Systematic review of the effectiveness of standalone passive countermeasures on microgravity-induced physiologic deconditioning.

A systematic review of literature was conducted to evaluate the effectiveness of passive countermeasures in ameliorating the cardiopulmonary and musculoskeletal effects of gravitational unloading on humans during spaceflight. This systematic review is the third of a series being conducted by the European Space Agency to evaluate the effectiveness of countermeasures to physiologic deconditioning during spaceflight. With future long-duration space missions on the horizon, it is critical to understand the effectiveness of existing countermeasures to promote astronaut health and improve the probability of future mission success. An updated search for studies examining passive countermeasures was conducted in 2021 to supplement results from a broader search conducted in 2017 for all countermeasures. Ground-based analogue and spaceflight studies were included in the search. A total of 647 articles were screened following removal of duplicates, of which 16 were included in this review. Data extraction and analysis, quality assessment of studies, and transferability of reviewed studies to actual spaceflight based on their bed-rest protocol were conducted using dedicated tools created by the Aerospace Medicine Systematic Review Group. Of the 180 examined outcomes across the reviewed studies, only 20 were shown to have a significant positive effect in favour of the intervention group. Lower body negative pressure was seen to significantly maintain orthostatic tolerance (OT) closer to baseline as comparted to control groups. It also was seen to have mixed efficacy with regards to maintaining resting heart rate close to pre-bed rest values. Whole body vibration significantly maintained many balance-related outcome measures close to pre-bed rest values as compared to control. Skin surface cooling and centrifugation both showed efficacy in maintaining OT. Centrifugation also was seen to have mixed efficacy with regards to maintaining VO2max close to pre-bed rest values. Overall, standalone passive countermeasures showed no significant effect in maintaining 159 unique outcome measures close to their pre-bed rest values as compared to control groups. Risk of bias was rated high or unclear in all studies due to poorly detailed methodologies, poor control of confounding variables, and other sources of bias (i.e. inequitable recruitment of participants leading to a higher male:female ratios). The bed-rest transferability (BR) score varied from 2-7, with a median score of 5. Generally, most studies had good BR transferability but underreported on factors such as control of sunlight or radiation exposure, diet, level of exercise and sleep-cycles. We conclude that: (1) Lack of standardisation of outcome measurement and methodologies has led to large heterogeneity amongst studies; (2) Scarcity of literature and high risk of bias amongst existing studies limits the statistical power of results; and (3) Passive countermeasures have little or no efficacy as standalone measures against cardiopulmonary and musculoskeletal deconditioning induced by spaceflight related to physiologic deterioration due to gravity un-loading.

Systematic review of the use of ultrasound for venous assessment and venous thrombosis screening in spaceflight.

The validity of venous ultrasound (V-US) for the diagnosis of deep vein thrombosis (DVT) during spaceflight is unknown and difficult to establish in diagnostic accuracy and diagnostic management studies in this context. We performed a systematic review of the use of V-US in the upper-body venous system in spaceflight to identify microgravity-related changes and the effect of venous interventions to reverse them, and to assess appropriateness of spaceflight V-US with terrestrial standards. An appropriateness tool was developed following expert panel discussions and review of terrestrial diagnostic studies, including criteria relevant to crew experience, in-flight equipment, assessment sites, ultrasound modalities, and DVT diagnosis. Microgravity-related findings reported as an increase in internal jugular vein (IJV) cross-sectional area and pressure were associated with reduced, stagnant, and retrograde flow. Changes were on average responsive to venous interventions using lower body negative pressure, Bracelets, Valsalva and Mueller manoeuvres, and contralateral IJV compression. In comparison with terrestrial standards, spaceflight V-US did not meet all appropriateness criteria. In DVT studies (n = 3), a single thrombosis was reported and only ultrasound modality criterion met the standards. In the other studies (n = 15), all the criteria were appropriate except crew experience criterion, which was appropriate in only four studies. Future practice and research should account for microgravity-related changes, evaluate individual effect of venous interventions, and adopt Earth-based V-US standards.

Effects of whole-body vibration or resistive-vibration exercise on blood clotting and related biomarkers: a systematic review.

