The effect of bed rest on balance control in healthy adults: A systematic scoping review.

The objective of this study was to determine the effect of bed rest on balance control and the mechanisms responsible for these changes. Searches were conducted in six databases. Studies had to be conducted on healthy adults who were subjected to bed rest (≥5 days), with balance control measures obtained before and after bed rest in order to be included. Risk of bias was assessed using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. After screening 9,785 articles, 18 were included for qualitative synthesis. Fifteen studies found decrements in at least one balance control measure following bed rest, either compared to baseline or controls, with eight studies observing impairments in >50% of their balance control measures. Of the 14 studies that included an intervention, four (mechanical stimuli, lower-body negative pressure, and training targeting strength, balance and/or aerobic capacity) successfully offset the majority of balance control deficits and targeted the musculoskeletal and cardiovascular systems. The findings of this review support bed rest negatively affecting balance control in healthy individuals. In clinical populations, these deficits may be further accentuated due to various comorbidities that impact balance control systems. PROSPERO Registration: CRD42018098887.

Bed rest: outdated following traumatic solid organ injury?

INTRODUCTION: This systematic review aimed to evaluate early ambulation protocols implemented for traumatic solid organ injury. METHODS: The electronic databases PubMed, Medline (Ovid), Embase and Cochrane Library were searched without time constraint to identify prospective and retrospective analyses, randomised controlled trials, cohort studies, and case series that investigated early ambulation in solid organ trauma. RESULTS: Six studies met the predefined inclusion criteria and were reviewed. Three studies investigated early ambulation protocols in direct comparison with bed rest. The remaining three studies were early ambulation case series. In all studies there was no convincing evidence to suggest differences in clinical outcomes between early ambulation and bed rest protocols. In all studies early ambulation resulted in a reduced length of hospitalisation and decreased cost to national healthcare services. CONCLUSIONS: This systematic review has found preliminary evidence that suggests bed rest has no clinical benefit in those with low-grade to mid-grade (grades 1-2) solid organ injury. Further studies are required to inform guidance to improve trauma patient outcomes.

12 versus 24 h bed rest after acute ischemic stroke thrombolysis: a preliminary experience.

BACKGROUND: The practice of ≥24 h of bed rest after acute ischemic stroke thrombolysis is common among hospitals, but its value compared to shorter periods of bed rest is unknown. METHODS: Consecutive adult patients with a diagnosis of ischemic stroke who had received intravenous thrombolysis treatment from 1/1/2010 until 4/13/2016, identified from the local ischemic stroke registry, were included. Standard practice bed rest for ≥24 h, the protocol prior to 1/27/2014, was retrospectively compared with standard practice bed rest for ≥12 h, the protocol after that date. The primary outcome was favorable discharge location (defined as home, home with services, or acute rehabilitation). Secondary outcome measures included incidence of pneumonia, NIHSS at discharge, and length of stay. RESULTS: 392 patients were identified (203 in the ≥24 h group, 189 in the ≥12 h group). There was no significant difference in favorable discharge outcome in the ≥24 h bed rest protocol compared with the ≥12 h bed rest protocol in multivariable logistic regression analysis (76.2% vs. 70.9%, adjusted OR 1.20 CI 0.71-2.03). Compared with the ≥24 h bed rest group, pneumonia rates (8.3% versus 1.6%, adjusted OR 0.12 CI 0.03-0.55), median discharge NIHSS (3 versus 2, adjusted p = .034), and mean length of stay (5.4 versus 3.5 days, adjusted p = .006) were lower in the ≥12 h bed rest group. CONCLUSION: Compared with ≥24 h bed rest, ≥12 h bed rest after acute ischemic stroke reperfusion therapy appeared to be similar. A non-inferiority randomized trial is needed to verify these findings.

Efficacy of fluid loading as a countermeasure to the hemodynamic and hormonal changes of 28-h head-down bed rest.

After exposure to microgravity, or head-down bed rest (HDBR), fluid loading is often used with the intent of increasing plasma volume and maintaining mean arterial pressure during orthostatic stress. Nine men (aged 18-32 years) underwent three randomized trials with lower body negative pressure (LBNP) before and after: (1) 4-h of sitting with fluid loading (1 g sodium chloride/125 mL of water starting 2.5-h before LBNP), (2) 28-h of 6-degree HDBR without fluid loading, and (3) 28-h of 6-degree HDBR with fluid loading. LBNP was progressive from 0 to -40 mmHg. After 28-h HDBR, fluid loading did not protect against the loss of plasma volume (-280 ± 64 mL without fluid loading, -207 ± 86 with fluid loading, P = 0.472) nor did it protect against a drop of mean arterial pressure (P = 0.017) during LBNP (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 88 ± 4 to 85 ± 4 mmHg without fluid loading and 93 ± 4 to 88 ± 5 mmHg with fluid loading, P = 0.557 between trials). However, fluid loading did protect against the loss of stroke volume index and central venous pressure observed after 28-h HDBR. Fluid loading also attenuated the increase of angiotensin II seen after 28-h HDBR and throughout the LBNP protocol (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 16.6 ± 3.4 to 23.7 ± 5.0 pg/mL without fluid loading and 6.1 ± 0.8 to 12.2 ± 2.3 pg/mL with fluid loading, P < 0.001 between trials). Our results indicate that fluid loading did not protect against plasma volume loss due to HDBR or change blood pressure responses to LBNP. However, changes in central venous pressure, stroke volume and fluid regulatory hormones could potentially influence longer duration studies and those with more severe orthostatic stress.

Four days of bed rest increases intrinsic mitochondrial respiratory capacity in young healthy males.

