Effects of strict prolonged bed rest on cardiorespiratory fitness: systematic review and meta-analysis.

PubMed

Ried-Larsen, Mathias; Aarts, Hugo M; Joyner, Michael J

2017-10-01

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 (V̇o 2max ) 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 V̇o 2max 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. V̇o 2max declined linearly across bed rest duration. No statistical difference in the decline among studies reporting V̇o 2max as l/min (-0.3% per day) compared with studies reporting V̇o 2max 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 V̇o 2max However, 15-26% of the variation in the decline in V̇o 2max was explained by the pre-bed-rest V̇o 2max levels, independent of the duration of bed rest (i.e., higher pre-bed-rest V̇o 2max levels were associated with larger declines in V̇o 2max ). 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 (V̇o 2max ) to aerobic exercise training exist. However, less is known about the variability in the response of V̇o 2max to prolonged bed rest. This systematic review and meta-analysis showed that pre-bed-rest V̇o 2max values were inversely associated with the change in V̇o 2max independent of the duration of bed rest. Moreover, we identified a large knowledge gap about the causes of decline in V̇o 2max , particularly in postmenopausal women, which may have clinical implications. Copyright © 2017 the American Physiological Society.

The Effects of Long Duration Bed Rest on Brain Functional Connectivity and Sensorimotor Functioning

NASA Technical Reports Server (NTRS)

Cassady, K.; Koppelmans, V.; De Dios, Y.; Stepanyan, V.; Szecsy, D.; Gadd, N.; Wood, S.; Reuter-Lorenz, P.; Castenada, R. Riascos; Kofman, I.;

Artificial Gravity: Effects on Bone Turnover

NASA Technical Reports Server (NTRS)

Heer, M.; Zwart, S /R.; Baecker, N.; Smith, S. M.

2007-01-01

The impact of microgravity on the human body is a significant concern for space travelers. Since mechanical loading is a main reason for bone loss, artificial gravity might be an effective countermeasure to the effects of microgravity. In a 21-day 6 head-down tilt bed rest (HDBR) pilot study carried out by NASA, USA, the utility of artificial gravity (AG) as a countermeasure to immobilization-induced bone loss was tested. Blood and urine were collected before, during, and after bed rest for bone marker determinations. Bone mineral density was determined by DXA and pQCT before and after bed rest. Urinary excretion of bone resorption markers (n-telopeptide and helical peptide) were increased from pre-bed rest, but there was no difference between the control and the AG group. The same was true for serum c-telopeptide measurements. Bone formation markers were affected by bed rest and artificial gravity. While bone-specific alkaline phosphatase tended to be lower in the AG group during bed rest (p = 0.08), PINP, another bone formation marker, was significantly lower in AG subjects than CN before and during bed rest. PINP was lower during bed rest in both groups. For comparison, artificial gravity combined with ergometric exercise was tested in a 14-day HDBR study carried out in Japan (Iwase et al. J Grav Physiol 2004). In that study, an exercise regime combined with AG was able to significantly mitigate the bed rest-induced increase in the bone resorption marker deoxypyridinoline. While further study is required to more clearly differentiate bone and muscle effects, these initial data demonstrate the potential effectiveness of short-radius, intermittent AG as a countermeasure to the bone deconditioning that occurs during bed rest and spaceflight. Future studies will need to optimize not only the AG prescription (intensity and duration), but will likely need to include the use of exercise or other combined treatments.

Effects of 21 days of bed rest, with or without artificial gravity, on nutritional status of humans

PubMed Central

Zwart, S. R.; Crawford, G. E.; Gillman, P. L.; Kala, G.; Rodgers, A. S.; Rogers, A.; Inniss, A. M.; Rice, B. L.; Ericson, K.; Coburn, S.; Bourbeau, Y.; Hudson, E.; Mathew, G.; DeKerlegand, D. E.; Sams, C. F.; Heer, M. A.; Paloski, W. H.; Smith, S. M.

2009-01-01

Spaceflight and bed rest models of microgravity have profound effects on physiological systems, including the cardiovascular, musculoskeletal, and immune systems. These effects can be exacerbated by suboptimal nutrient status, and therefore it is critical to monitor nutritional status when evaluating countermeasures to mitigate negative effects of spaceflight. As part of a larger study to investigate the usefulness of artificial gravity as a countermeasure for musculoskeletal and cardiovascular deficits during bed rest, we tested the hypothesis that artificial gravity would have an effect on some aspects of nutritional status. Dietary intake was recorded daily before, during, and after 21 days of bed rest with artificial gravity (n = 8) or bed rest alone (n = 7). We examined body composition, hematology, general blood chemistry, markers of oxidative damage, and blood levels of selected vitamins and minerals before, during, and after the bed rest period. Several indicators of vitamin status changed in response to diet changes: serum α- and γ-tocopherol and urinary 4-pyridoxic acid decreased (P < 0.001) and plasma β-carotene increased (P < 0.001) in both groups during bed rest compared with before bed rest. A decrease in hematocrit (P < 0.001) after bed rest was accompanied by a decrease in transferrin (P < 0.001), but transferrin receptors were not changed. These data provide evidence that artificial gravity itself does not negatively affect nutritional status during bed rest. Likewise, artificial gravity has no protective effect on nutritional status during bed rest. PMID:19074571

Exercise Effects on the Course of Gray Matter Changes Over 70 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Koppelmans, V.; Ploutz-Snyder, L.; DeDios, Y. E.; Wood, S. J.; Reuter-Lorenz, P. A.; Kofman, I.; Bloomberg, J. J.; Mulavara, A. P.; Seidler, R. D.

2014-01-01

Long duration spaceflight affects posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes through direct effects on peripheral changes that result from reduced vestibular stimulation and body unloading. Effects of microgravity on sensorimotor function have been investigated on earth using bed rest studies. Long duration bed rest serves as a space-flight analogue because it mimics microgravity in body unloading and bodily fluid shifts. It has been hypothesized that the cephalad fluid shift that has been observed in microgravity could potentially affect central nervous system function and structure, and thereby indirectly affect sensorimotor or cognitive functioning. Preliminary results of one of our ongoing studies indeed showed that 70 days of long duration head down-tilt bed rest results in focal changes in gray matter volume from pre-bed rest to various time points during bed rest. These gray matter changes that could reflect fluid shifts as well as neuroplasticity were related to decrements in motor skills such as maintenance of equilibrium. In consideration of the health and performance of crewmembers both inand post-flight we are currently conducting a study that investigates the potential preventive effects of exercise on gray matter and motor performance changes that we observed over the course of bed rest. Numerous studies have shown beneficial effects of aerobic exercise on brain structure and cognitive performance in healthy and demented subjects over a large age range. We therefore hypothesized that an exercise intervention in bed rest could potentially mitigate or prevent the effects of bed rest on the central nervous system. Here we present preliminary outcomes of our study.

Reduction in peak oxygen uptake after prolonged bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Kozlowski, S.

1982-01-01

The hypothesis that the magnitude of the reduction in peak oxygen uptake (VO2) after bed rest is directly proportional to the level of pre-bed rest peak VO2 is tested. Complete pre and post-bed rest working capacity and body weight data were obtained from studies involving 24 men (19-24 years old) and 8 women (23-34 years old) who underwent bed rest for 14-20 days with no remedial treatments. Results of regression analyses of the present change in post-bed rest peak VO2 on pre-bed rest peak VO2 with 32 subjects show correlation coefficients of -0.03 (NS) for data expressed in 1/min and -0.17 for data expressed in ml/min-kg. In addition, significant correlations are found that support the hypothesis only when peak VO2 data are analyzed separately from studies that utilized the cycle ergometer, particularly with subjects in the supine position, as opposed to data obtained from treadmill peak VO2 tests. It is concluded that orthostatic factors, associated with the upright body position and relatively high levels of physical fitness from endurance training, appear to increase the variability of pre and particularly post-bed rest peak VO2 data, which would lead to rejection of the hypothesis.

Impact of 9 Days of Bed Rest on Hepatic and Peripheral Insulin Action, Insulin Secretion, and Whole-Body Lipolysis in Healthy Young Male Offspring of Patients With Type 2 Diabetes

PubMed Central

Alibegovic, Amra C.; Højbjerre, Lise; Sonne, Mette P.; van Hall, Gerrit; Stallknecht, Bente; Dela, Flemming; Vaag, Allan

2009-01-01

OBJECTIVE The aim of this study was to investigate the impact of 9 days of bed rest on insulin secretion, insulin action, and whole-body glucose and fat metabolism in first-degree relative (FDR) and matched control (CON) subjects. RESEARCH DESIGN AND METHODS A total of 13 FDR and 20 CON subjects participated in the study. All were studied before and after 9 days of bed rest using the clamp technique combined with indirect calorimetry preceded by an intravenous glucose tolerance test. Glucose and glycerol turnover rates were studied using stable isotope kinetics. RESULTS Bed rest caused a significant decrease in whole-body insulin sensitivity in both groups. Hepatic insulin resistance was elevated in FDR subjects prior to bed rest and was significantly augmented by bed rest in FDR (P < 0.01) but not in CON (P = NS) subjects. The rate of whole-body lipolysis decreased during bed rest in both FDR and CON subjects, with no significant differences between the groups. Insulin resistance induced by bed rest was fully accounted for by the impairment of nonoxidative glucose metabolism in both groups (overall P < 0.001). CONCLUSIONS Whole-body insulin action in both insulin-resistant FDR and healthy CON subjects deteriorates with 9 days of bed rest, converging toward similar degrees of whole-body insulin resistance. FDR subjects exhibit hepatic insulin resistance (HIR), which, in contrast to CON subjects, deteriorates in response to physical inactivity. FDR subjects exhibit reduced insulin secretion when seen in relation to their degree of HIR but not peripheral insulin resistance. PMID:19720789

Cardiorespiratory responses to exercise after bed rest in men and women

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Bernauer, E. M.; Stremel, R. W.; Greenleaf, J. E.

1977-01-01

The purpose of this study was to compare cardiorespiratory responses of men and women to submaximal and maximal workloads before and after bed rest (BR). Fifteen male college students (19-23 yr) and eight female nurses (23-34 yr) underwent 14 d and 17 d, respectively, of bed rest. The maximal work capacity test was performed in the supine position on a bicycle ergometer just before and immediately after bed rest. Compared with pre-BR values, after bed rest the maximal ventilatory volume was essentially unchanged in the men (+1.8%) and women (+2.3%), but maximal heart rate was elevated from 185 to 193 b/min (+4.3%) in the men and from 181 to 187 b/min (3.3%) in the women. Mean corpuscular volume was unchanged in both groups pre- and post-bed rest. It is concluded that the proportional deterioration in maximal VO2 following prolonged bed rest was essentially the same in young men and women.

Effect of 14 days of bed rest on urine metabolite excretion and plasma enzyme levels

NASA Technical Reports Server (NTRS)

Pace, N.; Grunbaum, B. W.; Kodama, A. M.; Rahlmann, D. F.; Newsom, B. D.

1974-01-01

After 1 week of ambulatory base-line measurement, a group of 8 men 19-26 years of age remained continuously recumbent for 14 days. Studies were continued for 1 week following the prolonged recumbency. Urine excretion rates for a number of constituents were determined 2 days before bed rest, on day 14 of bed rest, and day 6 after bed rest. Blood plasma samples were also obtained at these times, and analyzed for several enzymes. On day 14 of bed rest significant increases were observed in urine excretion of total osmotically-active substances, magnesium, calcium, phosphate, creatinine, hydroxyproline, and 17-OH corticosteroids. A decrease occurred in urinary glucose excretion. Plasma levels of alkaline phosphatase and LDH-3 were depressed, while plasma GPT was elevated. Many of these changes persisted on day 6 after bed rest, and are interpreted as concomitants of the disuse atrophy of the musculoskeletal system that characterizes prolonged bed rest and weightlessness.

Effects of head-down bed rest on complex heart rate variability: Response to LBNP testing

NASA Technical Reports Server (NTRS)

Goldberger, Ary L.; Mietus, Joseph E.; Rigney, David R.; Wood, Margie L.; Fortney, Suzanne M.

1994-01-01

Head-down bed rest is used to model physiological changes during spaceflight. We postulated that bed rest would decrease the degree of complex physiological heart rate variability. We analyzed continuous heart rate data from digitized Holter recordings in eight healthy female volunteers (age 28-34 yr) who underwent a 13-day 6 deg head-down bed rest study with serial lower body negative pressure (LBNP) trials. Heart rate variability was measured on a 4-min data sets using conventional time and frequency domain measures as well as with a new measure of signal 'complexity' (approximate entropy). Data were obtained pre-bed rest (control), during bed rest (day 4 and day 9 or 11), and 2 days post-bed rest (recovery). Tolerance to LBNP was significantly reduced on both bed rest days vs. pre-bed rest. Heart rate variability was assessed at peak LBNP. Heart rate approximate entropy was significantly decreased at day 4 and day 9 or 11, returning toward normal during recovery. Heart rate standard deviation and the ratio of high- to low-power frequency did not change significantly. We conclude that short-term bed rest is associated with a decrease in the complex variability of heart rate during LBNP testing in healthy young adult women. Measurement of heart rate complexity, using a method derived from nonlinear dynamics ('chaos theory'), may provide a sensitive marker of this loss of physiological variability, complementing conventional time and frequency domain statistical measures.

Association Between Cardiovascular and Intraocular Pressure Changes in a 14-day 6 deg Head Down Tilt (HDT) Bed Rest Study: Possible Implications in Retinal Anatomy

NASA Technical Reports Server (NTRS)

Cromwell, R. L.; Zanello, S. B.; Yarbough, P. O.; Ploutz-Snyder, R.; Taibbi, G.; Brewer, J. L.; Vizzeri, G.

2013-01-01

Mean IOP significantly increased while at 6deg HDT and returned towards pre-bed rest values upon leaving bed rest. While mean IOP increased during bed rest, it remained within the normal limits for subject safety. A diuretic shift and cardiovascular deconditioning occurs during in-bed rest, as expected. There was no demonstrable correlation between the largest change in IOP (pre/post) and cardiovascular measure changes (pre/post). Additional mixed effects linear regression modeling may reveal some subclinical physiological changes that might assist in describing the VIIP syndrome pathophysiology.

Effect of prolonged bed rest on lung volume in normal individuals

NASA Technical Reports Server (NTRS)

Beckett, W. S.; Vroman, N. B.; Nigro, D.; Thompson-Gorman, S.; Wilkerson, J. E.

1986-01-01

The effect of prolonged bed rest on the lung function was studied by measuring forced vital capacity (FVC) and total lung capacity (TLC) in normal subjects before, during, and after 11- to 12-day rest periods. It was found that both FVC and TLC increased during bed rest (compared with the ambulatory controls), while residual volume and functional residual capacity of the respiratory system did not change. It is concluded that the increase in TLC by prolonged bed rest is not dependent on alterations in plasma volume.

Long-duration space flight and bed rest effects on testosterone and other steroids.

PubMed

Smith, Scott M; Heer, Martina; Wang, Zuwei; Huntoon, Carolyn L; Zwart, Sara R

2012-01-01

Limited data suggest that testosterone is decreased during space flight, which could contribute to bone and muscle loss. The main objective was to assess testosterone and hormone status in long- and short-duration space flight and bed rest environments and to determine relationships with other physiological systems, including bone and muscle. Blood and urine samples were collected before, during, and after long-duration space flight. Samples were also collected before and after 12- to 14-d missions and from participants in 30- to 90-d bed rest studies. Space flight studies were conducted on the International Space Station and before and after Space Shuttle missions. Bed rest studies were conducted in a clinical research center setting. Data from Skylab missions are also presented. All of the participants were male, and they included 15 long-duration and nine short-duration mission crew members and 30 bed rest subjects. Serum total, free, and bioavailable testosterone were measured along with serum and urinary cortisol, serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, and SHBG. Total, free, and bioavailable testosterone was not changed during long-duration space flight but were decreased (P < 0.01) on landing day after these flights and after short-duration space flight. There were no changes in other hormones measured. Testosterone concentrations dropped before and soon after bed rest, but bed rest itself had no effect on testosterone. There was no evidence for decrements in testosterone during long-duration space flight or bed rest.

Blood volume responses of men and women to bed rest

NASA Technical Reports Server (NTRS)

Fortney, S. M.; Turner, C.; Steinmann, L.; Driscoll, T.; Alfrey, C.

1994-01-01

This paper reviews a series of studies that indicate that estrogens play an important role in blood volume regulation. The first study illustrates that the plasma volume (PV) of ambulatory women fluctuates during the menstrual cycle, increasing during periods of elevated estrogens. In the second study, it was shown that exogenous and endogenous elevations in blood estrogens attenuate the decrease in PV during bed rest. In the third study, the hypothesis was tested that women, who naturally have a higher blood estrogen content compared with men, will have a smaller loss of PV during bed rest. Ten men and ten women underwent a 13-day, 6 degrees head-down bed rest. Plasma volume and red cell mass (RCM) were measured before and after bed rest using 125I and 51Cr labeling, respectively. Before bed rest, the men and women had similar blood volume (BV) and PV (mL/kg body weight), but the women had a smaller (P < .01) RCM (22.2 +/- 0.9 versus 26.2 +/- 0.8 mL/kg, mean +/- SE). During bed rest, the decrease in RCM (mL/kg) was similar in men and women. However, the decrease in BV was greater in men (8.0 +/- 0.8 mL/kg versus 5.8 +/- 0.8 mL/kg), because of a greater reduction in PV (6.3 +/- 0.6 mL/kg versus 4.1 +/- 0.6 mL/kg). Because the decline in BV has been proposed to contribute to the cardiovascular deconditioning after bed rest, it is possible that women may experience less cardiac and circulatory strain on reambulation.

Cardiorespiratory responses to exercise after bed rest in men and women.

PubMed

Convertino, V A; Stremel, R W; Bernauer, E M; Greenleaf, J E

1977-01-01

The purpose of this study was to compare cardiorespiratory responses of men and women to submaximal and maximal workloads before and after bed rest (BR). Fifteen male college students (19-23 yr) and 8 female nurses (23-34 yr) underwent 14 d and 17 d, respectively of bed rest. The maximal work capacity test was performed in the supine position on a bicycle ergometer just before and immediately after bed rest. The women's maximal O2 uptake (maximal VO2) was 41% lower (P<0.05) than the men's before bed rest and 42% lower (P<0.05) after bed rest. During bed rest the women's maximal VO2 decreased from 2.06 to 1.86 liter/min (-9.7%, P<0.05), and that of the men decreased from 3.52 to 3.20 liter/min (-9.1%, P<0.05). Compared with pre-BR values, after bed rest the maximal ventilatory volume was essentially unchanged in the men (+1.8%) and women (+ 2.3%), but maximal heart rate was elevated from 185 to 193 b/min (+ 4.3%, P<0.05) in the men and from 181 to 187 b/min (3.3%, P<0.05) in the women. Submaximal VO2 was unchanged after bed rest in the men but was significantly reduced in the women; the women's Hct and RBC levels were lower (P<0.05) than comparable male data. Mean corpuscular volume was unchanged in both groups pre- and post-bed rest. It is concluded that the proportional deterioration in maximal VO2 following prolonged bed rest was essentially the same in young men and women.

Joint US/USSR study: Comparison of effects of horizontal and head-down bed rest

NASA Technical Reports Server (NTRS)

Sandler, Harold; Grigoriev, Anatoli I.

1990-01-01

An account is given of the results of the first joint U.S./U.S.S.R. bed rest study. The study was accomplished in two parts: A soviet part (May to June 1979) and an American part (July to August 1979). Both studies were conducted under identical conditions and provided a basis for comparison of physiologic reactions and standardizing procedures and methods. Each experiment consisted of three periods: 14 days of pre-bed rest control, 7 days of bed rest, and a 10 to 14 day recovery period. Ten males participated in each study, with five subjects experiencing horizontal bed rest and five subjects a -6 deg head-down body position. Biochemical and hormonal measurements were made of blood and urine, with particular attention to electrolyte metabolism and kidney function; cardio-pulmonary changes at rest and exercise; influence of Lower Body Negative Pressure (LBNP); and incremental exercise using a bicyle ergometer while supine and sitting. Expected moderate changes were noted to occur for various physiologic parameters. Clinical evidence pointed to the fact that head-down bed rest when compared to horizontal conditions more closely matched the conditions seen after manned spaceflight. For the most part, statistically significant differences between the two body positions were not observed.

Long Duration Head-Down Tilt Bed Rest Studies: Safety Considerations Regarding Vision Health

NASA Technical Reports Server (NTRS)

Cromwell, Ronita L.; Zanello, S. B.; Yarbough, P. O.; Ploutz-Snyder, Robert; Taibbi, G.; Vizzeri, G.

2012-01-01

Visual symptoms reported in astronauts returning from long duration missions in low Earth orbit, including hyperopic shift, choroidal folds, globe flattening and papilledema, are thought to be related to fluid shifts within the body due to microgravity exposure. Because of this possible relation to fluid shifts, safety considerations have been raised regarding the ocular health of head-down tilt (HDT) bed rest subjects. HDT is a widely used ground ]based analog that simulates physiological changes of spaceflight, including fluid shifts. Thus, vision monitoring has been performed in bed rest subjects in order to evaluate the safety of HDT with respect to vision health. Here we report ocular outcomes in 9 healthy subjects (age range: 27-48 years; Male/Female ratio: 8/1) completing bed rest Campaign 11, an integrated, multidisciplinary 70-day 6 degrees HDT bed rest study. Vision examinations were performed on a weekly basis, and consisted of office-based (2 pre- and 2 post-bed rest) and in-bed testing. The experimental design was a repeated measures design, with measurements for both eyes taken for each subject at each planned time point. Findings for the following tests were all reported as normal in each testing session for every subject: modified Amsler grid, red dot test, confrontational visual fields, color vision and fundus photography. Overall, no statistically significant differences were observed for any of the measures, except for both near and far visual acuity, which increased during the course of the study. This difference is not considered clinically relevant as may result from the effect of learning. Intraocular pressure results suggest a small increase at the beginning of the bed rest phase (p=0.059) and lesser increase at post-bed rest with respect to baseline (p=0.046). These preliminary results provide the basis for further analyses that will include correlations between intraocular pressure change pre- and post-bed rest, and optical coherence tomography measurements of the retina.

In Vivo measurement of human body composition. [during continuous bed rest

NASA Technical Reports Server (NTRS)

Pace, N.; Grunbaum, B. W.; Kodama, A. M.; Price, D. C.

1975-01-01

Physiological changes in human beings were studied during a 21 day bed rest regime. Results of blood analyses indicated clearly that major metabolic adjustments occurred during prolonged bed rest. However, urinary metabolic analyses showed variances attributed to specimen collection inaccuracies and the small number of test subjects.

Bed rest duration after sheath removal following percutaneous coronary interventions: a systematic review and meta-analysis.

PubMed

Mohammady, Mina; Atoof, Fatemeh; Sari, Ali Akbari; Zolfaghari, Mitra

2014-06-01

To explore the effect of bed rest duration after sheath removal following percutaneous coronary interventions on the incidence of vascular complications, back pain and urinary problems. According to the literature, the duration of bed rest after sheath removal following percutaneous coronary interventions ranges from 2-24 hours. Several studies have assessed the effect of duration of bed rest on vascular complications, but a clear final conclusion about the exact duration of bed rest has not been reached. Systematic review and meta-analysis. Cochrane Library, MEDLINE, SCOPUS, CINAHL, IranMedex and IranDoc were searched. No language limitation was applied. RCTs that used two different periods for ambulation were included. Two reviewers separately assessed the quality of each included study and extracted the data. Dichotomous outcomes were recorded as odds ratio with 95% confidence interval. Five studies involving 1115 participants were included in the review. Among them, two studies had three comparison groups. The studies considered a variety of periods as early and late ambulation, ranging from 2-10 hours. Totally, there were no statistically significant differences in the incidence of bleeding, pseudoaneurysm, arteriovenous fistula and urinary problems between early and late ambulation. There was a statistically significant reduction in the risk of haematoma formation at four to six hours of bed rest compared with eight hours of bed rest (odds ratio = 0·37, 95% CI: 0·15, 0·91). Back pain was reported in one study evaluating three hours of bed rest with an odds ratio of 0·45 (95% confidence interval: 0·28, 0·71) when compared with 10 hours of bed rest. Early ambulation after percutaneous coronary interventions is safe and feasible; however, the results should be used with caution as the majority of included studies had methodological flaws. The results of this study suggest that patients could be ambulated three to four hours after sheath removal following percutaneous coronary interventions and early ambulation dose does not increase the risk of vascular complications, but it moderates back pain occurrence. © 2013 John Wiley & Sons Ltd.

Long-Duration Space Flight and Bed Rest Effects on Testosterone and Other Steroids

PubMed Central

Heer, Martina; Wang, Zuwei; Huntoon, Carolyn L.; Zwart, Sara R.

2012-01-01

Context: Limited data suggest that testosterone is decreased during space flight, which could contribute to bone and muscle loss. Objective: The main objective was to assess testosterone and hormone status in long- and short-duration space flight and bed rest environments and to determine relationships with other physiological systems, including bone and muscle. Design: Blood and urine samples were collected before, during, and after long-duration space flight. Samples were also collected before and after 12- to 14-d missions and from participants in 30- to 90-d bed rest studies. Setting: Space flight studies were conducted on the International Space Station and before and after Space Shuttle missions. Bed rest studies were conducted in a clinical research center setting. Data from Skylab missions are also presented. Participants: All of the participants were male, and they included 15 long-duration and nine short-duration mission crew members and 30 bed rest subjects. Main Outcome Measures: Serum total, free, and bioavailable testosterone were measured along with serum and urinary cortisol, serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, and SHBG. Results: Total, free, and bioavailable testosterone was not changed during long-duration space flight but were decreased (P < 0.01) on landing day after these flights and after short-duration space flight. There were no changes in other hormones measured. Testosterone concentrations dropped before and soon after bed rest, but bed rest itself had no effect on testosterone. Conclusions: There was no evidence for decrements in testosterone during long-duration space flight or bed rest. PMID:22049169

Bed rest in singleton pregnancies for preventing preterm birth.

PubMed

Sosa, Claudio G; Althabe, Fernando; Belizán, José M; Bergel, Eduardo

2015-03-30

Bed rest in hospital or at home is widely recommended for the prevention of preterm birth. This advice is based on the observation that hard work and hard physical activity during pregnancy could be associated with preterm birth and with the idea that bed rest could reduce uterine activity. However, bed rest may have some adverse effects on other outcomes. To evaluate the effect of prescription of bed rest in hospital or at home for preventing preterm birth in pregnant women at high risk of preterm birth. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (18 December 2014), the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2014, Issue 12), MEDLINE (December 2014), EMBASE (December 2014), LILACS (December 2014), and bibliographies of relevant papers. Randomized, cluster-randomized and quasi-randomized controlled trials with reported data that assess clinical outcomes in women at high risk of spontaneous preterm birth who were prescribed bed rest in hospital or at home for preventing preterm birth, and their babies. Two review authors independently assessed eligibility, trial quality and extracted data. Two studies met the inclusion criteria. One study was not considered for the meta-analysis, since data combined singleton and multiple pregnancies. No differences in any maternal and perinatal outcomes were reported by the authors. This study was at low risk of selection, performance, detection and attrition bias. Only data from one study were included in the meta-analysis (1266 women). This study was at unclear risk of bias for most domains due to lack of reporting. Four hundred and thirty-two women were prescribed bed rest at home and a total of 834 women received a placebo (412) or no intervention (422). Preterm birth before 37 weeks was similar in both groups (7.9% in the intervention group versus 8.5% in the control group; risk ratio (RR) 0.92, 95% confidence interval (CI) 0.62 to 1.37). No other results were reported for any of the other primary or secondary outcomes. There is no evidence, either supporting or refuting the use of bed rest at home or in hospital, to prevent preterm birth. Although bed rest in hospital or at home is widely used as the first step of treatment, there is no evidence that this practice could be beneficial. Due to the potential adverse effects that bed rest could have on women and their families, and the increased costs for the healthcare system, clinicians should discuss the pros and cons of bed rest to prevent preterm birth. Potential benefits and harms should be discussed with women facing an increased risk of preterm birth. Appropriate research is mandatory. Future trials should evaluate both the effectiveness of bed rest, and the effectiveness of the prescription of bed rest, to prevent preterm birth.

Changes in mood status and neurotic levels during a 20-day bed rest

NASA Astrophysics Data System (ADS)

Ishizaki, Yuko; Ishizaki, Tatsuro; Fukuoka, Hideoki; Kim, Chang-Sun; Fujita, Masayo; Maegawa, Yuko; Fujioka, Hiroshi; Katsura, Taisaku; Suzuki, Yoji; Gunji, Atsuaki

2002-04-01

This study evaluated changes of mood status and depressive and neurotic levels in nine young male subjects during a 20-day 6° head-down tilting bed rest and examined whether exercise training modified these changes. Participants were asked to complete psychometrical inventories on before, during, and after the bed rest experiment. Depressive and neurotic levels were enhanced during bed rest period according to the Japanese version of Zung's Self-rating Depression Scale and the Japanese version of the General Health Questionnaire. Mood state "vigor" was impaired and "confusion" was increased during bed rest and recumbent control periods compared to pre-bed rest and ambulatory control periods according to the Japanese version of Profiles of Mood State, whereas the mood "tension-anxiety", "depression-dejection", "anger-hostility" and "fatigue" were relatively stable during experiment. Isometric exercise training did not modify these results. Microgravity, along with confinement to bed and isolation from familiar environments, induced impairment of mental status.

Attenuated sympathetic nerve responses after 24 hours of bed rest

NASA Technical Reports Server (NTRS)

Khan, Mazhar H.; Kunselman, Allen R.; Leuenberger, Urs A.; Davidson, William R Jr; Ray, Chester A.; Gray, Kristen S.; Hogeman, Cynthia S.; Sinoway, Lawrence I.

2002-01-01

Bed rest reduces orthostatic tolerance. Despite decades of study, the cause of this phenomenon remains unclear. In this report we examined hemodynamic and sympathetic nerve responses to graded lower body negative pressure (LBNP) before and after 24 h of bed rest. LBNP allows for baroreceptor disengagement in a graded fashion. We measured heart rate (HR), cardiac output (HR x stroke volume obtained by echo Doppler), and muscle sympathetic nerve activity (MSNA) during a progressive and graded LBNP paradigm. Negative pressure was increased by 10 mmHg every 3 min until presyncope or completion of -60 mmHg. After bed rest, LBNP tolerance was reduced in 11 of 13 subjects (P <.023), HR was greater (P <.002), cardiac output was unchanged, and the ability to augment MSNA at high levels of LBNP was reduced (rate of rise for 30- to 60-mmHg LBNP before bed rest 0.073 bursts x min(-1) x mmHg(-1); after bed rest 0.035 bursts x min(-1) x mmHg(-1); P < 0.016). These findings suggest that 24 h of bed rest reduces sympathetic nerve responses to LBNP.

Evaluation of a Reverse Gradient Garment for prevention of bed-rest deconditioning

NASA Technical Reports Server (NTRS)

Sandler, H.; Dolkas, D.; Newsom, B.; Webb, P.; Annis, J.; Pace, N.; Grunbaum, B. W.

1983-01-01

A Reverse Gradient Garment (RGG) was used to intermittently induce venous pooling in the extremities of a magnitude similar to that seen in going from a lying to standing position during the course of a 15-d period of horizontal bed rest. Venous pooling failed to improve bed-rest-induced losses in +2.5 Gz and +3.0 Gz centrifugation tolerance or to prevent increased heart-rate responses to lower-body negative pressure (LBNP). Four subjects served as controls, four were treated. Tests during the 7-d recovery period showed fluid/electrolyte and body composition values to have returned to pre-bed-rest levels with continued depression of acceleration tolerance times (56% decreased at +2.5 Gz and 74% decreased at +3.0 Gz compared to pre-bed-rest levels) and exaggerated blood insulin response on glucose tolerance testing (blood insulin for treated group increased 95% at 1 h before bed rest and 465% during recovery). This study demonstrates that the physiologic changes after bed rest persist for significant periods of time. Acceleration tolerance time proved to be a sensitive test for the deconditioning process.

Branched-chain amino acid supplementation during bed rest: effect on recovery

NASA Technical Reports Server (NTRS)

Stein, T. P.; Donaldson, M. R.; Leskiw, M. J.; Schluter, M. D.; Baggett, D. W.; Boden, G.

2003-01-01

Bed rest is associated with a loss of protein from the weight-bearing muscle. The objectives of this study are to determine whether increasing dietary branched-chain amino acids (BCAAs) during bed rest improves the anabolic response after bed rest. The study consisted of a 1-day ambulatory period, 14 days of bed rest, and a 4-day recovery period. During bed rest, dietary intake was supplemented with either 30 mmol/day each of glycine, serine, and alanine (group 1) or with 30 mmol/day each of the three BCAAs (group 2). Whole body protein synthesis was determined with U-(15)N-labeled amino acids, muscle, and selected plasma protein synthesis with l-[(2)H(5)]phenylalanine. Total glucose production and gluconeogenesis from alanine were determined with l-[U-(13)C(3)]alanine and [6,6-(2)H(2)]glucose. During bed rest, nitrogen (N) retention was greater with BCAA feeding (56 +/- 6 vs. 26 +/- 12 mg N. kg(-1). day(-1), P < 0.05). There was no effect of BCAA supplementation on either whole body, muscle, or plasma protein synthesis or the rate of 3-MeH excretion. Muscle tissue free amino acid concentrations were increased during bed rest with BCAA (0.214 +/- 0.066 vs. 0.088 +/- 0.12 nmol/mg protein, P < 0.05). Total glucose production and gluconeogenesis from alanine were unchanged with bed rest but were significantly reduced (P < 0.05) with the BCAA group in the recovery phase. In conclusion, the improved N retention during bed rest is due, at least in part, to accretion of amino acids in the tissue free amino acid pools. The amount accreted is not enough to impact protein kinetics in the recovery phase but does improve N retention by providing additional essential amino acids in the early recovery phase.

Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults.

PubMed

Deutz, Nicolaas E P; Pereira, Suzette L; Hays, Nicholas P; Oliver, Jeffery S; Edens, Neile K; Evans, Chris M; Wolfe, Robert R

2013-10-01

Loss of muscle mass due to prolonged bed rest decreases functional capacity and increases hospital morbidity and mortality in older adults. To determine if HMB, a leucine metabolite, is capable of attenuating muscle decline in healthy older adults during complete bed rest. A randomized, controlled, double-blinded, parallel-group design study was carried out in 24 healthy (SPPB ≥ 9) older adult subjects (20 women, 4 men), confined to complete bed rest for ten days, followed by resistance training rehabilitation for eight weeks. Subjects in the experimental group were treated with HMB (calcium salt, 1.5 g twice daily - total 3 g/day). Control subjects were treated with an inactive placebo powder. Treatments were provided starting 5 days prior to bed rest till the end rehabilitation phase. DXA was used to measure body composition. Nineteen eligible older adults (BMI: 21-33; age: 60-76 year) were evaluable at the end of the bed rest period (Control n = 8; Ca-HMB n = 11). Bed rest caused a significant decrease in total lean body mass (LBM) (2.05 ± 0.66 kg; p = 0.02, paired t-test) in the Control group. With the exclusion of one subject, treatment with HMB prevented the decline in LBM over bed rest -0.17 ± 0.19 kg; p = 0.23, paired t-test). There was a statistically significant difference between treatment groups for change in LBM over bed rest (p = 0.02, ANOVA). Sub-analysis on female subjects (Control = 7, HMB = 8) also revealed a significant difference in change in LBM over bed rest between treatment groups (p = 0.04, ANOVA). However, differences in function parameters could not be observed, probably due to the sample size of the study. In healthy older adults, HMB supplementation preserves muscle mass during 10 days of bed rest. These results need to be confirmed in a larger trial. Copyright © 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

The ratio of animal protein intake to potassium intake is a predictor of bone resorption in space flight analogues and in ambulatory subjects

NASA Technical Reports Server (NTRS)

Zwart, Sara R.; Hargens, Alan R.; Smith, Scott M.

2004-01-01

BACKGROUND: Bone loss is a critical concern for space travelers, and a dietary countermeasure would be of great benefit. Dietary protein and potassium-associated bicarbonate precursors may have opposing effects on the acid-base balance in the body and therefore on bone loss. OBJECTIVE: In 2 studies, we examined the ability of dietary protein and potassium to predict markers of bone metabolism. DESIGN: In the first study, 8 pairs of male identical twins were assigned to 1 of 2 groups: bed rest (sedentary, or SED, group) or bed rest with supine treadmill exercise in a lower-body negative pressure chamber (EX group). In a second study, groups of 4 subjects lived in a closed chamber for 60 or 91 d, and dietary data were collected for two or three 5-d sessions. Urinary calcium, N-telopeptide, and pyridinium cross-links were measured before bed rest; on bed rest days 5-6, 12-13, 19-20, and 26-27; and daily during the chamber studies. Data were analyzed by Pearson's correlation (P < 0.05). RESULTS: The ratio of animal protein intake to potassium intake was significantly correlated with N-telopeptide in the SED group during bed rest weeks 3 and 4 (r = 0.77 and 0.80) and during the 91-d chamber study (r = 0.75). The ratio of animal protein intake to potassium intake was positively correlated with pyridinium cross-links before bed rest in the EX group (r = 0.83), in the EX group during bed rest week 1 (r = 0.84), and in the SED group during bed rest week 2 (r = 0.72) but not during either chamber study. In both studies, these relations were not significant with the ratio of vegetable protein intake to potassium intake. CONCLUSIONS: The ratio of animal protein intake to potassium intake may affect bone in ambulatory and bed-rest subjects. Changing this ratio may help to prevent bone loss on Earth and during space flight.

International Standardization of Bed Rest Standard Measures

NASA Technical Reports Server (NTRS)

Cromwell, Ronita L.

2010-01-01

This slide presentation gives an overview of the standardization of bed rest measures. The International Countermeasures Working Group attempted to define and agree internationally on standard measurements for spaceflight based bed rest studies. The group identified the experts amongst several stakeholder agencys. It included information on exercise, muscle, neurological, psychological, bone and cardiovascular measures.

Evaluation of positive G sub Z tolerance following simulated weightlessness (bedrest)

NASA Technical Reports Server (NTRS)

Jacobson, L. B.; Hyatt, K. H.; Sullivan, R. W.; Cantor, S. A.; Sandler, H.; Rositano, S. A.; Mancini, R. E.

1973-01-01

The magnitude of physiologic changes which are known to occur in human subjects exposed to varying levels of + G sub Z acceleration following bed rest simulation of weightlessness was studied. Bed rest effects were documented by fluid and electrolyte balance studies, maximal exercise capability, 70 deg passive tilt and lower body negative pressure tests and the ability to endure randomly prescribed acceleration profiles of +2G sub Z, +3G sub Z, and +4G sub Z. Six healthy male volunteers were studied during two weeks of bed rest after adequate control observations, followed by two weeks of recovery, followed by a second two-week period of bed rest at which time an Air Force cutaway anti-G suit was used to determine its effectiveness as a countermeasure for observed cardiovascular changes during acceleration. Results showed uniform and significant changes in all measured parameters as a consequence of bed rest including a reduced ability to tolerate +G sub Z acceleration. The use of anti-G suits significantly improved subject tolerance to all G exposures and returned measured parameters such as heart rate and blood pressure towards or to pre-bed-rest (control) values in four of the six cases.

