaedic Research Laboratories, Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California; and
| | - Adnan Cutuk
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California
| | - Shantanu Patil
- Orthopaedic Research Laboratories, Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California; and
| | - Nick Steklov
- Orthopaedic Research Laboratories, Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California; and
| | - Timothy B. Neuschwander
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California
| | - Sabine Meuche
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California
| | - Clifford W. Colwell
- Orthopaedic Research Laboratories, Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California; and
| | - Alan R. Hargens
- Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California
| |
Collapse
|
26
|
Zuj KA, Edgell H, Shoemaker JK, Custaud MA, Arbeille P, Hughson RL. WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest. J Appl Physiol (1985) 2012; 113:434-41. [PMID: 22653986 DOI: 10.1152/japplphysiol.00445.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study tested the hypothesis that cardiovascular effects of sublingual nitroglycerin (NG) would be exaggerated after 56 days of 6° head-down bed rest (HDBR) in women, and that an aerobic and resistive exercise countermeasure (EX, n = 8) would reduce the effect compared with HDBR without exercise (CON, n = 7). Middle cerebral artery maximal blood flow velocity (CBFV), cardiac stroke volume (SV), and superficial femoral artery blood flow (Doppler ultrasound) were recorded at baseline rest and for 5 min following 0.3 mg sublingual NG. Post-HDBR, NG caused greater increases in heart rate (HR) in CON compared with EX (+24.9 ± 7.7 and +18.8 ± 6.6 beats/min, respectively, P < 0.0001). The increase in HR combined with reductions in SV to maintain cardiac output. Systolic, mean, and pulse pressures were reduced 5-10 mmHg by NG, but total peripheral resistance was only slightly reduced at 3 min after NG. Reductions in CBFV of -12.5 ± 3.8 cm/s were seen after NG, but a reduction in the Doppler resistance index suggested dilation of the middle cerebral artery with no differences after HDBR. The femoral artery dilated with NG and blood flow was reduced ∼50% with the appearance of large negative waves suggesting a marked increase in downstream resistance, but there were no effects of HDBR. In general, responses of women to NG were not altered by HDBR; the greater increase in HR in CON but not EX was probably a consequence of cardiovascular deconditioning. These results contrast with the hypothesis and a previous investigation of men after HDBR by revealing no change in cardiovascular responses to exogenous nitric oxide.
Collapse
Affiliation(s)
- K A Zuj
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | | | | | | | | | | |
Collapse
|
27
|
Zwart SR, Booth SL, Peterson JW, Wang Z, Smith SM. Vitamin K status in spaceflight and ground-based models of spaceflight. J Bone Miner Res 2011; 26:948-54. [PMID: 21541997 PMCID: PMC3179302 DOI: 10.1002/jbmr.289] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 10/01/2010] [Accepted: 11/05/2010] [Indexed: 01/27/2023]
Abstract
Bone loss is a well-documented change during and after long-duration spaceflight. Many types of countermeasures to bone loss have been proposed, including vitamin K supplementation. The objective of this series of studies was to measure change in vitamin K status in response to microgravity under a variety of spaceflight and spaceflight analog (model) conditions, including long-duration spaceflight studies (n = 15), three bed rest studies (n = 15, 49, and 24), and a 14-day saturation dive (n = 6). In crew members who flew 2-6 months on the International Space Station, in-flight and postflight plasma phylloquinone concentrations were unchanged from the preflight mean. Consistent with this finding, urinary γ-carboxyglutamic acid (GLA), a measure of vitamin K-dependent protein turnover, did not change in response to flight. Serum undercarboxylated osteocalcin (%ucOC), a measure of vitamin K function, was generally unchanged in response to flight. Spaceflight findings were corroborated by findings of no changes in phylloquinone, urinary GLA, or %ucOC during or after bed rest in three separate bed rest studies (21-90 days in duration) or after a 14-day saturation dive. The data presented here do not support either a need for vitamin K supplementation during spaceflight or the suggestion of using vitamin K as a bone loss countermeasure in spaceflight.
