Effectiveness of resistive exercise countermeasures in bed rest to maintain muscle strength and power
– A Systematic Review –
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1
European Astronaut Centre (EAC), Germany
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2
Faculty of Health and Life Sciences, Northumbria University, United Kingdom
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3
Peninsula Dental School, Plymouth University, United Kingdom
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4
Institut für Biomechanik und Orthopädie, Deutsche Sporthochschule Köln, Germany
1 Background
The evolution of exercise hardware and prescriptions have allowed astronauts to be exposed for long durations to microgravity (µG) and to return to Earth’s gravitational field in relatively good physical condition [1]. However, not all astronauts appear to benefit equally from the prescribed exercises with the majority still experiencing multi-systems space physiological deconditioning [1]. Furthermore, future deep space explorations beyond low earth orbit will impose additional constraints upon the ability to perform exercise countermeasures. For instance, the size of exploration vehicles and cis-lunar stations [2; 3] will prohibit the use of relatively heavy and large hardware currently used on the International Space Station (ISS) [1; 4].
Therefore, exercise effectiveness to counteract space deconditioning needs to be further improved to (a) minimize the anticipated risks that future missions beyond low earth orbit will constitute [5]; and to (b) assure that after prolonged exposure times to µG astronauts will be able to operate autonomously and safely in extra-terrestrial (hypo-) gravity environments [6].
Data from exercise countermeasure studies that have been conducted in space, or in terrestrial analogues constitute a valuable knowledge base that should be taken into account for the development of novel exercise regimen and exercise hardware. To this date, however, there has not been a systematic approach to synthesize the findings of these studies and the flow of information between physiological research and operational implementation is frequently sub-optimal. It is therefore the aim of this project to synthesize data from both space- and terrestrial analogue-studies to help inform the development of novel exercise concepts and hardware for exploration missions.
The broad scope of a series of systematic literature reviews seeks to evaluate the effect of active exercise countermeasures, passive countermeasures (e.g. centrifugation) and nutritional countermeasures on musculoskeletal, cardiovascular, and cardiopulmonary parameters in microgravity and its ground-based analogues. The data presented at this conference include initial results of this project, focusing on the effectiveness of various resistive exercise protocols to maintain muscle strength and power in bed rest.
2 Material and methods
Guidelines of the Cochrane Collaboration [7] and tools provided by the Aerospace Medicine Systematic Review Group [8] were used to conduct this review.
2.1 Search strategy
PubMed, Web of Science, Embase, NASA’s and ESA’s life sciences archives (Life Science Data Archive, Technical Reports Server and Erasmus Experiment Archive), as well as the database of the German Aerospace Centre (elib) and the Institute of Electrical and Electronics Engineers (IEEE) were searched.
2.2 Criteria for included studies
Initially found studies were screened using the Cochrane PICO-model: Participants (Patients: P) had to be human adults (men or women). The intervention (I) had to be either a space mission, a bed rest study, or a dry immersion study that used an active, passive, or nutritional countermeasure. Control groups (Comparison: C) had to refrain from countermeasure use. Outcomes (O) had to be either a cardiopulmonary, a cardiovascular, or a musculoskeletal parameter. Only studies with a minimum duration of five days conducted in µG, bed rest, or dry immersion were included. Full texts were obtained of all studies that met the above criteria.
2.3 Calculation of effect sizes
Calculation of effect sizes was performed to compare mean effects between control and intervention groups. The effect sizes were bias corrected using weighted (accounting for n = sample size) pooled standard deviations as per Hedge’s g method [9]. Thresholds of <-0.2, -0.2, 0.2, 0.6, 1.2, and >1.2 were defined as negative, trivial, small, moderate, large, and very large effects between control and intervention groups [10]. To compare pre- and post-differences for each group, mean differences (post mean value – pre mean value) were calculated.
3 Results
The initial search resulted in 4031 studies, with 10 included in the present analysis (Figure 1). The final 10 included studies were either randomized controlled, or controlled studies. The effect sizes are presented in Figure 2. Seven of the parameters analyzed parameters show a very large effect, nine a large effect, 10 a moderate effect, three a small effect, seven a trivial effect, and one a negative effect. A summary of the main study characteristics is shown in Figure 3. In the intervention groups, 19 of the 37 outcome parameters decreased after bed rest, whereas in the control group all outcome parameters decreased.