Cardiovascular Adaptations to Long Duration Head Down Tilt Bed Rest

NASA Technical Reports Server (NTRS)

Platts, Steven H.; Meck, Janice V.; Martin, David S.; Freeman-Perez, Sondra A.; Riberio, Christine; Garcia, Kathleen M.; Waters, Wendy W.

2007-01-01

Orthostatic hypotension is a recognized risk for crewmembers returning from space. Numerous cardiovascular mechanisms have been proposed to account for this problem including vascular and cardiac dysfunction. We studied arterial and cardiac function in 6-degree head-down tilt bed rest, which is the most widely accepted ground-based analog of spaceflight. Eleven subjects are included in this study (8 men and 3 women). Data analysis was limited to the first 49 days, and compared to pre-bed rest baseline data. Using ultrasound, data was collected on arterial diameters and flows at baseline and during reactive hyperemia and following administration of nitroglycerin. Echocardiography was used to acquire information regarding systolic and diastolic function as well as ventricular mass and diameter. Plasma volumes were significantly decreased by 7 days of bed rest and stayed down through 49 days. There were no differences in reactive hyperemic response in the arm at any time point. However, the hyperemic response in the leg was significantly increased at day 49. Arterial responses to nitroglycerin did not change over the duration of bed rest (day effect) in either the arm or leg, but there was a significant difference between the arm and the leg responses. There was a marked decrease in anterior tibial intimal-medial thickness at days 21, 35 and 49. Several cardiac functional parameters including IVRT, Mitral e-wave, ejection time, velocity of circumferential shortening and myocardial performance index were significantly changed following 49 days of bed rest. These data show that some cardiovascular measures change during bed rest, while others do not. Further study is needed to determine if these measures can provide any insight into the effects of bed rest, or spaceflight, on human cardiovascular performance.

Bed rest after cardiovascular implantable electronic device placement: systematic review and meta-analysis.

PubMed

Ceroni, Antonella; Busca, Erica; Caristia, Silvia; Milani, Simona; Casarotto, Roberta; Buratti, Giulia; Gaboardi, Samanta; Croso, Antonella; Dal Molin, Alberto

2018-01-01

Bed rest is prescribed for all patients after cardiovascular implantable electronic device (CIED) placement but to a varied extent. Different clinical protocols exist. To assess the effects of different lengths of bed rest on complications and patient comfort after CIED implantation. We searched MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, CINAHL, SCOPUS. We included randomized and quasi-randomized controlled trials. Two of the authors independently selected trials, assessed the risk of bias, and extracted data. We included 2 RCTs. There was no evidence that shorter bed rest was more harmful than longer bed rest in terms of lead displacement (RR 0.681, 95% CI [0.063, 7.332]) and hematoma (RR 1.642, 95% CI [0.282, 9.560]). None of the studies reported the assessment of bleeding, back pain, or urinary discomfort. Shorter periods of bed rest appear to be as safe as longer ones. However, to confirm these results, further larger trials are needed.

Prolonged head-down tilt exposure reduces maximal cutaneous vasodilator and sweating capacity in humans

NASA Technical Reports Server (NTRS)

Crandall, C. G.; Shibasaki, M.; Wilson, T. E.; Cui, J.; Levine, B. D.

2003-01-01

Cutaneous vasodilation and sweat rate are reduced during a thermal challenge after simulated and actual microgravity exposure. The effects of microgravity exposure on cutaneous vasodilator capacity and on sweat gland function are unknown. The purpose of this study was to test the hypothesis that simulated microgravity exposure, using the 6 degrees head-down tilt (HDT) bed rest model, reduces maximal forearm cutaneous vascular conductance (FVC) and sweat gland function and that exercise during HDT preserves these responses. To test these hypotheses, 20 subjects were exposed to 14 days of strict HDT bed rest. Twelve of those subjects exercised (supine cycle ergometry) at 75% of pre-bed rest heart rate maximum for 90 min/day throughout HDT bed rest. Before and after HDT bed rest, maximal FVC was measured, via plethysmography, by heating the entire forearm to 42 degrees C for 45 min. Sweat gland function was assessed by administering 1 x 10(-6) to 2 M acetylcholine (9 doses) via intradermal microdialysis while simultaneously monitoring sweat rate over the microdialysis membranes. In the nonexercise group, maximal FVC and maximal stimulated sweat rate were significantly reduced after HDT bed rest. In contrast, these responses were unchanged in the exercise group. These data suggest that 14 days of simulated microgravity exposure, using the HDT bed rest model, reduces cutaneous vasodilator and sweating capacity, whereas aerobic exercise training during HDT bed rest preserves these responses.

The metabolic cost of an integrated exercise program performed during 14 days of bed rest.

PubMed

Scott, Jessica M; Hackney, Kyle; Downs, Meghan; Guined, Jamie; Ploutz-Snyder, Robert; Fiedler, James; Cunningham, David; Ploutz-Snyder, Lori

2014-06-01

Exercise countermeasures designed to mitigate muscle atrophy during long-duration spaceflight may not be as effective if crewmembers are in negative energy balance (energy output > energy input). This study determined the energy cost of supine exercise (resistance, interval, aerobic) during the spaceflight analogue of bed rest. Nine subjects (eight men and one woman; 34.5 +/- 8.2 yr) completed 14 d of bed rest and concomitant exercise countermeasures. Body mass and basal metabolic rate (BMR) were assessed before and during bed rest. Exercise energy expenditure was measured during and immediately after [excess post-exercise oxygen consumption (EPOC)] each of five different exercise protocols (30-s, 2-min, and 4-min intervals, continuous aerobic, and a variety of resistance exercises) during bed rest. On days when resistance and continuous aerobic exercise were performed daily, energy expenditure was significantly greater (2879 +/- 280 kcal) than 2-min (2390 +/- 237 kcal), 30-s (2501 +/- 264 kcal), or 4-min (2546 +/- 264 kcal) exercise. There were no significant differences in BMR (pre-bed rest: 1649 +/- 216 kcal; week 1: 1632 +/- 174 kcal; week 2:1657 +/- 176 kcal) or body mass (pre-bed rest: 75.2 +/- 10.1 kg; post-bed rest: 75.2 +/- 9.6 kg). These findings highlight the importance of energy balance for long-duration crewmembers completing a high-intensity exercise program with multiple exercise sessions daily.

Circulating microRNAs Correlated with Bone Loss Induced by 45 Days of Bed Rest

PubMed Central

Ling, Shukuan; Zhong, Guohui; Sun, Weijia; Liang, Fengji; Wu, Feng; Li, Hongxing; Li, Yuheng; Zhao, Dingsheng; Song, Jinping; Jin, Xiaoyan; Wu, Xiaorui; Song, Hailin; Li, Qi; Li, Yinghui; Chen, Shanguang; Xiong, Jianghui; Li, Yingxian

2017-01-01

The purpose of this study was to find the circulating microRNAs (miRNAs) co-related with bone loss induced by bed rest, and testify whether the selected miRNAs could reflect the bone mineral status of human after bed-rest. We analyzed plasma miRNA levels of 16 subjects after 45 days of −6° head-down tilt bed rest, which is a reliable model for the simulation of microgravity. We characterize the circulating miRNA profile in individuals after bed rest and identify circulating miRNAs which can best reflect the level of bone loss induced by bed rest. Expression profiling of circulating miRNA revealed significant downregulation of 37 miRNAs and upregulation of 2 miRNAs, while only 11 of the downregulated miRNAs were further validated in a larger volunteer cohort using qPCR. We found that 10 of these 11 miRNAs (miR-103, 130a, 1234, 1290, 151-5p, 151-3p, 199a-3p, 20a, 363, and 451a) had ROC curve that distinguished the status after bed rest. Importantly, significant positive correlations were identified between bone loss parameters and several miRNAs, eventually miR-1234 showed clinical significance in detecting the bone loss of individuals after 45 days of bed rest. PMID:28261104

Effect of bed rest and exercise on body balance

NASA Technical Reports Server (NTRS)

Haines, R. F.

1974-01-01

A battery of 11 body balance tests was administered to 7 men before and after 14 days of bedrest. Seven men who had not undergone bed rest served as controls. During bed rest, each subject underwent daily either isotonic, isometric, or no leg exercise. The results showed that, for the bed-rested no exercise, isotonic exercise, and isometric exercise groups, 2 weeks of bed rest produces significant body balance decrements on 3, 4, and 5 of the 11 tests, respectively. Daily leg exercise did not prevent the debilitating effects of bed rest on body balance. After bed rest, balance skill was relearned rapidly so that in most tests, performance had reached prebed-rest levels by the third recovery day. These data suggest that balance impairment is not due to loss of muscular strength in the legs but, perhaps, to a bed-rest-related change in the neurally coded information to postural control centers.

Early processing variations in selective attention to the color and direction of moving stimuli during 30 days head-down bed rest

NASA Astrophysics Data System (ADS)

Wang, Lin-Jie; He, Si-Yang; Niu, Dong-Bin; Guo, Jian-Ping; Xu, Yun-Long; Wang, De-Sheng; Cao, Yi; Zhao, Qi; Tan, Cheng; Li, Zhi-Li; Tang, Guo-Hua; Li, Yin-Hui; Bai, Yan-Qiang

2013-11-01

Dynamic variations in early selective attention to the color and direction of moving stimuli were explored during a 30 days period of head-down bed rest. Event-related potentials (ERPs) were recorded at F5, F6, P5, P6 scalp locations in seven male subjects who attended to pairs of bicolored light emitting diodes that flashed sequentially to produce a perception of movement. Subjects were required to attend selectively to a critical feature of the moving target, e.g., color or direction. The tasks included: a no response task, a color selective response task, a moving direction selective response task, and a combined color-direction selective response task. Subjects were asked to perform these four tasks on: the 3rd day before bed rest; the 3rd, 15th and 30th day during the bed rest; and the 5th day after bed rest. Subjects responded quickly to the color than moving direction and combined color-direction response. And they had a longer reaction time during bed rest on the 15th and 30th day during bed rest after a relatively quicker response on the 3rd day. Using brain event-related potentials technique, we found that in the color selective response task, the mean amplitudes of P1 and N1 for target ERPs decreased in the 3rd day during bed rest and 5th day after bed rest in comparison with pre-bed rest, 15th day and 30th day during bed rest. In the combined color-direction selective response task, the P1 latencies for target ERPs on the 3rd and 30th day during bed rest were longer than on the 15th day during bed rest. As 3rd day during bed rest was in the acute adaptation period and 30th day during bed rest was in the relatively adaptation stage of head-down bed rest, the results help to clarify the effects of bed rest on different task loads and patterns of attention. It was suggested that subjects expended more time to give correct decision in the head-down tilt bed rest state. A difficulty in the recruitment of brain resources was found in feature selection task, but no variations were detected in the no response and direction selective response tasks. It is suggested that the negative shift in color selective response task on the 3rd day of bed rest are a result of fluid redistribution. And feature selection was more affected than motion selection in the head down bed rest. The variations in cognitive processing speed observed for the combined color-direction selective response task are suggested to reflect the interaction between top-down mechanisms and hierarchical physiological characteristics during 30 days head-down bed rest.

Bed rest attenuates sympathetic and pressor responses to isometric exercise in antigravity leg muscles in humans.

PubMed

Kamiya, Atsunori; Michikami, Daisaku; Shiozawa, Tomoki; Iwase, Satoshi; Hayano, Junichiro; Kawada, Toru; Sunagawa, Kenji; Mano, Tadaaki

2004-05-01

Although spaceflight and bed rest are known to cause muscular atrophy in the antigravity muscles of the legs, the changes in sympathetic and cardiovascular responses to exercises using the atrophied muscles remain unknown. We hypothesized that bed rest would augment sympathetic responses to isometric exercise using antigravity leg muscles in humans. Ten healthy male volunteers were subjected to 14-day 6 degrees head-down bed rest. Before and after bed rest, they performed isometric exercises using leg (plantar flexion) and forearm (handgrip) muscles, followed by 2-min postexercise muscle ischemia (PEMI) that continues to stimulate the muscle metaboreflex. These exercises were sustained to fatigue. We measured muscle sympathetic nerve activity (MSNA) in the contralateral resting leg by microneurography. In both pre- and post-bed-rest exercise tests, exercise intensities were set at 30 and 70% of the maximum voluntary force measured before bed rest. Bed rest attenuated the increase in MSNA in response to fatiguing plantar flexion by approximately 70% at both exercise intensities (both P < 0.05 vs. before bed rest) and reduced the maximal voluntary force of plantar flexion by 15%. In contrast, bed rest did not alter the increase in MSNA response to fatiguing handgrip and had no effects on the maximal voluntary force of handgrip. Although PEMI sustained MSNA activation before bed rest in all trials, bed rest entirely eliminated the PEMI-induced increase in MSNA in leg exercises but partially attenuated it in forearm exercises. These results do not support our hypothesis but indicate that bed rest causes a reduction in isometric exercise-induced sympathetic activation in (probably atrophied) antigravity leg muscles.

Effect of rowing ergometry and oral volume loading on cardiovascular structure and function during bed rest

PubMed Central

Hastings, Jeffrey L.; Krainski, Felix; Snell, Peter G.; Pacini, Eric L.; Jain, Manish; Bhella, Paul S.; Shibata, Shigeki; Fu, Qi; Palmer, M. Dean

2012-01-01

This study examined the effectiveness of a short-duration but high-intensity exercise countermeasure in combination with a novel oral volume load in preventing bed rest deconditioning and orthostatic intolerance. Bed rest reduces work capacity and orthostatic tolerance due in part to cardiac atrophy and decreased stroke volume. Twenty seven healthy subjects completed 5 wk of −6 degree head down bed rest. Eighteen were randomized to daily rowing ergometry and biweekly strength training while nine remained sedentary. Measurements included cardiac mass, invasive pressure-volume relations, maximal upright exercise capacity, and orthostatic tolerance. Before post-bed rest orthostatic tolerance and exercise testing, nine exercise subjects were given 2 days of fludrocortisone and increased salt. Sedentary bed rest led to cardiac atrophy (125 ± 23 vs. 115 ± 20 g; P < 0.001); however, exercise preserved cardiac mass (128 ± 38 vs. 137 ± 34 g; P = 0.002). Exercise training preserved left ventricular chamber compliance, whereas sedentary bed rest increased stiffness (180 ± 170%, P = 0.032). Orthostatic tolerance was preserved only when exercise was combined with volume loading (−10 ± 22%, P = 0.169) but not with exercise (−14 ± 43%, P = 0.047) or sedentary bed rest (−24 ± 26%, P = 0.035) alone. Rowing and supplemental strength training prevent cardiovascular deconditioning during prolonged bed rest. When combined with an oral volume load, orthostatic tolerance is also preserved. This combined countermeasure may be an ideal strategy for prolonged spaceflight, or patients with orthostatic intolerance. PMID:22345434

Association Between Cardiovascular and Intraocular Pressure Changes in a 14-Day 6 deg Head Down Tilt (HDT) Bed Rest Study: Possible Implications in Retinal Anatomy

NASA Technical Reports Server (NTRS)

Cromwell, Ronita; Zanello, Susana; Yarbough, Patrice; Ploutz-Snyder, Robert; Taibbi, Giovanni; Vizzeri, Gianmarco

2013-01-01

Visual symptoms and intracranial pressure increase reported in astronauts returning from long duration missions in low Earth-orbit are thought to be related to fluid shifts within the body due to microgravity exposure. Because of this possible relation to fluid shifts, studies conducted in head-down tilt (HDT) bed rest are being monitored for potential changes in ocular health. These measures will also serve to determine whether HDT is a suitable ground-based analog to model subclinical cardiovascular and ocular changes that could shed light on the etiology of the VIIP syndrome observed in spaceflight. Sixteen healthy normotensive (12M, 4F, age range 29-54 years), non-smoker and normal weight subjects, volunteered to participate in a 14 day 6 deg head HDT study conducted at the NASA Flight Analogs Research Unit (FARU). This facility provides standard bed rest conditions (diet, wake/sleep time, time allowed in sunlight) during the time that the subjects stay at the FARU. Cardiovascular parameters were obtained in supine posture at BR-5, BR+0, and BR+3 and ocular monitoring was performed weekly. Intraocular pressure (IOP) increased from pre-bed rest BR-3) to the third day into bed rest (BR+3). Values reached a plateau towards the end of the bed rest phase (BR10) and decreased within the first three days of recovery (BR+2) returning to levels comparable to baseline at BR-3. As expected, most cardiovascular parameters were affected by 14 days of HDT bed rest. Plasma volume decreased as a result of bed rest but recovered to baseline levels by BR+3. Indications of cardiovascular deconditioning included increase in both systolic and diastolic blood pressure and heart rate, and a decrease in stroke volume and cardiac output between BR-5 and BR+3. Due to the experimental design of this study, we were not able to test the hypothesis that fluid shifts might be involved in the IOP increase during the bed rest phase, since cardiovascular measures were not available for those time points. There was no correlation between the largest change in IOP (BR-3 versus BR3) and cardiovascular measure changes between baseline (BR-5) and post bed rest (BR+2). While no clinically relevant visual changes were observed during the study, measurement of various retinal parameters was performed with optical coherence tomography (OCT). A decrease in central subfield retinal thickness was observed between BR+2 and baseline at BR-10, but no association was observed with IOP changes. This work investigates the time course of changes in IOP during 14-day HDT bed rest in an attempt to characterize HDT bed rest as a model of the VIIP syndrome and delve into its etiology.

Retrospective Study of Serum Sclerostin Measurements in Bed Rest Subjects

NASA Technical Reports Server (NTRS)

Spatz, J. M.; Fields, E. E.; Yu, E. W.; Divieti, Pajevic P.; Bouxsein, M. L.; Sibonga, M. L.; Zwart, S. R.; Smith, S. M.

2011-01-01

Animal models and human studies suggest that osteocytes regulate the skeleton s response to mechanical unloading at the cellular level in part by an increase in sclerostin, an inhibitor of the anabolic Wnt pathway. However, few studies have reported changes in serum sclerostin in humans exposed to reduced mechanical loading. Thus, we determined changes in serum sclerostin and bone turnover markers in healthy adult men who participated in a controlled bed rest study. Seven healthy adult men (31 +/- 3 yrs old) underwent 90-day six-degree head down tilt bed rest at the University of Texas Medical Branch in Galveston's Institute for Translational Sciences - Clinical Research Center (ITS-CRC). Serum sclerostin, PTH, serum markers of bone turnover (bone specific alkaline phosphatase, RANKL/OPG, and osteocalcin), urinary calcium and phosphorus excretion, and 24 hour pooled urinary markers of bone resorption (NTX, DPD, PYD) were evaluated pre-bed rest (BL), bed rest day 28 (BR-28), bed rest day 60 (BR-60), and bed rest day 90 (BR-90). In addition, bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry (DXA) at BL, BR-60, and post bed rest day 5 (BR+5). Data are reported as mean +/- standard deviation. We used repeated measures ANOVA to compare baseline values to BR-28, BR-60, and BR-90. RESULTS Consistent with prior reports, BMD declined significantly (1-2% per month) at weight-bearing skeletal sites (spine, hip, femur neck, and calcaneus). Serum sclerostin levels were elevated above BL at BR-28 (+29% +/- 20%, p = 0.003), BR-60 (+42% +/- 31%, p < 0.001), and BR-90 (22% +/- 21%, p = 0.07). Serum PTH levels were reduced at BR-28 (-17% +/- 16%, p = 0.02), BR-60 (-24% +/- 14%, p = 0.03), and returned to baseline at BR-90 (-21% +/- 21%, p = 0.14). Serum bone turnover markers did not change, however urinary bone resorption markers and calcium were significantly elevated following bed rest (p < 0.01). CONCLUSION We observed an increase of serum sclerostin associated with decreased serum PTH and elevated bone resorption markers in otherwise healthy men subjected to long-term immobilization.

Static Histomorphometry of the iliac crest after 360 days of antiorthostatic bed rest with and without countermeasures

NASA Astrophysics Data System (ADS)

Thomsen, J. S.; Morukov, B. V.; Vico, L.; Saparin, P. I.; Gowin, W.

The loss of bone during immobilization is well-known and investigated, whereas the structural changes human cancellous bone undergoes during disuse is less well examined. The aim of the study was to examine the influence of hypokinesia on the static histomorphometric measures of the iliac crest using a 360-day-long bed rest experiment, simulating exposure to microgravity. Eight healthy males underwent 360 days of 5° head-down tilt bed rest. Three subjects were treated with the bisphosphonate Xidifon (900 mg/day) combined with a treadmill and ergonometer exercise regimen (1--2 hours/day) for the entire study period. Five subjects underwent 120 days of bed rest without countermeasures followed by 240 days of bed rest with the treadmill and ergonometer exercise regimen. Transiliac bone biopsies were obtained either at day 0 and 360 or at day 0, 120, and 360 at alternating sides of the ileum. The biopsies were embedded in methylmethacrylate, cut in 7-μm-thick sections, stained with Goldner trichrome, and static histomorphometry was performed. 120 days of bed rest without countermeasures resulted in decreased trabecular bone volume (-6.3%, p = 0.046) and trabecular number (-10.2%, p = 0.080) and increased trabecular separation (14.7%, p = 0.020), whereas 240 days of subsequent bed rest with exercise treatment prevented further significant deterioration of the histomorphometric measures. 360 days of bed rest with bisphosphonate and exercise treatment did not induce any significant changes in any of the histomorphometric measures. The study showed that 120 days of antiorthostatic bed rest without countermeasures induced significant deterioration of iliac crest trabecular bone histomorphometric properties. There are indications that the immobilization induced changes involve a loss of trabeculae rather than a general thinning of the trabeculae. On average, the countermeasures consisting of either bisphosphonate and exercise or exercise alone were able to either prevent or stop immobilization induced changes of the iliac trabecular bone structure. Limitation: due to the inhomogeneous distribution of the trabecular bone structure of the iliac crest, it should be carefully considered whether paired sets of iliac crest bone biopsies are well-suited for studies of microgravity induced changes of trabecular bone structure.

Vitamin D in Real and Simulated Weightlessness: Implications for Earth

NASA Technical Reports Server (NTRS)

Rice, Barbara L.; Zwart, Sara R.; Smith, Scott M.

2006-01-01

Vitamin D deficiency has reemerged as a public health concern in the United States. It is also a concern for astronauts because spacecraft are shielded from ultraviolet light, leaving diet as the sole source of vitamin D. We report here the findings from four studies: one evaluation of astronauts before and after 4- to 6-month missions to the International Space Station, and the other three from a ground-based analog for space flight, long-term bed rest. For the space flight study, blood samples were collected before the flight and within hours of landing after it. Crewmembers (n = 11) were provided vitamin D supplements (as cholecalciferol (10 g/d) throughout the mission. The average number of vitamin D supplements reported to be consumed per week was 5.7 plus or minus 4.0. The vitamin D status indicator serum 25-hydroxycholecalciferol was 25% less after landing (48 plus or minus 20) than before flight (63 plus or minus 16) (P less than 0.01). A series of three studies was undertaken to evaluate nutritional changes during and after 60 or 90 days of -6 deg. head-down-tilt bed rest. A total of 11 subjects (8 M, 3 F; age 26-55 y) participated in the studies. Blood and urine were collected twice before bed rest and once per month during bed rest. During bed rest the average dietary intake of vitamin D for the three studies was 4.84 plus or minus 0.16 (study 1), 6.24 plus or minus 0.81 (study 2), and 7.16 plus or minus 1.40 (study 3) micrograms/day. In study 1 only, subjects were given a daily supplement of 10 g vitamin D (as ergocalciferol). Data were analyzed using repeated-measures ANOVA. In the first study, 7 days after the end of the bed rest, serum 25-hydroxycholecalciferol was 30% less than it was before bed rest (p less than 0.05). In the second and third studies, during or after bed rest the serum 25-hydroxycholecalciferol concentration was not significantly different from its concentration before bed rest. These data demonstrate that vitamin D intake is critical for individuals not exposed to the sun. Although we studied astronauts and healthy subjects in bed rest, the implications of our results also apply to people living in northern latitudes and others who receive little exposure to sunlight, such as elderly people who seldom go outdoors. The inability of supplements to maintain vitamin D status is also an important finding, and highlights the need for careful food selection to ensure adequate vitamin D intake.

Effects of long-term head-down-tilt bed rest and different training regimes on the coagulation system of healthy men

PubMed Central

Haider, Thomas; Gunga, Hanns-Christian; Matteucci-Gothe, Raffaella; Sottara, Elke; Griesmacher, Andrea; Belavý, Daniel L; Felsenberg, Dieter; Werner, Andreas; Schobersberger, Wolfgang

2013-01-01

Immobility plus preexisting chronic disease or acute trauma can activate the coagulation system, thus increasing the risk for thromboembolic events. The effects of long-term bed-rest immobility and microgravity on the coagulation system of healthy persons (e.g., during crewed Mars missions) have not yet been studied. The main objective of the second Berlin BedRest Study (BBR2-2) “Coagulation Part” was to investigate adaptations of the hemostatic system during long-term bed rest (60 days) under simulated microgravity (6° head-down-tilt [6°HDT]) and after mobilization in three different volunteer groups (randomly assigned to CTR= inactive control group; RE= resistive exercise only group; and RVE= resistive exercise with whole-body vibration group). In 24 males (aged 21–45 years), before, during, and after long-term bed rest, key parameters of coagulation were measured from venous blood samples: D-dimer (DD), thrombin–antithrombin III complex (TAT), and prothrombin fragment F1 + 2 (PT-F1 + 2). Additionally, modified rotational thrombelastometry (ROTEM®) analysis was performed. Times of exploratory analyses were as follows: baseline data collection 2 days before bed rest (BDC-2); eight different days of 6°HDT bed rest (HDT1–HDT60), and two different days after reambulation (R + 3 and R + 6). We found significant changes in DD, TAT, and PT-F1 + 2 over the total time course, but no consistent effect of physical interventions (RE, RVE) on these parameters. Notably, no parameter reached levels indicative of intravascular thrombin formation. All ROTEM® parameters remained within the normal range and no pathological traces were found. Sixty days of 6°HDT bed rest are not associated with pronounced activation of the coagulation system indicative of intravascular thrombus formation in healthy volunteers independent of the training type during the bed rest. PMID:24400137

Decreased bed rest post-percutaneous coronary intervention with a 7-French arterial sheath and its effects on vascular complications.

PubMed

Wentworth, Laura J; Bechtum, Elizabeth L; Hoffman, Jessica G; Kramer, Robert R; Bartel, David C; Slusser, Joshua P; Tilbury, Ralph Thomas

2018-01-01

To compare the incidence of femoral access puncture site complications in the control group, who underwent 6 hr of bed rest, with patients in the case group, who underwent 4 hr of bed rest. The ideal bed rest length after percutaneous coronary intervention with a 7-French arterial sheath has been investigated by nursing practice. However, in this larger-sheath-size group, best practices have not been determined, and bed rest time continues to vary markedly among institutions. Retrospective study. Data were retrieved from the National Cardiovascular Data Registry and electronic health records in this retrospective study. Sample size was 401 patients: 152 case patients with 4-hr bed rest and 249 controls with 6-hr bed rest. Case group data were obtained from 20 May 2013-31 December 2014; and control group data, 15 June 2011-20 May 2013. National Cardiovascular Data Registry event rates were generally low in both groups: Only three patients in each group had a bleeding event within 72 hr (2% vs. 1%) and no patient and only two controls had arteriovenous fistula (0% vs. 1%). Complications documented in the electronic health records with institutional femoral access puncture site complication definitions identified bleeding at the access site in eight case patients (5%) and nine controls (4%). Haematoma at the access site occurred in 21 case patients (14%) and 25 controls (10%). The practice change of decreasing bed rest from 6-4 hr for patients with 7-French arterial sheaths post-percutaneous coronary intervention was associated with no significant change in femoral access puncture site complications in either National Cardiovascular Data Registry data or institutional electronic health records data. This introduces expanded evidence of safety in decreasing bed rest length in larger (7-French) arterial sheaths post-percutaneous coronary intervention. © 2017 John Wiley & Sons Ltd.

Effects of Bed Rest on Conduction Velocity of the Triceps Surae Stretch Reflex and Postural Control

NASA Technical Reports Server (NTRS)

Reschke, M. F.; Wood, S. J.; Cerisano, J. M.; Kofman, I. S.; Fisher, E. A.; Esteves, J. T.; Taylor, L. C.; DeDios, Y. E.; Harm, D. L.

2011-01-01

Despite rigorous exercise and nutritional management during space missions, astronauts returning from microgravity exhibit neuromuscular deficits and a significant loss in muscle mass in the postural muscles of the lower leg. Similar changes in the postural muscles occur in subjects participating in long-duration bed rest studies. These adaptive muscle changes manifest as a reduction in reflex conduction velocity during head-down bed rest. Because the stretch reflex encompasses both the peripheral (muscle spindle and nerve axon) and central (spinal synapse) components involved in adaptation to calf muscle unloading, it may be used to provide feedback on the general condition of neuromuscular function, and might be used to evaluate the effectiveness of countermeasures aimed at preserving muscle mass and function during periods of unloading. Stretch reflexes were measured on 18 control subjects who spent 60 to 90 days in continuous 6 deg head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 degrees at a peak velocity of about 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender. Computerized posturography was also conducted on these same subjects before and after bed rest as part of the standard measures. Peak-to-peak sway was measured during Sensory Organization Tests (SOTs) to evaluate changes in the ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Although no gender differences were found, a significant increase in reflex latency and a significant decrease in CV were observed during the bed rest period, with a return to baseline 3 to 5 days after bed rest, depending on the duration of bed rest. In addition, a relationship between CV and loss of muscle strength in the lower leg was observed post bed rest for most subjects. Immediately post-bed rest, most subjects showed decreased performance on SOTs, with the greater decrements on sway-referenced support and head movement conditions. Post-bed rest decrements were less than typically observed following spaceflight. Decrements in postural control and the stretch reflex can be primarily attributed to the unloading mechanisms this ground-based analog provides. The stretch reflex is a concise test measurement that can be obtained during the head-down phase of bed rest, as it does not interfere with the bed rest paradigm. This makes it an ideal tool that can detect, early on, whether a countermeasure is successful in preserving muscle function.

Vestibular and Somatosensory Covergence in Postural Equilibrium Control: Insights from Spaceflight and Bed Rest Studies

NASA Technical Reports Server (NTRS)

Mulavara, A. P.; Batson, C. D.; Buxton, R. E.; Feiveson, A. H.; Kofman, I. S.; Lee, S. M. C.; Miller, C. A.; Peters, B. T.; Phillips, T.; Platts, S. H.;

Body Unloading Associated with Space Flight and Bed-rest Impacts Functional Performance

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Ballard, K. L.; Batson, C. D.; Buxton, R. E.; Feiveson, A. H.; Kofman, I. S.; Lee, S. M. C.; Miller, C. A.; Mulavara, A. P.; Peters, B. T.;

Markers of bone resorption and calcium metabolism are related to dietary intake patterns in male and female bed rest subjects

NASA Technical Reports Server (NTRS)

Smith, Scott M.; Zwart, S. R.; Hargens, A. r.

2006-01-01

Dietary potassium and protein intakes predict net endogenous acid production in humans. Intracellular buffers, including exchangeable bone mineral, play a crucial role in balancing chronic acid-base perturbations in the body; subsequently, chronic acid loads can potentially contribute to bone loss. Bone is lost during space flight, and a dietary countermeasure would be desirable for many reasons. We studied the ability of diet protein and potassium to predict levels of bone resorption markers in males and females. Identical twin pairs (8 M, 7 F) were assigned to 2 groups: bed rest (sedentary, SED) or bed rest with supine treadmill exercise in a lower body negative pressure chamber (EX). Diet was controlled for 3 d before and 30 d of bed rest (BR). Urinary Ca, N-telopeptide (NTX), and pyridinium crosslinks (PYD) were measured before and on days 5, 12, 19, and 26 of BR. Data were analyzed by Pearson correlation (P<0.05). The ratio of dietary animal protein/potassium intake was not correlated with NTX before BR for males or females, but they were positively correlated in both groups of males during bed rest. Dietary animal protein/potassium and urine Ca were correlated before and during bed rest for the males, and only during bed rest for the females. Conversely, the ratio of dietary vegetable protein/potassium intake was negatively correlated with urinary calcium during bed rest for the females, but there was no relationship between vegetable protein/potassium intake and bone markers for the males. These data suggest that the ratio of animal protein/potassium intake may affect bone, particularly in bed rest subjects. These data show that the type of protein and gender may be additional factors that modulate the effect of diet on bone metabolism during bed rest. Altering this ratio may help prevent bone loss on Earth and during space flight.

Molecular biomarkers monitoring human skeletal muscle fibres and microvasculature following long-term bed rest with and without countermeasures

PubMed Central

Salanova, M; Schiffl, G; Püttmann, B; Schoser, B G; Blottner, D

2008-01-01

The cellular mechanisms of human skeletal muscle adaptation to disuse are largely unknown. The aim of this study was to determine the morphological and biochemical changes of the lower limb soleus and vastus lateralis muscles following 60 days of head-down tilt bed rest in women with and without exercise countermeasure using molecular biomarkers monitoring functional cell compartments. Muscle biopsies were taken before (pre) and after bed rest (post) from a bed rest-only and a bed rest exercise group (n = 8, each). NOS1 and NOS3/PECAM, markers of myofibre ‘activity’ and capillary density, and MuRF1 (E3 ubiquitin-ligase), a marker of proteolysis, were documented by confocal immunofluorescence and immunoblot analyses. Morphometrical parameters (myofibre cross-sectional area, type I/II distribution) were largely preserved in muscles from the exercise group with a robust trend for type II hypertrophy in vastus lateralis. In the bed rest-only group, the relative NOS1 immunostaining intensity was decreased at type I and II myofibre membranes, while the bed rest plus exercise group compensated for this loss particularly in soleus. In the microvascular network, NOS3 expression and the capillary-to-fibre ratio were both increased in the exercise group. Elevated MuRF1 immunosignals found in subgroups of atrophic myofibres probably reflected accelerated proteolysis. Immunoblots revealed overexpression of the MuRF1 protein in the soleus of the bed rest-only group (> 35% vs. pre). We conclude that exercise countermeasure during bed rest affected both NOS/NO signalling and proteolysis in female skeletal muscle. Maintenance of NO signalling mechanisms and normal protein turnover by exercise countermeasure may be crucial steps to attenuate human skeletal muscle atrophy and to maintain cell function following chronic disuse. PMID:18221329

Amino acid supplementation alters bone metabolism during simulated weightlessness

NASA Technical Reports Server (NTRS)

Zwart, S. R.; Davis-Street, J. E.; Paddon-Jones, D.; Ferrando, A. A.; Wolfe, R. R.; Smith, S. M.

2005-01-01

High-protein and acidogenic diets induce hypercalciuria. Foods or supplements with excess sulfur-containing amino acids increase endogenous sulfuric acid production and therefore have the potential to increase calcium excretion and alter bone metabolism. In this study, effects of an amino acid/carbohydrate supplement on bone resorption were examined during bed rest. Thirteen subjects were divided at random into two groups: a control group (Con, n = 6) and an amino acid-supplemented group (AA, n = 7) who consumed an extra 49.5 g essential amino acids and 90 g carbohydrate per day for 28 days. Urine was collected for n-telopeptide (NTX), deoxypyridinoline (DPD), calcium, and pH determinations. Bone mineral content was determined and potential renal acid load was calculated. Bone-specific alkaline phosphatase was measured in serum samples collected on day 1 (immediately before bed rest) and on day 28. Potential renal acid load was higher in the AA group than in the Con group during bed rest (P < 0.05). For all subjects, during bed rest urinary NTX and DPD concentrations were greater than pre-bed rest levels (P < 0.05). Urinary NTX and DPD tended to be higher in the AA group (P = 0.073 and P = 0.056, respectively). During bed rest, urinary calcium was greater than baseline levels (P < 0.05) in the AA group but not the Con group. Total bone mineral content was lower after bed rest than before bed rest in the AA group but not the Con group (P < 0.05). During bed rest, urinary pH decreased (P < 0.05), and it was lower in the AA group than the Con group. These data suggest that bone resorption increased, without changes in bone formation, in the AA group.

Long-duration head-down bed rest: project overview, vital signs, and fluid balance.

PubMed

Meck, Janice V; Dreyer, Sherlene A; Warren, L Elisabeth

2009-05-01

Spaceflight has profound effects on the human body. Many of these effects can be induced with head-down bed rest, which has been a useful ground-based analog. With limited resources aboard the International Space Station for human research, the bed rest analog will be a primary platform on which countermeasures will be developed and tested for lunar and Mars mission scenarios. NASA Johnson Space Center, in conjunction with the University of Texas Medical Branch (UTMB), has created the NASA Flight Analogs Project (FAP), a research program with the overall objective of using head-down bed rest to evaluate, compare, and refine candidate countermeasures to spaceflight deconditioning. This paper serves as an overview and describes the standard conditions, the standard set of subject screening criteria, and the standard set of measurements for all FAP bed rest subjects. Heart rate and diastolic pressures decreased transiently at the onset of bed rest. Fluid balance showed an early diuresis, which stabilized within 3 d. In this supplement, detailed results from multiple disciplines are presented in a series of reports. The following reports describe multi-disciplinary results from the standard measurements by which the responses to bed rest will be assessed and by which countermeasures will be evaluated. The data presented in this overview are meant to serve as a context in which to view the data presented in the discipline specific manuscripts. The dietary support and behavioral health papers provide additional information regarding those aspects of implementing bed rest studies successfully.

Sensitivity of whole body protein synthesis to amino acid administration during short-term bed rest.

PubMed

Biolo, Gianni; Ciocchi, Beniamino; Lebenstedt, Marion; Heer, Martina; Guarnieri, Gianfranco

2002-07-01

We tested the hypothesis that a reduced stimulation of whole-body protein synthesis by amino acid administration represents a major mechanism for the bed rest-induced loss of lean body mass. Healthy young subjects and matched controls were studied on the last day of a 14-day bed rest or ambulatory period, as part of the overall protocol "Short-term Bed Rest - Integrated Physiology" set up by the German Aerospace Centre (DLR) in co-operation with the European Space Agency. A balanced mixture of essential and non-essential amino acids was intravenously infused in the postabsorptive state for 3 hours at the rate of 0.1 g/kg/hour. The oxidative and non-oxidative (i.e., to protein synthesis) disposal of the infused leucine was determined by stable isotope and mass spectrometry techniques. The clearance of total infused amino acids tended to be greater (P=0.07) in the ambulatory group than in the bed rest group. When leucine clearance was partitioned between its oxidative and non-oxidative (i.e., to protein synthesis) components, the results indicated that the oxidative disposal was not statistically different in the bed rest and in the ambulatory groups. In contrast, the non-oxidative leucine disposal (i.e., to protein synthesis) was about 20% greater (P<0.01) in the ambulatory group than in the bed rest group. In conclusion, these preliminary data suggest that 14-day bed rest impairs the ability to utilise exogenous amino acids for protein synthesis.