Whole-body vibration (WBV) and resistive vibration exercise (RVE) are utilized as countermeasures against bone loss, muscle wasting, and physical deconditioning. The safety of the interventions, in terms of the risk of inducing undesired blood clotting and venous thrombosis, is not clear. We therefore performed the present systematic review of the available scientific literature on the issue. The review was conducted following the guidelines by the Space Biomedicine Systematic Review Group, based on Cochrane review guidelines. The relevant context or environment of the studies was "ground-based environment"; space analogs or diseased conditions were not included. The search retrieved 801 studies; 77 articles were selected for further consideration after an initial screening. Thirty-three studies met the inclusion criteria. The main variables related to blood markers involved angiogenic and endothelial factors, fibrinolysis and coagulation markers, cytokine levels, inflammatory and plasma oxidative stress markers. Functional and hemodynamic markers involved blood pressure measurements, systemic vascular resistance, blood flow and microvascular and endothelial functions. The available evidence suggests neutral or potentially positive effects of short- and long-term interventions with WBV and RVE on variables related to blood coagulation, fibrinolysis, inflammatory status, oxidative stress, cardiovascular, microvascular and endothelial functions. No significant warning signs towards an increased risk of undesired clotting and venous thrombosis were identified. If confirmed by further studies, WBV and RVE could be part of the countermeasures aimed at preventing or attenuating the muscular and cardiovascular deconditioning associated with spaceflights, permanence on planetary habitats and ground-based simulations of microgravity.

Skeletal muscle deconditioning during partial weight-bearing in rodents - A systematic review and meta-analysis.

Space agencies are planning to send humans back to the Lunar surface, in preparation for crewed exploration of Mars. However, the effect of hypogravity on human skeletal muscle is largely unknown. A recently established rodent partial weight-bearing model has been employed to mimic various levels of hypogravity loading and may provide valuable insights to better understanding how human muscle might respond to this environment. The aim of this study was to perform a systematic review regarding the effects of partial weight-bearing on the morphology and function of rodent skeletal muscle. Five online databases were searched with the following inclusion criteria: population (rodents), intervention (partial weight-bearing for ≥1 week), control (full weight-bearing), outcome(s) (skeletal muscle morphology/function), and study design (animal intervention). Of the 2,993 studies identified, eight were included. Partial weight-bearing at 20%, 40%, and 70% of full loading caused rapid deconditioning of skeletal muscle morphology and function within the first one to two weeks of exposure. Calf circumference, hindlimb wet muscle mass, myofiber cross-sectional area, front/rear paw grip force, and nerve-stimulated plantarflexion force were reduced typically by medium to very large effects. Higher levels of partial weight-bearing often attenuated deconditioning but failed to entirely prevent it. Species and sex mediated the deconditioning response. Risk of bias was low/unclear for most studies. These findings suggest that there is insufficient stimulus to mitigate muscular deconditioning in hypogravity settings highlighting the need to develop countermeasures for maintaining astronaut/cosmonaut muscular health on the Moon and Mars.

Bone deconditioning during partial weight-bearing in rodents - A systematic review and meta-analysis.

Space agencies are preparing to send humans to the Moon (16% Earth's gravity) and Mars (38% Earth's gravity), however, there is limited evidence regarding the effects of hypogravity on the skeletal system. A novel rodent partial weight-bearing (PWB) model may provide insight into how human bone responds to hypogravity. The aim of this study was to perform a systematic review investigating the effect of PWB on the structure and function of rodent bone. Five online databases were searched with the following inclusion criteria: population (rodents), intervention (PWB for ≥1-week), control (full weight-bearing), outcomes (bone structure/function), and study design (animal intervention). Of the 2,993 studies identified, eight were included. The main findings were that partial weight-bearing exposure for 21-28 days at 20%, 40%, and 70% of full loading causes: (1) loss of bone mineral density, (2) loss of trabecular bone volume, thickness, number, and increased separation, (3) loss of cortical area and thickness, and 4) reduced bone stiffness and strength. These findings predominately relate the tibia/femur of young/mature female mice, however, their deconditioning response appeared similar, but not identical, to male rats. A dose-response trend was frequently observed between the magnitude of deconditioning and PWB level. The deconditioning patterns in PWB resembled those in rodents and humans exposed to microgravity and microgravity analogs. The present findings suggest that countermeasures against bone deconditioning may be required for humans exploring the Lunar and Martian surfaces.

The Effects of Reconditioning Exercises Following Prolonged Bed Rest on Lumbopelvic Muscle Volume and Accumulation of Paraspinal Muscle Fat.

