Standardization of bed rest studies in the spaceflight context

Sundblad, Patrik; Орлов, О. И.; Angerer, Oliver; Ларина, И. М.; Cromwell, Ronita L.

doi:10.1152/japplphysiol.00089.2016

Cited by 33 publications

(42 citation statements)

References 6 publications

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“…By and large, the bed rest protocol was conducted according to the guidelines of the European Space Agency (Heer et al, 2009 ; MEDS-IMPS and I.d.M.e.P.S, 2010 ; Sundblad and Orlov, 2014 ). In the bed rest conditions, participants were confined to bed for 21 days.…”

Section: Methodsmentioning

confidence: 99%

“…Body sway changes following hypoxia seem to be more pronounced in the sagittal plane with eyes open (Nordahl et al, 1998 ). The present study was conducted within the framework of a larger study investigating the separate and combined effects of bed rest and hypoxia on the structure and function of several physiological system (PlanHab study; MEDS-IMPS and I.d.M.e.P.S, 2010 ; Debevec et al, 2014 ; Sundblad and Orlov, 2014 ). Specifically, the study was designed to address the concern that the hypoxic environments anticipated in future habitats on the Moon and Mars (Bodkin et al, 2006 ) may enhance the effect of reduced loading of the weight-bearing limbs due to the reduced gravity.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

et al. 2018

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Prolonged inactivity, such as bed rest induces several detrimental changes within a short timeframe. Impaired postural balance and responses of trunk muscles to (un)expected perturbations were both shown to be impaired after bed rest. Certain populations (e.g., astronauts) are exposed to hypoxic environment in addition to inactivity, similar to bed rest. While the isolated negative effects of hypoxia on postural balance have been observed before, no study to date has examined the combined effects of hypoxia and bed rest on postural balance or trunk muscle responses. In this study, we examined the effects of 21-day exposure to three conditions: (i) bed rest in hypoxic environment (HBR), (ii) bed rest in normoxic environment (NBR), and (iii) ambulatory hypoxic environment (HAMB). Fourteen healthy male subjects crossed over between conditions in a randomized order, with a 4-month break between conditions to ensure full recovery. Most body sway parameters indicated a similar deterioration of postural balance following both HBR and NBR. Similarly, both anticipatory and reactive responses of the trunk muscles (m. erector spinae and m. multifidus) were impaired after HBR and NBR to a similar degree and mostly unchanged after HAMB. Certain body sway parameters were impaired after HAMB, confirming that hypoxia alone can undermine postural balance. On the other hand, some trunk responses were improved after HAMB. In conclusion, the results of our study confirmed previous findings on negative effects of bed rest, but showed little or no additional effect of hypoxia during bed rest. Physical activity during bed rest is encouraged to preserve neuromuscular functions of the trunk. While the HBR condition in our study resembled conditions during space missions, our results could be relevant to other populations, such as patients with pulmonary diseases exposed to bed rest.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

et al. 2018

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“…Data from the remaining 11 subjects are presented here. Subject inclusion and exclusion criteria, along with dietary planning, followed guidelines set forth in Guidelines for Standardization of Bed Rest Studies in the Spaceflight Context (Sundblad et al 2014). Nonsmoking healthy male and female subjects needed to be aged 24-55 years, with body mass index of 20 to 30, satisfactorily complete physiological and psychological screening, and undergo a dual-energy X-ray absorptiometry bone density measurement.…”

Section: Subjectsmentioning

confidence: 99%

Unchanged cerebrovascular CO₂ reactivity and hypercapnic ventilatory response during strict head‐down tilt bed rest in a mild hypercapnic environment

Laurie

Christian

Kysar

et al. 2020

The Journal of Physiology

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Key points Carbon dioxide levels are mildly elevated on the International Space Station and it is unknown whether this chronic exposure causes physiological changes to astronauts. We combined ∼4 mmHg ambient PnormalCO2 with the strict head‐down tilt bed rest model of spaceflight and this led to the development of optic disc oedema in one‐half of the subjects. We demonstrate no change in arterialized PnormalCO2, cerebrovascular reactivity to CO2 or the hypercapnic ventilatory response. Our data suggest that the mild hypercapnic environment does not contribute to the development of spaceflight associated neuro‐ocular syndrome. Abstract Chronically elevated carbon dioxide (CO2) levels can occur in confined spaces such as the International Space Station. Using the spaceflight analogue 30 days of strict 6° head‐down tilt bed rest (HDTBR) in a mild hypercapnic environment (PnormalCO2 = ∼4 mmHg), we investigated arterialized PnormalCO2, cerebrovascular reactivity and the hypercapnic ventilatory response in 11 healthy subjects (five females) before, on days 1, 9, 15 and 30 of bed rest (BR), and 6 and 13 days after HDTBR. During all HDTBR time points, arterialized PnormalCO2 was not significantly different from the pre‐HDTBR measured in the 6° HDT posture, with a mean (95% confidence interval) increase of 1.2 mmHg (–0.2 to 2.5 mmHg, P = 0.122) on day 30 of HDTBR. Respiratory acidosis was never detected, although a mild metabolic alkalosis developed on day 30 of HDTBR by a mean (95% confidence interval) pH change of 0.032 (0.022–0.043; P < 0.001), which remained elevated by 0.021 (0.011–0.031; P < 0.001) 6 days after HDTBR. Arterialized pH returned to pre‐HDTBR levels 13 days after BR with a change of –0.001 (–0.009 to 0.007; P = 0.991). Compared to pre‐HDTBR, cerebrovascular reactivity during and after HDTBR did not change. Baseline ventilation, ventilatory recruitment threshold and the slope of the ventilatory response were similar between pre‐HDTBR and all other time points. Taken together, these data suggest that the mildly increased ambient PnormalCO2 combined with 30 days of strict 6° HDTBR did not change arterialized PnormalCO2 levels. Therefore, the experimental conditions were not sufficient to elicit a detectable physiological response.

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“…Compared to actual space flight, bed rest studies have the advantage that they have fewer confounding factors, and bed rest provides the most common method to investigate the effectiveness of nutritional spaceflight countermeasures [48]. The bed rest methodology of included studies was good with most studies matching the "ideal design" of a bed rest study [49]. However, all studies failed to address whether sunlight exposure was prohibited which is problematic as sunlight exposure stimulates vitamin D synthesis that might itself act as a countermeasure [50], and potentially affect the physiological systems investigated in this systematic review.…”

Section: Quality Of Evidence and Overall Completenessmentioning

confidence: 99%

Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning–A Systematic Review

et al. 2020

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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

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Standardization of bed rest studies in the spaceflight context

Cited by 33 publications

References 6 publications

The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

Unchanged cerebrovascular CO₂ reactivity and hypercapnic ventilatory response during strict head‐down tilt bed rest in a mild hypercapnic environment

Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning–A Systematic Review

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Standardization of bed rest studies in the spaceflight context

Cited by 33 publications

References 6 publications

The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

The Effect of Bed Rest and Hypoxic Environment on Postural Balance and Trunk Automatic (Re)Actions in Young Healthy Males

Unchanged cerebrovascular CO2 reactivity and hypercapnic ventilatory response during strict head‐down tilt bed rest in a mild hypercapnic environment

Effectiveness of nutritional countermeasures in microgravity and its ground-based analogues to ameliorate musculoskeletal and cardiopulmonary deconditioning–A Systematic Review

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Unchanged cerebrovascular CO₂ reactivity and hypercapnic ventilatory response during strict head‐down tilt bed rest in a mild hypercapnic environment