Bed rest in singleton pregnancies for preventing preterm birth.

PubMed

Sosa, C; Althabe, F; Belizán, J; Bergel, E

2004-01-01

Bed rest in hospital or at home is widely recommended for the prevention of preterm birth. This advice is based on the observation that hard work and hard physical activity during pregnancy could be associated with preterm birth and with the idea that bed rest could reduce uterine activity. However, bed rest may have some adverse effects on other outcomes. To evaluate the effect of prescription of bed rest in hospital or at home for preventing preterm birth in pregnant women at high risk of preterm birth. We searched the Cochrane Pregnancy and Childbirth Group trials register (July 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003), MEDLINE (July 2003), LILACS (July 2003), EMBASE (July 2003), POPLINE (July 2003) and bibliographies of relevant papers. Randomized and quasi-randomized controlled trials with reported data that assess clinical outcomes in women at high risk of spontaneous preterm birth who were prescribed bed rest in hospital or at home for preventing preterm birth, and their babies. Two reviewers independently assessed eligibility, trial quality and extracted data. One study met the inclusion criteria (1266 women). This trial has uncertain methodological quality due to lack of reporting. Four hundred and thirty-two women were prescribed bed rest at home and a total of 834 women received a placebo (412) or no intervention (422). Preterm birth before 37 weeks was similar in both groups (7.9% in the intervention group versus 8.5% in the control group), and the relative risk was 0.92 with a 95% confidence interval from 0.62 to 1.37. No other results were available. There is no evidence, either supporting or refuting the use of bed rest at home or in hospital, to prevent preterm birth. Although bed rest in hospital or at home is widely used as the first step of treatment, there is no evidence that this practice could be beneficial. Due to the potential adverse effects that bed rest could have on women and their families, and the increased costs for the healthcare system, clinicians should not routinely advise women to rest in bed to prevent preterm birth. Potential benefits and harms should be discussed with women facing an increased risk of preterm birth. Appropriate research is mandatory. Future trials should evaluate both the effectiveness of bed rest, and the effectiveness of the prescription of bed rest, to prevent preterm birth.

Prevention of disuse osteoporosis: Effect of sodium fluoride during five weeks of bed rest

NASA Technical Reports Server (NTRS)

Schneider, Victor S.

1987-01-01

An attempt was made to modify factors which promote disuse osteoporosis and thereby prevent it from occurring. Since fluoride is currently used to enhance bone formation in the treatment of low turnover osteoporosis, it was hypothesized that if the fluoride ion was available over a long period of time that it would slow the demonstrated loss of calcium by inhibiting bone resorption and enhancing bone formation. This study was used to determine whether oral medication with sodium F will modify or prevent 5 weeks of bed rest induced disuse osteoporosis, to determine the longitudinal effects of 5 weeks of bed rest on PTH, CT and calcitriol, to measure muscle volume changes and metabolic activity by magnetic resonance imaging and magnetic resonance spectroscopy during prolonged bed rest, to measure changes in peak muscle strength and fatigability, and to measure bone turnover in bone biopsies. Subjects were studied during 1 week of equilibration, 4 weeks of control ambulation, 5 weeks of bed rest, and 1 week of reambulation.

Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery.

PubMed

Mekjavic, Igor B; Golja, Petra; Tipton, Michael J; Eiken, Ola

2005-10-01

The present study evaluated the effect of 35 days of experimental horizontal bed-rest on exercise and immersion thermoregulatory function. Fifteen healthy male volunteers were assigned to either a Control (n = 5) or Bed-rest (n = 10) group. Thermoregulatory function was evaluated during a 30-min bout of submaximal exercise on a cycle ergometer, followed immediately by a 100-min immersion in 28 degrees C water. For the Bed-rest group, exercise and immersion thermoregulatory responses observed post-bed-rest were compared with those after a 5 week supervised active recovery period. In both trials, the absolute work load during the exercise portion of the test was identical. During the exercise and immersion, we recorded skin temperature, rectal temperature, the difference in temperature between the forearm and third digit of the right hand (DeltaT(forearm-fingertip))--an index of skin blood flow, sweating rate from the forehead, oxygen uptake and heart rate at minute intervals. Subjects provided ratings of temperature perception and thermal comfort at 5-min intervals. Exercise thermoregulatory responses after bed-rest and recovery were similar. Subjective ratings of temperature perception and thermal comfort during immersion indicated that subjects perceived similar combinations of Tsk and Tre to be warmer and thermally less uncomfortable after bed-rest. The average (SD) exercise-induced increase in Tre relative to resting values was not significantly different between the Post-bed-rest (0.4 (0.2) degrees C) and Recovery (0.5 (0.2) degrees C) trials. During the post-exercise immersion, the decrease in Tre, relative to resting values, was significantly (P < 0.05) greater in the Post-bed-rest trial (0.9 (0.5) degrees C) than after recovery (0.4 (0.3) degrees C). DeltaT(forearm-fingertip) was 5.2 (0.9) degrees C and 5.8 (1.0) degrees C at the end of the post-bed-rest and recovery immersions, respectively. The gain of the shivering response (increase in VO(2) relative to the decrease in Tre; VO(2)/Tre) was 1.19 l min(-1) degrees C(-1) in the Recovery trial, and was significantly attenuated to 0.51 l min(-1) degrees C(-1) in the Post-bed-rest trial. The greater cooling rate observed in the post-bed-rest trial is attributed to the greater heat loss and reduced heat production. The former is the result of attenuated cold-induced vasoconstriction and enhanced sweating rate, and the latter a result of a lower shivering VO(2) response.

Physiological responses of women to simulated weightlessness: A review of the first female bed-rest study

NASA Technical Reports Server (NTRS)

Sandler, H.; Winter, D. L.

1978-01-01

Subjects were exposed to centrifugation, to lower body negative pressure (LBNP), and to exericse stress both before and after bed rest. Areas studied were centrifugation tolerance, fluid electrolyte changes and hematology, tolerance to LBNP, physical working capacity, biochemistries, blood fibrinolytic activity, female metabolic and hormonal responses, circadian alterations, and gynecology. Results were compared with the responses observed in similarly bed-rested male subjects. The bed-rested females showed deconditioning responses similar to those of the males, although with some differences. Results indicate that women are capable of coping with exposure to weightlessness and, moreover, that they may be more sensitive subjects for evaluating countermeasures to weightlessness and developing criteria for assessing applicants for shuttle voyages.

Exercise countermeasures for bed-rest deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, John (Editor)

1993-01-01

The purpose for this 30-day bed rest study was to investigate the effects of short-term, high intensity isotonic and isokinetic exercise training on maintenance of working capacity (peak oxygen uptake), muscular strength and endurance, and on orthostatic tolerance, posture and gait. Other data were collected on muscle atrophy, bone mineralization and density, endocrine analyses concerning vasoactivity and fluid-electrolyte balance, muscle intermediary metabolism, and on performance and mood of the subjects. It was concluded that: The subjects maintained a relatively stable mood, high morale, and high esprit de corps throughout the study. Performance improved in nearly all tests in almost all the subjects. Isotonic training, as opposed to isokinetic exercise training, was associated more with decreasing levels of psychological tension, concentration, and motivation; and improvement in the quality of sleep. Working capacity (peak oxygen uptake) was maintained during bed rest with isotonic exercise training; it was not maintained with isokinetic or no exercise training. In general, there was no significant decrease in strength or endurance of arm or leg muscles during bed rest, in spite of some reduction in muscle size (atrophy) of some leg muscles. There was no effect of isotonic exercise training on orthostasis, since tilt-table tolerance was reduced similarly in all three groups following bed rest. Bed rest resulted in significant decreases of postural stability and self-selected step length, stride length, and walking velocity, which were not influenced by either exercise training regimen. Most pre-bed rest responses were restored by the fourth day of recovery.

Dietary Support of Extended-Duration Bed Rest Studies

NASA Technical Reports Server (NTRS)

Inniss, A. M.; Rice, B. L.; Smith, S. M.

2006-01-01

Dietary control and nutrient intake are critical aspects of any metabolic study, but this is especially true in the case of bed rest studies. We sought to define nutrient requirements, develop menus, and implement them in a series of three long-duration bed rest studies. With regard to energy intake, the goal was to maintain subject body weight to within 3% of their body weight on day 3 of bed rest (after fluid shift had occurred). For other nutrients, intakes were based on the NASA space flight nutritional requirements (with some adaptations based on the ground-based model used here). A secondary goal was to develop menus with foods similar to those expected to be approved for space flight (however, this was relaxed to attain desired nutrient intakes). This paper also describes the role of the research dietitian as part of the multi-disciplinary team and the importance of the metabolic kitchen staff. It also provides insight into some of the dietary challenges that arise during extended-duration bed rest studies. Regardless of the overall objective of the study, nutrition must be carefully planned, implemented, and monitored for results to be uncompromised.

Analysis of Arterial Mechanics During Head-Down-Tilt Bed Rest

NASA Technical Reports Server (NTRS)

Elliott, Morgan B.; Martin, David S.; Westby, Christian M.; Stenger, Michael B.; Platts, Steven H.

2014-01-01

Carotid, brachial, and tibial arteries reacted differently to HDTBR. Previous studies have not analyzed the mechanical properties of the human brachial or anterior tibial arteries. After slight variations during bed-rest, arterial mechanical properties and IMT returned to pre-bed rest values, with the exception of tibial stiffness and PSE, which continued to be reduced post-bed rest while the DC remained elevated. The tibial artery remodeling was probably due to decreased pressure and volume. Resulting implications for longer duration spaceflight are unclear. Arterial health may be affected by microgravity, as shown by increased thoracic aorta stiffness in other ground based simulations (Aubert).

Focal Gray Matter Plasticity as a Function of Long Duration Bedrest: Preliminary Results

NASA Technical Reports Server (NTRS)

Koppelmans, V.; Erdeniz, B.; De Dios, Y. E.; Wood, S. J.; Reuter-Lorenz, P. A.; Kofman, I.; Bloomberg, J. J.; Mulavara, A. P.; Seidler, R. D.

2014-01-01

Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. It is unknown whether and how spaceflight impacts sensorimotor brain structure and function, and whether such changes may potentially underlie behavioral effects. Long duration head down tilt bed rest has been used repeatedly as an exclusionary analog to study microgravity effects on the sensorimotor system [1]. Bed rest mimics microgravity in body unloading and bodily fluid shifts. We are currently testing sensorimotor function, brain structure, and brain function pre and post a 70-day bed rest period. We will acquire the same measures on NASA crewmembers starting in 2014. Here we present the results of the first eight bed rest subjects. Subjects were assessed at 12 and 7 days before-, at 7, 30, and 70 days in-, and at 8 and 12 days post 70 days of bed rest at the NASA bed rest facility, UTMB, Galveston, TX, USA. At each time point structural MRI scans (i.e., high resolution T1-weighted imaging and Diffusion Tensor Imaging (DTI)) were obtained using a 3T Siemens scanner. Focal changes over time in gray matter density were assessed using the voxel based morphometry 8 (VBM8) toolbox under SPM. Focal changes in white matter microstructural integrity were assessed using tract based spatial statistics (TBSS) as part of the FMRIB software library (FSL). TBSS registers all DTI scans to standard space. It subsequently creates a study specific white matter skeleton of the major white matter tracts. Non-parametric permutation based t-tests and ANOVA's were used for voxel-wise comparison of the skeletons. For both VBM and TBSS, comparison of the two pre bed rest measurements did not show significant differences. VBM analysis revealed decreased gray matter density in bilateral areas including the frontal medial cortex, the insular cortex and the caudate nucleus from pre to in bed rest. Over the same time period, there was an increase in gray matter density in the cerebellum, occipital, and parietal cortices. The majority of these changes did not recover from during to post bed rest. TBSS analyses will also be presented. Extended bed rest, which is an analog for microgravity, can result in gray matter changes and potentially in microstructural white matter changes in areas that are important for neuromotor behavior and cognition. These changes did not recover at two weeks post bed rest. These results have significant public health implications, and will also aid in interpretation of our future data obtained pre and post spaceflight. Whether the effects of bed rest wear off at longer times post bed rest, and if they are associated with behavior are important questions that warrant further research.

Simulated microgravity [bed rest] has little influence on taste, odor or trigeminal sensitivity

NASA Technical Reports Server (NTRS)

Vickers, Z. M.; Rice, B. L.; Rose, M. S.; Lane, H. W.

2001-01-01

Anecdotal evidence suggests that astronauts' perceptions of foods in space flight may differ from their perceptions of the same foods on Earth. Fluid shifts toward the head experienced in space may alter the astronauts' sensitivity to odors and tastes, producing altered perceptions. Our objective was to determine whether head-down bed rest, which produces similar fluid shifts, would produce changes in sensitivity to taste, odor or trigeminal sensations. Six subjects were rested three times prior to bed rest, three times during bed rest and two times after bed rest to determine their threshold sensitivity to the odors isoamylbutyrate and menthone, the tastants sucrose, sodium chloride, citric acid, quinine and monosodium glutamate, and to capsaicin. Thresholds were measured using a modified staircase procedure. Self-reported congestion was also recorded at each test time. Thresholds for monosodium glutamate where slightly higher during bed rest. None of the other thresholds were altered by bed rest.

Use of bed rest and head-down tilt to simulate spaceflight-induce immune system changes

NASA Technical Reports Server (NTRS)

Schmitt, D. A.; Schaffar, L.; Taylor, G. R.; Loftin, K. C.; Schneider, V. S.; Koebel, A.; Abbal, M.; Sonnenfeld, G.; Lewis, D. E.; Reuben, J. R.;

Study report on modification of the long term circulatory model for the simulation of bed rest

NASA Technical Reports Server (NTRS)

Leonard, J. I.; Grounds, D. J.

1977-01-01

Modifications were made of the circulatory, fluid, and electrolyte control model which was based on the model of Guyton. The modifications included separate leg compartments and the addition of gravity dependency. It was found that these modifications allowed for more accurate bed rest simulation by simulating changes in the orthostatic gradient and simulating the response to the fluid shifts associated with bed rest.

Bed rest suppresses bioassayable growth hormone release in response to muscle activity

NASA Technical Reports Server (NTRS)

McCall, G. E.; Goulet, C.; Grindeland, R. E.; Hodgson, J. A.; Bigbee, A. J.; Edgerton, V. R.

1997-01-01

Hormonal responses to muscle activity were studied in eight men before (-13 or -12 and -8 or -7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased (P < 0.05) BGH by 66% at -13 or -12 days (2,146 +/- 192 to 3,565 +/- 197 microg/l) and by 92% at -8 or -7 days (2,162 +/- 159 to 4,161 +/- 204 microg/l). After 2 or 3 days of bed rest, there was no response of BGH to the muscle activity, a pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 +/- 211 to 2,085 +/- 109 microg/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 +/- 117 to 2,379 +/- 473 microg/l; P < 0.05), and by 10 or 11 days the BGH response was similar to that before bed rest (1,881 +/- 75 to 4,160 +/- 315 microg/l; P < 0.05). These data demonstrate that the ambulatory state of an individual can have a major impact on the release of BGH, but not IGH, in response to a single bout of muscle activity.

Evaluation of Treadmill Exercise in a Lower Body Negative Pressure Chamber as a Countermeasure for Weightlessness-Induced Bone Loss: a Bed Rest Study with Identical Twins

NASA Technical Reports Server (NTRS)

Smith, Scott M.; Davis-Street, Janis E.; Fesperman, J. Vernell; Calkins, D. S.; Bawa, Maneesh; Macias, Brandon R.; Meyer, R. Scott; Hargens, Alan R.

2003-01-01

Counteracting bone loss is required for future space exploration. We evaluated the ability of treadmill exercise in a LBNP chamber to counteract bone loss in a 30-day bed rest study. Eight pairs of identical twins were randomly assigned to sedentary control or exercise groups. Exercise within LBNP decreased the bone resorption caused by bed rest and may provide a countermeasure for spaceflight. INTRODUCTION: Bone loss is one of the greatest physiological challenges for extended-duration space missions. The ability of exercise to counteract weightlessness-induced bone loss has been studied extensively, but to date, it has proven ineffective. We evaluated the effectiveness of a combination of two countermeasures-treadmill exercise while inside a lower body negative pressure (LBNP) chamber-on bone loss during a 30-day bed rest study. MATERIALS AND METHODS: Eight pairs of identical twins were randomized into sedentary (SED) or exercise/LBNP (EX/LBNP) groups. Blood and urine samples were collected before, several times during, and after the 30-day bed rest period. These samples were analyzed for markers of bone and calcium metabolism. Repeated measures ANOVA was used to determine statistical significance. Because identical twins were used, both time and group were treated as repeated variables. RESULTS: Markers of bone resorption were increased during bed rest in samples from sedentary subjects, including the collagen cross-links and serum and urinary calcium concentrations. For N-telopeptide and deoxypyridinoline, there were significant (p < 0.05) interactions between group (SED versus EX/LBNP) and phase of the study (sample collection point). Pyridinium cross-links were increased above pre-bed rest levels in both groups, but the EX/LBNP group had a smaller increase than the SED group. Markers of bone formation were unchanged by bed rest in both groups. CONCLUSIONS: These data show that this weight-bearing exercise combined with LBNP ameliorates some of the negative effects of simulated weightlessness on bone metabolism. This protocol may pave the way to counteracting bone loss during spaceflight and may provide valuable information about normal and abnormal bone physiology here on Earth.

The effect of supplemental oral phosphate on the bone mineral changes during prolonged bed rest

PubMed Central

Hulley, Stephen B.; Vogel, John M.; Donaldson, Charles L.; Bayers, Jon H.; Friedman, Ronald J.; Rosen, Sheldon N.

1971-01-01

Five healthy young men were studied during 24-30 wk of continuous bed rest. During the first 12 wk of bed rest, untreated subjects increased calcium excretion in the urine by 109 mg/day and in the feces by 147 mg/day. The rate of total body calcium loss was 0.5-0.7% per month. Losses of central calcaneus mineral, assessed by gamma ray transmission scanning, occurred at a tenfold higher rate, whereas the mineral content of the radius did not change. Changes in phosphorus balance resembled the calcium pattern, and increased excretion of nitrogen and hydroxyproline also occurred during bed rest. Upon reambulation, the subjects' calcium balance became positive in 1 month and recovery of their calcaneus mineral was complete within 10-20 wk. Treatment with potassium phosphate supplements (1327 mg P/day) entirely prevented the hypercalciuria of bed rest, but fecal calcium tended to increase. During the first 12 wk, calcium balance was slightly less negative (mean - 193 mg/day) than during bed rest without added phosphate (mean - 267 mg/day). This effect was not seen during the second 12 wk of bed rest. The patterns of magnesium excretion were similar to those of calcium. Fecal and urinary phosphorus excretions were doubled, and phosphorus balance became positive (+ 113 mg/day). Mineral loss from the central calcaneus was similar to that of untreated subjects. It is concluded that this form of phosphate supplementation reduces urinary calcium excretion but does not prevent bone loss during bed rest. PMID:5129304

Focal Gray Matter Plasticity as a Function of Long Duration Head Down Tilted Bed Rest: Preliminary Results

NASA Technical Reports Server (NTRS)

Koppelmans, V.; Erdeniz, B.; DeDios, Y. E.; Wood, S. J.; Reuter-Lorenz, P. A.; Kofman, I.; Bloomberg, J. J.; Mulavara, A. P.; Seidler, R. D.

2014-01-01

Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether these sensorimotor changes are solely related to peripheral changes from reduced vestibular stimulation, body unloading, body fluid shifts or that they may be related to structural and functional brain changes is yet unknown. However, a recent study reported associations between microgravity and flattening of the posterior eye globe and protrusion of the optic nerve [1] possibly as the result of increased intracranial pressure due to microgravity induced bodily fluid shifts [3]. Moreover, elevated intracranial pressure has been related to white matter microstructural damage [2]. Thus, it is possible that spaceflight may affect brain structure and thereby cognitive functioning. Long duration head down tilt bed rest has been suggested as an exclusionary analog to study microgravity effects on the sensorimotor system [4]. Bed rest mimics microgravity in body unloading and bodily fluid shifts. In consideration of the health and performance of crewmembers both in- and post-flight, we are conducting a prospective longitudinal 70-day bed rest study as an analog to investigate the effects of microgravity on brain structure [5]. Here we present results of the first six subjects. Six subjects were assessed at 12 and 7 days before-, at 7, 30, and 70 days in-, and at 8 and 12 days post 70 days of bed rest at the NASA bed rest facility in UTMB, Galveston, TX, USA. At each time point structural MRI scans (i.e., high resolution T1-weighted imaging and Diffusion Tensor Imaging (DTI)) were obtained using a 3T Siemens scanner. Focal changes over time in gray matter density were assessed using the voxel based morphometry 8 (VBM8) toolbox under SPM. Longitudinal processing in VBM8 includes linear registration of each scan to the mean of the subject and subsequently transforming all scans in to MNI space by applying the warp from the mean subject to MNI to the individual gray matter segmentations. Modulation was applied so that all images represented the volume of the original structure in native space. Voxel wise analysis was carried out on the gray matter images after smoothing, using a flexible factorial design with family wise error correction. Focal changes in white matter microstructural integrity were assessed using tract based spatial statistics (TBSS) as part of FMRIB software library (FSL). TBSS registers all DTI scans to standard space. It subsequently creates a study specific white matter skeleton of the major white matter tracts. For each subject, for each DTI metric (i.e. fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD)), the maximum value in a line perpendicular to the skeleton tract is projected to the skeleton. Non-parametric permutation based t-tests and ANOVA's were used for voxel-wise comparison of the skeletons. For both VBM and TBSS, comparison of pre bed rest measurements did not show significant differences. VBM analysis revealed decreased gray matter density in bilateral areas including the frontal medial cortex, the insular cortex and the caudate (see Figure) from 'pre to in bed rest'. Over the same time period, there was an increase in gray matter density in the cerebellum, occipital-, and parietal cortex, including the precuneus (see Figure). The majority of these changes did not recover from 'during to post bed rest'. TBSS analysis did not reveal significant changes in white matter microstructural integrity after correction for multiple comparisons. Uncorrected analyses (p<.015) revealed an increase in RD in the cerebellum and brainstem from pre bed rest to the first week in bed rest that did not recover post bed rest. Extended bed rest, which is an analog for microgravity, can result in gray matter changes and potentially in microstructural white matter changes in areas that are important for neuro motor behavior and cognition. These changes did not recover at two weeks post bed rest. Whether the effects of bed rest wear off at longer times post bed rest, and if they are associated with behavior are important questions that warrant further research.

Calcium kinetics during bed rest with artificial gravity and exercise countermeasures

USDA-ARS?s Scientific Manuscript database

We assessed the potential for countermeasures to lessen the loss of bone calcium during bed rest. Subjects ingested less calcium during bed rest, and with artificial gravity, they also absorbed less calcium. With exercise, they excreted less calcium. To retain bone during bed rest, calcium intake ne...

Changes in intervertebral disc cross-sectional area with bed rest and space flight

NASA Technical Reports Server (NTRS)

LeBlanc, A. D.; Evans, H. J.; Schneider, V. S.; Wendt, R. E. 3rd; Hedrick, T. D.

1994-01-01

STUDY DESIGN. We measured the cross-sectional area of the intervertebral discs of normal volunteers after an overnight rest; before, during, and after 5 or 17 weeks of bed rest; and before and after 8 days of weightlessness. OBJECTIVES. This study sought to determine the degree of expansion of the lumbar discs resulting from bed rest and space flight. SUMMARY OF BACKGROUND DATA. Weightlessness and bed rest, an analog for weightlessness, reduce the mechanical loading on the musculoskeletal system. When unloaded, intervertebral discs will expand, increasing the nutritional diffusion distance and altering the mechanical properties of the spine. METHODS. Magnetic resonance imaging was used to measure the cross-sectional area and transverse relaxation time (T2) of the intervertebral discs. RESULTS. Overnight or longer bed rest causes expansion of the disc area, which reaches an equilibrium value of about 22% (range 10-40%) above baseline within 4 days. Increases in disc area were associated with modest increases in disc T2. During bed rest, disc height increased approximately 1 mm, about one-half of previous estimates based on body height measurements. After 5 weeks of bed rest, disc area returned to baseline within a few days of ambulation, whereas after 17 weeks, disc area remained above baseline 6 weeks after reambulation. After 8 days of weightlessness, T2, disc area, and lumbar length were not significantly different from baseline values 24 hours after landing. CONCLUSIONS. Significant adaptive changes in the intervertebral discs can be expected during weightlessness. These changes, which are rapidly reversible after short-duration flights, may be an important factor during and after long-duration missions.

Countermeasures and Functional Testing in Head-Down Tilt Bed Rest (CFT 70)

NASA Technical Reports Server (NTRS)

Cromwell, Ronita L.

2013-01-01

This 70-day bed rest campaign was comprised of 6 integrated studies and conducted at the NASA Flight Analogs Research Unit (FARU). The FARU is located at the University of Texas Medical Branch, Galveston, Texas and is a satellite unit of the Institute for Translational Sciences - Clinical Research Center. This presentation will describe the FARU, discuss the utility of the bed rest platform for use in these studies, and introduce the studies that participated in the CFT 70 bed rest campaign. Information in this presentation will serve as the background for subsequent talks from each individual study. Individual study presentations will discuss preliminary results from completed subjects. Studies included in CFT70 were: ? Physiological Factors Contributing to Post Flight Changes in Functional Performance. J. Bloomberg, NASA ? Integrated Resistance and Aerobic Training Study. L. Ploutz-Snyder, USRA ? Testosterone Supplementation as a Countermeasure Against Musculoskeletal losses during Space Exploration. R. Urban, University of Texas Medical Branch ? Effects of Retronasal Smelling, Variety and Choice on Appetite & Satiety. J. Hunter, Cornell University ? AD ASTRA: Automated Detection of Attitudes and States through Transaction Recordings Analysis. C. Miller, Smart Information Flow Technologies, LLC ? Bed Rest as a Spaceflight Analog to Study Neuro-cognitive Changes: Extent, Longevity, and Neural Bases. R. Seidler, University of Michigan

Effects of Bed-Rest on Urea and Creatinine: Correlation with Changes in Fat-Free Mass

PubMed Central

Bilancio, Giancarlo; Lombardi, Cinzia; Pisot, Rado; De Santo, Natale G.; Cavallo, Pierpaolo; Cirillo, Massimo

2014-01-01

Background Bed-rest experiments are designed for investigation on catabolic effects of hypokinetic conditions and/or for microgravity simulation in on-ground aerospace research. Bed-rest effects include a reduction in fat-free mass and muscle mass. Urea and creatinine are catabolites of endogenous protein and of muscular energetic metabolism which are excreted mainly by the kidney. The study investigated on urea, creatinine, and kidney function during bed-rest. Methods Twenty healthy young men underwent a 7-day adaptation period (day-6 to day-0) and a 35-day bed-rest experiment (day1 to day35) during normocaloric diet. Urine were collected from day-3 to day0 (baseline) and from day1 to day35. Blood samples and anthropometrical data were collected at day0 (baseline) and bed-rest days 7, 14, 21, 28, and 35. Results Bed-rest reduced plasma volume, weight, fat-free mass, and muscle mass (P<0.001). During bed-rest there was a transient increase in plasma and urinary urea, a decrease in plasma creatinine, and no change in urinary creatinine. The overall integral of changes from day0 to day35 was on average +101.7 mg/dL for plasma urea (95%CI = +43.4/+159.9), +82.2 g/24 h for urinary urea (95%CI = +55.8/+108.7), −2.5 mg/dL for plasma creatinine (95%CI = −3.1/−1.9). Bed-rest reduced plasma cistatyn C also, which was used as mass-independent marker of glomerular filtration rate (−13.1%, P<0.05). Correlations with final reduction in fat-free mass and muscle mass were significant for the overall integral of changes in urinary urea from day0 to day35 (R = 0.706, P<0.001) and for early changes in urinary urea and plasma urea from day0 to day7 (R = 0.566, P = 0.009 and R = 0.715, P<0.001, respectively). Conclusions Study results shows that urea is a marker of catabolic conditions secondary to hypokinetic conditions. PMID:25265226

Effects of bed-rest on urea and creatinine: correlation with changes in fat-free mass.

PubMed

Bilancio, Giancarlo; Lombardi, Cinzia; Pisot, Rado; De Santo, Natale G; Cavallo, Pierpaolo; Cirillo, Massimo

2014-01-01

Bed-rest experiments are designed for investigation on catabolic effects of hypokinetic conditions and/or for microgravity simulation in on-ground aerospace research. Bed-rest effects include a reduction in fat-free mass and muscle mass. Urea and creatinine are catabolites of endogenous protein and of muscular energetic metabolism which are excreted mainly by the kidney. The study investigated on urea, creatinine, and kidney function during bed-rest. Twenty healthy young men underwent a 7-day adaptation period (day-6 to day-0) and a 35-day bed-rest experiment (day1 to day35) during normocaloric diet. Urine were collected from day-3 to day0 (baseline) and from day1 to day35. Blood samples and anthropometrical data were collected at day0 (baseline) and bed-rest days 7, 14, 21, 28, and 35. Bed-rest reduced plasma volume, weight, fat-free mass, and muscle mass (P<0.001). During bed-rest there was a transient increase in plasma and urinary urea, a decrease in plasma creatinine, and no change in urinary creatinine. The overall integral of changes from day0 to day35 was on average +101.7 mg/dL for plasma urea (95%CI = +43.4/+159.9), +82.2 g/24 h for urinary urea (95%CI = +55.8/+108.7), -2.5 mg/dL for plasma creatinine (95%CI = -3.1/-1.9). Bed-rest reduced plasma cistatyn C also, which was used as mass-independent marker of glomerular filtration rate (-13.1%, P<0.05). Correlations with final reduction in fat-free mass and muscle mass were significant for the overall integral of changes in urinary urea from day0 to day35 (R = 0.706, P<0.001) and for early changes in urinary urea and plasma urea from day0 to day7 (R = 0.566, P = 0.009 and R = 0.715, P<0.001, respectively). Study results shows that urea is a marker of catabolic conditions secondary to hypokinetic conditions.

[Kidney stone formation during space flight and long-term bed rest].

PubMed

Okada, Atsushi; Ichikawa, Jun; Tozawa, Keiichi

2011-10-01

Microgravity environment like space flight or a condition requiring long-term bed-rest increase bone resorption and decrease bone formation, inducing the rapid decrease of bone minerals to osteoporosis. Bone mineral loss increases urinary calcium excretion and the risk of urinary stone formation. To clarify the influence of the conditions on renal stone formation, a 90-day bed rest test was performed to analyze the mechanism of microgravity or bed rest-induced stone formation and prevention by bisphosphonate medication and bed-rest exercise. As the results, renal stone formation was observed in control and exercise groups and no stone was seen in the medication group. In the medication group, urinary calcium excretion and relative supersaturation of calcium oxalate were lower than in the control group throughout the bed-rest and recovery period. Bisphosphonate is useful for the prevention of renal stone formation during space flight and long-term bed-rest.

Decreasing ventromedial prefrontal cortex deactivation in risky decision making after simulated microgravity: effects of −6° head-down tilt bed rest

PubMed Central

Rao, Li-Lin; Zhou, Yuan; Liang, Zhu-Yuan; Rao, Henyi; Zheng, Rui; Sun, Yan; Tan, Cheng; Xiao, Yi; Tian, Zhi-Qiang; Chen, Xiao-Ping; Wang, Chun-Hui; Bai, Yan-Qiang; Chen, Shan-Guang; Li, Shu

2014-01-01

Space is characterized by risk and uncertainty. As humans play an important role in long-duration space missions, the ability to make risky decisions effectively is important for astronauts who spend extended time periods in space. The present study used the Balloon Analog Risk Task to conduct both behavioral and fMRI experiments to evaluate the effects of simulated microgravity on individuals' risk-taking behavior and the neural basis of the effect. The results showed that participants' risk-taking behavior was not affected by bed rest. However, we found that the ventromedial prefrontal cortex (VMPFC) showed less deactivation after bed rest and that the VMPFC activation in the active choice condition showed no significant difference between the win outcome and the loss outcome after bed rest, although its activation was significantly greater in the win outcome than in the loss outcome before bed rest. These results suggested that the participants showed a decreased level of value calculation after the bed rest. Our findings can contribute to a better understanding of the effect of microgravity on individual higher-level cognitive functioning. PMID:24904338

The T-Allele of TCF7L2 rs7903146 Associates With a Reduced Compensation of Insulin Secretion for Insulin Resistance Induced by 9 Days of Bed Rest

PubMed Central

Alibegovic, Amra C.; Sonne, Mette P.; Højbjerre, Lise; Hansen, Torben; Pedersen, Oluf; van Hall, Gerrit; Holst, Jens J.; Stallknecht, Bente; Dela, Flemming; Vaag, Allan

2010-01-01

OBJECTIVE The aim of this study was to determine whether the type 2 diabetes–associated T-allele of transcription factor 7-like 2 (TCF7L2) rs7903146 associates with impaired insulin secretion to compensate for insulin resistance induced by bed rest. RESEARCH DESIGN AND METHODS A total of 38 healthy young Caucasian men were studied before and after bed rest using the hyperinsulinemic-euglycemic clamp technique combined with indirect calorimetry preceded by an intravenous glucose tolerance test. The TCF7L2 rs7903146 was genotyped using allelic discrimination performed with an ABI 7900 system. The genetic analyses were done assuming a dominant model of inheritance. RESULTS The first-phase insulin response (FPIR) was significantly lower in carriers of the T-allele compared with carriers of the CC genotype before bed rest, with and without correction for insulin resistance. The incremental rise of FPIR in response to insulin resistance induced by bed rest was lower in carriers of the T-allele (P < 0.001). Fasting plasma glucagon levels were significantly lower in carriers of the T-allele before and after bed rest. While carriers of the CC genotype developed increased hepatic insulin resistance, the TCF7L2 rs7903146 did not influence peripheral insulin action or the rate of lipolysis before or after bed rest. CONCLUSIONS Healthy carriers of the T-allele of TCF7L2 rs7903146 exhibit a diminished increase of insulin secretion in response to intravenous glucose to compensate for insulin resistance as induced by bed rest. Reduced paracrine glucagon stimulation may contribute to the impairment of β-cell function in the carriers TCF7L2 rs7903146 T-allele associated with increased risk of type 2 diabetes. PMID:20107109

Exercise and Transversus Abdominis Muscle Atrophy after 60-d Bed Rest.

PubMed

Belavý, Daniel Ludovic; Gast, Ulf; Felsenberg, Dieter

2017-02-01

This study aimed to investigate atrophy in the deep abdominal muscles, spinal extensors, and the effect of high-load resistive exercise with and without whole-body vibration after 60 d of strict bed rest. Twenty-four subjects underwent 60 d of head-down tilt bed rest and performed either resistive vibration exercise (RVE), resistive exercise only (RE), or no exercise control (2nd Berlin BedRest Study). The thickness of the transversus abdominis, internal oblique, and erector spinae muscles and the area of the multifidus muscle were measured bilaterally via real-time ultrasound. Intention-to-treat analysis was implemented, and P values were adjusted by the false discovery rate method. At the end of the bed rest, transversus abdominis thickness was reduced by 18.3% in the inactive group (P = 0.00011) with no significant change in the RVE (-4.0%; P = 0.014 vs control) or RE (-5.0%; P = 0.10 vs control) groups. In the inactive subjects, internal oblique thickness reduced by 10.6% (P = 0.0025) and by 7% (P > 0.05) in each of the training groups. The lengthening of the lumbar spine was greatest on day 1 (+7.4%, P = 0.004) and day 2 (+6.3%, P = 0.004; day 54: +4.1%, P = 0.023). A 4.7% reduction of multifidus area was observed on day 1 of bed rest (P = 0.0049) and a 4.2% reduction of erector spinae thickness was observed on day 2 (P = 0.0011). Extensor atrophy and spinal lengthening was not affected by exercise. No significant difference was seen between RVE and RE. Bed rest leads to atrophy of the transversus abdominis and internal oblique muscles. The exercise program, which implemented lower-limb and back extension exercises against shoulder restraints, was able to reduce atrophy seen in transversus abdominis in bed rest.

The effects of bed rest on crew performance during simulated shuttle reentry. Volume 1: Study overview and physiological results

NASA Technical Reports Server (NTRS)

Chambers, A.; Vykukal, H. C.

1974-01-01

A centrifuge study was carried out to measure physiological stress and control task performance during simulated space shuttle orbiter reentry. Jet pilots were tested with, and without, anti-g-suit protection. The pilots were exposed to simulated space shuttle reentry acceleration profiles before, and after, ten days of complete bed rest, which produced physiological deconditioning similar to that resulting from prolonged exposure to orbital zero g. Pilot performance in selected control tasks was determined during simulated reentry, and before and after each simulation. Physiological stress during reentry was determined by monitoring heart rate, blood pressure, and respiration rate. Study results indicate: (1) heart rate increased during the simulated reentry when no g protection was given, and remained at or below pre-bed rest values when g-suits were used; (2) pilots preferred the use of g-suits to muscular contraction for control of vision tunneling and grayout during reentry; (3) prolonged bed rest did not alter blood pressure or respiration rate during reentry, but the peak reentry acceleration level did; and (4) pilot performance was not affected by prolonged bed rest or simulated reentry.

Human skeletal muscle protein breakdown during spaceflight

NASA Technical Reports Server (NTRS)

Stein, T. P.; Schluter, M. D.

1997-01-01

Human spaceflight is associated with a loss of body protein. Excretion of 3-methylhistidine (3-MH) in the urine is a useful measurement of myofibrillar protein breakdown. Bed rest, particularly with 6 degrees head-down tilt, is an accepted ground-based model for human spaceflight. The objectives of this report were to compare 3-MH excretion from two Life Sciences shuttle missions (duration 9.5 and 15 days, n = 9) and from 17 days of bed rest (n = 7) with 6 degrees head-down tilt. The bed rest study was designed to mimic an actual Life Sciences spaceflight and so incorporated an extensive battery of physiological tests focused on the musculoskeletal system. Results showed that nitrogen retention, based on excretion of nitrogen in the urine, was reduced during both bed rest [from 22 +/- 1 to 1 +/- 5 mg N x kg(-1) x day(-1) (n = 7; P < 0.05)] and spaceflight [from 57 +/- 9 to 19 +/- 3 mg N x kg(-1) x day(-1) (n = 9; P < 0.05)]. 3-MH excretion was unchanged with either bed rest [pre-bed rest 5.30 +/- 0.29 vs. bed rest 5.71 +/- 0.30 micromol 3-MH x kg(-1) x day(-1), n = 7; P = not significant (NS)] or spaceflight [preflight 4.98 +/- 0.37 vs. 4.59 +/- 0.39 micromol 3-MH x kg(-1) x day(-1) in-flight, n = 9; P = NS]. We conclude that 1) 3-MH excretion was unaffected by spaceflight on the shuttle or with bed rest plus exercise, and 2) because protein breakdown (elevated 3-MH) was increased on Skylab but not on the shuttle, it follows that muscle protein breakdown is not an inevitable consequence of spaceflight.