Reduced muscle size and accumulation of paraspinal muscle fat content (PFC) have been reported in lumbopelvic muscles after spaceflights and head-down tilt (HDT) bed rest. While some information is available regarding reconditioning programs on muscle atrophy recovery, the effects on the accumulation of PFC are unknown. Recently, a device (the Functional Re-adaptive Exercise Device-FRED) has been developed which aims to specifically recruit lumbopelvic muscles. This study aimed to investigate the effects of a standard reconditioning (SR) program and SR program supplemented by FRED (SR + FRED) on the recovery of the lumbopelvic muscles following 60-day HDT bed rest. Twenty-four healthy participants arrived at the facility for baseline data collection (BDC) before the bed rest period. They remained in the facility for 13-day post-HDT bed rest and were randomly allocated to one of two reconditioning programs: SR or SR + FRED. Muscle volumes of the lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles were measured from axial T1-weighted magnetic resonance imaging (MRI) at all lumbar intervertebral disc levels. PFC was determined using a chemical shift-based lipid/water Dixon sequence. Each lumbopelvic muscle was segmented into four equal quartiles (from medial to lateral). MRI of the lumbopelvic region was conducted at BDC, Day-59 of bed rest (HDT59), and Day-13 after reconditioning (R13). Comparing R13 with BDC, the volumes of the LM muscle at L4/L5 and L5/S1, LES at L1/L2, and QL at L3/L4 had not recovered (all-p < 0.05), and the PM muscle remained larger at L1/L2 (p = 0.001). Accumulation of PFC in the LM muscle at the L4/L5 and L5/S1 levels remained higher in the centro-medial regions at R13 than BDC (all-p < 0.05). There was no difference between the two reconditioning programs. A 2-week reconditioning program was insufficient to fully restore all volumes of lumbopelvic muscles and reverse the accumulation of PFC in the muscles measured to BDC values, particularly in the LM muscle at the lower lumbar levels. These findings suggest that more extended reconditioning programs or alternative exercises may be necessary to fully restore the size and properties of the lumbopelvic muscles after prolonged bed rest.

Search for Venous Endothelial Biomarkers Heralding Venous Thromboembolism in Space: A Qualitative Systematic Review of Terrestrial Studies.

Background: The recent discovery of a venous thrombosis in the internal jugular vein of an astronaut has highlighted the need to predict the risk of venous thromboembolism in otherwise healthy individuals (VTE) in space. Virchow's triad defines the three classic risk factors for VTE: blood stasis, hypercoagulability, and endothelial disruption/dysfunction. Among these risk factors, venous endothelial disruption/dysfunction remains incompletely understood, making it difficult to accurately predict risk, set up relevant prophylactic measures and initiate timely treatment of VTE, especially in an extreme environment. Methods: A qualitative systematic review focused on endothelial disruption/dysfunction was conducted following the guidelines produced by the Space Biomedicine Systematic Review Group, which are based on Cochrane review guidelines. We aimed to assess the venous endothelial biochemical and imaging markers that may predict increased risk of VTE during spaceflight by surveying the existing knowledge base surrounding these markers in analogous populations to astronauts on the ground. Results: Limited imaging markers related to endothelial dysfunction that were outside the bounds of routine clinical practice were identified. While multiple potential biomarkers were identified that may provide insight into the etiology of endothelial dysfunction and its link to future VTE, insufficient prospective evidence is available to formally recommend screening potential astronauts or healthy patients with any currently available novel biomarker. Conclusion: Our review highlights a critical knowledge gap regarding the role biomarkers of venous endothelial disruption have in predicting and identifying VTE. Future population-based prospective studies are required to link potential risk factors and biomarkers for venous endothelial dysfunction to occurrence of VTE.

Intramuscular lipid concentration increased in localized regions of the lumbar muscles following 60 day bedrest.