4 Discussion
The main findings of the present study were (1) that effect sizes show a wide range and that (2) approximately half of the intervention groups and (3) all control groups had negative mean differences between pre- and post-values. This shows that treatment effects of resistive exercise regimen vary significantly across interventions, and that all control groups and half of the intervention groups lost muscle strength and power.
The majority of effect sizes are in favor of resistive exercise intervention groups compared to control groups. Consequently, and unsurprisingly, resistive exercise during bed rest appears superior to no countermeasure in preserving muscle strength and power. However, effect sizes vary significantly across outcome parameters. Of the 39 parameters that were included, most effect sizes show a small to very large effect [10] in favor of the intervention groups. Differences among study characteristics such as training protocols, study durations and quality, subject groups and their baseline values, or differences between test protocols employed to measure muscle strength and power might account for this variation and should be addressed in follow-up studies.
To conclude, resistive exercise appears not always to be sufficient to maintain muscle strength and power during bed rest. Differences among study characteristics need to be further analyzed to explain different results. Other forms of exercise (e.g. concurrent training, high intensity interval training, plyometric training) should also be investigated to optimize exercise countermeasure prescriptions for human space flight to preserve muscle strength and power of astronauts.
Acknowledgments
This study was funded by ESA (HRE-OM).
Acknowledgements
This study was funded by ESA (HRE-OM).
References
References
[1] D.W. Korth, Exercise countermeasure hardware evolution on ISS: the first decade. Aerospace medicine and human performance 86 (2015) A7-A13.
[2] NASA, Orion Quick Facts.
[3] C. Gebhardt, Delving Deeper into NASA’s DSH configurations and support craft. (2012).
[4] N. Petersen, P. Jaekel, A. Rosenberger, T. Weber, J. Scott, F. Castrucci, G. Lambrecht, L. Ploutz-Snyder, V. Damann, I. Kozlovskaya, and J. Mester, Exercise in space: the European Space Agency approach to in-flight exercise countermeasures for long-duration missions on ISS. Extrem Physiol Med 5 (2016) 9.
[5] NASA Human Research Program Roadmap, 2018.
[6] C. Richter, B. Braunstein, A. Winnard, M. Nasser, and T. Weber, Human Biomechanical and Cardiopulmonary Responses to Partial Gravity - A Systematic Review. Front Physiol 8 (2017) 583.
[7] J.P.T. Higgins, and S. Green, Cochrane handbook for systematic reviews of interventions version 5.1. 0 [updated March 2011], The Cochrane Collaboration. Available from www.handbook.cochrane.org, 2011.
[8] Aerospace Medicine Systematic Review Group, 2018.
[9] P. Ellis, The Essential Guide to Effect Sizes: Statistical Power, Meta-Analysis, and the Interpretation of Research Results., Cambridge University Press, New York, 2010.
[10] W. Hopkins, S. Marshall, A. Batterham, and J. Hanin, Progressive statistics for studies in sports medicine and exercise science. Medicine+ Science in Sports+ Exercise 41 (2009) 3.
[11] Rayyan QCRI, the Systematic Reviews web app, 2018.
Keywords:
exercise countermeasures,
Bed Rest,
Space Flight,
Muscle Strength,
muscle power
Conference:
39th ISGP Meeting & ESA Life Sciences Meeting, Noordwijk, Netherlands, 18 Jun - 22 Jun, 2018.
Presentation Type:
Extended abstract
Topic:
Analogues and Countermeasure Research
Citation:
Fiebig
L,
Winnard
AJ,
Nasser
M,
Braunstein
B,
Scott
J,
Green
D and
Weber
T
(2019). Effectiveness of resistive exercise countermeasures in bed rest to maintain muscle strength and power
– A Systematic Review –.
Front. Physiol.
Conference Abstract:
39th ISGP Meeting & ESA Life Sciences Meeting.
doi: 10.3389/conf.fphys.2018.26.00020
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Received:
02 Dec 2018;
Published Online:
16 Jan 2019.
*
Correspondence:
Ms. Leonie Fiebig, European Astronaut Centre (EAC), Cologne, Germany, leonie.fiebig@hotmail.de