Limited effect of fly-wheel and spinal mobilization exercise countermeasures on lumbar spine deconditioning during 90 d bed-rest in the Toulouse LTBR study

NASA Astrophysics Data System (ADS)

Belavý, Daniel L.; Ohshima, Hiroshi; Bareille, Marie-Pierre; Rittweger, Jörn; Felsenberg, Dieter

2011-09-01

We examined the effect of high-load fly-wheel (targeting the lower-limb musculature and concurrent loading of the spine via shoulder restraints) and spinal movement countermeasures against lumbar spine muscle atrophy, disc and spinal morphology changes and trunk isokinetic torque loss during prolonged bed-rest. Twenty-four male subjects underwent 90 d head-down tilt bed-rest and performed either fly-wheel (FW) exercises every three days, spinal movement exercises in lying five times daily (SpMob), or no exercise (Ctrl). There was no significant impact of countermeasures on losses of isokinetic trunk flexion/extension ( p≥0.65). Muscle volume change by day-89 of bed-rest in the psoas, iliacus, lumbar erector spinae, lumbar multifidus and quadratus lumborum, as measured via magnetic resonance imaging (MRI), was statistically similar in all three groups ( p≥0.33). No significant effect on MRI-measures of lumbar intervertebral disc volume, spinal length and lordosis ( p≥0.09) were seen either, but there was some impact ( p≤0.048) on axial plane disc dimensions (greater reduction than in Ctrl) and disc height (greater increases than in Ctrl). MRI-data from subjects measured 13 and 90-days after bed-rest showed partial recovery of the spinal extensor musculature by day-13 after bed-rest with this process complete by day-90. Some changes in lumbar spine and disc morphology parameters were still persistent 90-days after bed-rest. The present results indicate that the countermeasures tested were not optimal to maintain integrity of the spine and trunk musculature during bed rest.

Prevention of bone mineral changes induced by bed rest: Modification by static compression simulating weight bearing, combined supplementation of oral calcium and phosphate, calcitonin injections, oscillating compression, the oral diophosphonatedisodium etidronate, and lower body negative pressure

NASA Technical Reports Server (NTRS)

Schneider, V. S.; Hulley, S. B.; Donaldson, C. L.; Vogel, J. M.; Rosen, S. N.; Hantman, D. A.; Lockwood, D. R.; Seid, D.; Hyatt, K. H.; Jacobson, L. B.

1974-01-01

The phenomenon of calcium loss during bed rest was found to be analogous to the loss of bone material which occurs in the hypogravic environment of space flight. Ways of preventing this occurrence are investigated. A group of healthy adult males underwent 24-30 weeks of continuous bed rest. Some of them were given an exercise program designed to resemble normal ambulatory activity; another subgroup was fed supplemental potassium phosphate. The results from a 12-week period of treatment were compared with those untreated bed rest periods. The potassium phosphate supplements prevented the hypercalciuria of bed rest, but fecal calcium tended to increase. The exercise program did not diminish the negative calcium balance. Neither treatment affected the heavy loss of mineral from the calcaneus. Several additional studies are developed to examine the problem further.

A single day of bed rest, irrespective of energy balance, does not affect skeletal muscle gene expression or insulin sensitivity.

PubMed

Dirks, Marlou L; Stephens, Francis B; Jackman, Sarah R; Galera Gordo, Jesús; Machin, David J; Pulsford, Richard M; van Loon, Luc J C; Wall, Benjamin T

2018-06-01

What is the central question of this study? What are the initial metabolic and molecular events that underpin bed rest-induced skeletal muscle deconditioning, and what is the contribution of energy balance? What is the main finding and its importance? A single day of bed rest, irrespective of energy balance, did not lead to overt changes in skeletal muscle gene expression or insulin sensitivity. More than 1 day of physical inactivity is required to observe the insulin resistance and robust skeletal muscle transcriptional responses associated with bed rest and consequent alterations in energy balance. The initial metabolic and molecular events that underpin disuse-induced skeletal muscle deconditioning, and the contribution of energy balance, remain to be investigated. Ten young, healthy men (age 25 ± 1 years; body mass index 25.3 ± 0.8 kg·m -2 ) underwent three 24 h laboratory-based experimental periods in a randomized, crossover manner: (i) controlled habitual physical activity with an energy-balanced diet (CON); (ii) strict bed rest with a diet to maintain energy balance (BR-B); and (iii) strict bed rest with a diet identical to CON, consequently resulting in positive energy balance. Continuous glucose monitoring was performed throughout each visit, with vastus lateralis muscle biopsies and an oral glucose tolerance test performed before and after. In parallel with muscle samples collected from a previous 7 day bed rest study, biopsies were used to examine the expression of genes associated with the regulation of muscle mass and insulin sensitivity. A single day of bed rest, irrespective of energy balance, did not lead to overt changes in whole-body substrate oxidation, indices of insulin sensitivity [i.e. homeostatic model assessment of insulin resistance, BR-B from 2.7 ± 1.7 to 3.1 ± 1.5 (P > 0.05) and Matsuda index, BR-B from 5.9 ± 3.3 to 5.2 ± 2.9 (P > 0.05)] or 24 h glycaemic control/variability compared with CON. Seven days of bed rest led to ∼30-55% lower expression of genes involved in insulin signalling, lipid storage/oxidation and muscle protein breakdown, whereas no such changes were observed after 1 day of bed rest. In conclusion, more than a single day of physical inactivity is required to observe the insulin resistance and robust skeletal muscle transcriptional responses associated with bed rest and consequent alterations in energy balance. © 2018 The Authors. Experimental Physiology © 2018 The Physiological Society.

Effect Of Leg Exercise On Vascular Volumes During Bed Rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Vernikos, J.; Wade, C. E.; Barnes, P. R.

1993-01-01

Report describes experiments on effects of no-exercise regimen and of two leg-exercise regimens on volumes of plasma, volumes of red blood cells, densities of bodies, and water balances of 19 men (32 to 42 years old) confined to minus 6 degrees-head-down bed rest for 30 days. Purpose of study to determine whether either or both exercise regimens maintain plasma volume and to relate levels of hypovolemia to body fluid balances. Results showed during bed rest, plasma volume maintained in isotomic group but not in other two groups, and no significant differences in body densities, body weights, or water balances among three groups. Concludes isotonic-exercise regimen better than isokinetic-exercise regimen for maintaining plasma volume during prolonged exposure to bed rest.

Biochemical and hemodynamic changes in normal subjects during acute and rigorous bed rest and ambulation

NASA Astrophysics Data System (ADS)

Zorbas, Yan G.; Kakurin, Vassily J.; Afonin, Victor B.; Yarullin, Vladimir L.

2002-06-01

Rigorous bed rest (RBR) induces significant biochemical and circulatory changes. However, little is known about acute rigorous bed rest (ARBR). Measuring biochemical and circulatory variables during ARBR and RBR the aim of this study was to establish the significance of ARBR effect. Studies were done during 3 days of a pre-bed rest (BR) period and during 7 days of ARBR and RBR period. Thirty normal male individuals aged, 24.1±6.3 years were chosen as subjects. They were divided equally into three groups: 10 subjects placed under active control conditions served as unrestricted ambulatory control subjects (UACS), 10 subjects submitted to an acute rigorous bed rest served as acute rigorous bed rested subjects (ARBRS) and 10 subjects submitted to a rigorous bed rest served as rigorous bed rested subjects (RBRS). The UACS were maintained under an average running distance of 9.7 km day -1. For the ARBR effect simulation, ARBRS were submitted abruptly to BR for 7 days. They did not have any prior knowledge of the exact date and time when they would be asked to confine to RBR. For the RBR effect simulation, RBRS were subjected to BR for 7 days on a predetermined date and time known to them right away from the start of the study. Plasma renin activity (PRA), plasma cortisol (PC), plasma aldosterone (PA), plasma and urinary sodium (Na) and potassium (K) levels, heart rate (HR), cardiac output (CO), and arterial blood pressure (ABP) increased significantly, and urinary aldosterone (UA), stroke volume (SV) and plasma volume (PV) decreased significantly ( p<0.05) in ARBRS and RBRS as compared with their pre-BR values and the values in UACS. Electrolyte, hormonal and hemodynamic responses were significantly ( p<0.05) greater and occurred significantly faster ( p<0.05) during ARBR than RBR. Parameters change insignificantly ( p>0.05) in UACS compared with pre-BR control values. It was concluded that, the more abruptly muscular activity is restricted in experimental subjects while they are very active, the greater hemodynamic and biochemical change there is and probably in individuals whose muscular activity is abruptly terminated after an accident or sudden illness.

WISE-2005 Protective Effect of Exercise within LBNP Countermeasure Detected by Heart Rate Response to Low Levels of LBNP

NASA Technical Reports Server (NTRS)

Hughson, R. L.; Shoemaker, J. K.; Hargens, A. R.; Mattar, L.; Edgell, H.; Kerbeci, P.; Arbeille, Ph.

2006-01-01

Sixteen women were studied before, during and after a 60 day, continu ous 6" head-down bed-rest (HDBR). Subjects were randomly assigned to two groups: Control (no countermeasures) and Exercise+LBNP (supine ru nning within an LBNP chamber for 40-min followed by 10-min passive L BNP for 3-4 days/week, plus flywheel resistive training of the legs e very third day). Cardiovascular responses were observed before bed re st, on day 50 of HDBR and R+8 after bed rest. Subjects were supine in the LBNP device with suction applied at 0, -10, -20 and -30 mmHg LBN P for 2-min per stage. In the pre-bed rest testing, there was no diff erence in HR between the groups at rest or at -30 mmHg. On HDBR day 50, HR was elevated at supine rest for the Con not the Ex group, whil e at -30 mmHg HR was elevated above pre-HDBR for both groups, but the magnitude of increase from Pre- to HDBR day 50 was less for the Ex g roup than for the Con group. The change in HR on HDBR day 50 is an im portant indicator as it was less than 24-hours after the Exercise+LBN P countermeasure on day 49. After bed rest, no specific countermeasu res were provided in the first week, so HR responses on day R+8 refle cted the effects of bed rest with or without countermeasure plus any recovery from simply returning to the upright posture. Relative to th e Pre-bed rest responses, HR on day R+8 had recovered in the Ex group but was still elevated in the Con group. These results indicate that the cardiovascular response to LBNP is preserved to a greater degre e during bed rest by the countermeasures, and further that the cardio vascular response returned to pre-bed rest much more rapidly in the E xercise+LBNP group than hi the group that received no cardiovascular countermeasures.

Effects of a spaceflight analog environment on brain connectivity and behavior.

PubMed

Cassady, Kaitlin; Koppelmans, Vincent; Reuter-Lorenz, Patricia; De Dios, Yiri; Gadd, Nichole; Wood, Scott; Castenada, Roy Riascos; Kofman, Igor; Bloomberg, Jacob; Mulavara, Ajitkumar; Seidler, Rachael

2016-11-01

Sensorimotor functioning is adaptively altered following long-duration spaceflight. The question of whether microgravity affects other central nervous system functions such as brain network organization and its relationship with behavior is largely unknown, but of importance to the health and performance of astronauts both during and post-flight. In the present study, we investigate the effects of prolonged exposure to an established spaceflight analog on resting state brain functional connectivity and its association with behavioral changes in 17 male participants. These bed rest participants remained in bed with their heads tilted down six degrees below their feet for 70 consecutive days. Resting state functional magnetic resonance imaging (rs-fMRI) and behavioral data were obtained at seven time points averaging around: 12 and 8days prior to bed rest; 7, 50, and 70days during bed rest; and 8 and 12days after bed rest. To assess potential confounding effects due to scanning interval or task practice, we also acquired rs-fMRI and behavioral measurements from 14 control participants at four time points. 70days of head-down tilt (HDT) bed rest resulted in significant changes in the functional connectivity of motor, somatosensory, and vestibular areas of the brain. Moreover, several of these network alterations were significantly associated with changes in sensorimotor and spatial working memory performance, which suggests that neuroplasticity mechanisms may facilitate adaptation to the microgravity analog environment. The findings from this study provide novel insights into the underlying neural mechanisms and operational risks of spaceflight analog-related changes in sensorimotor performance. Copyright © 2016 Elsevier Inc. All rights reserved.

Attenuation of the protein wasting associated with bed rest by branched-chain amino acids

NASA Technical Reports Server (NTRS)

Stein, T. P.; Schluter, M. D.; Leskiw, M. J.; Boden, G.

1999-01-01

Bed rest is generally accepted as being an appropriate ground-based model for human spaceflight. The objectives of this study were to test the hypothesis that increasing the amount of branched-chain amino acids (BCAAs) in the diet could attenuate the protein loss associated with bed rest. Nineteen healthy subjects were randomized into two groups according to diet. During the 6 d of bed rest, the diets were supplemented with either 30 mmol/d each of three non-essential amino acids, glycine, serine, and alanine (control group), or with 30 mmol/d each of the BCAAs, leucine, isoleucine, and valine (BCAA group). Nutrition was supplied as a commercially available defined formula diet at a rate of 1.3 x REE. Nitrogen (N) balance and urinary 3-MeH excretion were determined for the 6 d. In our results, the urine-based estimate of N balance was 22.2 +/- 14.4 (n = 9) mg N.kg-1.d-1 and 60.5 +/- 10.1 mg (n = 8) N.kg-1.d-1 for the control and BCAA-supplemented groups, respectively (P < 0.05). Urinary 3-MeH excretion was unchanged in both groups with bed rest. We conclude that BCAA supplementation attenuates the N loss during short-term bed rest.

Lower body negative pressure treadmill exercise as a countermeasure for bed rest-induced bone loss in female identical twins.

PubMed

Zwart, Sara R; Hargens, Alan R; Lee, Stuart M C; Macias, Brandon R; Watenpaugh, Donald E; Tse, Kevin; Smith, Scott M

2007-02-01

Supine weight-bearing exercise within lower body negative pressure (LBNP) alleviates some of the skeletal deconditioning induced by simulated weightlessness in men. We examined this potential beneficial effect in women. Because dietary acid load affected the degree of bone resorption in men during bed rest, we also investigated this variable in women. Subjects were 7 pairs of female identical twins assigned at random to 2 groups, sedentary bed rest (control) or bed rest with supine treadmill exercise within LBNP. Dietary intake was controlled and monitored. Urinary calcium and markers of bone resorption were measured before bed rest and on bed rest days 5/6, 12/13, 19/20, and 26/27. Bone mineral content was assessed by dual-energy X-ray absorptiometry before and after bed rest. Data were analyzed by repeated-measures two-way analysis of variance. Pearson correlation coefficients were used to define the relationships between diet and markers of bone metabolism and to estimate heritability of markers. During bed rest, all markers of bone resorption and urinary calcium and phosphorus increased (P<0.001); parathyroid hormone (P=0.06), bone-specific alkaline phosphatase (P=0.06), and 1,25-dihydroxyvitamin D (P=0.09) tended to decrease. LBNP exercise tended to mitigate bone density loss. The ratio of dietary animal protein to potassium was positively correlated with urinary calcium excretion for all weeks of bed rest in the control group, but only during weeks 1 and 3 in the exercise group. Pre-bed rest data suggested that many markers of bone metabolism have strong genetic determinants. Treadmill exercise within LBNP had less of a protective effect on bone resorption during bed rest in women than previously published results had shown for its effect in men, but the same trends were observed for both sexes. Dietary acid load of these female subjects was significantly correlated with calcium excretion but not with other bone resorption markers.

Behavioral and Psychological Issues in Long Duration Head-down Bed Rest

NASA Technical Reports Server (NTRS)

Seaton, Kimberly A.; Bowie, Kendra; Sipes, Walter A.

2008-01-01

Behavioral health services, similar to those offered to the U.S. astronauts who complete six-month missions on board the International Space Station, were provided to 13 long-duration head-down bed rest participants. Issues in psychological screening, selection, and support are discussed as they relate to other isolated and confined environments. Psychological services offered to participants are described, and challenges in subject selection and retention are discussed. Psychological support and training provided to both subjects and study personnel have successfully improved the well-being of study participants. Behavioral health services are indispensable to long-duration head-down tilt bed rest studies.

Effects of acute exercise on attenuated vagal baroreflex function during bed rest

NASA Technical Reports Server (NTRS)

Convertino, Victor A.; Doerr, Donald F.; Guell, Antonio; Marini, J.-F.

1992-01-01

We measured carotid baroreceptor-cardiac reflex responses in six healthy men, 24 h before and 24 h after a bout of leg exercise during 6 deg head-down bed rest to determine if depressed vagal baroreflex function associated with exposure to microgravity environments could be reversed by a single exposure to acute intense exercise. Baroreflex responses were measured before bed rest and on day 7 of bed rest. An exercise bout consisting of dynamic and isometric actions of the quadriceps at graded speeds and resistances was performed on day 8 of bed rest and measurements of baroreflex response were repeated 24 h later. Vagally-mediated cardiac responses were provoked with ramped neck pressure-suction sequences comprising pressure elevations to +40 mm Hg, followed by serial, R-wave triggered 15 mm Hg reductions, to -65 mm Hg. Baroreceptor stimulus-cardiac response relationships were derived by plotting each R-R interval as a function of systolic pressure less the neck chamber pressure applied during the interval. Compared with pre-bed rest baseline measurements, 7 d of bed rest decreased the gain (maximum slope) of the baroreflex stimulus-response relationship by 16.8 +/- 3.4 percent (p less than 0.05). On day 9 of bed rest, 24 h after exercise, the maximum slope of the baroreflex stimulus-response relationship was increased (p less than 0.05) by 10.7 +/- 3.7 percent above pre-bed rest levels and 34.3 +/- 7.9 percent above bed rest day 7. Our data verify that vagally-mediated baroreflex function is depressed by exposure to simulated microgravity and demonstrate that this effect can be acutely reversed by exposure to a single bout of intense exercise.

Automatic Blood Pressure Measurements During Exercise

NASA Technical Reports Server (NTRS)

Weaver, Charles S.

1985-01-01

Microprocessor circuits and a computer algorithm for automatically measuring blood pressure during ambulatory monitoring and exercise stress testing have been under development at SRI International. A system that records ECG, Korotkov sound, and arm cuff pressure for off-line calculation of blood pressure has been delivered to NASA, and an LSLE physiological monitoring system that performs the algorithm calculations in real-time is being constructed. The algorithm measures the time between the R-wave peaks and the corresponding Korotkov sound on-set (RK-interval). Since the curve of RK-interval versus cuff pressure during deflation is predictable and slowly varying, windows can be set around the curve to eliminate false Korotkov sound detections that result from noise. The slope of this curve, which will generally decrease during exercise, is the inverse of the systolic slope of the brachial artery pulse. In measurements taken during treadmill stress testing, the changes in slopes of subjects with coronary artery disease were markedly different from the changes in slopes of healthy subjects. Measurements of slope and O2 consumption were also made before and after ten days of bed rest during NASA/Ames Research Center bed rest studies. Typically, the maximum rate of O2 consumption during the post-bed rest test is less than the maximum rate during the pre-bed rest test. The post-bed rest slope changes differ from the pre-bed rest slope changes, and the differences are highly correlated with the drop in the maximum rate of O2 consumption. We speculate that the differences between pre- and post-bed rest slopes are due to a drop in heart contractility.

The Physiology of Bed Rest. Chapter 39

NASA Technical Reports Server (NTRS)

Fortney, Suzanne M.; Schneider, Victor S.; Greenleaf, John E.

1996-01-01

Prolonged rest in bed has been utilized by physicians and other health-care workers to immobilize and confine patients for rehabilitation and restoration of health since time immemorial. The sitting or horizontal position is sought by the body to relieve the strain of the upright or vertical postures, for example during syncopal situations, bone fractures, muscle injuries, fatigue, and probably also to reduce energy expenditure. Most health-care personnel are aware that adaptive responses occurring during bed rest proceed concomitantly with the healing process; signs and symptoms associated with the former should be differentiated from those of the latter. Not all illnesses and infirmities benefit from prolonged bed rest. Considerations in prescribing bed rest for patients-including duration, body position, mode and duration of exercise, light-dark cycles, temperature, and humidity-have not been investigated adequately. More recently, adaptive physiological responses have been measured in normal, healthy subjects in the horizontal or slightly head-down postures during prolonged bed rest as analogs for the adaptive responses of astronauts exposed to the microgravity environment of outer and bed-rest research.

Energy expenditure and balance during spaceflight on the space shuttle

NASA Technical Reports Server (NTRS)

Stein, T. P.; Leskiw, M. J.; Schluter, M. D.; Hoyt, R. W.; Lane, H. W.; Gretebeck, R. E.; LeBlanc, A. D.

1999-01-01

The objectives of this study were as follows: 1) to measure human energy expenditure (EE) during spaceflight on a shuttle mission by using the doubly labeled water (DLW) method; 2) to determine whether the astronauts were in negative energy balance during spaceflight; 3) to use the comparison of change in body fat as measured by the intake DLW EE, 18O dilution, and dual energy X-ray absorptiometry (DEXA) to validate the DLW method for spaceflight; and 4) to compare EE during spaceflight against that found with bed rest. Two experiments were conducted: a flight experiment (n = 4) on the 16-day 1996 life and microgravity sciences shuttle mission and a 6 degrees head-down tilt bed rest study with controlled dietary intake (n = 8). The bed rest study was designed to simulate the flight experiment and included exercise. Two EE determinations were done before flight (bed rest), during flight (bed rest), and after flight (recovery). Energy intake and N balance were monitored for the entire period. Results were that body weight, water, fat, and energy balance were unchanged with bed rest. For the flight experiment, decreases in weight (2.6 +/- 0.4 kg, P < 0.05) and N retention (-2. 37 +/- 0.45 g N/day, P < 0.05) were found. Dietary intake for the four astronauts was reduced in flight (3,025 +/- 180 vs. 1,943 +/- 179 kcal/day, P < 0.05). EE in flight was 3,320 +/- 155 kcal/day, resulting in a negative energy balance of 1,355 +/- 80 kcal/day (-15. 7 +/- 1.0 kcal. kg-1. day-1, P < 0.05). This corresponded to a loss of 2.1 +/- 0.4 kg body fat, which was within experimental error of the fat loss determined by 18O dilution (-1.4 +/- 0.5 kg) and DEXA (-2.4 +/- 0.4 kg). All three methods showed no change in body fat with bed rest. In conclusion, 1) the DLW method for measuring EE during spaceflight is valid, 2) the astronauts were in severe negative energy balance and oxidized body fat, and 3) in-flight energy (E) requirements can be predicted from the equation: E = 1.40 x resting metabolic rate + exercise.

The NASA Performance Assessment Workstation: cognitive performance during head-down bed rest.

PubMed

Shehab, R L; Schlegel, R E; Schiflett, S G; Eddy, D R

1998-01-01

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 degrees head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.

The NASA performance assessment workstation: Cognitive performance during head-down bed rest

NASA Astrophysics Data System (ADS)

Shehab, Randa L.; Schlegel, Robert E.; Schiflett, Samuel G.; Eddy, Douglas R.

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 ° head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.

Age-related differences in lean mass, protein synthesis and skeletal muscle markers of proteolysis after bed rest and exercise rehabilitation

PubMed Central

Tanner, Ruth E; Brunker, Lucille B; Agergaard, Jakob; Barrows, Katherine M; Briggs, Robert A; Kwon, Oh Sung; Young, Laura M; Hopkins, Paul N; Volpi, Elena; Marcus, Robin L; LaStayo, Paul C; Drummond, Micah J

2015-01-01

Abstract Bed rest-induced muscle loss and impaired muscle recovery may contribute to age-related sarcopenia. It is unknown if there are age-related differences in muscle mass and muscle anabolic and catabolic responses to bed rest. A secondary objective was to determine if rehabilitation could reverse bed rest responses. Nine older and fourteen young adults participated in a 5-day bed rest challenge (BED REST). This was followed by 8 weeks of high intensity resistance exercise (REHAB). Leg lean mass (via dual-energy X-ray absorptiometry; DXA) and strength were determined. Muscle biopsies were collected during a constant stable isotope infusion in the postabsorptive state and after essential amino acid (EAA) ingestion on three occasions: before (PRE), after bed rest and after rehabilitation. Samples were assessed for protein synthesis, mTORC1 signalling, REDD1/2 expression and molecular markers related to muscle proteolysis (MURF1, MAFBX, AMPKα, LC3II/I, Beclin1). We found that leg lean mass and strength decreased in older but not younger adults after bedrest (P < 0.05) and was restored after rehabilitation. EAA-induced mTORC1 signalling and protein synthesis increased before bed rest in both age groups (P < 0.05). Although both groups had blunted mTORC1 signalling, increased REDD2 and MURF1 mRNA after bedrest, only older adults had reduced EAA-induced protein synthesis rates and increased MAFBX mRNA, p-AMPKα and the LC3II/I ratio (P < 0.05). We conclude that older adults are more susceptible than young persons to muscle loss after short-term bed rest. This may be partially explained by a combined suppression of protein synthesis and a marginal increase in proteolytic markers. Finally, rehabilitation restored bed rest-induced deficits in lean mass and strength in older adults. Key points Five days of bed rest resulted in a reduction in leg lean mass and strength in older adults. After bed rest, older (but not younger) adults had reduced amino acid-induced anabolic sensitivity (blunted muscle protein synthesis; MPS) and enhanced markers associated with the ubiquitin proteasome and autophagy–lysosomal systems (increase in molecular markers related to muscle proteolysis). Younger adults did not lose leg lean mass (via DXA) after 5 days of bed rest despite blunted amino acid-induced mTORC1 signalling and increased skeletal muscle REDD1, REDD2 and MURF1 mRNA expression. Exercise rehabilitation restored bed rest-induced deficits in lean mass, strength, nutrient-induced protein anabolism (protein synthesis and mTORC1 signalling) and select muscle proteolytic markers in older adults. PMID:26173027

Bed rest and activity restriction for women at risk for preterm birth: a survey of Canadian prenatal care providers.

PubMed

Sprague, Ann E; O'Brien, Beverley; Newburn-Cook, Christine; Heaman, Maureen; Nimrod, Carl

2008-04-01

To explore the practices of Canadian obstetricians, family physicians, and midwives in recommending bed rest or activity restriction for women at risk for preterm birth (PTB) and to assess the decisional conflict experienced by care providers when they recommend these therapies. A self-administered mail survey of prenatal care providers was carried out using Dillman's Tailored Design Method. Analysis included descriptive statistics and analysis of variance. The survey was distributed to 1441 potential participants; of these, 1172 were eligible participants, and 516 (44.2%) completed the survey. For women at risk of PTB, 60 of 170 obstetricians (35%), 88 of 206 family practitioners (42.7%), and 30 of 140 midwives (21.4%) recommended bed rest in hospital; 110 of 170 obstetricians (64.7%), 144 of 206 family practitioners (69.9%), and 73 of 140 midwives (52.1%) recommended bed rest at home. These recommendations occurred despite the response from about two thirds of each professional group that the effectiveness of bed rest was in the fair-to-poor range in helping to prevent PTB. The mean score on the Provider Decision Process Assessment Instrument, measuring decisional conflict for all care provider groups, was 30 (SD 7.4) (possible score range 12-60). There were no significant differences in decisional conflict scores among provider groups (F [2,347] = 2.24; P = 0.11). Care providers have been discouraged from routinely recommending bed rest for women at risk of PTB because of potential adverse side effects. This study demonstrates that most Canadian prenatal care providers have not been persuaded to incorporate these recommendations into practice. Except for women with multiple gestation, there is inconsistent practice in recommending bed rest and activity restriction. Additionally, Canadian prenatal care providers have some decisional conflict about using this therapy. These results provide some of the first Canadian perspectives on the practice of prescribing therapeutic bed rest for PTB.

Electrical impedance measurements in the arm and the leg during a thirty day bed rest study

NASA Technical Reports Server (NTRS)

Cardus, David; Jaweed, Mazher; McTaggart, Wesley

1995-01-01

The need to detect, follow, and understand the effects of gravity on body fluid distribution is a constant stimulus to the quest for new techniques in this area of research. One of these techniques is electrical bioimpedance spectroscopy (BIS). Although not new, this is a technique whose applications to biomedical research are fairly recent. What is new is the development of instrumentation that has made practical the use of impedance spectroscopy in the biomedical setting, particularly in studies involving human subjects. The purpose of this paper is to report impedance spectroscopy observations made on a subject who was submitted to bed rest for a period of thirty days. These observations were made as part of a study on muscle atrophy during a thirty day head down bed rest. Since bed rest studies are very costly in human and financial terms, and technically difficult to realize, we felt that even though the present study deals only with a single case it was worthy of reporting because it illustrates kinds of questions impedance spectroscopy may help to answer in microgravity research.

Effect of long-term hypokinesia on the electrolytic composition of the blood in patients with osteoarticular tuberculosis

NASA Technical Reports Server (NTRS)

Zakutaeva, V. P.

1980-01-01

Seventy-six patients with osteoarticular tuberculosis were divided into two groups, one of which was required to maintain strict bed rest and the other of which was allowed unrestricted motor activity. A study of blood electrolyte composition in the two groups revealed that bed rest for these patients results in decreased plasma potassium calcium, and magnesium content, but that these indices improved after the patients were allowed to move freely. The study suggests that patients with osteoarticular tuberculosis who are on bed rest be carefully observed for alterations in blood electrolytes and that proper electrolyte balance be maintained.

VO2 kinetics of constant-load exercise following bed-rest-induced deconditioning

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Goldwater, D. J.; Sandler, H.

1984-01-01

Previous studies have shown that the oxygen uptake kinetics during exercise and recovery may be changed by alterations in work intensity, prior exercise, muscle group involvement, ambient conditions, posture, disease state, and level of physical conditioning. However, the effects of detraining on oxygen uptake kinetics have not been determined. The present investigation has the objective to determine the effects of deconditioning following seven days of continuous head-down bed rest on changes in steady-state oxygen uptake, O2 deficit, and recovery oxygen uptake during the performance of constant-load exercise. The obtained results may provide support for previous proposals that submaximal oxygen uptake was significantly reduced following bed rest. The major finding was that bed-rest deconditioning resulted in a reduction of total O2 transport/utilization capacity during the transient phase of upright but not supine exercise.

Effect of antiorthostatic bed rest on hepatic blood flow in man.

PubMed

Putcha, L; Cintron, N M; Vanderploeg, J M; Chen, Y; Habis, J; Adler, J

1988-04-01

Physiological changes that occur during exposure to weightlessness may induce alterations in blood flow to the liver. Estimation of hepatic blood flow (HBF) using ground-based weightlessness simulation models may provide insight into functional changes of the liver in crewmembers during flight. In the present study HBF, indirectly estimated by indocyanine green (ICG) clearance, is compared in 10 subjects during the normal ambulatory condition and antiorthostatic (-6 degrees) bed rest. Plasma clearance of ICG was determined following intravenous administration of a 0.5-mg.kg-1 dose of ICG to each subject on two separate occasions, once after being seated for 1 h and once after 24 h of head-down bed rest. After 24 h of head-down bed rest, hepatic blood flow did not change significantly from the respective control value.

Bed rest from the perspective of the high-risk pregnant woman.

PubMed

Gupton, A; Heaman, M; Ashcroft, T

1997-01-01

To describe the experience of prolonged bed rest from the perspective of women during high-risk pregnancies. A focused ethnographic study that used interviews, participant diaries, and field notes as data sources. Participants were obtained from an acute-care hospital antepartum unit and an antepartum home care program. Twenty-four women with complications of pregnancy requiring prolonged bed rest (range, 7-50 days). A model of the stress process in pregnant women on bed rest emerged from the data analysis. Stressors were grouped into situational (sick role, lack of control, uncertainty, concerns regarding fetus's well-being, and being tired of waiting), environmental (feeling like a prisoner, being bored, and having a sense of missing out), and family (role reversal and worry about older children) categories. Two main mediators of stress were social support and coping. Families, friends, and professionals were perceived as sources of support. Women used coping strategies, such as keeping a positive attitude, taking it 1 day at a time, doing it for the baby, getting used to it, setting goals, and keeping busy. Manifestations of stress were evidenced by adverse physical symptoms, emotional reactions, and altered social relationships. Prolonged bed rest is a stressful experience for pregnant women at high risk. Understanding the stress process in pregnant women confined to bed rest may assist nurses in developing interventions to reduce stressors and enhance mediators.

Retrospective analysis of treatment modalities in diabetic muscle infarction

PubMed Central

Onyenemezu, Ikenna; Capitle, Eugenio

2014-01-01

Background Diabetic muscle infarction (DMI) is a spontaneous necrosis of skeletal muscle of unknown etiology. The major risk factor is longstanding uncontrolled diabetes mellitus (DM). Optimal treatment for DMI is not known. The purpose of this study was to analyze the outcome of surgical treatment, physiotherapy, and bed rest in DMI. Methods We searched Medline from its inception to April 2013. We selected cases that provided sufficient data on recovery duration, recurrences, and non-recurrences. Baseline characteristics, including age, sex, microvascular complications, lesion size estimated on magnetic resonance imaging, type of diabetes, and duration of diabetes were assessed. The primary outcome was mean time to recovery from initial treatment and secondary outcomes were mean time to recurrence and recurrence rate. Results Mean time to recovery was 149 (95% confidence interval [CI] 113–186), 71 (95% CI 47–96), and 43 (95% CI 30–57) days for surgery, physiotherapy and bed rest, respectively. These figures were statistically significant only for surgery versus physiotherapy and surgery versus bed rest (P<0.01). Mean time to recurrence was 30, 107, and 297 days for surgery, physiotherapy, and bed rest, respectively. The recurrence rate was 57%, 44%, and 24% for surgery, physiotherapy, and bed rest, respectively. Conclusion Our results show a similar outcome for physiotherapy as compared with bed rest. It also confirms nonsurgical treatment as a better therapeutic option compared with surgical treatment. PMID:27790029

Effects Of Exercise During Bed Rest

NASA Technical Reports Server (NTRS)

Greenleaf, John E.; Bernauer, Edmund M.

1993-01-01

Pair of reports adds to growing body of knowledge of physical deconditioning caused by prolonged bed rest and effectiveness of various exercise regimens in preserving or restoring fitness. Major objective to determine what regimens to prescribe to astronauts before flight, during prolonged weightlessness, and immediately before returning to Earth. Knowledge also benefits patients confined by illness or injury. First report discusses experiment on effects of two types of periodic, intense, short-duration exercise during bed rest. Experiment also discussed in documents "Effects Of Exercise During Prolonged Bed Rest" (ARC-12190), and "Isotonic And Isokinetic Exercise During Bed Rest" (ARC-12180). Second report reviews knowledge acquired with view toward development of protocols for exercise regimens.

Role of skin blood flow and sweating rate in exercise thermoregulation after bed rest

NASA Technical Reports Server (NTRS)

Lee, Stuart M C.; Williams, W. Jon; Schneider, Suzanne M.

2002-01-01

Two potential mechanisms, reduced skin blood flow (SBF) and sweating rate (SR), may be responsible for elevated intestinal temperature (T(in)) during exercise after bed rest and spaceflight. Seven men underwent 13 days of 6 degrees head-down bed rest. Pre- and post-bed rest, subjects completed supine submaximal cycle ergometry (20 min at 40% and 20 min at 65% of pre-bed rest supine peak exercise capacity) in a thermoneutral room. After bed rest, T(in) was elevated at rest (+0.31 +/- 0.12 degrees C) and at the end of exercise (+0.33 +/- 0.07 degrees C). Percent increase in SBF during exercise was less after bed rest (211 +/- 53 vs. 96 +/- 31%; P < or = 0.05), SBF/T(in) threshold was greater (37.09 +/- 0.16 vs. 37.33 +/- 0.13 degrees C; P < or = 0.05), and slope of SBF/T(in) tended to be reduced (536 +/- 184 vs. 201 +/- 46%/ degrees C; P = 0.08). SR/T(in) threshold was delayed (37.06 +/- 0.11 vs. 37.34 +/- 0.06 degrees C; P < or = 0.05), but the slope of SR/T(in) (3.45 +/- 1.22 vs. 2.58 +/- 0.71 mg x min-1 x cm-2 x degrees C-1) and total sweat loss (0.42 +/- 0.06 vs. 0.44 +/- 0.08 kg) were not changed. The higher resting and exercise T(in) and delayed onset of SBF and SR suggest a centrally mediated elevation in the thermoregulatory set point during bed rest exposure.

Artificial Gravity as a Bone Loss Countermeasure in Simulated Weightlessness

NASA Technical Reports Server (NTRS)

Smith, S. M.; Zwart, S. R.; Crawford, G. E.; Gillman, P. L.; LeBlanc, A.; Shackelford, L. C.; Heer, M. A.

2007-01-01

The impact of microgravity on the human body is a significant concern for space travelers. We report here initial results from a pilot study designed to explore the utility of artificial gravity (AG) as a countermeasure to the effects of microgravity, specifically to bone loss. After an initial phase of adaptation and testing, 15 male subjects underwent 21 days of 6 head-down bed rest to simulate the deconditioning associated with space flight. Eight of the subjects underwent 1 h of centrifugation (AG, 1 gz at the heart, 2.5 gz at the feet) each day for 21 days, while 7 of the subjects served as untreated controls (CN). Blood and urine were collected before, during, and after bed rest for bone marker determinations. At this point, preliminary data are available on the first 8 subjects (6 AG, and 2 CN). Comparing the last week of bed rest to before bed rest, urinary excretion of the bone resorption marker n-telopeptide increased 95 plus or minus 59% (mean plus or minus SD) in CN but only 32 plus or minus 26% in the AG group. Similar results were found for another resorption marker, helical peptide (increased 57 plus or minus 0% and 35 plus or minus 13% in CN and AG respectively). Bone-specific alkaline phosphatase, a bone formation marker, did not change during bed rest. At this point, sample analyses are continuing, including calcium tracer kinetic studies. These initial data demonstrate the potential effectiveness of short-radius, intermittent AG as a countermeasure to the bone deconditioning that occurs during bed rest.

Aerobic exercise deconditioning and countermeasures during bed rest.

PubMed

Lee, Stuart M C; Moore, Alan D; Everett, Meghan E; Stenger, Michael B; Platts, Steven H

2010-01-01

Bed rest is a well-accepted model for spaceflight in which the physiologic adaptations, particularly in the cardiovascular system, are studied and potential countermeasures can be tested. Bed rest without countermeasures results in reduced aerobic capacity and altered submaximal exercise responses. Aerobic endurance and factors which may impact prolonged exercise, however, have not been well studied. The initial loss of aerobic capacity is rapid, occurring in parallel with the loss of plasma volume. Thereafter, the reduction in maximal aerobic capacity proceeds more slowly and is influenced by central and peripheral adaptation. Exercise capacity can be maintained during bed rest and may be improved during recovery with appropriate countermeasures. Plasma volume restoration, resistive exercise, orthostatic stress, aerobic exercise, and aerobic exercise plus orthostatic stress all have been tested with varying levels of success. However, the optimal combination of elements-exercise modality, intensity, duration, muscle groups exercised and frequency of aerobic exercise, orthostatic stress, and supplementary resistive or anaerobic exercise training-has not been systematically evaluated. Currently, frequent (at least 3 days per week) bouts of intense exercise (interval-style and near maximal) with orthostatic stress appears to be the most efficacious method to protect aerobic capacity during bed rest. Further refinement of protocols and countermeasure hardware may be necessary to insure the success of countermeasures in the unique environment of space.

The Influence of Roughness and Pyrethroid Formulations on Bed Bug (Cimex lectularius L.) Resting Preferences.