BACKGROUND CONTEXT: Prolonged bedrest induces accumulation of intramuscular lipid concentration (ILC) in the lumbar musculature; however, spatial distribution of ILC has not been determined. Artificial gravity (AG) mitigates some adaptations induced by 60 day bedrest by creating a head-to-feet force while participants are in a supine position. PURPOSE: To quantify the spatial distribution of accumulation of ILC in the lumbar musculature after 60 day bedrest, and whether this can be mitigated by AG exposure. STUDY DESIGN: Prospective longitudinal study. PATIENT SAMPLE: Twenty-four healthy individuals (8 females) participated in the study: Eight received 30 min continuous AG (cAG); Eight received 6 × 5 min AG (iAG), interspersed with rests; Eight were not exposed to AG (CRTL). OUTCOME MEASURES: From 3T magnetic resonance imaging (MRI), axial images were selected to assess lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles from L1/L2 to L5/S1 intervertebral disc levels. Chemical shift-based 2-echo lipid and/or water Dixon sequence was used to measure tissue composition. Each lumbar muscle was segmented into four equal quartiles (from medial to lateral). METHODS: Participants arrived at the facility for the baseline data collection before undergoing a 60 day strict 6° head-down tilt (HDT) bedrest period. MRI of the lumbopelvic region was conducted at baseline and Day-59 of bedrest. Participants performed all activities, including hygiene, in 6° HDT and were discouraged from moving excessively or unnecessarily. RESULTS: At the L4/L5 and L5/S1 intervertebral disc levels, 60-day bedrest induced a greater increase in ILC in medial and lateral regions (∼+4%) of the LM than central regions (∼+2%; p<.05). A smaller increase in ILC was induced in the lateral region of LES (∼+1%) at L1/L2 and L2/L3 than at the centro-medial region (∼+2%; p<.05). There was no difference between CRTL and intervention groups. CONCLUSIONS: Inhomogeneous spatial distribution of accumulation of ILC was found in the lumbar musculature after 60 day bedrest. These findings might reflect pathophysiological mechanisms related to muscle disuse and contribute to localized lumbar spine dysfunction. Altered spatial distribution of ILC may impair lumbar spine function after prolonged body unloading, which could increase injury risk to vulnerable soft tissues, such as the lumbar intervertebral discs. These novel results may represent a new biomarker of lumbar deconditioning for astronauts, bedridden, sedentary individuals, or those with chronic back pain. Changes are potentially modifiable but not by the AG protocols tested here.

Gluteal Muscle Atrophy and Increased Intramuscular Lipid Concentration Are Not Mitigated by Daily Artificial Gravity Following 60-Day Head-Down Tilt Bed Rest.

Exposure to spaceflight and head-down tilt (HDT) bed rest leads to decreases in the mass of the gluteal muscle. Preliminary results have suggested that interventions, such as artificial gravity (AG), can partially mitigate some of the physiological adaptations induced by HDT bed rest. However, its effect on the gluteal muscles is currently unknown. This study investigated the effects of daily AG on the gluteal muscles during 60-day HDT bed rest. Twenty-four healthy individuals participated in the study: eight received 30 min of continuous AG; eight received 6 × 5 min of AG, interspersed with rest periods; eight belonged to a control group. T1-weighted Dixon magnetic resonance imaging of the hip region was conducted at baseline and day 59 of HDT bed rest to establish changes in volumes and intramuscular lipid concentration (ILC). Results showed that, across groups, muscle volumes decreased by 9.2% for gluteus maximus (GMAX), 8.0% for gluteus medius (GMED), and 10.5% for gluteus minimus after 59-day HDT bed rest (all p < 0.005). The ILC increased by 1.3% for GMAX and 0.5% for GMED (both p < 0.05). Neither of the AG protocols mitigated deconditioning of the gluteal muscles. Whereas all gluteal muscles atrophied, the ratio of lipids to intramuscular water increased only in GMAX and GMED muscles. These changes could impair the function of the hip joint and increased the risk of falls. The deconditioning of the gluteal muscles in space may negatively impact the hip joint stability of astronauts when reexpose to terrestrial gravity.

Developing, Implementing, and Applying Novel Techniques During Systematic Reviews of Primary Space Medicine Data.