Bed rest leads to impaired glucose tolerance. Whether this is linked to maladaptation's in skeletal muscle mitochondrial function and in particular to the level of reactive oxygen species (ROS) is at present unknown. The aim of this longitudinal study was to quantify skeletal muscle mitochondrial function (respiratory capacity and ROS production) together with glucose tolerance after 4 days of strict bed rest in healthy young male subjects (n = 14). Mitochondrial function was determined in permeabilized muscle fibers using high-resolution respirometry and fluorometry, mitochondrial content (citrate synthase [CS] activity) and antioxidant protein expression levels were assessed in parallel to this. Glucose tolerance was determined by means of oral glucose tolerance tests. Intrinsic mitochondrial respiratory capacity was augmented after the bed rest period (CI + IIP : 0.43 ± 0.12 vs. 0.55 ± 0.14 [pmol/sec/mg]/CS activity), due to a decreased CS activity (158 ± 39 vs. 129 ± 25 mU/mg dw.). No differences were observed in ROS production (per mg of tissue or when normalized to CS activity). Furthermore, the protein content for catalase was increased while superoxide dismutase and glutathione peroxidase remained unaffected. These findings were accompanied by an impaired glucose tolerance after the bed rest period (Matsuda index: 12 ± 6 vs. 9 ± 5). The change in intrinsic mitochondrial respiratory capacity could be an early indication in the development of impaired glucose tolerance. The increased catalase protein content might explain that no change was seen in ROS production after 4 days of bed rest. Whether these findings can be extrapolated to lifestyle-dependent decrements in physical activity and the development of type-2-diabetes remains unknown.

Perceived acceptability and preferences for low-intensity early activity interventions of older hospitalized medical patients exposed to bed rest: a cross sectional study.

BACKGROUND: Hospitalized older patients spend most of their time in bed, putting them at risk of experiencing orthostatic intolerance. Returning persons to their usual upright activity level is the most effective way to prevent orthostatic intolerance but some older patients have limited activity tolerance, supporting the need for low-intensity activity interventions. Consistent with current emphasis on patient engagement in intervention design and evaluation, this study explored older hospitalized patients' perceived acceptability of, and preference for, two low-intensity early activity interventions (bed-to-sitting and sitting-to-walking), and characteristics (gender, illness severity, comorbidity, illnesses and medications with orthostatic effects, and baseline functional capacity) associated with perceived acceptability and preference. METHODS: A convenience sample was recruited from in-patient medical units of two hospitals in Ontario, Canada and included 60 cognitively intact adults aged 65+ who were admitted for a medical condition within the past 72 h, spent ≥ 24 consecutive hours on a stretcher or in bed, presented with ≥ 2 chronic diseases, understood English, and were able to ambulate before admission. A cross-sectional observational design was used. Participants were presented written and oral descriptions and a 2-min video of each intervention. The sequence of the interventions' presention was randomized. Following the presentation, a research nurse administered measures of perceived acceptability and preference, and collected health and demographic data. Perceived acceptability and preference for the interventions were measured using the Treatment Acceptability and Preferences Scale. Illness severity was measured using the Modified Early Warning Score. Comorbidity was assessed with the Age Adjusted Charlson Comorbidity Scale and the Cumulative Illness Rating Scale - for Geriatrics. Baseline functional capacity was measured using the Duke Activity Status Index. RESULTS: Participants' perceived acceptability of both interventions clustered above the scale midpoint. Most preferred the sitting-to-walking intervention (n = 26; 43.3%). While none of the patient characteristics were associated with intervention acceptability, illness severity (odds ratio = 1.9, p = 0.04) and medications with orthostatic effects (odds ratio = 9.9, p = 0.03) were significantly associated with intervention preference. CONCLUSIONS: The interventions examined in this study were found to be acceptable to older adults, supporting future research examining their feasibility and effectiveness.

Markers of bone metabolism during 14 days of bed rest in young and older men.

OBJECTIVE: We aimed at comparing markers of bone metabolism during unloading in young and older men, and to assess countermeasure effectiveness. METHODS: 16 older (60±2 years) and 8 younger men (23±3 years) underwent bed rest (BR) for 14 days. A subgroup of the Older performed cognitive training during BR and supplemented protein and potassium bicarbonate afterwards. Biochemical markers of bone and calcium/phosphate metabolism were assessed. RESULTS: At baseline urinary NTX and CTX were greater in younger than in older subjects (P<0.001), but increased during BR (P<0.001) by a similar amount (P>0.17). P1NP was greater in young than in older subjects (P<0.001) and decreased during BR in the Young (P<0.001). Sclerostin increased during BR across groups (P=0.016). No systematic effects of the countermeasure were observed. CONCLUSION: In men, older age did not affect control of bone metabolism, but bone turnover was reduced. During BR formation markers were reduced only in younger men whereas resorption markers increased to a comparable extent. Thus, we assume that older men are not at an elevated, and possibly even at a reduced risk to lose bone when immobilized.

Early Mobilization and Rehabilitation in the ICU: Moving Back to the Future.

Despite the historical precedent of mobilizing critically ill patients, bed rest is common practice in ICUs worldwide, especially for mechanically ventilated patients. ICU-acquired weakness is an increasingly recognized problem, with sequelae that may last for months and years following ICU discharge. The combination of critical illness and bed rest results in substantial muscle wasting during an ICU stay. When initiated shortly after the start of mechanical ventilation, mobilization and rehabilitation can play an important role in decreasing the duration of mechanical ventilation and hospital stay and improving patients' return to functional independence. This review summarizes recent evidence supporting the safety, feasibility, and benefits of early mobilization and rehabilitation of mechanically ventilated patients and presents a brief summary of future directions for this field.

From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006).

Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body's upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10-15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures--exercise (aerobic, resistive, vibration), nutritional and pharmacological--are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health.