PubMed

Hottel, Benjamin A; Pereira, Roberto M; Koehler, Philip G

2015-05-12

Two-choice tests were conducted to examine the effect of surface roughness on the resting preference of bed bugs, Cimex lectularius L., on copper, basswood, and acrylic materials. The influence of pyrethroid formulation applications on resting preferences was also evaluated. Bed bugs were given the choice of resting between two sanded halves of each material tested. One half was sanded with a P60 grit sandpaper and the other with a less rough P600 grit sandpaper. A significantly higher proportion of bed bugs chose to rest on the rougher P60 grit sanded half of all materials tested. Pyrethroid applications were made to either the P60 grit half or both halves of acrylic arenas and resting preferences were again assessed. Behavioral responses of bed bugs to pyrethroid formulation applications varied depending on the bed bug strain used and the formulation applied. Bed bugs would still rest on the P60 grit half when Suspend SC formulation (0.06% deltamethrin) was applied; however, an avoidance response was observed from a bed bug strain susceptible to D-Force aerosol formulations (0.06% deltamethrin). The avoidance behavior is likely attributed to one, more than one, or even an interaction of multiple spray constituents and not the active ingredient.

Triiodothyronine increases calcium loss in a bed rest antigravity model for space flight.

PubMed

Smith, Steven R; Lovejoy, Jennifer C; Bray, George A; Rood, Jennifer; Most, Marlene M; Ryan, Donna H

2008-12-01

Bed rest has been used as a model to simulate the effects of space flight on bone metabolism. Thyroid hormones accelerate bone metabolism. Thus, supraphysiologic doses of this hormone might be used as a model to accelerate bone metabolism during bed rest and potentially simulate space flight. The objective of the study was to quantitate the changes in bone turnover after low doses of triiodothyronine (T(3)) added to short-term bed rest. Nine men and 5 women were restricted to bed rest for 28 days with their heads positioned 6 degrees below their feet. Subjects were randomly assigned to receive either placebo or oral T(3) at doses of 50 to 75 microg/d in a single-blind fashion. Calcium balance was measured over 5-day periods; and T(3), thyroxine, thyroid-stimulating hormone, immunoreactive parathyroid hormone, osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline were measured weekly. Triiodothyronine increased 2-fold in the men and 5-fold in the women during treatment, suppressing both thyroxine and thyroid-stimulating hormone. Calcium balance was negative by 300 to 400 mg/d in the T(3)-treated volunteers, primarily because of the increased fecal loss that was not present in the placebo group. Urinary deoxypyridinoline to creatinine ratio, a marker of bone resorption, increased 60% in the placebo group during bed rest, but more than doubled in the T(3)-treated subjects (P < .01), suggesting that bone resorption was enhanced by treatment with T(3). Changes in serum osteocalcin and bone-specific alkaline phosphatase, markers of bone formation, were similar in T(3)- and placebo-treated subjects. Triiodothyronine increases bone resorption and fecal calcium loss in subjects at bed rest.

Physiological and Functional Alterations after Spaceflight and Bed Rest.

PubMed

Mulavara, Ajitkumar P; Peters, Brian T; Miller, Chris A; Kofman, Igor S; Reschke, Millard F; Taylor, Laura C; Lawrence, Emily L; Wood, Scott J; Laurie, Steven S; Lee, Stuart M C; Buxton, Roxanne E; May-Phillips, Tiffany R; Stenger, Michael B; Ploutz-Snyder, Lori L; Ryder, Jeffrey W; Feiveson, Alan H; Bloomberg, Jacob J

2018-04-03

Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits. A test battery comprised of 7 functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular and neuromuscular adaptations to spaceflight. Astronauts were tested before and after 6-month spaceflights. Subjects were also tested before and after 70 days of 6° head-down bed rest, a spaceflight analog, to examine the role of axial body unloading on the spaceflight results. These subjects included Control and Exercise groups to examine the effects of exercise during bed rest. Spaceflight subjects showed the greatest decrement in performance during functional tasks that required the greatest demand for dynamic control of postural equilibrium which was paralleled by similar decrements in sensorimotor tests that assessed postural and dynamic gait control. Other changes included reduced lower limb muscle performance and increased heart rate to maintain blood pressure. Exercise performed during bed rest prevented detrimental change in neuromuscular and cardiovascular function, however, both bed rest groups experienced functional and balance deficits similar to spaceflight subjects. Bed rest data indicates that body support unloading experienced during spaceflight contributes to postflight postural control dysfunction. Further, the bed rest results in the Exercise group of subjects confirm that resistance and aerobic exercises performed during spaceflight can play an integral role in maintaining neuromuscular and cardiovascular function, which can help in reducing decrements in functional performance. These results indicate that a countermeasure to mitigate postflight postural control dysfunction is required to maintain functional performance.

Cardiovascular consequences of bed rest: effect on maximal oxygen uptake

NASA Technical Reports Server (NTRS)

Convertino, V. A.

1997-01-01

Maximal oxygen uptake (VO2max) is reduced in healthy individuals confined to bed rest, suggesting it is independent of any disease state. The magnitude of reduction in VO2max is dependent on duration of bed rest and the initial level of aerobic fitness (VO2max), but it appears to be independent of age or gender. Bed rest induces an elevated maximal heart rate which, in turn, is associated with decreased cardiac vagal tone, increased sympathetic catecholamine secretion, and greater cardiac beta-receptor sensitivity. Despite the elevation in heart rate, VO2max is reduced primarily from decreased maximal stroke volume and cardiac output. An elevated ejection fraction during exercise following bed rest suggests that the lower stroke volume is not caused by ventricular dysfunction but is primarily the result of decreased venous return associated with lower circulating blood volume, reduced central venous pressure, and higher venous compliance in the lower extremities. VO2max, stroke volume, and cardiac output are further compromised by exercise in the upright posture. The contribution of hypovolemia to reduced cardiac output during exercise following bed rest is supported by the close relationship between the relative magnitude (% delta) and time course of change in blood volume and VO2max during bed rest, and also by the fact that retention of plasma volume is associated with maintenance of VO2max after bed rest. Arteriovenous oxygen difference during maximal exercise is not altered by bed rest, suggesting that peripheral mechanisms may not contribute significantly to the decreased VO2max. However reduction in baseline and maximal muscle blood flow, red blood cell volume, and capillarization in working muscles represent peripheral mechanisms that may contribute to limited oxygen delivery and, subsequently, lowered VO2max. Thus, alterations in cardiac and vascular functions induced by prolonged confinement to bed rest contribute to diminution of maximal oxygen uptake and reserve capacity to perform physical work.

Lower body negative pressure treadmill exercise as a countermeasure for bed rest-induced bone loss in female identical twins

PubMed Central

Zwart, Sara R.; Hargens, Alan R.; Lee, Stuart M. C.; Macias, Brandon R.; Watenpaugh, Donald E.; Tse, Kevin; Smith, Scott M.

2007-01-01

Supine weight-bearing exercise within lower body negative pressure (LBNP) alleviates some of the skeletal deconditioning induced by simulated weightlessness in men. We examined the potential beneficial effect in women. Because dietary acid load affected the degree of bone resorption in men during bed rest, we also investigated this variable in women. Subjects were 7 pairs of female identical twins assigned at random to 2 groups, sedentary bed rest (control) or bed rest with supine treadmill exercise within LBNP. Dietary intake was controlled and monitored. Urinary calcium and markers of bone resorption were measured before bed rest (BR) and on BR days 5/6, 12/13, 19/20, and 26/27. Bone mineral content was assessed by dual-energy X-ray absorptiometry before and after bed rest. Data were analyzed by repeated measures two-way analysis of variance. Pearson correlation coefficients were used to define the relationships between diet and markers of bone metabolism, and to estimate heritability of markers. During bed rest, all markers of bone resorption and urinary calcium and phosphorus increased (P < 0.001); parathyroid hormone (P = 0.06), bone-specific alkaline phosphatase (P = 0.06), and 1,25-dihydroxyvitamin D (P = 0.09) tended to decrease. LBNP exercise tended to mitigate bone density loss. The ratio of dietary animal protein to potassium was positively correlated with urinary calcium excretion for all weeks of bed rest in the control group, but only during weeks 1 and 3 for the exercise group. Pre-bed rest data suggested that many markers of bone metabolism have strong genetic determinants. Treadmill exercise within LBNP had less of a protective effect on bone resorption during bed rest in women than previously-published results had shown for its effect in men, but the same trends were observed for both sexes. Dietary acid load of these female subjects was significantly correlated with calcium excretion but not with other bone resorption markers. PMID:17070743

Age-related differences in lean mass, protein synthesis and skeletal muscle markers of proteolysis after bed rest and exercise rehabilitation.

PubMed

Tanner, Ruth E; Brunker, Lucille B; Agergaard, Jakob; Barrows, Katherine M; Briggs, Robert A; Kwon, Oh Sung; Young, Laura M; Hopkins, Paul N; Volpi, Elena; Marcus, Robin L; LaStayo, Paul C; Drummond, Micah J

2015-09-15

Bed rest-induced muscle loss and impaired muscle recovery may contribute to age-related sarcopenia. It is unknown if there are age-related differences in muscle mass and muscle anabolic and catabolic responses to bed rest. A secondary objective was to determine if rehabilitation could reverse bed rest responses. Nine older and fourteen young adults participated in a 5-day bed rest challenge (BED REST). This was followed by 8 weeks of high intensity resistance exercise (REHAB). Leg lean mass (via dual-energy X-ray absorptiometry; DXA) and strength were determined. Muscle biopsies were collected during a constant stable isotope infusion in the postabsorptive state and after essential amino acid (EAA) ingestion on three occasions: before (PRE), after bed rest and after rehabilitation. Samples were assessed for protein synthesis, mTORC1 signalling, REDD1/2 expression and molecular markers related to muscle proteolysis (MURF1, MAFBX, AMPKα, LC3II/I, Beclin1). We found that leg lean mass and strength decreased in older but not younger adults after bedrest (P < 0.05) and was restored after rehabilitation. EAA-induced mTORC1 signalling and protein synthesis increased before bed rest in both age groups (P < 0.05). Although both groups had blunted mTORC1 signalling, increased REDD2 and MURF1 mRNA after bedrest, only older adults had reduced EAA-induced protein synthesis rates and increased MAFBX mRNA, p-AMPKα and the LC3II/I ratio (P < 0.05). We conclude that older adults are more susceptible than young persons to muscle loss after short-term bed rest. This may be partially explained by a combined suppression of protein synthesis and a marginal increase in proteolytic markers. Finally, rehabilitation restored bed rest-induced deficits in lean mass and strength in older adults. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Upright exercise or supine lower body negative pressure exercise maintains exercise responses after bed rest

NASA Technical Reports Server (NTRS)

Lee, S. M.; Bennett, B. S.; Hargens, A. R.; Watenpaugh, D. E.; Ballard, R. E.; Murthy, G.; Ford, S. R.; Fortney, S. M.

1997-01-01

Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of VO2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P < or = 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight.

Regulation of muscle sympathetic nerve activity after bed rest deconditioning

NASA Technical Reports Server (NTRS)

Pawelczyk, J. A.; Zuckerman, J. H.; Blomqvist, C. G.; Levine, B. D.

2001-01-01

Cardiovascular deconditioning reduces orthostatic tolerance. To determine whether changes in autonomic function might produce this effect, we developed stimulus-response curves relating limb vascular resistance, muscle sympathetic nerve activity (MSNA), and pulmonary capillary wedge pressure (PCWP) with seven subjects before and after 18 days of -6 degrees head-down bed rest. Both lower body negative pressure (LBNP; -15 and -30 mmHg) and rapid saline infusion (15 and 30 ml/kg body wt) were used to produce a wide variation in PCWP. Orthostatic tolerance was assessed with graded LBNP to presyncope. Bed rest reduced LBNP tolerance from 23.9 +/- 2.1 to 21.2 +/- 1.5 min, respectively (means +/- SE, P = 0.02). The MSNA-PCWP relationship was unchanged after bed rest, though at any stage of the LBNP protocol PCWP was lower, and MSNA was greater. Thus bed rest deconditioning produced hypovolemia, causing a shift in operating point on the stimulus-response curve. The relationship between limb vascular resistance and MSNA was not significantly altered after bed rest. We conclude that bed rest deconditioning does not alter reflex control of MSNA, but may produce orthostatic intolerance through a combination of hypovolemia and cardiac atrophy.

Cardiac atrophy after bed rest and spaceflight.

PubMed

Perhonen, M A; Franco, F; Lane, L D; Buckey, J C; Blomqvist, C G; Zerwekh, J E; Peshock, R M; Weatherall, P T; Levine, B D

2001-08-01

Cardiac muscle adapts well to changes in loading conditions. For example, left ventricular (LV) hypertrophy may be induced physiologically (via exercise training) or pathologically (via hypertension or valvular heart disease). If hypertension is treated, LV hypertrophy regresses, suggesting a sensitivity to LV work. However, whether physical inactivity in nonathletic populations causes adaptive changes in LV mass or even frank atrophy is not clear. We exposed previously sedentary men to 6 (n = 5) and 12 (n = 3) wk of horizontal bed rest. LV and right ventricular (RV) mass and end-diastolic volume were measured using cine magnetic resonance imaging (MRI) at 2, 6, and 12 wk of bed rest; five healthy men were also studied before and after at least 6 wk of routine daily activities as controls. In addition, four astronauts were exposed to the complete elimination of hydrostatic gradients during a spaceflight of 10 days. During bed rest, LV mass decreased by 8.0 +/- 2.2% (P = 0.005) after 6 wk with an additional atrophy of 7.6 +/- 2.3% in the subjects who remained in bed for 12 wk; there was no change in LV mass for the control subjects (153.0 +/- 12.2 vs. 153.4 +/- 12.1 g, P = 0.81). Mean wall thickness decreased (4 +/- 2.5%, P = 0.01) after 6 wk of bed rest associated with the decrease in LV mass, suggesting a physiological remodeling with respect to altered load. LV end-diastolic volume decreased by 14 +/- 1.7% (P = 0.002) after 2 wk of bed rest and changed minimally thereafter. After 6 wk of bed rest, RV free wall mass decreased by 10 +/- 2.7% (P = 0.06) and RV end-diastolic volume by 16 +/- 7.9% (P = 0.06). After spaceflight, LV mass decreased by 12 +/- 6.9% (P = 0.07). In conclusion, cardiac atrophy occurs during prolonged (6 wk) horizontal bed rest and may also occur after short-term spaceflight. We suggest that cardiac atrophy is due to a physiological adaptation to reduced myocardial load and work in real or simulated microgravity and demonstrates the plasticity of cardiac muscle under different loading conditions.

Cardiac atrophy after bed rest and spaceflight

NASA Technical Reports Server (NTRS)

Perhonen, M. A.; Franco, F.; Lane, L. D.; Buckey, J. C.; Blomqvist, C. G.; Zerwekh, J. E.; Peshock, R. M.; Weatherall, P. T.; Levine, B. D.

2001-01-01

Cardiac muscle adapts well to changes in loading conditions. For example, left ventricular (LV) hypertrophy may be induced physiologically (via exercise training) or pathologically (via hypertension or valvular heart disease). If hypertension is treated, LV hypertrophy regresses, suggesting a sensitivity to LV work. However, whether physical inactivity in nonathletic populations causes adaptive changes in LV mass or even frank atrophy is not clear. We exposed previously sedentary men to 6 (n = 5) and 12 (n = 3) wk of horizontal bed rest. LV and right ventricular (RV) mass and end-diastolic volume were measured using cine magnetic resonance imaging (MRI) at 2, 6, and 12 wk of bed rest; five healthy men were also studied before and after at least 6 wk of routine daily activities as controls. In addition, four astronauts were exposed to the complete elimination of hydrostatic gradients during a spaceflight of 10 days. During bed rest, LV mass decreased by 8.0 +/- 2.2% (P = 0.005) after 6 wk with an additional atrophy of 7.6 +/- 2.3% in the subjects who remained in bed for 12 wk; there was no change in LV mass for the control subjects (153.0 +/- 12.2 vs. 153.4 +/- 12.1 g, P = 0.81). Mean wall thickness decreased (4 +/- 2.5%, P = 0.01) after 6 wk of bed rest associated with the decrease in LV mass, suggesting a physiological remodeling with respect to altered load. LV end-diastolic volume decreased by 14 +/- 1.7% (P = 0.002) after 2 wk of bed rest and changed minimally thereafter. After 6 wk of bed rest, RV free wall mass decreased by 10 +/- 2.7% (P = 0.06) and RV end-diastolic volume by 16 +/- 7.9% (P = 0.06). After spaceflight, LV mass decreased by 12 +/- 6.9% (P = 0.07). In conclusion, cardiac atrophy occurs during prolonged (6 wk) horizontal bed rest and may also occur after short-term spaceflight. We suggest that cardiac atrophy is due to a physiological adaptation to reduced myocardial load and work in real or simulated microgravity and demonstrates the plasticity of cardiac muscle under different loading conditions.

Effect of exercise on the pseudodiabetes of bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1982-01-01

The effect of intensive isotonic exercise and isometric exercise (with its low metabolic rate) during bed rest on plasma insulin and glucose tolerance test was investigated. The subjects were seven healthy men, 19 to 22 years in age, 166 to 188 cm in height, and 62.40 to 103.80 kg in weight; maximal oxygen uptakes ranged from 3.36 to 4.38 liters/min. It appears that bed-rest-induced glucose intolerance is diminished with increasing energy expenditure during both bed rest and recovery.

Effects of three day bed-rest on circulatory, metabolic and hormonal responses to oral glucose load in endurance trained athletes and untrained subjects

NASA Technical Reports Server (NTRS)

Smorawinski, J.; Kubala, P.; Kaciuba-Uociako, H.; Nazar, K.; Titow-Stupnicka, E.; Greenleaf, J. E.

1996-01-01

Endurance trained long distance runners and untrained individuals underwent three days of bed rest and oral glucose loading. Before and after bed rest, individuals were given glucose tolerance tests, and their heart rates, blood pressure, blood glucose levels, insulin levels, and catecholamine interactions were measured. Results indicated that glucose tolerance is more affected by bed rest-induced deconditioning in untrained individuals than in trained individuals.

Treadmill Exercise Within LBNP as an Integrated Coutermeasure to Microgravity

NASA Technical Reports Server (NTRS)

Lee, Stuart; Hargens, A. R.; Schneider, S. M.; Watenpaugh, D. E.

2010-01-01

An integrated exercise countermeasure for microgravity is needed to protect multiple physiologic systems and save crew time. Such a countermeasure should protect orthostatic tolerance, upright ambulatory capability (including sprinting), aerobic capacity, muscle strength/endurance, and other physiologic parameters relevant to human performance. We developed a novel physiologic countermeasure, treadmill exercise within LBNP, for preventing cardiovascular and musculoskeletal deconditioning associated with prolonged bed rest and spaceflight. We evaluated 40 min of daily LBNP treadmill exercise by a battery of physiologic parameters relevant to maintaining exercise performance and health of both women and men during bed-rest (simulated microgravity) studies lasting from 5 to 60 days. For 30 day studies, we employed identical twins with one twin as the control and the other twin as the exerciser to improve comparative power. During the WISE 60-day HDT study, the treadmill exercise within LBNP was performed 3-4 days each week and resistive exercise was performed 2-3 days each week. Our treadmill within LBNP protocol maintained plasma volume and sprint speed (30 day HDT bed-rest studies of identical twins), orthostatic tolerance to a degree, upright exercise capacity, muscle strength and endurance, and some bone parameters during 30 day (twin studies) and 60 day (WISE-2005) bed-rest simulations of microgravity. When combining treadmill exercise within LBNP and resistive exercise (WISE), cardiac mass increased significantly in the exercise (EX) group during bed rest relative to controls (CON). Upright peak VO2, and knee extensor strength and endurance decreased significantly in CON subjects; but these parameters were preserved in the EX group. In the 60 day WISE study, each LBNP exercise session was followed immediately by 10 minutes of static LBNP, and the last such session occurred three days before the end of bed rest. Still, orthostatic tolerance was better maintained in the EX group than in the CON group. Therefore, these collective peer-reviewed results document that our treadmill exercise within LBNP countermeasure safely and efficiently protects multiple physiologic systems in women and men during bed-rest studies of up to 60 days. Supported by NASA grants NNJ04HF71G and NAG 9-1425, NIH grant GCRC M01 RR00827 and by WISE support from ESA, NASA, CSA, and CNES.

Artificial gravity as a multi-system countermeasure: effects on cognitive function.

PubMed

Seaton, Kimberly A; Slack, Kelley J; Sipes, Walter; Bowie, Kendra

2007-07-01

The Space Flight Cognitive Assessment Tool for Windows (WinSCAT) is used on the International Space Station to evaluate cognitive functioning after physical insult or trauma. The current study uses WinSCAT to assess cognitive functioning in a space flight analog (bed rest) environment where intermittent artificial gravity (AG) is being tested as a countermeasure. Fifteen male subjects (8 treatment, 7 control), who participated in 21 days of 6 degree head-down tilt bed rest, were assessed during the acclimatization phase, bed rest phase, and recovery phase. Individual differences were found within both the treatment and control groups. The treatment group accounted for more off-nominal WinSCAT scores than the control group. The length of time spent in bed rest was not associated with a change in cognitive function. Individual differences in underlying cognitive ability and motivation level are other possible explanations for the current findings.

Hypoxia Worsens Affective Responses and Feeling of Fatigue During Prolonged Bed Rest

PubMed Central

Stavrou, Nektarios A. M.; Debevec, Tadej; Eiken, Ola; Mekjavic, Igor B.

2018-01-01

Previous research, although limited, suggests that both hypoxia and bed rest influence psychological responses by exaggerating negative psychological responses and attenuating positive emotions. The present study investigated the effect of a 21-day prolonged exposure to normobaric hypoxia and bed rest on affective responses and fatigue. Eleven healthy participants underwent three 21-day interventions using a cross-over design: (1) normobaric hypoxic ambulatory confinement (HAMB), (2) normobaric hypoxic bed rest (HBR) and (3) normoxic bed rest (NBR). Affective and fatigue responses were investigated using the Activation Deactivation Adjective Check List, and the Multidimensional Fatigue Inventory, which were completed before (Pre), during (Day 7, Day 14, and Day 21) and after (Post) the interventions. The most negative psychological profile appeared during the HBR intervention. Specifically, tiredness, tension, general and physical fatigue significantly increased on days 7, 14, and 21, as well as at Post. After the HBR intervention, general and physical fatigue remained higher compared to Pre values. Additionally, a deterioration of psychological responses was also noted following HAMB and NBR. In particular, both hypoxia and BR per se induced subjective fatigue and negative affective responses. BR seems to exert a moderate negative effect on the sensation of fatigue, whereas exercise attenuates the negative effects of hypoxia as noted during the HAMB condition. In conclusion, our data suggest that the addition of hypoxia to bed rest-induced inactivity significantly worsens affective responses and feeling of fatigue. PMID:29628903

The effects of twelve weeks of bed rest on bone histology, biochemical markers of bone turnover, and calcium homeostasis in eleven normal subjects

NASA Technical Reports Server (NTRS)

Zerwekh, J. E.; Ruml, L. A.; Gottschalk, F.; Pak, C. Y.; Blomqvist, C. G. (Principal Investigator)

1998-01-01

This study was undertaken to examine the effects of 12 weeks of skeletal unloading on parameters of calcium homeostasis, calcitropic hormones, bone histology, and biochemical markers of bone turnover in 11 normal subjects (9 men, 2 women; 34 +/- 11 years of age). Following an ambulatory control evaluation, all subjects underwent 12 weeks of bed rest. An additional metabolic evaluation was performed after 12 days of reambulation. Bone mineral density declined at the spine (-2.9%, p = 0.092) and at the hip (-3.8%, p = 0.002 for the trochanter). Bed rest prompted a rapid, sustained, significant increase in urinary calcium and phosphorus as well as a significant increase in serum calcium. Urinary calcium increased from a pre-bed rest value of 5.3 mmol/day to values as high as 73 mmol/day during bed rest. Immunoreactive parathyroid hormone and serum 1,25-dihydroxyvitamin D declined significantly during bed rest, although the mean values remained within normal limits. Significant changes in bone histology included a suppression of osteoblastic surface for cancellous bone (3.1 +/- 1.3% to 1.9 +/- 1.5%, p = 0.0142) and increased bone resorption for both cancellous and cortical bone. Cortical eroded surface increased from 3.5 +/- 1.1% to 7.3 +/- 4.0% (p = 0.018) as did active osteoclastic surface (0.2 +/- 0.3% to 0.7 +/- 0.7%, p = 0.021). Cancellous eroded surface increased from 2.1 +/- 1.1% to 4.7 +/- 2.2% (p = 0.002), while mean active osteoclastic surface doubled (0.2 +/- 0.2% to 0.4 +/- 0.3%, p = 0.020). Serum biochemical markers of bone formation (osteocalcin, bone-specific alkaline phosphatase, and type I procollagen extension peptide) did not change significantly during bed rest. Urinary biochemical markers of bone resorption (hydroxyproline, deoxypyridinoline, and N-telopeptide of type I collagen) as well as a serum marker of bone resorption (type I collagen carboxytelopeptide) all demonstrated significant increases during bed rest which declined toward normal during reambulation. Thus, under the conditions of this study, the human skeleton appears to respond to unloading by a rapid and sustained increase in bone resorption and a more subtle decrease in bone formation.

Stretch Reflex as a Simple Measure to Evaluate the Efficacy of Potential Flight Countermeasures Using the Bed Rest Environment

NASA Technical Reports Server (NTRS)

Cerisano, J. M.; Reschke, M. F.; Kofman, I. S.; Fisher, E. A.; Harm, D. L.

2010-01-01

INTRODUCTION: Spaceflight is acknowledged to have significant effects on the major postural muscles. However, it has been difficult to separate the effects of ascending somatosensory changes caused by the unloading of these muscles during flight from changes in sensorimotor function caused by a descending vestibulo-cerebellar response to microgravity. It is hypothesized that bed rest is an adequate model to investigate postural muscle unloading given that spaceflight and bed rest may produce similar results in both nerve axon and muscle tissue. METHODS: To investigate this hypothesis, stretch reflexes were measured on 18 subjects who spent 60 to 90 days in continuous 6 head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 deg at a peak velocity of approximately 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender and compared with spaceflight data. RESULTS: Although no gender differences were found, bed rest induced changes in reflex latency and CV similar to the ones observed during spaceflight. Also, a relationship between CV and loss of muscle strength in the lower leg was observed for most bed rest subjects. CONCLUSION: Even though bed rest (limb unloading) alone may not mimic all of the synaptic and muscle tissue loss that is observed as a result of spaceflight, it can serve as a working analog of flight for the evaluation of potential countermeasures that may be beneficial in mitigating unwanted changes in the major postural muscles that are observed post flight.

The NASA Bed Rest Project

NASA Technical Reports Server (NTRS)

Rhodes, Bradley; Meck, Janice

2005-01-01

NASA s National Vision for Space Exploration includes human travel beyond low earth orbit and the ultimate safe return of the crews. Crucial to fulfilling the vision is the successful and timely development of countermeasures for the adverse physiological effects on human systems caused by long term exposure to the microgravity environment. Limited access to in-flight resources for the foreseeable future increases NASA s reliance on ground-based analogs to simulate these effects of microgravity. The primary analog for human based research will be head-down bed rest. By this approach NASA will be able to evaluate countermeasures in large sample sizes, perform preliminary evaluations of proposed in-flight protocols and assess the utility of individual or combined strategies before flight resources are requested. In response to this critical need, NASA has created the Bed Rest Project at the Johnson Space Center. The Project establishes the infrastructure and processes to provide a long term capability for standardized domestic bed rest studies and countermeasure development. The Bed Rest Project design takes a comprehensive, interdisciplinary, integrated approach that reduces the resource overhead of one investigator for one campaign. In addition to integrating studies operationally relevant for exploration, the Project addresses other new Vision objectives, namely: 1) interagency cooperation with the NIH allows for Clinical Research Center (CRC) facility sharing to the benefit of both agencies, 2) collaboration with our International Partners expands countermeasure development opportunities for foreign and domestic investigators as well as promotes consistency in approach and results, 3) to the greatest degree possible, the Project also advances research by clinicians and academia alike to encourage return to earth benefits. This paper will describe the Project s top level goals, organization and relationship to other Exploration Vision Projects, implementation strategy, address Project deliverables, schedules and provide a status of bed rest campaigns presently underway.

Artificial Gravity as a Multi-System Countermeasure to Bed Rest Deconditioning: Preliminary Results

NASA Technical Reports Server (NTRS)

Warren, L. E.; Paloski, William H.; Young, L. R.

2006-01-01

Artificial gravity paradigms may offer effective, efficient, multi-system protection from the untoward effects of adaptation to the microgravity of space or the hypogravity of planetary surfaces. Intermittent artificial gravity (AG) produced by a horizontal short-radius centrifuge (SRC) has recently been utilized on human test subjects deconditioned by bed rest. This presentation will review preliminary results of a 41 day study conducted at the University of Texas Medical Branch, Galveston, TX bed rest facility. During the first eleven days of the protocol, subjects were ambulatory, but confined to the facility. They began a carefully controlled diet, and participated in multiple baseline tests of bone, muscle, cardiovascular, sensory-motor, immunological, and psychological function. On the twelfth day, subjects entered the bed rest phase of the study, during which they were confined to strict 6deg head down tilt bed rest for 21 days. Beginning 24 hrs into this period, treatment subjects received one hour daily exposures to artificial gravity which was produced by spinning the subjects on a 3.0 m radius SRC. They were oriented radially in the supine position so that the centrifugal force was aligned with their long body axis, and while spinning, they "stood" on a force plate, supporting the centrifugal loading (2.5 g at the feet, 1.0 g at the heart). The subject station allowed free translation over approximately 10 cm to ensure full loading of the lower extremities and to allow for anti-orthostatic muscle contractions. Control subjects were positioned on the centrifuge but did not spin. Following the bed rest phase, subjects were allowed to ambulate again, but remained within the facility for an additional 9 days and participated in multiple follow-up tests of physiological function.

Effect of enforced physical inactivity induced by 60-day of bed rest on hepatic markers of NAFLD in healthy normal-weight women.

PubMed

Rudwill, Floriane; Bergouignan, Audrey; Gastebois, Caroline; Gauquelin-Koch, Guillemette; Lefai, Etienne; Blanc, Stéphane; Simon, Chantal

2015-06-01

Physical inactivity leads to a cluster of metabolic disorders that have been associated with non-alcoholic fatty liver diseases. We tested whether physical inactivity increases hepatic biomarkers of NAFLDs. Sixteen normal-weight healthy women (body mass index = 21.2 ± 0.5 kg/m(2) ) were studied under controlled energy balance conditions during a previous 60-day bed rest with (n = 8) or without (n = 8) a combined aerobic/resistive exercise protocol. Stored samples were retrospectively used to measure plasma hepatic markers, i.e. steatosis-related alanine and aspartate transaminases, cytokeratin 18 and angiopoietin-like 3, at baseline, after 30 and 60 days of bed rest. Fasting insulin and triglycerides were measured at baseline and after 30 days of bed rest. Two indexes were calculated, one combining alanine and aspartate transaminase and cytokeratin 18 and another cytokeratin 18, homeostasis model assessment of insulin resistance and aspartate aminotransferase. Sixty days of bed rest increased all hepatic markers (P < 0.05 for all) and the two indexes (P < 0.01 for both). Exercise significantly reduced the elevation in aspartate transaminase, cytokeratin 18 and both indexes (P < 0.02 for all) but not the increase in alanine transaminase and angiopoietin-like 3. Changes between baseline and 30 days of bed rest in triglycerides were positively associated with changes in aspartate transaminase (R(2) = 0.28, P = 0.04) suggesting a role of hypertriglyceridaemia in the alteration of liver metabolism under inactive conditions. Physical inactivity increases, independent of fat mass, hepatic markers of steatosis and steatohepatitis. Regular exercise can limit these physical inactivity-induced metabolic alterations. Future studies need to elucidate the underlying mechanisms. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of exercise on fluid exchange and body composition in man during 14-day bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Bernauer, E. M.; Juhos, L. T.; Young, H. L.; Morse, J. T.; Staley, R. W.

1977-01-01

A description is presented of an investigation in which body composition, fluid intake, and fluid and electrolyte losses were measured in seven normal, healthy men during three 2-wk bed-rest periods, separated by two 3-wk recovery periods. During bed rest the subjects remained in the horizontal position continuously. During the dietary control periods, body mass decreased significantly with all three regimens, including no exercise, isometric exercise, and isotonic excercise. During bed rest, body mass was essentially unchanged with no exercise, but decreased significantly with isotonic and isometric exercise. With one exception, there were no statistically significant changes in body density, lean body mass, or body fat content by the end of each of the three bed-rest periods.

LBNP/ergometer effects on female cardiovascular and muscle deconditioning in 15d head-down bed rest

NASA Astrophysics Data System (ADS)

Wang, Lin-Jie

2012-07-01

Female has already been an important part of astronaut corps but gender characteristics in weightlessness and countermeasure effects still not clearly elucidated. In this study the LBNP/Ergometer effects on female cardiovascular deconditioning and muscle atrophy in 15d head-down bed rest were explored. 22 female university students were recruited as volunteers that participated in the 15d head-down bed rest. They were divided into control group (Con,n=8), LBNP exercise group (LBNP,n=7) and LBNP combined with ergometer exercise group (LBNP+Ergo, n=7). Grade negative pressures of -10,-20,-30,-40mmHg 20 or 55min were used in LBNP exercise. In ergometer exercises the subjects must maintain 60-80% VO2peak of pre-bed rest at pedal speed of about 70cycle/min for 15min and the entire exercise duration was 30min. LBNP were performed at 6th,8th,10th,12th,and 13th day and Ergometer were operated at 4th,5th,7th,9th,11th day during bed rest. Before and after bed rest, cardiovascular tilt test were performed to evaluate orthostatic intolerance, supine cycle ergometer were used to test the cardiopulmonary function, MRI tests were operated to examine the volume variations of leg muscle groups and isokinetic test were given to test the muscle strength and endurance of knee. 40% of female subjects did not pass the tilt table test after bed rest and exercises made no difference. Compared with pre-BR, VO2max and VO2max /body weight, VO2/HRmax, maximal power and duration significantly decreased in CON group and LBNP group. For the ERGO+LBNP group, there were no visible different in the parameters of cardiopulmonary function except that maximal power and duration decreased. Muscle maximal voluntary contraction and muscle (quadriceps, rectus femoris, gastrocnemius and soleus) volume decreasing in non-predominant leg was larger in Con group than in LBNP+Ergo group. It is suggested that LBNP combined with ergometer in some degrees can counteract the cardiovascular and muscle deconditioning induced by 15d head-down bed rest.

Granular controls on the dispersion of bed load tracers

NASA Astrophysics Data System (ADS)

Jerolmack, D. J.; Martin, R. L.; Phillips, C. B.

2014-12-01

Coarse particles are transported in a river as bed load, i.e., they move in frequent contact with and are supported by the granular bed. This movement is typically intermittent and may be described by a series of steps are rests, the distributions of which determine particle dispersion. Laboratory and field studies of bed load tracer dispersion have reported sub- and super-diffusive behavior, both of which have been successfully reproduced with stochastic transport models. Although researchers have invoked heavy-tailed step lengths as the cause of anomalous dispersion, most observations report thin-tailed distributions. Little attention has been paid to rest periods, and stochastic transport models have not been connected to the underlying mechanics of particle motion. Based on theoretical and experimental evidence, we argue that step lengths are thin-tailed and do not control the longterm dispersion of bed load tracers; they are determined by momentum balance between the fluid and solid. Using laboratory experiments with both marbles and natural sediments, we demonstrate that the rest time distribution is power law, and argue that this distribution controls asymptotic dispersion. Observed rest times far exceed any hydrodynamic timescale. Experiments reveal that rest times of deposited particles are governed by fluctuations in river bed elevation; in particular, the return time for the bed to scour to the base of a deposited particle. Stochastic fluctuations in bed elevation are describable by an Ornstein-Uhlenbeck (mean-reverting random walk) model that contains two parameters, which we show are directly related to the granular shear rate and range of bed elevation fluctuations, respectively. Combining these results with the theory of asymmetric random walks (particles only move downstream), we predict superdiffusive behavior that is in quantitative agreement with our observations of tracer dispersion in a natural river.

Logistic Risk Model for the Unique Effects of Inherent Aerobic Capacity on (+)G(sub z) Tolerance Before and After Simulated Weightlessness

NASA Technical Reports Server (NTRS)

Ludwig, David A.; Convertino, Victor A.; Goldwater, Danielle J.; Sandler, Harold

1987-01-01

Small sample size (n less than 1O) and inappropriate analysis of multivariate data have hindered previous attempts to describe which physiologic and demographic variables are most important in determining how long humans can tolerate acceleration. Data from previous centrifuge studies conducted at NASA/Ames Research Center, utilizing a 7-14 d bed rest protocol to simulate weightlessness, were included in the current investigation. After review, data on 25 women and 22 men were available for analysis. Study variables included gender, age, weight, height, percent body fat, resting heart rate, mean arterial pressure, Vo(sub 2)max and plasma volume. Since the dependent variable was time to greyout (failure), two contemporary biostatistical modeling procedures (proportional hazard and logistic discriminant function) were used to estimate risk, given a particular subject's profile. After adjusting for pro-bed-rest tolerance time, none of the profile variables remained in the risk equation for post-bed-rest tolerance greyout. However, prior to bed rest, risk of greyout could be predicted with 91% accuracy. All of the profile variables except weight, MAP, and those related to inherent aerobic capacity (Vo(sub 2)max, percent body fat, resting heart rate) entered the risk equation for pro-bed-rest greyout. A cross-validation using 24 new subjects indicated a very stable model for risk prediction, accurate within 5% of the original equation. The result for the inherent fitness variables is significant in that a consensus as to whether an increased aerobic capacity is beneficial or detrimental has not been satisfactorily established. We conclude that tolerance to +Gz acceleration before and after simulated weightlessness is independent of inherent aerobic fitness.

Improvements and validation of the erythropoiesis control model for bed rest simulation

NASA Technical Reports Server (NTRS)

Leonard, J. I.

1977-01-01

The most significant improvement in the model is the explicit formulation of separate elements representing erythropoietin production and red cell production. Other modifications include bone marrow time-delays, capability to shift oxyhemoglobin affinity and an algorithm for entering experimental data as time-varying driving functions. An area of model development is suggested by applying the model to simulating onset, diagnosis and treatment of a hematologic disorder. Recommendations for further improvements in the model and suggestions for experimental application are also discussed. A detailed analysis of the hematologic response to bed rest including simulation of the recent Baylor Medical College bed rest studies is also presented.