BACKGROUND: The Aerospace Medicine Systematic Review Group was set up in 2016 to facilitate high quality and transparent synthesis of primary data to enable evidence-based practice. The group identified many research methods specific to space medicine that need consideration for systematic review methods. The group has developed space medicine specific methods to address this and trialed usage of these methods across seven published systematic reviews. This paper outlines evolution of space medicine synthesis methods and discussion of their initial application.METHODS: Space medicine systematic review guidance has been developed for protocol planning, quantitative and qualitative synthesis, sourcing gray data, and assessing quality and transferability of space medicine human spaceflight simulation study environments.RESULTS: Decision algorithms for guidance and tool usage were created based on usage. Six reviews used quantitative methods in which no meta-analyses were possible due to lack of controlled trials or reporting issues. All reviews scored the quality and transferability of space simulation environments. One review was qualitative. Several research gaps were identified.CONCLUSION: Successful use of the developed methods demonstrates usability and initial validity. The current space medicine evidence base resulting in no meta-analyses being possible shows the need for standardized guidance on how to synthesize data in this field. It also provides evidence to call for increasing use of controlled trials, standardizing outcome measures, and improving minimum reporting standards. Space medicine is a unique field of medical research that requires specific systematic review methods.Winnard A, Caplan N, Bruce-Martin C, Swain P, Velho R, Meroni R, Wotring V, Damann V, Weber T, Evetts S, Laws J. Developing, implementing, and applying novel techniques during systematic reviews of primary space medicine data. Aerosp Med Hum Perform. 2021; 92(8):681688.

Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest.

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (n = 8); 30-min continuous AG daily (n = 8); and intermittent 6 × 5 min AG daily (n = 8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root mean square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the center of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis; obliquus externus and internus abdominis; transversus abdominis; erector spinae at L1, L2, L3, and L4 vertebral levels; and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P < 0.05) and delayed APAs of the trunk muscles following bed rest (all P < 0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P < 0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed.NEW & NOTEWORTHY This study presents novel insights into the effect of artificial gravity (AG) on the deterioration of standing balance and anticipatory postural adjustments (APAs) of trunk muscles induced by 60-day strict head-down bed rest. The results indicated severe balance dysfunction and delayed APAs during rapid arm movement. AG partially mitigated the deterioration in standing balance and may thus be considered as a potential countermeasure for future planetary surface explorations. Optimization of AG protocols might enhance effects.

Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bed rest.

Exposure to axial unloading induces adaptations in paraspinal muscles, as shown after spaceflights. This study investigated whether daily exposure to artificial gravity (AG) mitigated lumbar spine flattening and muscle atrophy associated with 60-day head-down tilt (HDT) bed rest (Earth-based space analog). Twenty-four healthy individuals participated in the study: 8 received 30-min continuous AG; 8 received 6 × 5-min AG interspersed with rest periods; and 8 received no AG exposure (control group). Magnetic resonance imaging (MRI) of the lumbopelvic region was conducted at baseline (BDC) and at day 59 of HDT (HDT59). Longitudinal relaxation time (T1)-weighted images were used to assess morphology of the lumbar spine (spinal length, intervertebral disk angles, disk area) and volumes of the lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles from L1/L2 to L5/S1 vertebral levels. A chemical shift-based two-point lipid/water Dixon sequence was used to evaluate muscle composition. Results showed that spinal length and disk area increased (P < 0.05); intervertebral disk angles (P < 0.05) and muscle volumes of LM, LES, and QL reduced (P < 0.01); and lipid-to-water ratio for the LM and LES muscles increased (P < 0.01) after HDT59 in all groups. Neither of the AG protocols mitigated the lumbar spinae deconditioning induced by HDT bed rest. The increase in lipid-to-water ratio in LM and LES muscles indicates an increased relative intramuscular lipid concentration. Altered muscle composition in atrophied muscles may impair lumbar spine function after body unloading, which could increase injury risk to vulnerable soft tissues. This relationship needs further investigation.NEW & NOTEWORTHY This study presents novel insights into the morphological adaptations occurring in the lumbar spine after 60-day head-down bed rest and the potential role of artificial gravity (AG) to mitigate them. Results demonstrated no protective effect of AG protocols used in this study. In atrophied paraspinal muscles, the ratio of lipids versus intramuscular water increased in the postural lumbar muscles, which could impair muscle function during upright standing. These findings have relevance for future space explorations.

Inspiratory muscle training for improving inspiratory muscle strength and functional capacity in older adults: a systematic review and meta-analysis.