Collapse
Affiliation(s)
- Sara R Zwart
- Division of Space Life Sciences, Universities Space Research AssociationHouston, TX, USA
| | - Sarah L Booth
- Jean Mayer USDA Human Nutrition Center on Aging at Tufts UniversityBoston, MA, USA
| | - James W Peterson
- Jean Mayer USDA Human Nutrition Center on Aging at Tufts UniversityBoston, MA, USA
| | - Zuwei Wang
- Enterprise Advisory Services, Inc.Houston, TX, USA
| | - Scott M Smith
- Human Adaptation and Countermeasures Division, NASA Lyndon B. Johnson Space CenterHouston, TX, USA
| |
Collapse
|
28
|
Hodges GJ, Mattar L, Zuj KA, Greaves DK, Arbeille PM, Hughson RL, Shoemaker JK. WISE-2005: prolongation of left ventricular pre-ejection period with 56 days head-down bed rest in women. Exp Physiol 2010; 95:1081-8. [DOI: 10.1113/expphysiol.2010.054254] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
29
|
Shibata S, Perhonen M, Levine BD. Supine cycling plus volume loading prevent cardiovascular deconditioning during bed rest. J Appl Physiol (1985) 2010; 108:1177-86. [PMID: 20223994 DOI: 10.1152/japplphysiol.01408.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There are two possible mechanisms contributing to the excessive fall of stroke volume (and its contribution to orthostatic intolerance) in the upright position after bed rest or spaceflight: reduced cardiac filling due to hypovolemia and/or a less distensible heart due to cardiac atrophy. We hypothesized that preservation of cardiac mechanical function by exercise training, plus normalization of cardiac filling with volume infusion, would prevent orthostatic intolerance after bed rest. Eighteen men and three women were assigned to 1) exercise countermeasure (n=14) and 2) no exercise countermeasure (n=7) groups during bed rest. Bed rest occurred in the 6 degrees head-down tilt position for 18 days. The exercise regimen was prescribed to compensate for the estimated cardiac work reduction between bed rest and ambulatory periods. At the end of bed rest, the subjects were further divided into two additional groups for post-bed rest testing: 1) volume loading with intravenous dextran to normalize cardiac filling pressure and 2) no volume loading. Dextran infusion was given to half of the exercise group and all of the sedentary group after bed rest, leading ultimately to three groups: 1) exercise plus volume infusion; 2) exercise alone; and 3) volume infusion alone. Exercise training alone preserved left ventricular mass and distensibility as well as upright exercise capacity, but lower body negative pressure (LBNP) tolerance was still depressed. LBNP tolerance was maintained only when exercise training was accompanied by dextran infusion. Dextran infusion alone following bed rest without exercise maintained neither orthostatic tolerance nor upright exercise capacity. We conclude that daily supine cycle exercise sufficient to prevent cardiac atrophy can prevent orthostatic intolerance after bed rest only when combined with plasma volume restoration. This maintenance of orthostatic tolerance was achieved by neither exercise nor dextran infusion alone. Cardiac atrophy and hypovolemia are likely to contribute independently to orthostatic intolerance after bed rest.
Collapse
Affiliation(s)
- Shigeki Shibata
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, and University of Texas Southwestern Medical Center at Dallas, 7232 Greenville Ave., Suite 435, Dallas, TX 75231, USA
| | | | | |
Collapse
|
30
|
Hargens AR, Richardson S. Cardiovascular adaptations, fluid shifts, and countermeasures related to space flight. Respir Physiol Neurobiol 2009; 169 Suppl 1:S30-3. [PMID: 19615471 DOI: 10.1016/j.resp.2009.07.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2009] [Revised: 06/24/2009] [Accepted: 07/02/2009] [Indexed: 10/20/2022]
Abstract
Significant progress has been made related to understanding cardiovascular adaptations to microgravity and development of countermeasures to improve crew re-adaptation to gravity. The primary ongoing issues are orthostatic intolerance after flight, reduced exercise capacity, the effect of vascular-smooth muscle loss on other physiologic systems, development of efficient and low-cost countermeasures to counteract these losses, and an understanding of fluid shift mechanisms. Previous animal studies of cardiovascular adaptations offer evidence that prolonged microgravity remodels walls of blood vessels, which in turn, is important for deconditioning of the cardiovascular system and other functions of the body. Over the past 10 years, our studies have documented that treadmill exercise within lower body negative pressure counteracts most physiologic decrements with bed rest in both women and men. Future studies should improve hardware and protocols to protect crew members during prolonged missions. Finally, it is proposed that transcapillary fluid shifts in microgravity may be related to the loss of tissue weight and external compression of blood vessels.
Collapse
Affiliation(s)
- Alan R Hargens
- Department of Orthopaedic Surgery, University of California, UCSD Medical Center, San Diego, 92103-8894, United States.
| | | |
Collapse
|