WISE 2005-2006: 60-days of Head-Down Bed Rest Increases the Incidence of Menstrual Cycle Disruption

NASA Astrophysics Data System (ADS)

Wade, Charles

Objective: It has been suggested that acute bed rest of short duration (11 days) disrupts the menstrual cycle of healthy subjects. Furthermore, use of countermeasures such as heavy exercise or dietary manipulations may adversely effect the menstrual cycle. We hypothesized that bed rest of 60 days and the use of countermeasures would increase the incidence of disruption of the menstrual cycle (MC). Methods: Twenty-four healthy subjects with a mean age of 32±0.8 yr, body mass of 59±0.8 kg and MC lengths of 25-32 days were enrolled. Three months prior to the study subjects did not use hormonal birth control methods. Subjects were assigned to one of three groups (n=8 per group): control, exercise countermeasures, and dietary countermeasures. MC lengthening was defined as an increase in duration of 10 or more days. Analysis was performed accounting for the effects of bedrest as well as treatment group. Results: Effects of countermeasures were not significant in the present analysis. After the conclusion of the study, subjects were classified as either normal (N; n=16) or oligomenorrhea (O; n=8) as determined by MC length during the pre-bed rest (PB) and bed rest (BR) periods. During the control period prior to bed rest one subject (4%) had an increase MC length. During the control period the average MC length was 31±0.8 days with a leutinizing hormone (LH) surge 12±0.8 days prior to menses. The duration of menses was 4±0.4 days. During BR there was an increase to 33% (p¡0.05) in the number of subjects having MC lengthening. In these subjects the mean length was increased from 31±0.9 to 62±8.2 days (p¡0.05). There was no change in the period from the LH surge prior to the next menses, 11±0.8 days, or duration of menses, 4±0.2 days. Plasma LH, follicle stimulating hormone (FSH), prolacin (PRL), progesterone (PRG), estradiol (E2), dehydroepiandrosterone sulfate (DHEA-S), aldosterone (Aldo), testosterone (T) and cortisol (C) were measured during PB, BR, early post bed rest (day 0-day 60;EPBR) and late post bed rest (day 60-day 367;LPBR). Plasma PRG was significantly higher (p¡0.02) in the N group before BR and continued throughout the BR period. A significant difference in E2 was observed in the N group between PB and BR, BR and EPBR, and EPBR and LPBR (p¡0.01). E2 was significantly different between N and O during BR (p¡0.02). No differences were observed in the other plasma measurements. Daily urine samples demonstrated no changes in C or Aldo over the course of the study. At 6 and 12 months following completion of the study all subjects reported normal MC. Conclusion: The lengthening of menstrual cycle during bed rest is a result of a delay in ovulation due to the absence of a LH surge (ovulation) associated with lower PRG and E2 levels. In females, changes in menstrual cycles may be a contributing factor to the adverse responses to bed rest such as loss of bone mass, reductions in blood volume and decreased work performance.

Exercise Effects on the Brain and Sensorimotor Function in Bed Rest

NASA Technical Reports Server (NTRS)

Koppelmans, V.; Cassady, K.; De Dios, Y. E.; Szecsy, D.; Gadd, N.; Wood, S. J.; Reuter-Lorenz, R. A.; Kofman, I.; Bloomberg, J. J.; Mulavara, A. P.;

Focal Gray Matter Plasticity as a Function of Long Duration Head-down Tilt Bed Rest

NASA Technical Reports Server (NTRS)

Koppelmans, Vincent; Erdeniz, Burak; DeDios, Yiri; Wood, Scott; Reuter-Lorenz, Patricia; Kofman, Igor; Bloomberg, Jacob; Mulavara, Ajitkumar; Seidler, Rachael

2014-01-01

Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether these sensorimotor changes may be related to structural and functional brain changes is yet unknown. However, increased intracranial pressure that by itself has been related to microgravity-induced bodily fluid shifts: [1] has been associated with white matter microstructural damage, [2] Thus, it is possible that spaceflight may affect brain structure and thereby cognitive functioning. Long duration head-down tilt bed rest has been suggested as an exclusionary analog to study microgravity effects on the sensorimotor system, [3] Bed rest mimics microgravity in body unloading and bodily fluid shifts. In consideration of the health and performance of crewmembers both in- and post-flight, we are conducting a prospective longitudinal 70-day bed rest study as an analog to investigate the effects of microgravity on brain structure, and [4] Here we present results of the first eight subjects.

Automated electroencephalography system and electroencephalographic correlates of space motion sickness, part 2. [sleep characteristics

NASA Technical Reports Server (NTRS)

Frost, J. D., Jr.

1976-01-01

Sleep pattern alterations were detected in two subjects by electroencephalographic, electrographic, and electromyographic monitoring before, during and after a 28 day bed rest. Standardized criteria were used for data analysis. During the second half of the bed-rest period, sleep latency and stage 3 increased, while total sleep time, stage 2, and REM latency decreased. In addition, during bed rest both subjects showed an increase in the number of REM periods and a slight increase in stage REM amount. No major alterations were seen in the recovery period. Of the alterations found to be associated with bed rest, only one, the increase in stage 3 sleep, was also seen consistently during Skylab. Conversely, none of the postflight changes seen following Skylab were observed during the post-bed-rest recovery period.

Effects of head-down-tilt bed rest on cerebral hemodynamics during orthostatic stress

NASA Technical Reports Server (NTRS)

Zhang, R.; Zuckerman, J. H.; Pawelczyk, J. A.; Levine, B. D.; Blomqvist, C. G. (Principal Investigator)

1997-01-01

Our aim was to determine whether the adaptation to simulated microgravity (microG) impairs regulation of cerebral blood flow (CBF) during orthostatic stress and contributes to orthostatic intolerance. Twelve healthy subjects (aged 24 +/- 5 yr) underwent 2 wk of -6 degrees head-down-tilt (HDT) bed rest to simulate hemodynamic changes that occur when humans are exposed to microG. CBF velocity in the middle cerebral artery (transcranial Doppler), blood pressure, cardiac output (acetylene rebreathing), and forearm blood flow were measured at each level of a ramped protocol of lower body negative pressure (LBNP; -15, -30, and -40 mmHg x 5 min, -50 mmHg x 3 min, then -10 mmHg every 3 min to presyncope) before and after bed rest. Orthostatic tolerance was assessed by using the cumulative stress index (CSI; mmHg x minutes) for the LBNP protocol. After bed rest, each individual's orthostatic tolerance was reduced, with the group CSI decreased by 24% associated with greater decreases in cardiac output and greater increases in systemic vascular resistance at each level of LBNP. Before bed rest, mean CBF velocity decreased by 14, 10, and 45% at -40 mmHg, -50 mmHg, and maximal LBNP, respectively. After bed rest, mean velocity decreased by 16% at -30 mmHg and by 21, 35, and 39% at -40 mmHg, -50 mmHg, and maximal LBNP, respectively. Compared with pre-bed rest, post-bed-rest mean velocity was less by 11, 10, and 21% at -30, -40, and -50 mmHg, respectively. However, there was no significant difference at maximal LBNP. We conclude that cerebral autoregulation during orthostatic stress is impaired by adaptation to simulated microG as evidenced by an earlier and greater fall in CBF velocity during LBNP. We speculate that impairment of cerebral autoregulation may contribute to the reduced orthostatic tolerance after bed rest.

Changes in Cartilage Morphology of the Knee after 14-days of Bed Rest

NASA Astrophysics Data System (ADS)

Liphardt, A.-M.; Mündermann, A.; Koo, S.; Bäcker, N.; Andriacchi, T.; Zange, J.; Mester, J.; Heer, M.

Introduction While there are still many unanswered questions related to the effects of space flight and disuse on cartilage health and cartilage morphology the number of in vivo experiments in humans is small For muscle and bone tissue it is well known that unloading results in degeneration of those tissues Also for cartilage previous studies in patients suggest that unloading causes cartilage degeneration Studies using immobilization as a model of unloading help to investigate the importance of experiencing mechanical loads for the maintenance of healthy biological tissues The goal of our study was to investigate whether bed rest induced immobilization has a negative effect on articular cartilage in healthy subjects and if vibration training is a potential counter-measure for these negative effects Methods Eight male healthy subjects 78 1 pm 9 5 kg 179 pm 9 6 cm 26 pm 5 years performed a 14-day bed rest in 6 r -head down tilt HDT The study was designed in a cross-over-design where each subject received a training intervention vib in one phase and no intervention con in the other phase During the training intervention subjects trained 2 x 5-minutes per day at 20 Hz with 2 -- 4 mm amplitude on a vibration plate Galileo 900 Magnet resonance MR imaging of the right knee was performed to measure articular cartilage thickness MR-images 2 mm slice thickness 0 35 mm x 0 35 mm in-plane resolution 448 x 512 pixels were taken before and after bed rest to investigate the effects of bed rest

Cardiac and Vascular Function in Bedrested Volunteers: Effects of Artificial Gravity Training

NASA Technical Reports Server (NTRS)

Meng, M.; Platts, S.; Stenger, M.; Diedrich, A.; Schlegel, T.; Natapoff, A.; Knapp, C.; Evans, J.

2007-01-01

Cardiovascular effects of an artificial gravity (AG) countermeasure on deconditioned male volunteers were studied. In two groups of men we measured cardiovascular parameters at rest and in response to 30 minutes of 80 deg. head up tilt (HUT) before, at the end of, and four days following 21 days of 6 deg. head down bed rest (HDBR). One group (N=7) underwent no countermeasure while the other (N=8) received a daily, one hour, dose (2.5 gz at the foot, decreasing to 1.0 gz at the heart) of AG training on the Johnson Space Center short radius centrifuge. Cardiovascular parameters measured included heart rate, blood pressure, stroke volume, cardiac output, peripheral vascular resistance, plasma volume shifts, and vasoactive hormones. Untrained subjects exhibited shorter tilt survival (on average 8 minutes shorter) compared to trained subjects. By the end of bed rest, mean heart rate (MHR) was elevated in both groups (both supine and during tilt). In addition, treated subjects demonstrated lower, tilt-induced, increases in MHR four days following HDBR, indicating a more rapid return to pre bed rest conditions. Results from an index of autonomic balance (percentage of MHR spectral power in the respiratory frequency range) in control of heart rate are consistent with the interpretation that parasympathetic nervous system withdrawal was responsible for both tilt- and bed rest-induced increases in MHR. Our data support our pre-study hypothesis that AG treatment would lessen cardiovascular effects of deconditioning in bed rested men and suggest that AG should be further pursued as a space flight countermeasure.

Circadian rhythm asynchrony in man during hypokinesis.

NASA Technical Reports Server (NTRS)

Winget, C. M.; Vernikos-Danellis, J.; Cronin, S. E.; Leach, C. S.; Rambaut, P. C.; Mack, P. B.

1972-01-01

Posture and exercise were investigated as synchronizers of certain physiologic rhythms in eight healthy male subjects in a defined environment. Four subjects exercised during bed rest. Body temperature (BT), heart rate, plasma thyroid hormone, and plasma steroid data were obtained from the subjects for a 6-day ambulatory equilibration period before bed rest, 56 days of bed rest, and a 10-day recovery period after bed rest. The results indicate that the mechanism regulating the circadian rhythmicity of the cardiovascular system is rigorously controlled and independent of the endocrine system, while the BT rhythm is more closely aligned to the endocrine system.

Artificial Gravity as a Multi-System Countermeasure: Effects on Cognitive Function

NASA Technical Reports Server (NTRS)

Sipes, Walter E.; Seaton, Kim; Slack, Kellely; Bowie, Kendra

2007-01-01

The Space Flight Cognitive Assessment Tool for Windows (WinSCAT) is a medical requirement on the International Space Station, and its purpose is to evaluate cognitive functioning after physical insult (e.g., head trauma, decompression sickness, exposure to toxic gases, medication side effects). The current objective is to assess cognitive functioning in a long duration space mission analog environment where Artificial Gravity is being applied as a countermeasure in a Bed Rest study. Methods: Fifteen male subjects (8 treatment and 7 control) who participated in 21 days of -6 degree head-down bed rest were assessed. Three practice and three baseline WinSCAT test sessions were administered during the pre-bed rest phase of study participation. During the bed rest phase, the WinSCAT test was scheduled every other day, following the centrifuge, for a total of 10 test sessions. (The treatment group received 60 minutes of centrifugation each day during the 21 days of bed rest. The control subjects were strapped to the centrifuge for the same length of time as the treatment group but were not spun.) During the post-bed rest (reconditioning) phase, the test was administered 4 times. Results: Individual differences were found both within and between the treatment and control groups. After controlling for the number of subjects in each group, the treatment group accounted for more off-nominal WinSCAT scores than the control group. Conclusions:There is some preliminary evidence that centrifuge spinning might negatively impact cognitive functioning. However, due to sample size limitations, it cannot be ascertained whether there were significant differences in cognitive performance between the treatment and control groups. If centrifugation had a negative effect on cognitive functioning, consistent decrements would be expected to be found with all treatment subjects across time. Individual differences in underlying cognitive ability and motivation level are other possible explanations for the results found in this study.

Alendronate and Resistive Exercise Countermeasures Against Bed Rest-Induced Bone Loss: Biochemical Markers of Bone and Calcium Metabolism

NASA Technical Reports Server (NTRS)

Smith, Scott M.; Nillen, Jeannie L.; Davis-Street, Janis E.; DeKerlegand, Diane E.; LeBlanc, Adrian; Shackelford, Linda C.

2001-01-01

Weightlessness-induced bone loss must be counteracted to ensure crew health during extendedduration space missions. Studies were conducted to assess two bone loss countermeasures in a ground-based model: horizontal bed rest. Following a 3-wk ambulatory adaptation period, male and female subjects (aged 21-56 y) completed a 17-wk bed rest protocol. Subjects were assigned to one of three treatments: alendronate (ALEN; 10 mg/d, n=6), resistive exercise (RE; 1.5 h/d, 6 d/wk, n=8), or control (CN; no countermeasure, n=8). Dietary intake was adjusted to maintain body weight. Endocrine and biochemical indices were measured in blood and urine using standard laboratory methods. All data reported are expressed as percent change from individual pre-bedrest data. Serum calcium changed little during bed rest, and tended to decrease (4-8%) in ALEN subjects. In RE subjects, bone alkaline phosphatase and osteocalcin were increased >65 and >30%, respectively, during bed rest, while these were unchanged or decreased in ALEN and CN subjects. Urinary calcium was increased 50% in CN subjects, but was unchanged or decreased in both ALEN and RE groups. Urinary n-telopeptide excretion was increased 40-50% in CN and RE subjects, but decreased 20% in ALEN subjects. Pyridinium crosslink and deoxypyridinoline excretion were increased 20-50% during bed rest. These data suggest that RE countermeasures are effective at increasing markers of bone formation in an analog of weightlessness, while ALEN reduces markers of bone resorption. Counteracting the bone loss of space flight may require both pharmacologic and exercise countermeasures.

Plasma lactic dehydrogenase activities in men during bed rest with exercise training

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Juhos, L. T.; Young, H. L.

1985-01-01

Peak oxygen uptake and the activity of lactic dehydrogenase (LDH-T) and its five isoenzymes were measured by spectrophotometer in seven men before, during, and after bed rest and exercise training. Exercise training consisted of isometric leg exercises of 250 kcal/hr for a period of one hour per day. It is found that LDH-T was reduced by 0.05 percent in all three regimens by day 10 of bed rest, and that the decrease occurred at different rates. The earliest reduction in LDH-T activity in the no-exercise regimen was associated with a decrease in peak oxygen uptake of 12.3 percent. It is concluded that isometric (aerobic) muscular strength training appear to maintain skeletal muscle integrity better during bed rest than isotonic exercise training. Reduced hydrostatic pressure during bed rest, however, ultimately counteracts the effects of both moderate isometric and isotonic exercise training, and may result in decreased LDH-T activity.

Physiological responses to prolonged bed rest in humans: A compendium of research, 1981-1988

NASA Technical Reports Server (NTRS)

Luu, Phuong B.; Ortiz, Vanessa; Barnes, Paul R.; Greenleaf, John E.

1990-01-01

Clinical observations and results form more basic studies that help to elucidate the physiological mechanisms of the adaptation of humans to prolonged bed rest. If the authors' abstract or summary was appropriate, it was included. In some cases a more detailed synopsis was provided under the subheadings of purpose, methods, results, and conclusions.

Bed Rest is an Analog to Study the Physiological Changes of Spaceflight and to Evaluate Countermeasures

NASA Technical Reports Server (NTRS)

Pfannenstiel, P.; Ottenbacher, M.; Inniss, A.; Ware, D.; Anderson, K.; Stranges, S.; Keith, K.; Cromwell, R.; Neigut. J.; Powell, D.

2012-01-01

The UTMB/NASA Flight Analog Research Unit is an inpatient unit with a bionutrition kitchen and unique testing areas for studying subjects subjected to 6 degree head-down complete bed rest for prolonged periods as an analog for zero gravity. Bed rest allows study of physiological changes and performance of functional tasks representative of critical interplanetary mission operations and measures of the efficacy of countermeasures designed to protect against the resulting deleterious effects. METHODS/STUDY POPULATION: Subjects are healthy adults 24-55 years old; 60 75 in tall; body mass index 18.5-30; and bone mineral density normal by DXA scan. Over 100 subjects have been studied in 7 campaigns since 2004. The iRAT countermeasure combines high intensity interval aerobic exercises on alternating days with continuous aerobic exercise. Resistance exercise is performed 3 days per week. Subjects are tested on an integrated suite of functional and interdisciplinary physiological tests before and after 70 days of total bed rest. RESULTS/ANTICIPATED RESULTS: It is anticipated that post-bed rest functional performance will be predicted by a weighted combination of sensorimotor, cardiovascular and muscle physiological factors. Control subjects who do not participate in the exercise countermeasure will have significantly greater decreases in these parameters. DISCUSSION/SIGNIFICANCE OF IMPACT: Astronauts experience alterations in multiple physiological systems due to exposure to the microgravity, leading to disruption in the ability to perform functional tasks after reintroduction to a gravitational environment. Current flight exercise countermeasures are not fully protective of cardiovascular, muscle and bone health. There is a need to refine and optimize countermeasures to mitigate health risks associated with long-term space missions.

Gradient Compression Stockings may Prevent Recovery after Bed Rest Deconditioning

NASA Technical Reports Server (NTRS)

Stenger, Michael B.; Lee, Stuart M.; Westby, Christian M.; Willig, Michael C.; Platts, Steven H.

2011-01-01

Introduction: Astronauts continue to wear a compression garment during and immediately after landing to prevent orthostatic intolerance (OI). We recently developed a custom-fitted, 3-piece garment that consists of thigh-high stockings with biker-style shorts that provides continuous, gradient compression: 55 mmHg at the ankle that decreases to approximately 20 mmHg at the top of the leg and 15 mmHg over the abdomen. This garment has been shown to be effective in preventing symptoms of OI during a short stand test after Space Shuttle missions, but symptoms may persist for several days after a long-duration mission in some astronauts. The purpose of this study was to confirm the effectiveness of wearing these elastic, gradient compression garments during orthostatic testing after 2 weeks of 6 degree head-down tilt bed rest as a model of spaceflight and to determine whether they would impact recovery after bed rest. Methods: Eight (5 treatment, 3 control) of 16 subjects have completed this study to-date. All subjects wore the 3-piece garment from waking until tilt testing (3 h) as a simulation of the timeline for astronauts on landing day (BR+0). Control subjects removed the garment after the tilt test. Treatment subjects wore the garment for the remainder of the day and wore lower compression thigh-high only garments on the day after bed rest (BR+1). Blood pressure, heart rate, and stroke volume responses to a 15-min 80 degree head-up tilt test were determined before 2 weeks of 6 degree head-down tilt, and on BR+0 and BR+1. Plasma volume (PV) was measured before each of these test sessions. Data are mean SE. Results: Compression garments prevented signs of OI on BR+0; all subjects in both groups completed the full 15-min test. Heart rate responses to tilt were lower on BR+0 than all other test days. Control subjects demonstrated a marginal PV decrease after bed rest, but showed typical recovery the day after bed rest (BR+0: 2.32 plus or minus 0.15 L to BR+1: 2.79 plus or minus 0.15 L). Treatment subjects did not recover PV the day after bed rest (BR+0: 2.61 plus or minus 0.23 L to BR+1: 2.61 plus or minus 0.23 L). Conclusion: Abdomen-high compression garments, which are effective in preventing post-bed rest orthostatic intolerance, may slow recovery of PV. Modified garments with reduced compression may be necessary to prevent prolonging recovery.

PlanHab study: assessment of psycho-neuroendocrine function in male subjects during 21 d of normobaric hypoxia and bed rest.

PubMed

Strewe, C; Zeller, R; Feuerecker, M; Hoerl, M; Kumprej, I; Crispin, A; Johannes, B; Debevec, T; Mekjavic, I; Schelling, G; Choukèr, A

2017-03-01

Immobilization and hypoxemia are conditions often seen in patients suffering from severe heart insufficiency or primary pulmonary diseases (e.g. fibrosis, emphysema). In future planned long-duration and exploration class space missions (including habitats on the moon and Mars), healthy individuals will encounter such a combination of reduced physical activity and oxygen tension by way of technical reasons and the reduced gravitational forces. These overall unconventional extraterrestrial conditions can result in yet unknown consequences for the regulation of stress-permissive, psycho-neuroendocrine responses, which warrant appropriate measures in order to mitigate foreseeable risks. The Planetary Habitat Simulation Study (PlanHab) investigated these two space-related conditions: bed rest as model of reduced gravity and normobaric hypoxia, with the aim of examining their influence on psycho-neuroendocrine responses. We hypothesized that both conditions independently increase measures of psychological stress and enhance neuroendocrine markers of stress, and that these effects would be exacerbated by combined treatment. The cross-over study composed of three interventions (NBR, normobaric normoxic horizontal bed rest; HBR, normobaric hypoxic horizontal bed rest; HAMB, normobaric hypoxic ambulatory confinement) with 14 male subjects during three sequential campaigns separated by 4 months. The psychological state was determined through three questionnaires and principal neuroendocrine responses were evaluated by measuring cortisol in saliva, catecholamine in urine, and endocannabinoids in blood. The results revealed no effects after 3 weeks of normobaric hypoxia on psycho-neuroendocrine responses. Conversely, bed rest induced neuroendocrine alterations that were not influenced by hypoxia.

Effects of Long Duration Spaceflight on Venous and Arterial Compliance: Bed Rest

NASA Technical Reports Server (NTRS)

Ribeiro, L. Christine; Platts, Steven H.; Laurie, Steven S.; Lee, Stuart M. C.; Martin, David S.; Ploutz-Snyder, Robert J.; Stenger, Michael B.

2017-01-01

The primary objective was to determine whether a high sodium diet during bed rest induced alterations in vascular compliance and was related to the incidence of VIIP. Ocular structural and functional measures and vascular ultrasound of the head and neck were acquired in bed rest subjects completing 10-14 days in 6deg head-down tilt.

Zinc, copper, and nitrogen balances during bed rest and fluoride supplementation in healthy adult males

NASA Technical Reports Server (NTRS)

Krebs, J. M.; Schneider, V. S.; LeBlanc, A. D.

1988-01-01

The effects of bed rest and fluoride supplementation on zinc, copper, and nitrogen balances and Zn and Cu serum levels were measured in 15 healthy males. Subjects aged 19-54 y remained on a metabolic research ward for 10 wk. During weeks 1-5, subjects were ambulatory. During wks 6-10 they remained in continuous bed rest. During weeks 3-10 nine subjects received 10 or 20 mg F/d as sodium fluoride. Daily urine and weekly fecal composites were made and biweekly fasting blood samples were taken. Dietary intakes were 1.40 +/- 0.17 mg Cu/d (22.0 +/- 2.7 mumol Cu/d), 10.82 +/- 0.49 mg Zn/d (165.6 +/- 7.6 mumol Zn/d), and 14.27 +/- 0.23 g N/d (1019 +/- 16 mmol N/d). Bed rest increased urinary Zn and N excretions and fecal Zn excretions and decreased Zn balance (p less than 0.05) whereas Cu balance was unchanged. During bed rest, F supplementation increased Zn and N balances compared with untreated control subjects (p less than 0.05). These results are compatible with bone and muscle atrophy during bed rest and increased bone formation with F supplementation.

Effects of long-duration bed rest on structural compartments of m. soleus in man

NASA Technical Reports Server (NTRS)

Belozerova, I.; Shenkman, B.; Mazin, M.; Leblanc, A.; LeBlanc, A. D. (Principal Investigator)

2001-01-01

Magnetic resonance imaging (MRI), histomorphometry and electron microscopy of muscle demonstrate that long-term exposure to actual or simulated weightlessness (including head down bed rest) leads to decreased volume of antigravity muscles in mammals. In muscles interbundle space is occupied by the connective tissue. Rat studies show that hindlimb unloading induces muscle fiber atrophy along with increase in muscle non-fiber connective tissue compartment. Beside that, usually 20% of the muscle fiber volume is comprised by non-contractile (non-myofibrillar) compartment. The aim of the present study was to compare changes in muscle volume, and in muscle fiber size with alterations in myofibrillar apparatus, and in connective tissue compartment in human m. soleus under conditions of 120 day long head down bed rest (HDBR).

Increased Brain Activation for Foot Movement During 70-Day 6 Deg Head-Down Bed Rest (HDBR): Evidence from Functional Magnetic Resonance Imaging (fMRI)

NASA Technical Reports Server (NTRS)

Yuan, P.; Koppelmans, V.; Cassady, K.; Cooke, K.; De Dios, Y. E.; Stepanyan, V.; Szecsy, D.; Gadd, N.; Wood, S. J.; Reuter-Lorenz, P. A.;

The Metabolic Cost of a High Intensity Exercise Program During Bed Rest

NASA Technical Reports Server (NTRS)

Hackney, Kyle; Everett, Meghan; Guined, Jamie; Cunningham, Daid

2012-01-01

Background: Given that disuse-related skeletal muscle atrophy may be exacerbated by an imbalance between energy intake and output, the amount of energy required to complete exercise countermeasures is an important consideration in the well being of subject health during bed rest and spaceflight. Objective: To evaluate the energy cost of a high intensity exercise program performed during short duration bed rest. Methods: 9 subjects (8 male and 1 female; 34.5 +/- 8.2 years) underwent 14 days of bed rest and exercise countermeasures. Exercise energy expenditure and excess post exercise oxygen consumption (EPOC) were collected once in each of 5 different exercise protocols (30 second, 2 minute and 4 minute intervals, continuous aerobic and a variety of resistance exercises) during bed rest. Body mass, basal metabolic rate (BMR), upper and lower leg muscle, subcutaneous, and intramuscular adipose tissue (IMAT) volumes were assessed before and at the end of bed rest. Results: There were no significant differences in body mass (pre: 75.1 +/- 10.5 kg; post: 75.2 +/- 10.1 kg), BMR (pre: 1649 +/- 216 kcal; post: 1657 +/- 177 kcal), muscle subcutaneous, or IMAT volumes (Table 2) after 14 days of bed rest and exercise. Body mass was maintained with an average daily intake of 2710 +/- 262 kcal (36.2 +/- 2.1 kcal/kg/day), while average daily energy expenditure was 2579 +/-311 kcal (34.5 +/- 3.6 kcal/kg/day). Exercise energy expenditure was significantly greater as a result of continuous aerobic exercise than all other exercise protocols.

Lunar Analog Feasibility Study Results

NASA Technical Reports Server (NTRS)

Cromwell, Ronita L.; Neigut, Joe

2009-01-01

This slide presentation reviews a study designed to determine the feasibility of using a 9.5 deg head-up tilt bed rest model to simulate the effects of the 1/6 g load to the human body that exists on the lunar surface. The effect of different types of compression stockings, the pre-bed rest diet, and the use of a specific exercise program were reviewed for comfort, force verification and plasma volume shift

Induced venous pooling and cardiorespiratory responses to exercise after bed rest

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Sandler, H.; Webb, P.; Annis, J. F.

1982-01-01

Venous pooling induced by a specially constructed garment is investigated as a possible means for reversing the reduction in maximal oxygen uptake regularly observed following bed rest. Experiments involved a 15-day period of bed rest during which four healthy male subjects, while remaining recumbent in bed, received daily 210-min venous pooling treatments from a reverse gradient garment supplying counterpressure to the torso. Results of exercise testing indicate that while maximal oxygen uptake endurance time and plasma volume were reduced and maximal heart rate increased after bed rest in the control group, those parameters remained essentially unchanged for the group undergoing venous pooling treatment. Results demonstrate the importance of fluid shifts and venous pooling within the cardiovascular system in addition to physical activity to the maintenance of cardiovascular conditioning.

The use of actimetry to assess changes to the rest-activity cycle.

PubMed

Carvalho Bos, Sandra; Waterhouse, Jim; Edwards, Ben; Simons, Ries; Reilly, Thomas

2003-11-01

The endogenous circadian oscillator (the body clock) is slow to adjust to altered rest-activity patterns. As a result, several negative consequences arise during night work and after time-zone transitions. The process of adjustment can be assessed by measurements of the sleep electroencephalogram (EEG), core temperature or melatonin secretion, for example, but these techniques are very difficult to apply in field studies, and make very great demands upon both experimenters and subjects. We have sought to establish if the activity record, measured conveniently and unobtrusively by a monitor attached to the wrist, can be treated in ways that enable estimates to be made of the disruption caused by changes to the rest-activity cycle, and the process of adjustment to them. In Part A, we describe the calculation and assessment of a series of "activity indices" that measure the overall activity pattern, activity when out of bed or in bed, or the activity in the hours adjacent to going to bed or getting up. The value of the indices was assessed by measuring changes to them in subjects undergoing night work or undergoing time-zone transitions. In both cases, there is a large body of literature describing the changes that would be expected. First, night workers (working 2 to 4 successive night shifts) were investigated during rest days and night shifts. The indices indicated that night work was associated with lower activity when the subjects were out of bed and higher activity when in bed. Some indices also measured when subjects took an afternoon nap before starting a series of night shifts and gave information about the process of adjustment to night work and recovery from it. Second, in studies from travelers crossing six or more time zones to the east or west, the indices indicated that there were changes to the rest-activity cycle immediately after the flights, both in its overall profile and when activity of the subjects in bed or out of bed was considered, and that adjustment took place on subsequent days. By focusing on those indices describing the activity records during the last hour in bed (LHIB) and the first hour out of bed (FHOB), some evidence was found for incomplete adjustment of the body clock, and for differences between westward and eastward flights. In Part B, the battery of indices are applied to the activity records of long-haul pilots, whose activity patterns showed a mixture of effects due to night work and time-zone transitions. Actimetry was performed during the flights themselves and during the layover days (which were either rest or work days). The indices indicated that all pilots had disrupted rest-activity cycles caused by night flights, and that there were added problems for those who had also undergone time-zone transitions. Rest days were valuable for normalizing the activity profile. For those pilots who flew to the west, adjustment was by delay, though not all aspects of the rest-activity cycle adjusted immediately; for those who flew to the east, some attempted to advance their rest-activity cycle while others maintained home-based activity profiles. The indices indicated that the activity profile was disrupted more in those pilots who attempted to advance their rest-activity cycle. We conclude that objective estimates of the disruption caused to the rest-activity cycle and the circadian system can be obtained by suitable analysis of the activity record.

Evaluation of potentially significant increase of lead in the blood during long-term bed rest and space flight.

PubMed

Kondrashov, Vladislav; Rothenberg, Stephen J; Chettle, David; Zerwekh, Joseph

2005-02-01

We address a gap in the knowledge of lead turnover under conditions of prolonged bed rest and microgravity by developing a quantitative model of the amount of lead returned to blood circulation from bone. We offer the hypothesis that skeletal unloading, such as typically occurs during extended bed rest or microgravity, will result in bone lead being released to the blood, as has already been demonstrated in the case of calcium. We use initial bone lead concentrations to develop predictive models of blood lead elevation. Our theoretical calculations with typical bone lead loads measured in today's 40-60-year-old generation, suggest that the estimated blood lead concentrations in long duration (e.g., 100 days) space flight could average between 20 and 40 microg dl(-1), a range with well-established toxic effects. For a similar duration of bed rest, estimated blood lead concentration could be as high as 10-20 microg dl(-1), which is a level of concern, particularly if we consider females of childbearing age. The preliminary experimental results were obtained under multi-institutional collaborations, with the main outcome received from an on-going bed rest study, Prevention of Microgravity-Induced Stone Risk by KMgCitrate, conducted at the General Clinical Research Center (GCRC) of the University of Texas Southwestern Medical Center, Dallas. Based on theoretical modeling and some preliminary experimental results, this concept may have important clinical implications by allowing prediction of the magnitude of blood lead elevation, thereby establishing the means to prevent lead toxicity during long duration space flight of astronauts and in conditions of prolonged bed rest such as complicated pregnancy, spinal cord injury induced paralysis and comatose patients.

One Week of Bed Rest Leads to Substantial Muscle Atrophy and Induces Whole-Body Insulin Resistance in the Absence of Skeletal Muscle Lipid Accumulation.

PubMed

Dirks, Marlou L; Wall, Benjamin T; van de Valk, Bas; Holloway, Tanya M; Holloway, Graham P; Chabowski, Adrian; Goossens, Gijs H; van Loon, Luc J C

2016-10-01

Short (<10 days) periods of muscle disuse, often necessary for recovery from illness or injury, lead to various negative health consequences. The current study investigated mechanisms underlying disuse-induced insulin resistance, taking into account muscle atrophy. Ten healthy, young males (age: 23 ± 1 years; BMI: 23.0 ± 0.9 kg · m(-2)) were subjected to 1 week of strict bed rest. Prior to and after bed rest, lean body mass (dual-energy X-ray absorptiometry) and quadriceps cross-sectional area (CSA; computed tomography) were assessed, and peak oxygen uptake (VO2peak) and leg strength were determined. Whole-body insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. Additionally, muscle biopsies were collected to assess muscle lipid (fraction) content and various markers of mitochondrial and vascular content. Bed rest resulted in 1.4 ± 0.2 kg lean tissue loss and a 3.2 ± 0.9% decline in quadriceps CSA (both P < 0.01). VO2peak and one-repetition maximum declined by 6.4 ± 2.3 (P < 0.05) and 6.9 ± 1.4% (P < 0.01), respectively. Bed rest induced a 29 ± 5% decrease in whole-body insulin sensitivity (P < 0.01). This was accompanied by a decline in muscle oxidative capacity, without alterations in skeletal muscle lipid content or saturation level, markers of oxidative stress, or capillary density. In conclusion, 1 week of bed rest substantially reduces skeletal muscle mass and lowers whole-body insulin sensitivity, without affecting mechanisms implicated in high-fat diet-induced insulin resistance. © 2016 by the American Diabetes Association.

Collagen cross-link excretion during space flight and bed rest

NASA Technical Reports Server (NTRS)

Smith, S. M.; Nillen, J. L.; Leblanc, A.; Lipton, A.; Demers, L. M.; Lane, H. W.; Leach, C. S.; LeBlanc, A. (Principal Investigator)

1998-01-01

Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this bone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PYD) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short (14-day) and long (119-day) bed-rest studies. During space flight, the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden.

Exercise Training During Bed Rest Attenuates Deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Hargens, Alan R. (Technical Monitor)

1995-01-01

A 30-day 6 deg. head-down bed rest study was conducted to evaluate high-intensity, short-duration, alternating isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent isokinetic exercise (IKE) training regiments designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (acclimation) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volume, (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (a) attenuated the decrease in peak VO2 by 50%, (b) attenuated loss of red cell volume by 40%, but had no effect on loss of plasma volume, (c) induced positive body water balance, (d) had no adverse effect on quality of sleep or concentration, and (e) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regiments, and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

Clinical physiology of bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1993-01-01

Maintenance of optimal health in humans requires the proper balance between exercise, rest, and sleep as well as time in the upright position. About one-third of a lifetime is spent sleeping; and it is no coincidence that sleeping is performed in the horizontal position, the position in which gravitational influence on the body is minimal. Although enforced bed rest is necessary for the treatment of some ailments, in some cases it has probably been used unwisely. In addition to the lower hydrostatic pressure with the normally dependent regions of the cardiovascular system, body fuid compartments during bed rest in the horizontal body position, and virtual elimination of compression on the long bones of the skeletal system during bed rest (hypogravia), there is often reduction in energy metabolism due to the relative confinement (hypodynamia) and alteration of ambulatory circadian variations in metabolism, body temperature, and many hormonal systems. If patients are also moved to unfamiliar surroundings, they probably experience some feelings of anxiety and some sociopsychological problems. Adaptive physiological responses during bed rest are normal for that environment. They are attempts by the body to reduce unnecessary energy expenditure, to optimize its function, and to enhance its survival potential. Many of the deconditioning responses begin within the first day or two of bed rest; these early responses have prompted physicians to insist upon early resumption of the upright posture and ambulation of bedridden patients.

Thyroid and adrenal cortical rhythmicity during bed rest.

NASA Technical Reports Server (NTRS)

Vernikos-Danellis, J.; Leach, C. S.; Winget, C. M.; Rambaut, P. C.; Mack, P. B.

1972-01-01

The effects of prolonged bed rest on adrenocortical and thyroid function were assessed in eight healthy males, aged 20-40 years, who were submitted to bed rest for 56 days on a 14L:10D regimen (lights-on, 9:00 AM). Four of these subjects exercised three times daily throughout the experiment. Circulating cortisol, triiodothyronine, and thyroxine, concentrations were determined in blood samples drawn at four hourly intervals for 48-hr periods before, 10, 20, 30, 42, and 54 days during, and 10 days post-bed rest. Significant fluctuations in the circulating levels of all three hormones occurred with peaks at 7:30 AM. The suggestion is advanced that thyroid rhythms may be posture dependent.

Exercise Responses after Inactivity

NASA Technical Reports Server (NTRS)

Convertino, Victor A.

1986-01-01

The exercise response after bed rest inactivity is a reduction in the physical work capacity and is manifested by significant decreases in oxygen uptake. The magnitude of decrease in maximal oxygen intake V(dot)O2max is related to the duration of confinement and the pre-bed-rest level of aerobic fitness; these relationships are relatively independent of age and gender. The reduced exercise performance and V(dot)O2max following bed rest are associated with various physiological adaptations including reductions in blood volume, submaximal and maximal stroke volume, maximal cardiac output, sceletal muscle tone and strength, and aerobic enzyme capacities, as well as increases in venous compliance and submaximal and maximal heart rate. This reduction in physiological capacity can be partially restored by specific countermeasures that provide regular muscular activity or orhtostatic stress or both during the bed rest exposure. The understanding of these physiological and physical responses to exercise following bed rest inactivity has important implications for the solution to safety and health problems that arise in clinical medicine, aerospace medicine, sedentary living, and aging.

In vivo bone remodeling rates determination and compressive stiffness variations before, during 60 days bed rest and two years follow up: A micro-FE-analysis from HR-pQCT measurements of the berlin Bed Rest Study-2

NASA Astrophysics Data System (ADS)

Ritter, Zully; Belavy, Daniel; Baumann, Wolfgang W.; Felsenberg, Dieter

2017-03-01

Bed rest studies are used for simulation and study of physiological changes as observed in unloading/non-gravity environments. Amongst others, bone mass reduction, similar as occurring due to aging osteoporosis, combined with bio-fluids redistribution and muscle atrophy have been observed and analyzed. Advanced radiological methods of high resolution such as HR-pQCT (XtremeCT) allow 3D-visualizing in vivo bone remodeling processes occurring during absence/reduction of mechanical stimuli (0 to <1 g) as simulated by bed rest. Induced bone micro-structure (e.g. trabecular number, cortical thickness, porosity) and density variations can be quantified. However, these parameters are average values of each sample and important information regarding bone mass distribution and within bone mechanical behaviour is lost. Finite element models with hexa-elements of identical size as the HR-pQCT measurements (0.082 mm×0.082 mm×0.082 mm, ca. 7E6 elements/sample) can be used for subject-specific in vivo stiffness calculation. This technique also allows quantifying if bone microstructural changes represent a risk of mechanical bone collapse (fracture).