BACKGROUND: The ageing process can result in the decrease of respiratory muscle strength and consequently increased work of breathing and associated breathlessness during activities of daily living in older adults. OBJECTIVE: This systematic review and meta-analysis aims to determine the effects of inspiratory muscle training (IMT) in healthy older adults. METHODS: A systematic literature search was conducted across four databases (Medline/Pubmed, Web of Science, Cochrane Library CINAHL) using a search strategy consisting of both MeSH and text words including older adults, IMT and functional capacity. The eligibility criteria for selecting studies involved controlled trials investigating IMT via resistive or threshold loading in older adults (>60 years) without a long-term condition. RESULTS: Seven studies provided mean change scores for inspiratory muscle pressure and three studies for functional capacity. A significant improvement was found for maximal inspiratory pressure (PImax) following training (n = 7, 3.03 [2.44, 3.61], P = <0.00001) but not for functional capacity (n = 3, 2.42 [-1.28, 6.12], P = 0.20). There was no significant correlation between baseline PImax and post-intervention change in PImax values (n = 7, r = 0.342, P = 0.453). CONCLUSIONS: IMT can be beneficial in terms of improving inspiratory muscle strength in older adults regardless of their initial degree of inspiratory muscle weakness. Further research is required to investigate the effect of IMT on functional capacity and quality of life in older adults.

The Potential of Fasting and Caloric Restriction to Mitigate Radiation Damage-A Systematic Review.

Detrimental health effects from ionizing radiation to living organisms is one of the key concerns identified and addressed by Radiation Protection institutions, nationally and internationally on Earth and for human spaceflight. Thus, new methods for mitigating the adverse effects of ionizing radiation are urgently needed for terrestrial health and deep space exploration. Caloric restriction and (intermittent-) fasting have been reported to elicit a variety of immediate and long-term physiological effects. The rapidly growing body of evidence of research studies investigating the effects of caloric restriction and dietary fasting points toward a multitude of benefits affecting numerous physiological systems. Therefore, a systematic review was performed to evaluate the evidence of caloric restriction and dietary fasting on the physiological response to ionizing radiation in humans and animals. All experimental studies of humans, animals, and eukaryotic cell lines available in PubMed, Cochrane library, and specialized databases were searched comparing irradiation post-caloric restriction or fasting to a non-nutritionally restricted control group on a broad range of outcomes from molecular to clinical responses. The initial search yielded 2,653 records. The final analysis included 11 studies. Most studies investigated survival rate or cancer occurrence in animals. Included studies did not reveal any benefit from pre exposure caloric restriction, except when performed with post radiation caloric restriction. However, the effects of pre-exposure fasting suggest increased resilience to ionizing radiation.

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

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.

Hypogravity reduces trunk admittance and lumbar muscle activation in response to external perturbations.

Reduced paraspinal muscle size and flattening of spinal curvatures have been documented after spaceflight. Assessment of trunk adaptations to hypogravity can contribute to development of specific countermeasures. In this study, parabolic flights were used to investigate spinal curvature and muscle responses to hypogravity. Data from five trials at 0.25 g, 0.50 g, and 0.75 g were recorded from six participants positioned in a kneeling-seated position. During the first two trials, participants maintained a normal, upright posture. In the last three trials, small-amplitude perturbations were delivered in the anterior direction at the T10 level. Spinal curvature was estimated with motion capture cameras. Trunk displacement and contact force between the actuator and participant were recorded. Muscle activity responses were collected by intramuscular electromyography (iEMG) of the deep and superficial lumbar multifidus, iliocostalis lumborum, longissimus thoracis, quadratus lumborum, transversus abdominis, obliquus internus, and obliquus externus muscles. The root mean square iEMG and the average spinal angles were calculated. Trunk admittance and muscle responses to perturbations were calculated as closed-loop frequency-response functions. Compared with 0.75 g, 0.25 g resulted in lower activation of the longissimus thoracis (P = 0.002); lower responses of the superficial multifidus at low frequencies (P = 0.043); lower responses of the superficial multifidus (P = 0.029) and iliocostalis lumborum (P = 0.043); lower trunk admittance (P = 0.037) at intermediate frequencies; and stronger responses of the transversus abdominis at higher frequencies (P = 0.032). These findings indicate that exposure to hypogravity reduces trunk admittance, partially compensated by weaker stabilizing contributions of the paraspinal muscles and coinciding with an apparent increase of deep abdominal muscle activity.NEW & NOTEWORTHY This study presents for the first time novel insights into the adaptations to hypogravity of spinal curvatures, trunk stiffness, and paraspinal muscle activity. We showed that exposure to hypogravity reduces the displacement of the trunk by an applied perturbation, partially compensated by weaker stabilizing contributions of the paraspinal muscles and concomitant increase in abdominal muscle responses. These findings may have relevance for future recommendations for planetary surface explorations.