Hormonal regulation of fluid and electrolytes during prolonged bed rest - Implications for microgravity

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1989-01-01

The results of studies on the physiological changes of body fluids and electrolytes during bed rest with and without exercise training are overviewed to determine the effect of exercise and to assess the role of hormonal regulation in fluid-electrolyte responses to hypogravity. Special attention is given to fluid shifts observed in spacecraft personnel during space missions. It is concluded that, despite an apparent uncoupling of prominent hormonal interactions during bed-rest deconditioning (and, possibly, during microgravity), the exercise-training-induced hypervolemia helps to counter the hypohydrostatic-induced dehydration. Thus, it was found that, after nearly a year of spaceflight during which one cosmonaut exercised for about 4 hr per day, the water balance and physiological functioning were not disturbed significantly.

Nitrosative stress in human skeletal muscle attenuated by exercise countermeasure after chronic disuse.

PubMed

Salanova, Michele; Schiffl, Gudrun; Gutsmann, Martina; Felsenberg, Dieter; Furlan, Sandra; Volpe, Pompeo; Clarke, Andrew; Blottner, Dieter

2013-01-01

Activity-induced nitric oxide (NO) imbalance and "nitrosative stress" are proposed mechanisms of disrupted Ca(2+) homeostasis in atrophic skeletal muscle. We thus mapped S-nitrosylated (SNO) functional muscle proteins in healthy male subjects in a long-term bed rest study (BBR2-2 Study) without and with exercise as countermeasure in order to assess (i) the negative effects of chronic muscle disuse by nitrosative stress, (ii) to test for possible attenuation by exercise countermeasure in bed rest and (iii) to identify new NO target proteins. Muscle biopsies from calf soleus and hip vastus lateralis were harvested at start (Pre) and at end (End) from a bed rest disuse control group (CTR, n=9) and two bed rest resistive exercise groups either without (RE, n=7) or with superimposed vibration stimuli (RVE, n=7). At subcellular compartments, strong anti-SNO-Cys immunofluorescence patterns in control muscle fibers after bed rest returned to baseline following vibration exercise. Total SNO-protein levels, Nrf-2 gene expression and nucleocytoplasmic shuttling were changed to varying degrees in all groups. Excess SNO-protein levels of specific calcium release/uptake proteins (SNO-RyR1, -SERCA1 and -PMCA) and of contractile myosin heavy chains seen in biopsy samples of chronically disused skeletal muscle were largely reduced by vibration exercise. We also identified NOS1 as a novel NO target in human skeletal muscle controlled by activity driven auto-nitrosylation mechanisms. Our findings suggest that aberrant levels of functional SNO-proteins represent signatures of uncontrolled nitrosative stress management in disused human skeletal muscle that can be offset by exercise as countermeasure.

Space-flight simulations of calcium metabolism using a mathematical model of calcium regulation

NASA Technical Reports Server (NTRS)

Brand, S. N.

1985-01-01

The results of a series of simulation studies of calcium matabolic changes which have been recorded during human exposure to bed rest and space flight are presented. Space flight and bed rest data demonstrate losses of total body calcium during exposure to hypogravic environments. These losses are evidenced by higher than normal rates of urine calcium excretion and by negative calcium balances. In addition, intestinal absorption rates and bone mineral content are assumed to decrease. The bed rest and space flight simulations were executed on a mathematical model of the calcium metabolic system. The purpose of the simulations is to theoretically test hypotheses and predict system responses which are occurring during given experimental stresses. In this case, hypogravity occurs through the comparison of simulation and experimental data and through the analysis of model structure and system responses. The model reliably simulates the responses of selected bed rest and space flight parameters. When experimental data are available, the simulated skeletal responses and regulatory factors involved in the responses agree with space flight data collected on rodents. In addition, areas within the model that need improvement are identified.

Energy absorption, lean body mass, and total body fat changes during 5 weeks of continuous bed rest

NASA Technical Reports Server (NTRS)

Krebs, Jean M.; Evans, Harlan; Kuo, Mike C.; Schneider, Victor S.; Leblanc, Adrian D.

1990-01-01

The nature of the body composition changes due to inactivity was examined together with the question of whether these changes are secondary to changes in energy absorption. Volunteers were 15 healthy males who lived on a metabolic research ward under close staff supervision for 11 weeks. Subjects were ambulatory during the first six weeks and remained in continuous bed rest for the last five weeks of the study. Six male volunteers (age 24-61 years) were selected for body composition measurements. Nine different male volunteers (age 21-50 years) were selected for energy absorption measurements. The volunteers were fed weighed conventional foods on a constant 7-d rotation menu. The average daily caloric content was 2,592 kcal. Comparing the five weeks of continuous bed rest with the previous six weeks of ambulation, it was observed that there was no change in energy absorption or total body weight during bed rest, but a significant decrease in lean body mass and a significant increase in total body fat (p less than 0.05).

Pyridoxic acid excretion during low vitamin B-6 intake, total fasting, and bed rest

NASA Technical Reports Server (NTRS)

Coburn, S. P.; Thampy, K. G.; Lane, H. W.; Conn, P. S.; Ziegler, P. J.; Costill, D. L.; Mahuren, J. D.; Fink, W. J.; Pearson, D. R.; Schaltenbrand, W. E.

1995-01-01

Vitamin B-6 metabolism in 10 volunteers during 21 d of total fasting was compared with results from 10 men consuming a diet low only in vitamin B-6 (1.76 mumol/d) and with men consuming a normal diet during bed rest. At the end of the fast mean plasma concentrations of vitamin B-6 metabolites and urinary excretion of 4-pyridoxic acid tended to be higher in the fasting subjects than in the low-vitamin B-6 group. The fasting subjects lost approximately 10% of their total vitamin B-6 pool and approximately 13% of their body weight. The low-vitamin B-6 group lost only approximately 4% of their vitamin B-6 pool. Compared with baseline, urinary excretion of pyridoxic acid was significantly increased during 17 wk of bed rest. There was no increase in pyridoxic acid excretion during a second 15-d bed rest study. These data suggest the possibility of complex interactions between diet and muscle metabolism that may influence indexes that are frequently used to assess vitamin B-6 status.

Mean 24-hours sympathetic nervous system activity decreases during head-down tilted bed rest but not during microgravity

NASA Astrophysics Data System (ADS)

Christensen, Nj; Heer, M.; Ivanova, K.; Norsk, P.

Sympathetic nervous system activity is closely related to gravitational stress in ground based experiments. Thus a high activity is present in the standing-up position and a very low activity is observed during acute head-out water immersion. Adjustments in sympathetic activity are necessary to maintain a constant blood pressure during variations in venous return. Head-down tilted bed rest is applied as a model to simulate changes observed during microgravity. The aim of the present study was to test the hypothesis that mean 24-hours sympathetic activity was low and similar during space flight and in ground based observation obtained during long-term head-down tilted bed rest. Forearm venous plasma noradrenaline was measured by a radioenzymatic technique as an index of muscle sympathetic activity and thrombocyte noradrenaline and adrenaline were measured as indices of mean 24-hours sympathoadrenal activity. Previous results have indicated that thrombocyte noradrenaline level has a half-time of 2 days. Thus to reflect sympathetic activity during a specific experiment the study period must last for at least 6 days and a sample must be obtained within 12 hours after the experiment has ended. Ten normal healthy subjects were studied before and during a 14 days head-down tilted bed rest as well as during an ambulatory study period of a similar length. The whole experiment was repeated while the subjects were on a low calorie diet. Thrombocyte noradrenaline levels were studied in 4 cosmonauts before and within 12 hours after landing after more than 7 days in flight. Thrombocyte noradrenaline decreased markedly during the head-down tilted bed rest (p<0.001), whereas there were no significant changes in the ambulatory study. Plasma noradrenaline decreased in the adaptation period but not during the intervention. During microgravity thrombocyte noradrenaline increased in four cosmonauts and the percentage changes were significantly different in cosmonauts and in subjects participating in the head down tilted bed rest study (170± 29% (Mean± SEM) vs. 57± 7%, respectively; p<0.001). The elevated sympathetic nervous system activity is most likely a regulatory response to combined effects of a reduced plasma volume and an increased vascular capacity in flight.

An overview of the issues: physiological effects of bed rest and restricted physical activity

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Bloomfield, S. A.; Greenleaf, J. E.

1997-01-01

Reduction of exercise capacity with confinement to bed rest is well recognized. Underlying physiological mechanisms include dramatic reductions in maximal stroke volume, cardiac output, and oxygen uptake. However, bed rest by itself does not appear to contribute to cardiac dysfunction. Increased muscle fatigue is associated with reduced muscle blood flow, red cell volume, capillarization and oxidative enzymes. Loss of muscle mass and bone density may be reflected by reduced muscle strength and higher risk for injury to bones and joints. The resultant deconditioning caused by bed rest can be independent of the primary disease and physically debilitating in patients who attempt to reambulate to normal active living and working. A challenge to clinicians and health care specialists has been the identification of appropriate and effective methods to restore physical capacity of patients during or after restricted physical activity associated with prolonged bed rest. The examination of physiological responses to bed rest deconditioning and exercise training in healthy subjects has provided significant information to develop effective rehabilitation treatments. The successful application of acute exercise to enhance orthostatic stability, daily endurance exercise to maintain aerobic capacity, or specific resistance exercises to maintain musculoskeletal integrity rather than the use of surgical, pharmacological, and other medical treatments for clinical conditions has been enhanced by investigation and understanding of underlying mechanisms that distinguish physical deconditioning from the disease. This symposium presents an overview of cardiovascular and musculoskeletal deconditioning associated with reduced physical work capacity following prolonged bed rest and exercise training regimens that have proven successful in ameliorating or reversing these adverse effects.

The effect of 8 days of strict bed rest on the incretin effect in healthy volunteers.

PubMed

Nielsen, Signe Tellerup; Harder-Lauridsen, Nina Majlund; Benatti, Fabiana Braga; Wedell-Neergaard, Anne-Sophie; Lyngbæk, Mark Preben; Møller, Kirsten; Pedersen, Bente Klarlund; Krogh-Madsen, Rikke

2016-03-15

Bed rest and physical inactivity are the consequences of hospital admission for many patients. Physical inactivity induces changes in glucose metabolism, but its effect on the incretin effect, which is reduced in, e.g., Type 2 diabetes, is unknown. To investigate how 8 days of strict bed rest affects the incretin effect, 10 healthy nonobese male volunteers underwent 8 days of strict bed rest. Before and after the intervention, all volunteers underwent an oral glucose tolerance test (OGTT) followed by an intravenous glucose infusion (IVGI) on the following day to mimic the blood glucose profile from the OGTT. Blood glucose, serum insulin, serum C-peptide, plasma incretin hormones [glucagon-like peptide (GLP-1) and glucose-dependent insulinotropic peptide (GIP)], and serum glucagon were measured serially during both the OGTT and the IVGI. The incretin effect is calculated as the relative difference between the area under the curve for the insulin response during the OGTT and that of the corresponding IVGI, respectively. Concentrations of glucose, insulin, C-peptide, and GIP measured during the OGTT were higher after the bed rest intervention (all P < 0.05), whereas there was no difference in the levels of GLP-1 and Glucagon. Bed rest led to a mean loss of 2.4 kg of fat-free mass, and induced insulin resistance evaluated by the Matsuda index, but did not affect the incretin effect (P = 0.6). In conclusion, 8 days of bed rest induces insulin resistance, but we did not see evidence of an associated change in the incretin effect. Copyright © 2016 the American Physiological Society.

Calcium kinetics during bed rest with artificial gravity and exercise countermeasures

PubMed Central

Smith, S. M.; Castaneda-Sceppa, C.; O’Brien, K. O.; Abrams, S. A.; Gillman, P.; Brooks, N. E.; Cloutier, G. J.; Heer, M.; Zwart, S. R.; Wastney, M. E.

2015-01-01

Summary We assessed the potential for countermeasures to lessen the loss of bone calcium during bed rest. Subjects ingested less calcium during bed rest, and with artificial gravity, they also absorbed less calcium. With exercise, they excreted less calcium. To retain bone during bed rest, calcium intake needs to be maintained. Introduction This study aims to assess the potential for artificial gravity (AG) and exercise (EX) to mitigate loss of bone calcium during space flight. Methods We performed two studies: (1) a 21-day bed rest (BR) study with subjects receiving 1 h/day AG (n=8) or no AG (n=7) and (2) a 28-day BR study with 1 h/day resistance EX (n=10) or no EX (n=3). In both studies, stable isotopes of Ca were administered orally and intravenously, at baseline and after 10 days of BR, and blood, urine, and feces were sampled for up to 14 days post dosing. Tracers were measured using thermal ionization mass spectrometry. Data were analyzed by compartmental modeling. Results Less Ca was absorbed during BR, resulting in lower Ca balance in BR+AG (−6.04±3.38 mmol/day, P=0.023). However, Ca balance did not change with BR+EX, even though absorbed Ca decreased and urinary Ca excretion increased, because endogenous excretion decreased, and there was a trend for increased bone deposition (P=0.06). Urinary N-telopeptide excretion increased in controls during BR, but not in the EX group. Markers of bone formation were not different between treatment groups for either study. Ca intake decreased during BR (by 5.4 mmol/day in the AG study and 2.8 mmol/day in the EX study), resulting in lower absorbed Ca. Conclusions During BR (or space flight), Ca intake needs to be maintained or even increased with countermeasures such as exercise, to enable maintenance of bone Ca. PMID:24861908

Understanding the Effects of Long-duration Space Flight on Astronant Functional Task Performance

NASA Technical Reports Server (NTRS)

Bloomberg, Jacob J.; Batson, Crystal D.; Buxton, Roxanne E.; Feiveson, Al H.; Kofman, Igor S.; Lee, Stuart M. C.; Miller, Chris A.; Mulavara, Ajitkumar P.; Peters, Brian T.; Phillips, Tiffany;

Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest.

PubMed

Stremel, R W; Convertino, V A; Bernauer, E M; Greenleaf, J E

1976-12-01

Bed rest deconditioning was assessed in seven healthy men (19-22 yr) following three 14-day periods of controlled activity during recumbency by measuring submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate, and plasma volume. Exercise regimens were performed in the supine position and included a) two 30-min periods daily of intermittent static exercise at 21% of maximal leg extension force, and b) two 30-min periods of dynamic bicycle ergometer exercise daily at 68% of VO2max. No prescribed exercise was performed during the third bed rest period. Compared with their respective pre-bed rest control values, VO2max decreased (P less than 0.05) under all exercise conditions; -12.3% with no exercise, -9.2% with dynamic exercise, but only -4.8% with static exercise. Maximal heart rate was increased by 3.3% to 4.9% (P less than 0.05) under the three exercise conditions, while plasma volume decreased (P less than 0.05) -15.1% with no exercise and -10.1% with static, but only -7.8% (NS) with dynamic exercise. Since neither the static nor dynamic exercise training regimes minimized the changes in all the variables studied, some combination of these two types of exercise may be necessary for maximum protection from the effects of the bed deconditioning.

Psychological Stress Can Be Decreased by Traditional Thai Massage.

PubMed

Sripongngam, Thanarat; Eungpinichpong, Wichai; Sirivongs, Dhavee; Kanpittaya, Jaturat; Tangvoraphonkchai, Kamonwan; Chanaboon, Sutin

2015-06-01

The purpose of this study was to investigate the immediate effects of traditional Thai massage (TTM) on psychological stress and heart rate variability (HRV). Thirty healthy participants were randomly allocated in two groups, a TTM group (n = 15) who received a 1-hour session with moderate pressure of whole body TTM or a control group (n=15) who rested on the bedfor 1 hour All ofthem were given a 10-minute mental arithmetic test to induce psychological stress after which they received a 1-hour session of TTM or bed rest. Psychological stress and HR V were measured at baseline and immediately after mental arithmetic test, and immediately after TTM or bed rest. The studyfound that psychological stress was signficantly increased (p<0.05) after mental arithmetic test in both groups. Comparison on these measures between immediately after mental arithmetic test and after TTM or bed rest revealed that psychological stress was significantly decreased (p<0.05) and HR Vwas significantly increased (p<0.05) in both groups. Root mean square of successive differences (RMSSD) and low frequency were significantly increased (p<0.05) only in the TTM group. However; all of these measures were found without significant difference when groups were compared. TTM and bed rest could decrease psychological stress and HRV

Effect of heat acclimation on sitting orthostatic tolerance in the heat after 48 and 96 hour bed rest in men

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Matter, M., Jr.

1995-01-01

The purpose of this pilot study was to investigate sitting orthostatic tolerance and determine potentially adverse signs and symptoms that would incapacitate subjects in a hot environment (Gemini reentry cabin temperature profile) after 48 hr and 96 hr of horizontal bed rest (BR), which simulated microgravity deconditioning. Six college men (23-29 yr) were allocated into two groups: heat acclimated (three subjects: No. 1- control, No. 2- 48 hr BR, and No. 3- 96 hr BR) and nonheat acclimated (three subjects: No. 4- control, No. 5- 48 hr BR, and No. 6- 96 hr BR). After BR they sat in an ambient temperature of 57 C (135 F) for 30 min which then was decreased to 49 C (120 F) for up to 480 min. Tolerance time in the heat with seated orthostatic stress was 480 min (subject No. 1) and 180 min (subject No. 4) in the two ambulatory men, but was reduced to 22-150 min in the four bed-rested men irrespective of their heat acclimation status. Although heat acclimation appeared to enhance tolerance and attenuate accompanying physiological responses, as well as ameliorate the frequency and intensity of adverse signs and symptoms at termination of exposure, tolerance was reduced in the bed-rest deconditioned subjects regardless of their acclimation level. Thus, these few collective findings do not indicate an unequivocal positive effect of acute heat acclimation on sitting orthostatic tolerance in acute bed-rest deconditioned subjects.

Countermeasures against lumbar spine deconditioning in prolonged bed rest: resistive exercise with and without whole body vibration.

PubMed

Belavý, Daniel L; Armbrecht, Gabriele; Gast, Ulf; Richardson, Carolyn A; Hides, Julie A; Felsenberg, Dieter

2010-12-01

To evaluate the effect of short-duration, high-load resistive exercise, with and without whole body vibration on lumbar muscle size, intervertebral disk and spinal morphology changes, and low back pain (LBP) incidence during prolonged bed rest, 24 subjects underwent 60 days of head-down tilt bed rest and performed either resistive vibration exercise (n = 7), resistive exercise only (n = 8), or no exercise (n = 9; 2nd Berlin Bed-Rest Study). Discal and spinal shape was measured from sagittal plane magnetic resonance images. Cross-sectional areas (CSAs) of the multifidus, erector spinae, quadratus lumborum, and psoas were measured on para-axial magnetic resonance images. LBP incidence was assessed with questionnaires at regular intervals. The countermeasures reduced CSA loss in the multifidus, lumbar erector spinae and quadratus lumborum muscles, with greater increases in psoas muscle CSA seen in the countermeasure groups (P ≤ 0.004). There was little statistical evidence for an additional effect of whole body vibration above resistive exercise alone on these muscle changes. Exercise subjects reported LBP more frequently in the first week of bed rest, but this was only significant in resistive exercise only (P = 0.011 vs. control, resistive vibration exercise vs. control: P = 0.56). No effect of the countermeasures on changes in spinal morphology was seen (P ≥ 0.22). The results suggest that high-load resistive exercise, with or without whole body vibration, performed 3 days/wk can reduce lumbar muscle atrophy, but further countermeasure optimization is required.

Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest

NASA Technical Reports Server (NTRS)

Stremel, R. W.; Convertino, V. A.; Bernauer, E. M.; Greenleaf, J. E.

1976-01-01

Results are presented for an experimental study designed to compare the effects of heavy static and dynamic exercise training during 14 days of bed rest on the cardiorespiratory responses to submaximal and maximal exercise performed by seven healthy men aged 19-22 yr. The parameters measured were submaximal and maximal oxygen uptake, minute ventilation, heart rate, and plasma volume. The results indicate that exercise alone during bed rest reduces but does not eliminate the reduction in maximal oxygen uptake. An additional positive hydrostatic effect is therefore necessary to restore maximal oxygen uptake to ambulatory control levels. The greater protective effect of static exercise on maximal oxygen uptake is probably due to a greater hydrostatic component from the isometric muscular contraction. Neither the static nor the dynamic exercise training regimes are found to minimize the changes in all the variables studied, thereby suggesting a combination of static and dynamic exercises.

Characteristics of fast voluntary and electrically evoked isometric knee extensions during 56 days of bed rest with and without exercise countermeasure

PubMed Central

Gerrits, K. H. L.; Rittweger, J.; Felsenberg, D.; Stegeman, D. F.; de Haan, A.

2008-01-01

The contractile characteristics of fast voluntary and electrically evoked unilateral isometric knee extensions were followed in 16 healthy men during 56 days of horizontal bed rest and assessed at bed rest days 4, 7, 10, 17, 24, 38 and 56. Subjects were randomized to either an inactive control group (Ctrl, n = 8) or a resistive vibration exercise countermeasure group (RVE, n = 8). No changes were observed in neural activation, indicated by the amplitude of the surface electromyogram, or the initial rate of voluntary torque development in either group during bed rest. In contrast, for Ctrl, the force oscillation amplitude at 10 Hz stimulation increased by 48% (P < 0.01), the time to reach peak torque at 300 Hz stimulation decreased by 7% (P < 0.01), and the half relaxation time at 150 Hz stimulation tended to be slightly reduced by 3% (P = 0.056) after 56 days of bed rest. No changes were observed for RVE. Torque production at 10 Hz stimulation relative to maximal (150 Hz) stimulation was increased after bed rest for both Ctrl (15%; P < 0.05) and RVE (41%; P < 0.05). In conclusion, bed rest without exercise countermeasure resulted in intrinsic speed properties of a faster knee extensor group, which may have partly contributed to the preserved ability to perform fast voluntary contractions. The changes in intrinsic contractile properties were prevented by resistive vibration exercise, and voluntary motor performance remained unaltered for RVE subjects as well. PMID:18386049

Physiological responses to prolonged bed rest and fluid immersion in man: A compendium of research (1974 - 1980)

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Silverstein, L.; Bliss, J.; Langenheim, V.; Rosson, H.; Chao, C.

1982-01-01

Water immersion and prolonged bed rest reproduce nearly all the physiological responses observed in astronauts in the weightless state. Related to actual weightlessness, given responses tend to occur sooner in immersion and later in bed rest. Much research was conducted on humans using these two techniques, especially by Russian scientists. Abstracts and annotations of reports that appeared in the literature from January 1974 through December 1980 are compiled and discussed.

Symposium Conclusion: Women's cardiovascular health after bed rest or space flight

NASA Astrophysics Data System (ADS)

Hughson, Richard L.; Arbeille, Phillipe; Shoemaker, Kevin; Edgell, Heather

The Canadian Space Agency has recently funded research on two long-duration missions to study cardiovascular deconditioning associated with bed rest or space flight. The first, Women's International Space simulation for Exploration (WISE-2005) examined the responses during a 60-day head down bed rest (HDBR) of 24 women with or without a countermeasure that consisted of supine treadmill running within a lower body negative pressure (LBNP) device followed by 10-minutes resting LBNP and on different days high intensity resistance exercise on a flywheel device. The second study, Cardiovascular and cerebrovascular Control on return from the International Space Station (CCISS) is currently underway with two male astronauts tested and the first woman anticipated later this year. Women have been previously identified as being more susceptible to orthostatic intolerance than men after both bed rest and space flight studies. Thus, in the WISE-2005 study we examined responses of the cardiovascular system after HDBR in women and compared these to previously published data from men. We found that after HDBR women have a greater increase in heart rate with infusion of the drug isoproterenol and this was consistent with observations in men. However, during drug infusion the women had a reduction in leg vascular resistance while men had an increase. The exercise countermeasure group had preserved heart rate and leg vascular resistance responses to drug infusion. The ability to vasoconstrict the legs and splanchnic region is critical to maintenance of upright posture after HDBR and space flight. In the WISE-2005 study, subjects who were able to constrict the legs and/or splanchnic region after HDBR were much less likely to have a marked drop in blood pressure before the end of 10-minutes upright tilt, and subjects who performed the countermeasure were more likely to be in this group of tilt test finishers. These data provide new insight into mechanisms that might be responsible for fainting after bed rest or space flight, and they can be used to understand why specific populations such as the elderly might be more likely to faint during life on Earth. Supported by Canadian Space Agency.

Physiological responses to prolonged bed rest and fluid immersion in humans

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1984-01-01

For many centuries, physicians have used prolonged rest in bed and immersion in water in the treatment of ailments and disease. Both treatments have positive remedial effects. However, adverse physiological responses become evident when patients return to their normal daily activities. The present investigation is concerned with an analysis of the physiological changes during bed rest and the effects produced by water immersion. It is found that abrupt changes in body position related to bed rest cause acute changes in fluid compartment volumes. Attention is given to fluid shifts and body composition, renal function and diuresis, calcium and phosphorus metabolism, and orthostatic tolerance. In a discussion of water immersion, fluid shifts are considered along with cardiovascular-respiratory responses, renal function, and natriuretic and diuretic factors.

Indices of Psychological Strain During Hypoxis Bedrest

NASA Astrophysics Data System (ADS)

Stavrou, Nektarios A.; McDonnell, Adam C.; Eiken, Ola; Mekjavic, Igor B.

2013-02-01

Much attention has been devoted to the physiological changes that occur during bed rest. However, there has been a lack of focus on the psychological aspects per se. We investigated indices of psychological strain during three 10-d interventions, designed to assess the combined effects of inactivity/unloading and normobaric hypoxia on several physiological systems. Eleven male participants underwent three 10-d campaigns in a randomized manner: 1) normobaric hypoxic ambulatory confinement (HAMB), 2) normobaric hypoxic bed rest (HBR) and 3) normoxic bed rest (NBR). The most negative psychological profile appeared on BR10 of HBR and HAmb conditions (hypoxic conditions). Concomitantly a decrease in positive emotions was observed from BR-2 to BR10. Bed rest and exposure to hypoxic environments seems to exert a negative effect on person’s psychological mood.

NASA's Functional Task Test: Providing Information for an Integrated Countermeasure System

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Feiveson, A. H.; Laurie, S. S.; Lee, S. M. C.; Mulavara, A. P.; Peters, B. T.; Platts, S. H.; Ploutz-Snyder, L. L.; Reschke, M. F.; Ryder, J. W.;

Understanding the Effects of Spaceflight on Head-trunk Coordination During Walking and Obstacle Avoidance

NASA Technical Reports Server (NTRS)

Madansingh, S.; Bloomberg, J. J.

2014-01-01

Prolonged exposure to spaceflight conditions results in a battery of physiological changes, some of which contribute to sensorimotor and neurovestibular deficits. Upon return to Earth, functional performance changes are tested using the Functional Task Test (FTT), which includes an obstacle course to observe post-flight balance and postural stability, specifically during turning. The goal of this study was to quantify changes in movement strategies during turning events by observing the latency between head-and-trunk coordinated movements. It was hypothesized that subjects experiencing neurovestibular adaptations would exhibit head-to-trunk locking ('en bloc' movement) during turning, exhibited by a decrease in latency between head and trunk movement. FTT data samples were collected from 13 ISS astronauts and 26 male 70-day head down tilt bed rest subjects, including bed rest controls (10 BRC) and bed rest exercisers (16 BRE). Samples were analyzed three times pre-exposure, immediately post-exposure (0 or 1 day post) and 2-to-3 times during recovery from the unloading environment. Two 3D inertial measurements units (XSens MTx) were attached to subjects, one on the head and one on the upper back. This study focused primarily on the yaw movements about the subject's center of rotation. Time differences (latency) between head and trunk movement were averaged across a slalom obstacle portion, consisting of three turns (approximately three 60° turns). All participants were grouped as 'decreaser' or 'increaser,' relating to their change in head-to-trunk movement latency between pre- and post- environmental adaptation measures. Space flight unloading (ISS) showed a bimodal response between the 'increaser' and 'decreaser' group, while both bed rest control (BRC) and bed rest exercise (BRE) populations showed increased preference towards a 'decreaser' categorization, displaying greater head-trunk locking. It is clear that changes in movement strategies are adopted during exposure to an unloading environment. These results further the understanding of vestibular-somatosensory convergence and support the use of bed rest as an exclusionary model to better understand sensorimotor changes in space flight.

Long Duration Head Down Tilt Bed Rest and Spaceflight Effects on Neurocognitive Performance: Extent, Longevity and Neural Bases

NASA Technical Reports Server (NTRS)

Seidler, R. D.; Mulavara, A. P.; Koppelmans, V.; Cassady, K.; Yuan, P.; Kofman, I. S.; De Dios, Y. E.; Riascos-Castaneda, R. F.; Wood, S. J.; Bloomberg, J. J.

2017-01-01

We have recently completed a long duration head down tilt bed rest (HDBR) study in which we performed structural and functional magnetic resonance brain imaging to identify the relationships between changes in neurocognitive function and neural structural alterations in a spaceflight analog environment. We are also collecting the same measures in crewmembers prior to and following a six month International Space Station mission. We will present data demonstrating that bed rest resulted in functional mobility and balance deterioration with recovery post-HDBR. We observed numerous changes in brain structure, function, and connectivity relative to a control group which were associated with pre to post bed rest changes in sensorimotor function. For example, gray matter volume (GMv) increased in posterior parietal areas and decreased in frontal regions. GMv increases largely overlapped with fluid decreases and vice versa. Larger increases in precentral gyrus (M1)/ postcentral gyrus (S1+2) GMv and fluid decreases were associated with smaller balance decrements. Vestibular activation in the bilateral insular cortex increased with bed rest and subsequently recovered. Larger increases in vestibular activation in multiple brain regions were associated with greater decrements in balance and mobility. We found connectivity increases between left M1 with right S1+2 and the superior parietal lobule, and right vestibular cortex with the cerebellum. Decreases were observed between right Lobule VIII with right S1+2 and the supramarginal gyrus, right posterior parietal cortex (PPC) with occipital regions, and the right superior posterior fissure with right Crus I and II. Connectivity strength between left M1 and right S1+2/superior parietal lobule increased the most in individuals that exhibited the least balance impairments. In sum, we observed HDBR-related changes in measures of brain structure, function, and network connectivity, which correlated with indices of sensorimotor function. Recovery was observed post HDBR but remained incomplete at 12 days post-HDBR. Preliminary findings from our parallel ongoing flight study will be compared and contrasted with bed rest results during this presentation.

High-Intensity Jump Training Is Tolerated during 60 Days of Bed Rest and Is Very Effective in Preserving Leg Power and Lean Body Mass: An Overview of the Cologne RSL Study.

PubMed

Kramer, Andreas; Kümmel, Jakob; Mulder, Edwin; Gollhofer, Albert; Frings-Meuthen, Petra; Gruber, Markus

2017-01-01

Space agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance. 23 male participants (29±6 years, 181±6 cm, 77±7 kg) were confined to a bed rest facility for 90 days: a 15-day ambulatory measurement phase, a 60-day six-degree head-down-tilt bed rest phase (HDT), and a 15-day ambulatory recovery phase. Participants were randomly allocated to the jump training group (JUMP, n = 12) or the control group (CTRL, n = 11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system. The training group had to complete 5-6 sessions per week. Peak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of HDT. Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03). Resting heart rate during recovery was significantly increased for CTRL but not for JUMP (interaction effect p<0.001). Participants tolerated the near-daily high-intensity jump training and maintained high peak forces and high power output during 60 days of bed rest. The countermeasure was effective in preserving lean body mass and partly preventing cardiac deconditioning with only several minutes of training per day.

Supine Lower Body Negative Pressure Exercise Maintains Upright Exercise Capacity in Male Twins during 30 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Lee, Stuart M. C.; Schneider, Suzanne M.; Boda, Wanda L.; Watenpaugh, Donald E.; Macias, Brandon R.; Meyer, R. Scott; Hargens, Alan R.

2006-01-01

Exercise capacity is reduced following both short and long duration exposures to microgravity. We have shown previously that supine lower body negative pressure with exercise (LBNP(sub ex) maintains upright exercise capacity in men after 5d and 15d bed rest, as a simulation of microgravity. We hypothesized that LBNP(sub ex) would protect upright exercise capacity (VO2pk) and sprint performance in eight sets of identical male twins during a 30-d bed rest. Twins within each set were randomly assigned to either a control group (CON) who performed no exercise or to an exercise group (EX) who performed a 40-min interval (40-80% pre-BR VO2pk) LBNP(sub ex) (55+/-4 mmHg) exercise protocol, plus 5 min of resting LBNP, 6 d/wk. LBNP produced footward force equivalent to 1.0- 1.2 times body weight. Pre- and post-bed rest, subjects completed an upright graded exercise test to volitional fatigue and sprint test of 30.5 m. After bed rest, VO2pk was maintained in the EX subjects (-3+/-3%), but was significantly decreased in the CON subjects (-24+/-4%). Sprint time also was increased in the CON subjects (24+/-8%), but maintained in the EX group (8+/-2%). The performance of a supine, interval exercise protocol with LBNP maintains upright exercise capacity and sprint performance during 30 d of bed rest. This exercise countermeasure protocol may help prevent microgravity-induced deconditioning during long duration space flight.

Energy absorption, lean body mass, and total body fat changes during 5 weeks of continuous bed rest.

PubMed

Krebs, J M; Schneider, V S; Evans, H; Kuo, M C; LeBlanc, A D

1990-04-01

Inactivity causes profound changes. We determined the nature of the body composition changes due to inactivity, and sought to determine if these changes are secondary to changes in energy absorption. Volunteers were 15 healthy males who lived on a metabolic research ward under close staff supervision for 11 weeks. Subjects were ambulatory during the first 6 weeks and remained in continuous bed rest for the last 5 weeks of the study. Six male volunteers (age 24-61 years, height 175.7 +/- 4.2 cm) were selected for body composition measurements. Nine different male volunteers (age 21-50 years, height 177.7 +/- 5.0 cm) were selected for energy absorption measurements. The volunteers were fed weighed conventional foods on a constant 7-d rotation menu. The average daily caloric content was 2,592 kcal. Comparing the 5 weeks of continuous bed rest with the previous 6 weeks of ambulation we observed: no change in energy absorption or total body weight during bed rest, but a significant decrease in lean body mass and a significant increase in total body fat (p less than 0.05).

Effect of head-down-tilt bed rest and hypovolemia on dynamic regulation of heart rate and blood pressure

NASA Technical Reports Server (NTRS)

Iwasaki, K. I.; Zhang, R.; Zuckerman, J. H.; Pawelczyk, J. A.; Levine, B. D.; Blomqvist, C. G. (Principal Investigator)

2000-01-01

Adaptation to head-down-tilt bed rest leads to an apparent abnormality of baroreflex regulation of cardiac period. We hypothesized that this "deconditioning response" could primarily be a result of hypovolemia, rather than a unique adaptation of the autonomic nervous system to bed rest. To test this hypothesis, nine healthy subjects underwent 2 wk of -6 degrees head-down bed rest. One year later, five of these same subjects underwent acute hypovolemia with furosemide to produce the same reductions in plasma volume observed after bed rest. We took advantage of power spectral and transfer function analysis to examine the dynamic relationship between blood pressure (BP) and R-R interval. We found that 1) there were no significant differences between these two interventions with respect to changes in numerous cardiovascular indices, including cardiac filling pressures, arterial pressure, cardiac output, or stroke volume; 2) normalized high-frequency (0.15-0.25 Hz) power of R-R interval variability decreased significantly after both conditions, consistent with similar degrees of vagal withdrawal; 3) transfer function gain (BP to R-R interval), used as an index of arterial-cardiac baroreflex sensitivity, decreased significantly to a similar extent after both conditions in the high-frequency range; the gain also decreased similarly when expressed as BP to heart rate x stroke volume, which provides an index of the ability of the baroreflex to alter BP by modifying systemic flow; and 4) however, the low-frequency (0.05-0.15 Hz) power of systolic BP variability decreased after bed rest (-22%) compared with an increase (+155%) after acute hypovolemia, suggesting a differential response for the regulation of vascular resistance (interaction, P < 0.05). The similarity of changes in the reflex control of the circulation under both conditions is consistent with the hypothesis that reductions in plasma volume may be largely responsible for the observed changes in cardiac baroreflex control after bed rest. However, changes in vasomotor function associated with these two conditions may be different and may suggest a cardiovascular remodeling after bed rest.

Physiology Of Prolonged Bed Rest

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1991-01-01

Report describes physiological effects of prolonged bed rest. Rest for periods of 24 hours or longer deconditions body to some extent; healing proceeds simultaneously with deconditioning. Report provides details on shifts in fluid electrolytes and loss of lean body mass, which comprises everything in body besides fat - that is, water, muscle, and bone. Based on published research.

Using Natural Stable Calcium Isotopes to Rapidly Assess Changes in Bone Mineral Balance Using a Bed Rest Model to Induce Bone Loss

NASA Technical Reports Server (NTRS)

Morgan, J. L. L.; Skulan, J. L.; Gordon, G. E.; Smith, Scott M.; Romaniello, S. J.; Anbar, A. D.

2012-01-01

Metabolic bone diseases like osteoporosis result from the disruption of normal bone mineral balance (BMB) resulting in bone loss. During spaceflight astronauts lose substantial bone. Bed rest provides an analog to simulate some of the effects of spaceflight; including bone and calcium loss and provides the opportunity to evaluate new methods to monitor BMB in healthy individuals undergoing environmentally induced-bone loss. Previous research showed that natural variations in the Ca isotope ratio occur because bone formation depletes soft tissue of light Ca isotopes while bone resorption releases that isotopically light Ca back into soft tissue (Skulan et al, 2007). Using a bed rest model, we demonstrate that the Ca isotope ratio of urine shifts in a direction consistent with bone loss after just 7 days of bed rest, long before detectable changes in bone mineral density (BMD) occur. The Ca isotope variations tracks changes observed in urinary N-teleopeptide, a bone resorption biomarker. Bone specific alkaline phosphatase, a bone formation biomarker, is unchanged. The established relationship between Ca isotopes and BMB can be used to quantitatively translate the changes in the Ca isotope ratio to changes in BMD using a simple mathematical model. This model predicts that subjects lost 0.25 0.07% ( SD) of their bone mass from day 7 to day 30 of bed rest. Given the rapid signal observed using Ca isotope measurements and the potential to quantitatively assess bone loss; this technique is well suited to study the short-term dynamics of bone metabolism.