Use of pedometers as a tool to promote daily physical activity levels in patients with COPD: a systematic review and meta-analysis.

The aim of this study was to examine the use of pedometers as a tool to promote daily physical activity levels in patients with COPD.A systematic review meta-analysis of pedometer physical activity promotion in patients with COPD was conducted. Medline/PubMed, Cochrane Library, Web of Science and CINAHL were searched from inception to January 2019. The search strategy included the following keywords: physical activity promotion, pulmonary rehabilitation and daily physical activity. The eligibility criteria for selecting studies were randomised controlled trials reporting pedometer physical activity promotion in patients with COPD.Improvements in steps per day were found with pedometer physical activity promotion either standalone (n=12, mean 0.53 (95% CI 0.29-0.77); p=0.00001) or alongside pulmonary rehabilitation (n=7, 0.51 (0.13-0.88); p=0.006). A subgroup analysis reported significant differences in the promotion of physical activity based on baseline physical activity levels and the type of instrument used to assess levels of physical activity.Future trials should consider the way in which pedometers are used to promote physical activity to inform clinical practice in the setting of pulmonary rehabilitation.

Effect of Time on Human Muscle Outcomes During Simulated Microgravity Exposure Without Countermeasures-Systematic Review.

Background: Space Agencies are planning human missions beyond Low Earth Orbit. Consideration of how physiological system adaptation with microgravity (µG) will be managed during these mission scenarios is required. Exercise countermeasures (CM) could be used more sparingly to decrease limited resource costs, including periods of no exercise. This study provides a complete overview of the current evidence, making recommendations on the length of time humans exposed to simulated µG might safely perform no exercise considering muscles only. Methods: Electronic databases were searched for astronaut or space simulation bed rest studies, as the most valid terrestrial simulation, from start of records to July 2017. Studies were assessed with the Quality in Prognostic Studies and bed rest analog studies assessed for transferability to astronauts using the Aerospace Medicine Systematic Review Group Tool for Assessing Bed Rest Methods. Effect sizes, based on no CM groups, were used to assess muscle outcomes over time. Outcomes included were contractile work capacity, muscle cross sectional area, muscle activity, muscle thickness, muscle volume, maximal voluntary contraction force during one repetition maximum, peak power, performance based outcomes, power, and torque/strength. Results: Seventy-five bed rest µG simulation studies were included, many with high risk of confounding factors and participation bias. Most muscle outcomes deteriorated over time with no countermeasures. Moderate effects were apparent by 7-15 days and large by 28-56 days. Moderate effects (>0.6) became apparent in the following order, power and MVC during one repetition maximum (7 days), followed by volume, cross sectional area, torques and strengths, contractile work capacity, thickness and endurance (14 days), then muscle activity (15 days). Large effects (>1.2) became apparent in the following order, volume, cross sectional area (28 days) torques and strengths, thickness (35 days) and peak power (56 days). Conclusions: Moderate effects on a range of muscle parameters may occur within 7-14 days of unloading, with large effects within 35 days. Combined with muscle performance requirements for mission tasks, these data, may support the design of CM programmes to maximize efficiency without compromising crew safety and mission success when incorporated with data from additional physiological systems that also need consideration.

Effect of time on biomechanics during exercise on the functional re-adaptive exercise device.

Mechanistic studies of the Functional Re-adaptive Exercise Device (FRED) have shown it automatically recruits Lumbar Multifidus (LM) and Transversus Abdominis (TrA) - two deep-spinal muscles that are atrophied and show altered motor control in low back pain (LBP). No studies have investigated the time required to familiarise to FRED exercise, which is required to inform future FRED based clinical trial protocols. This study therefore determined the effect of time, during FRED exercise, on biomechanical outcome measures, to establish the familiarisation period, and assess for loss of technique throughout a ten minute trial. A cohort comparison study of 148 participants, 70 experiencing low back pain, had lumbopelvic kinematics, exercise frequency and movement variability measured during a 10 minute trial. Magnitude-based inference was used to assess for familiarisation, using plots of variation over time with familiarised reference ranges. The no pain group took 170 seconds, and the back pain group took 150 seconds, to familiarise. A familiarisation period of at least 170 seconds (2.8 minutes) is recommended. This justifies, and provides a familiarisation time for use of the FRED as a motor control intervention.