Gender Differences in Bed Rest: Preliminary Analysis of Vascular Function

NASA Technical Reports Server (NTRS)

Platts, Steven H.; Stenger, Michael B.; Martin, David S.; Freeman-Perez, Sondra A.; Phillips, Tiffany; Ribeiro, L. Christine

2008-01-01

Orthostatic intolerance is a recognized consequence of spaceflight. Numerous studies have shown that women are more susceptible to orthostatic intolerance following spaceflight as well as bed rest, the most commonly used ground-based analog for spaceflight. One of the possible mechanisms proposed to account for this is a difference in vascular responsiveness between genders. We hypothesized that women and men would have differing vascular responses to 90 days of 6-degree head down tilt bed rest. Additionally, we hypothesized that vessels in the upper and lower body would respond differently, as has been shown in the animal literature. Thirteen subjects were placed in bedrest for 90 days (8 men, 5 women) at the Flight Analogs Unit, UTMB. Direct arterial and venous measurements were made with ultrasound to evaluate changes in vascular structure and function. Arterial function was assessed, in the arm and leg, during a reactive hyperemia protocol and during sublingual nitroglycerin administration to gauge the contributions of endothelial dependent and independent dilator function respectively. Venous function was assessed in dorsal hand and foot veins during the administration of pharmaceuticals to assess constrictor and dilator function. Both gender and day effects are seen in arterial dilator function to reactive hyperemia, but none are seen with nitroglycerin. There are also differences in the wall thickness in the arm vs the leg during bed rest, which return toward pre-bed rest levels by day 90. More subjects are required, especially females as there is not sufficient power to properly analyze venous function. Day 90 data are most underpowered.

Life and Microgravity Sciences Spacelab Mission: Human Research Pilot Study

NASA Technical Reports Server (NTRS)

Arnaud, Sara B. (Editor); Walker, Karen R. (Editor); Hargens, Alan (Editor)

1996-01-01

The Life Sciences, Microgravity Science and Spacelab Mission contains a number of human experiments directed toward identifying the functional, metabolic and neurological characteristics of muscle weakness and atrophy during space flight. To ensure the successful completion of the flight experiments, a ground-based pilot study, designed to mimic the flight protocols as closely as possible, was carried out in the head-down tilt bed rest model. This report records the rationales, procedures, preliminary results and estimated value of the pilot study, the first of its kind, for 12 of the 13 planned experiments in human research. The bed rest study was conducted in the Human Research Facility at Ames Research Center from July 11 - August 28, 1995. Eight healthy male volunteers performed the experiments before, during and after 17 days bed rest. The immediate purposes of this simulation were to integrate the experiments, provide data in a large enough sample for publication of results, enable investigators to review individual experiments in the framework of a multi-disciplinary study and relay the experience of the pilot study to the mission specialists prior to launch.

Anabolic resistance assessed by oral stable isotope ingestion following bed rest in young and older adult volunteers: Relationships with changes in muscle mass.

PubMed

Biolo, Gianni; Pišot, Rado; Mazzucco, Sara; Di Girolamo, Filippo Giorgio; Situlin, Roberta; Lazzer, Stefano; Grassi, Bruno; Reggiani, Carlo; Passaro, Angelina; Rittweger, Joern; Gasparini, Mladen; Šimunič, Boštjan; Narici, Marco

2017-10-01

Aging and experimental bed rest are associated with muscle atrophy and resistance to post-prandial stimulation of protein synthesis or anabolic resistance (AR). We have used in young and older adult volunteers, during short-term bed rest, a quick and non-invasive method, based on a single oral bolus of the stable isotope L[ring- 2 H 5 ]phenylalanine (D 5 Phe), to determine post-prandial AR, defined as ratio between irreversible hydroxylation and incorporation into body protein of ingested phenylalanine. We compared in older (O, 59 ± 1 y) and young (Y, 23 ± 1 y) healthy male volunteers the effects of two-week bed rest on post-prandial protein kinetics, assessed during absorption of a standard ready-to-use oral nutritional supplement, through stable-labeled isotope amino acid D 5 Phe, diluted in water, given as single oral load. The metabolic fate of D 5 Phe is either utilization for protein synthesis or irreversible hydroxylation to L[ring- 2 H 4 ]tyrosine (D 4 Tyr). AR was defined as ratio between the areas under the curves of D 4 Tyr-to-D 5 Phe plasma concentrations over 6 h meal absorption. To determine the relationships between AR and muscle changes following bed rest, quadriceps muscle volume (QMV) was determined by magnetic resonance imaging (MRI). At baseline, in pooled Y and O subjects, values of AR were inversely correlated with QMV (R = -0.75; p < 0.03). Following 2-weeks of inactivity, there were significant bed rest effects on AR (p < 0.01) and QMV (p < 0.03), as well as significant bed rest × group interaction for AR (p < 0.03; +9.2% in Y; +21.9% in O) and QMV (p < 0.05; -5.7% in Y; -%7.3 in O). In pooled subjects, the percentage delta changes in AR and QMV, induced by bed rest, were inversely correlated (R = -0.57; p < 0.05). Bed rest-induced AR is much greater in the older than in younger adults. We have developed a new, simple, non-invasive method for the assessment of AR. The results indicate that this metabolic abnormality is a key mechanism for sarcopenia of aging and inactivity. Copyright © 2016 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Zinc and copper balances in healthy adult males during and after 17 wk of bed rest

NASA Technical Reports Server (NTRS)

Krebs, J. M.; Schneider, V. S.; LeBlanc, A. D.; Kuo, M. C.; Spector, E.; Lane, H. W.

1993-01-01

The effects of long-term bed rest on zinc and copper balances were measured in seven healthy men. Volunteers aged 22-54 y (mean +/- SD, 34 +/- 12 y), 168-185 cm in height (173 +/- 5 cm), and 64-86 kg in weight (74 +/- 9 kg) remained on a metabolic ward for 29 wk. Subjects were ambulatory during weeks 1-5, remained in continuous bed rest for weeks 6-22, and were reambulated during weeks 23-29. Copper and zinc were measured in weekly urine and fecal composites. Dietary intakes provided (mean +/- SD) 19.2 +/- 1.2 mumol Cu (1.22 +/- 0.08 mg), 211 +/- 11 mumol Zn (13.81 +/- 0.72 mg), 25.2 +/- 1.2 mmol Ca (1011 +/- 46 mg), 1086 +/- 46 mmol N (15.21 +/- 0.65 g), and 48.1 +/- 1.4 mmol K (1489 +/- 44 mg)/d. Bed rest increased fecal zinc excretion and decreased zinc balance, whereas copper balance was unchanged. Reambulation decreased fecal zinc excretion and increased both zinc and copper balances. These results suggest that during long-term bed rest or space flight, individuals will lose total body zinc and will retain more zinc and copper when they reambulate.

Bone mineral measurement: Skylab experiment M-078.

PubMed

Vogel, J M

1975-01-01

The observation that bone mineral is lost in patients who are either immobilized or remain in bed for extended periods of time formed the basis for the concern that large amounts of bone mineral may be lost during long periods of weightlessness. This concern was magnified when early X-ray densitometry studies suggested that rather large amounts of mineral could be lost during rather short periods of weightlessness (4-14 days). Even though these Gemini results have recently been modified, they still reflect substantial losses in the upper extremity. This led to a series of prolonged bed-rest studies (30-36 weeks) which, in addition to careful calcium balance, also employed a newer, more precise method of estimating bone mineral in the radius, ulna, and os calcis. It employed an essentially monoenergetic photon source (125I) and a scintillation detector operating in a rectilinear scanning mode to measure bone mineral by the absorptiometric technique. Bed-rest studies revealed variable mineral losses but suggested that little if any is lost during 4-6 weeks, with variable amounts being lost in 8 weeks. Losses up to 40% were noted in the os calcis after 9 months, with essentially none in the radius and ulna. When this technique was employed during the Apollo 14, 15, and 16 missions, only one crewman (CMP Apollo 15) showed significant losses in the os calcis and none in the radius or ulna. These results were, therefore, in concert with the bed-rest data but at variance with the earlier Gemini data. The variability observed during bed rest was reconciled when it was observed that the rate of loss could be correlated with the initial 24-hour urinary hydroxyproline excretion and the initial os calcis mineral content. Prediction terms were established. Measurements of the SL-II crew after 28 days of weightlessness revealed no significant bone mineral losses. The Skylab data lie within the predicted limits obtained from the bed-rest data. The relevance of the prediction terms to the Skylab and longer missions discussed.

Bed Rest and Immobilization: Risk Factors for Bone Loss

MedlinePlus

... Loss Bed Rest and Immobilization: Risk Factors for Bone Loss Like muscle, bone is living tissue that ... bones adjust to the state of weightlessness. Maintaining Bone Health In general, healthy people who undergo prolonged ...

Day/Night Variability in Blood Pressure: Influence of Posture and Physical Activity

PubMed Central

2013-01-01

BACKGROUND Blood pressure (BP) is highest during the day and lowest at night. Absence of this rhythm is a predictor of cardiovascular morbidity and mortality. Contributions of changes in posture and physical activity to the 24-hour day/night rhythm in BP are not well understood. We hypothesized that postural changes and physical activity contribute substantially to the day/night rhythm in BP. METHODS Fourteen healthy, sedentary, nonobese, normotensive men (aged 19–50 years) each completed an ambulatory and a bed rest condition during which BP was measured every 30–60 minutes for 24 hours. When ambulatory, subjects followed their usual routines without restrictions to capture the “normal” condition. During bed rest, subjects were constantly confined to bed in a 6-degree head-down position; therefore posture was constant, and physical activity was minimized. Two subjects were excluded from analysis because of irregular sleep timing. RESULTS The systolic and diastolic BP reduction during the sleep period was similar in ambulatory (−11±2mmHg/−8±1mmHg) and bed rest conditions (−8±3mmHg/−4±2mmHg; P = 0.38/P = 0.12). The morning surge in diastolic BP was attenuated during bed rest (P = 0.001), and there was a statistical trend for the same effect in systolic BP (P = 0.06). CONCLUSIONS A substantial proportion of the 24-hour BP rhythm remained during bed rest, indicating that typical daily changes in posture and/or physical activity do not entirely explain 24-hour BP variation under normal ambulatory conditions. However, the morning BP increase was attenuated during bed rest, suggesting that the adoption of an upright posture and/or physical activity in the morning contributes to the morning BP surge. PMID:23535155

Effects of Bedding Material on the Lying Behavior in Stabled Horses

PubMed Central

NINOMIYA, Shigeru; AOYAMA, Masato; UJIIE, Yumiko; KUSUNOSE, Ryo; KUWANO, Atsutoshi

2008-01-01

The objective of this study was to investigate the effect of straw, sawdust, coconut husk (husk), and coconut fiber (fiber) on the welfare of stable horses by observing their resting behavior. Twenty horses with ages ranging from 3 to 21 years were used at the Equine Research Institute of the Japan Racing Association, Utsunomiya, Japan. Five horses were allocated to each bedding condition. The behavior of each horse was recorded by video camera for 3 days and was continuously sampled from 17:00 to 05:00. The total duration, the number of bouts, and the mean and the maximum duration of bouts in standing rest, sternal lying, and lateral lying were calculated and analysed by the Kruskal-Wallis test and post hoc Steel-Dwass test. There was no difference in the standing rest and the sternal lying among beddings. Significant differences were observed in these values in the lateral lying among the different beddings (P<0.05). The values of the means of the total duration, the number of bouts, and the mean and the maximum duration of bout in the lateral lying were greater when husk was used as the bedding material than when sawdust were used (P<0.05). The results of the observations show that the new bedding materials would be as usable as straw. However, lateral lying was observed less frequently when sawdust were used as bedding; this indicates that use of sawdust as bedding material will decrease the welfare of stabled horses. PMID:24833955

Magnesium and Space Flight

PubMed Central

Smith, Scott M.; Zwart, Sara R.

2015-01-01

Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD) before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female), 35 ± 7 years old). We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions. PMID:26670248

Magnesium and Space Flight.

PubMed

Smith, Scott M; Zwart, Sara R

2015-12-08

Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD) before, during, and after 4-6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female), 35 ± 7 years old). We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4-6-month space missions.

Comparison of Structural and Functional Ocular Outcomes Between 14- and 70 Day Bed Rest

NASA Technical Reports Server (NTRS)

Cromwell, R. L.; Taibbi, G.; Zanello, S. B.; Yarbough, P. O.; Ploutz-Snyder, R. J.; Vizzeri, G.

2016-01-01

Purpose: To compare structural and functional ocular outcomes in healthy human subjects undergoing 14- and/or 70-day head-down-tilt bed rest (HDTBR). We hypothesized the amount of HDTBR-induced ocular changes be affected by the HDTBR duration. Methods: The studies were conducted at the NASA Flight Analogs Research Unit, The University of Texas Medical Branch at Galveston, Galveston, TX. Participants were selected using NASA standard screening procedures. Standardized NASA screening procedures and bed rest conditions (e.g., strict sleep-wake cycle, standardized diet, continuous video monitoring) were implemented in both studies. Participants maintained a 6deg HDTBR position for 14 and/or 70 consecutive days and did not engage in exercise. Weekly ophthalmological examinations were conducted in the sitting (pre/post-bed rest only) and HDT positions. Ocular outcomes of interest included: near best-corrected visual acuity (BCVA); spherical equivalent, as determined by cycloplegic autorefraction; Goldmann applanation tonometry and iCare (Icare Finland Oy, Espoo, Finland) intraocular pressure (IOP) measurement; color vision; red dot test; modified Amsler grid test; confrontational visual field; stereoscopic color fundus photography; Spectralis OCT (Heidelberg Engineering, GmbH, Heidelberg, Germany) retinal nerve fiber layer thickness (RNFLT), peripapillary and macular retinal thicknesses. Mixed-effects linear models were used to compare pre- and post-HDTBR observations between 14- and 70-day HDTBR for our continuously scaled outcomes.

Effect of three day bed-rest on circulatory and hormonal responses to active orthostatic test in endurance trained athletes and untrained subjects

NASA Technical Reports Server (NTRS)

Kubala, P.; Smorawinski, J.; Kaciuba-Uscilko, H.; Nazar, K.; Bicz, B.; Greenleaf, J. E.

1996-01-01

Circulatory and hormonal parameters were measured in endurance-trained athletes and control subjects during orthostatic tolerance tests conducted prior to and after three days of bed rest. Heart rate and blood pressure changes due to bed rest appeared to be the same in both groups. Hormonal changes, however, were different between the two groups, with the athletes having decreased sympathoadrenal activity and increased plasma renin activity. Untrained subjects had changes in cortisol secretion only.

NASA Standard Measures Overview

NASA Technical Reports Server (NTRS)

Meck, Janice V.

2008-01-01

Due to the limited in-flight resources available for human physiological research in the foreseeable future, NASA has increased its reliance on head-down bed rest. NASA has created the Bed Rest Project at the Johnson Space Center, which is implemented on the 6th floor of the Children's Hospital at UTMB. It has been conducted for three years. The overall objective of the Project is to use bed rest to develop and evaluate countermeasures for the ill effects of space flight before flight resources are requested for refinement and final testing.

Renal stone risk in a simulated microgravity environment: impact of treadmill exercise with lower body negative pressure.

PubMed

Monga, Manoj; Macias, Brandon; Groppo, Eli; Kostelec, Monica; Hargens, Alan

2006-07-01

Prolonged exposure to microgravity during spaceflight causes metabolic changes that increase the risk of renal stone formation. Studies during the Gemini, Apollo, Skylab and Shuttle missions demonstrated alterations in renal function, fluid homeostasis and bone resorption that result in increased urinary supersaturation of calcium oxalate, brushite, sodium urate and uric acid. Developing countermeasures to increased urinary supersaturation is an important priority as the duration of space missions increases. A total of 11 sets of identical twins remained on 6-degree head down, tilt bed rest for 30 days to simulate prolonged microgravity. One twin per pair was randomly selected to exercise while supine in a lower body negative pressure chamber 6 days weekly for 40 minutes, followed by 5 minutes of resting lower body negative pressure at 50 mm Hg. The other twin served as a nonexercise control. Pressure in the exercise lower body negative pressure chamber (52 to 63 mm Hg) was adjusted to produce footward forces equivalent to those for upright running on Earth at 1.0 to 1.2 x body weight. Pre-bed rest urinary stone risk profiles were done elsewhere after 5 days of a standardized diet, consisting of 170 mEq sodium, 1,000 mg calcium, 0.8 gm/kg animal protein and 2,500 kcal, and then throughout the bed rest and recovery phases of the protocol. A significant increase in urinary calcium after just 1 week of bed rest was noted in the nonexercise control group (p = 0.001). However, no such increase was noted in the exercise group. Brushite supersaturation increased significantly from bed rest in each group, although the increase was significantly higher in the nonexercise control group than in the exercise group (p = 0.006). Calcium oxalate supersaturation increased during bed rest in the exercise group (p = 0.004). It trended toward a higher level in the nonexercise control group, although this did not achieve significance (p = 0.055) Mean urine volume +/- SD was significantly higher in the nonexercise control group than in the exercise group at bed rest week 2 and at week 3 (2.01 +/- 0.21 vs 1.63 0.18 l and 2.03 +/- 0.22 vs 1.81 +/- 0.20, respectively). Urinary pH was significantly higher in the nonexercise control group than in the exercise group at week 1 and week 3 (6.62 +/- 0.7 vs 6.49 +/- 0.5 and 6.58 +/- 0.6 vs 6.49 +/- 0.8, respectively, p = 0.01). Bed rest significantly alters the urinary environment to favor calculous formation. Lower body negative pressure chamber treadmill exercise offers some protection against increases in stone risk during simulated microgravity, particularly with regard to the risks of hypercalciuria and brushite stone formation. The use of lower body negative pressure to augment aerobic exercise in space may decrease the risk of stone formation in astronauts. Adjunct measures, including aggressive hydration and alkalinization therapy, should be considered.

Dynamics and certain mechanisms in the changes of the skeletal-muscular system of man under bedrest conditions

NASA Technical Reports Server (NTRS)

Oganov, V. G.

1977-01-01

Bed rest conditions evaluated varied in the longitudinal axis of the body, perpendicular to the vector gravitational forces, and the cranial portion of the body inclined from the horizontal. The duration of bed rest fluctuated in various experiments from 30 to 182 days. The state of muscle and neuromuscular system was judged on the basis of the recording of various functional indices, as well as by certain results of morphological and biochemical studies and data from the study of motor functions.

Cardiac atrophy in women following bed rest.

PubMed

Dorfman, Todd A; Levine, Benjamin D; Tillery, Tommy; Peshock, Ronald M; Hastings, Jeff L; Schneider, Suzanne M; Macias, Brandon R; Biolo, Gianni; Hargens, Alan R

2007-07-01

Both chronic microgravity exposure and long-duration bed rest induce cardiac atrophy, which leads to reduced standing stroke volume and orthostatic intolerance. However, despite the fact that women appear to be more susceptible to postspaceflight presyncope and orthostatic hypotension than male astronauts, most previous high-resolution studies of cardiac morphology following microgravity have been performed only in men. Because female athletes have less physiological hypertrophy than male athletes, we reasoned that they also might have altered physiological cardiac atrophy after bed rest. Magnetic resonance imaging was performed in 24 healthy young women (32.1 +/- 4 yr) to measure left ventricular (LV) and right ventricular (RV) mass, volumes, and morphology accurately before and after 60 days of 6 degrees head-down tilt (HDT) bed rest. Subjects were matched and then randomly assigned to sedentary bed rest (controls, n = 8) or two treatment groups consisting of 1) exercise training using supine treadmill running within lower body negative pressure plus resistive training (n = 8), or 2) protein (0.45 g x kg(-1) x day(-1) increase) plus branched-chain amino acid (BCAA) (7.2 g/day) supplementation (n = 8). After sedentary bed rest without nutritional supplementation, there were significant reductions in LV (96 +/- 26 to 77 +/- 25 ml; P = 0.03) and RV volumes (104 +/- 33 to 86 +/- 25 ml; P = 0.02), LV (2.2 +/- 0.2 to 2.0 +/- 0.2 g/kg; P = 0.003) and RV masses (0.8 +/- 0.1 to 0.6 +/- 0.1 g/kg; P < 0.001), and the length of the major axis of the LV (90 +/- 6 to 84 +/- 7 mm. P < 0.001), similar to what has been observed previously in men (8.0%; Perhonen MA, Franco F, Lane LD, Buckey JC, Blomqvist Zerwekh JE, Peshock RM, Weatherall PT, Levine BD. J Appl Physiol 91: 645-653, 2001). In contrast, there were no significant reductions in LV or RV volumes in the exercise-trained group, and the length of the major axis was preserved. Moreover, there were significant increases in LV (1.9 +/- 0.4 to 2.3 +/- 0.3 g/kg; P < 0.001) and RV masses (0.7 +/- 0.1 to 0.8 +/- 0.2 g/kg; P = 0.002), as well as mean wall thickness (9 +/- 2 to 11 +/- 1 mm; P = 0.02). The interaction between sedentary and exercise LV and RV masses was highly significant (P < 0.0001). Protein and BCAA supplementation led to an intermediate phenotype with no change in LV or RV mass after bed rest, but there remained a significant reduction in LV volume (103 +/- 14 to 80 +/- 16 ml; P = 0.02) and major-axis length (91 +/- 5 to 88 +/- 7 mm; P = 0.003). All subjects lost an equivalent amount of body mass (3.4 +/- 0.2 kg control; 3.1 +/- 0.04 kg exercise; 2.8 +/- 0.1 kg protein). Cardiac atrophy occurs in women similar to men following sedentary 60 days HDT bed rest. However, exercise training and, to a lesser extent, protein supplementation may be potential countermeasures to the cardiac atrophy associated with chronic unloading conditions such as in spaceflight and prolonged bed rest.

Regional changes in muscle mass following 17 weeks of bed rest

NASA Technical Reports Server (NTRS)

Leblanc, Adrian D.; Schneider, Victor S.; Evans, Harlan J.; Pientok, Colette; Rowe, Roger; Spector, Elisabeth

1992-01-01

This work reports on the muscle loss and recovery after 17 wk of continuous bed rest and 8 wk of reambulation in eight normal male volunteers. Muscle changes were assessed by urinary levels of 3-methylhistidine (3-MeH), nitrogen balance, dual-photon absorptiometry (DPA), magnetic resonance imaging (MRI), and isokinetic muscle performance. The total body lean tissue loss during bed rest calculated from nitrogen balance was 3.9 +/- 2.1 kg. Although the total loss is minimal, DPA scans showed that nearly all of the lean tissue loss occurred in the lower limbs. Similarly, MRI muscle volume measurements showed greater percent loss in the limbs relative to the back muscles. MRI, DPA, and nitrogen balance suggest that muscle atrophy continued throughout bed rest with rapid recovery after reambulaton. Isokinetic muscle strength decreased significantly in the thigh and calf with no loss in the arms and with rapid recovery during reambulation.

Effects of 45-day -6° head-down bed rest on the time-based prospective memory

NASA Astrophysics Data System (ADS)

Chen, SiYi; Zhou, RenLai; Xiu, LiChao; Chen, ShanGuang; Chen, XiaoPing; Tan, Cheng

2013-03-01

The research explored the effects of 45-day -6° head-down bed rest (HDBR) simulation of microgravity on the time-based prospective memory (PM) with 16 males. The time-based prospective memory task was performed on the 2nd day before HDBR, on the 11th, 20th, 32nd, and 40th days during HDBR, and on the 8th day after HDBR, and subjects' anxiety and depression feelings were recorded simultaneously using Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI). The results demonstrated that it showed decreased accuracy of PM responses and frequency of clock checks during and after bed rest; long term bed rest did not induce significant emotional changes. The deficit of prospective memory performance induced by long term HDBR may result from a lack of aerobic physical activity or changes in the prefrontal cortex, but it remains to be determined.

Natural Ca Isotope Composition of Urine as a Rapid Measure of Bone Mineral Balance

NASA Astrophysics Data System (ADS)

Skulan, J.; Gordon, G. W.; Morgan, J.; Romaniello, S. J.; Smith, S. M.; Anbar, A. D.

2011-12-01

Naturally occurring stable Ca isotope variations in urine are emerging as a powerful tool to detect changes in bone mineral balance. Bone formation depletes soft tissue of light Ca isotopes while bone resorption releases isotopically light Ca into soft tissue. Previously published work found that variations in Ca isotope composition could be detected at 4 weeks of bed rest in a 90-day bed rest study (data collected at 4, 8 and 12 weeks). A new 30-day bed rest study involved 12 patients on a controlled diet, monitored for 7 days prior to bed rest and 7 days post bed rest. Samples of urine, blood and food were collected throughout the study. Four times daily blood samples and per void urine samples were collected to monitor diurnal or high frequency variations. An improved chemical purification protocol, followed by measurement using multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) allowed accurate and precise determinations of mass-dependent Ca isotope variations in these biological samples to better than ±0.2% (δ44/42Ca) on <25 μg of Ca. Results from this new study show that Ca isotope ratios shift in a direction consistent with net bone loss after just 7 days, long before detectible changes in bone density by X-ray measurements occur. Consistent with this interpretation, the Ca isotope variations track changes observed in N-teleopeptide, a bone resorption biomarker. Bone-specific alkaline phosphatase, a bone formation biomarker, is unchanged over this period. Ca isotopes can in principle be used to quantify net changes in bone mass. Using a mass-balance model, our results indicate an average loss of 0.62 ± 0.16 % in bone mass over the course of this 30-day study. This is consistent with the rate of bone loss in longer-term studies as seen by X-ray measurements. This Ca isotope technique should accelerate the pace of discovery of new treatments for bone disease and provide novel insights into the dynamics of bone metabolism.

Study of bone mineral metabolism. [during body immobilization, bed rest, and space flight

NASA Technical Reports Server (NTRS)

Palmer, H. E.

1975-01-01

The use of Sr-85 as an indicator of the skeletal location and relative amount of bone demineralization which occurs during immobilization of the body or body parts, bed-rest or space flight was studied. The bone mineral replacement which occurs after immobilization was measured rather than the bone loss which occurs during immobilization. In a study with two adult beagle dogs, the Sr-85 uptake in a leg which had been immobilized for two months was 400 percent higher than the uptake in the legs in regular use. This increased uptake probably resulted from only a few percent loss in bone mineral and indicates that losses less than one percent can be easily detected and located. The sensitivity, simplicity, and low radiation dose associated with the use of this method indicates that it should receive consideration for use on humans in bed-rest and space flight studies. Methods for measuring changes in total body nitrogen and in assisting the Johnson Space Center in calibrating a whole body counter for total body potassium measurements were also investigated.

Intensive Exercise Training During Bed Rest Attenuates Deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1997-01-01

Intensive exercise training during bed rest attenuates deconditioning. Med. Sci. Sports Exerc., Vol. 29, No. 2, pp. 207-215, 1997. A 30-d 6 deg head-down bed rest project was conducted to evaluate variable high-intensity, short-duration, isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent resistive isokinetic exercise (IKE) training regimens designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (adaptive) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Major findings are summarized in this paper. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volumes, (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (f) attenuated the decrease in peak VO2 by 50%, (g) attenuated loss of red cell volume by 40% but had no effect on loss of plasma volume, (b) induced positive body water balance, (i) had no adverse effect on quality of sleep or concentration, and 0) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regimens and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

The Effects of Spaceflight and Head Down Tilt Bed Rest on Neurocognitive Performance: Extent, Longevity, and Neural Bases

NASA Technical Reports Server (NTRS)

Seidler, Rachael D.; Bloomberg, Jacob; Wood, Scott; Mulavara, Ajit; Kofman, Igor; De Dios, Yiri; Gadd, Nicole; Stepanyan, Vahagn

2017-01-01

Spaceflight effects on gait, balance, & manual motor control have been well studied; some evidence for cognitive deficits. Rodent cortical motor & sensory systems show neural structural alterations with spaceflight. specific Aims: Aim 1-Identify changes in brain structure, function, and network integrity as a function of head down tilt bed rest and spaceflight, and characterize their time course. Aim 2-Specify relationships between structural and functional brain changes and performance and characterize their time course.

A combination of whey protein and potassium bicarbonate supplements during head-down-tilt bed rest: Presentation of a multidisciplinary randomized controlled trial (MEP study)

NASA Astrophysics Data System (ADS)

Buehlmeier, Judith; Mulder, Edwin; Noppe, Alexandra; Frings-Meuthen, Petra; Angerer, Oliver; Rudwill, Floriane; Biolo, Gianni; Smith, Scott M.; Blanc, Stéphane; Heer, Martina

2014-02-01

Inactivity, as it appears during space flight and in bed rest, induces reduction of lean body and bone mass, glucose intolerance, and weakening of the cardiovascular system. Increased protein intake, whey protein in particular, has been proposed to counteract some of these effects, but has also been associated with negative effects on bone, likely caused by a correspondingly high ratio of acid to alkali precursors in the diet.

Disrupted resting-state functional architecture of the brain after 45-day simulated microgravity

PubMed Central

Zhou, Yuan; Wang, Yun; Rao, Li-Lin; Liang, Zhu-Yuan; Chen, Xiao-Ping; Zheng, Dang; Tan, Cheng; Tian, Zhi-Qiang; Wang, Chun-Hui; Bai, Yan-Qiang; Chen, Shan-Guang; Li, Shu

2014-01-01

Long-term spaceflight induces both physiological and psychological changes in astronauts. To understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on the functional architecture of the brain. In this study, we used resting-state functional MRI (rs-fMRI) to study whether the functional architecture of the brain is altered after 45 days of −6° head-down tilt (HDT) bed rest, which is a reliable model for the simulation of microgravity. Sixteen healthy male volunteers underwent rs-fMRI scans before and after 45 days of −6° HDT bed rest. Specifically, we used a commonly employed graph-based measure of network organization, i.e., degree centrality (DC), to perform a full-brain exploration of the regions that were influenced by simulated microgravity. We subsequently examined the functional connectivities of these regions using a seed-based resting-state functional connectivity (RSFC) analysis. We found decreased DC in two regions, the left anterior insula (aINS) and the anterior part of the middle cingulate cortex (MCC; also called the dorsal anterior cingulate cortex in many studies), in the male volunteers after 45 days of −6° HDT bed rest. Furthermore, seed-based RSFC analyses revealed that a functional network anchored in the aINS and MCC was particularly influenced by simulated microgravity. These results provide evidence that simulated microgravity alters the resting-state functional architecture of the brains of males and suggest that the processing of salience information, which is primarily subserved by the aINS–MCC functional network, is particularly influenced by spaceflight. The current findings provide a new perspective for understanding the relationships between microgravity, cognitive function, autonomic neural function, and central neural activity. PMID:24926242

Effects of 14 days of head-down tilt bed rest on cutaneous vasoconstrictor responses in humans

NASA Technical Reports Server (NTRS)

Wilson, Thad E.; Shibasaki, Manabu; Cui, Jian; Levine, Benjamin D.; Crandall, Craig G.

2003-01-01

This study tested the hypothesis that head-down tilt bed rest (HDBR) reduces adrenergic and nonadrenergic cutaneous vasoconstrictor responsiveness. Additionally, an exercise countermeasure group was included to identify whether exercise during bed rest might counteract any vasoconstrictor deficits that arose during HDBR. Twenty-two subjects underwent 14 days of strict 6 degrees HDBR. Eight of these 22 subjects did not exercise during HDBR, while 14 of these subjects exercised on a supine cycle ergometer for 90 min a day at 75% of pre-bed rest heart rate maximum. To assess alpha-adrenergic vasoconstrictor responsiveness, intradermal microdialysis was used to locally administer norepinephrine (NE), while forearm skin blood flow (SkBF; laser-Doppler flowmetry) was monitored over microdialysis membranes. Nonlinear regression modeling was used to identify the effective drug concentration that caused 50% of the cutaneous vasoconstrictor response (EC(50)) and minimum values from the SkBF-NE dose-response curves. In addition, the effects of HDBR on nonadrenergic cutaneous vasoconstriction were assessed via the venoarteriolar response of the forearm and leg. HDBR did not alter EC(50) or the magnitude of cutaneous vasoconstriction to exogenous NE administration regardless of whether the subjects exercised during HDBR. Moreover, HDBR did not alter the forearm venoarteriolar response in either the control or exercise groups during HDBR. However, HDBR significantly reduced the magnitude of cutaneous vasoconstriction due to the venoarteriolar response in the leg, and this response was similarly reduced in the exercise group. These data suggest that HDBR does not alter cutaneous vasoconstrictor responses to exogenous NE administration, whereas cutaneous vasoconstriction of the leg due to the venoarteriolar response is reduced after HDBR. It remains unclear whether attenuated venoarteriolar responses in the lower limbs contribute to reduced orthostatic tolerance after bed rest and spaceflight.

Carotid baroreflex response following 30 days exposure to simulated microgravity

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Doerr, D. F.; Eckberg, D. L.; Fritsch, J. M.; Vernikos-Danellis, J.

1989-01-01

The mechanism of the carotid-baroreflex response to weightlessness was investigated in human subjects exposed to simulated microgravity (30 days of 6-day head-down bed rest followed by 5 days of recovery). Baroreceptor-cardiac reflex responses were elicited by a complex sequence of pressure changes delivered to a neck chamber device. The shape of the sigmoid baroreceptor-cardiac response curve was examined for alterations and the occurrence of resetting, as well as for a possible association of the impaired baroreflex function with hypotension during the postexposure orthostatic stress. It was found that the exposure to head-down bed rest caused a significant shift on the R-R interval axis, which paralleled reductions and elevations in baseline HR such that the baseline R-R (operational point) remained in the same position on the response curve. This shift in the location of the reflex relation indicates a significant resetting of the carotid baroreceptors, which may represent an appropriate adaptation which contributes to the maintenance of a constant resting arterial blood pressure before, during, and after bed rest, observed in these study.

Effect of high sodium intake during 14 days of bed-rest on acid-base balance

NASA Astrophysics Data System (ADS)

Frings, P.; Baecker, N.; Heer, M.

Lowering mechanical load like in microgravity is the dominant stimulus leading to bone loss However high dietary sodium intake is also considered as a risk factor for osteoporosis and thereby might exacerbate the microgravity induced bone loss In a metabolic balance non bed-rest study we have recently shown that a very high sodium intake leads to an increased bone resorption most likely because of a mild metabolic acidosis Frings et al FASEB J 19 5 A1345 2005 To test if mild metabolic acidosis also occurs during immobilization we examined the effect of increased dietary sodium on bone metabolism and acid-base balance in eight healthy male test subjects mean age 26 25 pm 3 49 years body weight 77 98 pm 4 34 kg in our metabolic ward during a 14-day head-down tilt HDT bed-rest study The study was designed as a randomized crossover study with two study periods Each period was divided into three parts 4 ambulatory days with 200 mmol sodium intake 14 days of bed-rest with either 550 mmol or 50 mmol sodium intake and 3 recovery days with 200 mmol sodium intake The sodium intake was altered by variations in dietary sodium chloride content Blood pH P CO2 and P O2 were analyzed in fasting morning fingertip blood samples several times during the entire study Bicarbonate HCO 3 - and base excess BE were calculated according to the Henderson-Hasselbach equation Preliminary results in the acid-base balance from the first study period 4 subjects with 550 mmol and 4 subjects with 50 mmol sodium intake strongly

Vibration mechanosignals superimposed to resistive exercise result in baseline skeletal muscle transcriptome profiles following chronic disuse in bed rest.

PubMed

Salanova, Michele; Gambara, Guido; Moriggi, Manuela; Vasso, Michele; Ungethuem, Ute; Belavý, Daniel L; Felsenberg, Dieter; Cerretelli, Paolo; Gelfi, Cecilia; Blottner, Dieter

2015-11-24

Disuse-induced muscle atrophy is a major concern in aging, in neuromuscular diseases, post-traumatic injury and in microgravity life sciences affecting health and fitness also of crew members in spaceflight. By using a laboratory analogue to body unloading we perform for the first time global gene expression profiling joined to specific proteomic analysis to map molecular adaptations in disused (60 days of bed rest) human soleus muscle (CTR) and in response to a resistive exercise (RE) countermeasure protocol without and with superimposed vibration mechanosignals (RVE). Adopting Affymetrix GeneChip technology we identified 235 differently transcribed genes in the CTR group (end- vs. pre-bed rest). RE comprised 206 differentially expressed genes, whereas only 51 changed gene transcripts were found in RVE. Most gene transcription and proteomic changes were linked to various key metabolic pathways (glycolysis, oxidative phosphorylation, tricarboxylic acid (TCA) cycle, lipid metabolism) and to functional contractile structures. Gene expression profiling in bed rest identified a novel set of genes explicitly responsive to vibration mechanosignals in human soleus. This new finding highlights the efficacy of RVE protocol in reducing key signs of disuse maladaptation and atrophy, and to maintain a close-to-normal skeletal muscle quality outcome following chronic disuse in bed rest.

A New Method for Tracking Individual Particles During Bed Load Transport in a Gravel-Bed River

NASA Astrophysics Data System (ADS)

Tremblay, M.; Marquis, G. A.; Roy, A. G.; Chaire de Recherche Du Canada En Dynamique Fluviale

2010-12-01

Many particle tracers (passive or active) have been developed to study gravel movement in rivers. It remains difficult, however, to document resting and moving periods and to know how particles travel from one deposition site to another. Our new tracking method uses the Hobo Pendant G acceleration Data Logger to quantitatively describe the motion of individual particles from the initiation of movement, through the displacement and to the rest, in a natural gravel river. The Hobo measures the acceleration in three dimensions at a chosen temporal frequency. The Hobo was inserted into 11 artificial rocks. The rocks were seeded in Ruisseau Béard, a small gravel-bed river in the Yamaska drainage basin (Québec) where the hydraulics, particle sizes and bed characteristics are well known. The signals recorded during eight floods (Summer and Fall 2008-2009) allowed us to develop an algorithm which classifies the periods of rest and motion. We can differentiate two types of motion: sliding and rolling. The particles can also vibrate while remaining in the same position. The examination of the movement and vibration periods with respect to the hydraulic conditions (discharge, shear stress, stream power) showed that vibration occurred mostly before the rise of hydrograph and allowed us to establish movement threshold and response times. In all cases, particle movements occurred during floods but not always in direct response to increased bed shear stress and stream power. This method offers great potential to track individual particles and to establish a spatiotemporal sequence of the intermittent transport of the particle during a flood and to test theories concerning the resting periods of particles on a gravel bed.

WISE-2005: Integrative cardiovascular responses with LBNP during 60-day bed rest in women

NASA Astrophysics Data System (ADS)

Hughson, R. L.; Kerbeci, P.; Arbeille, P.; Mattar, L.; Shoemaker, J. K.

2005-08-01

During 2005, 24 women will take part in the Women International Space-simulation for Exploration (WISE). In this paper we report on the first phase that studied 4 Exercise (EX+LBNP), 4 nutrition (NUT), and 4 no countermeasure control (CON) subjects. The EX+LBNP group completed regular exercise on a treadmill inside LBNP, flywheel resistive exercise and static periods of LBNP, and had recovery days. The NUT group received daily protein supplements. Integrative cardiovascular responses were obtained and here we report data for heart rate during LBNP, blood volume and angiotensin II. LBNP was applied at 0, -10, -20 and -30 mmHg for 2-minutes for each stage. Blood was sampled pre- bed rest and on HDT-60. After 60-days head down bed rest, HR in the CON group increased by 6.1±2.8 bpm at rest and by 20.7±5.0 bpm at -30 mmHg LBNP. The EX+LBNP group had increases of 3.6±5.6 and 11.6±5.4 bpm, while the NUT group HR increased 2.6±3.1 and 9.4±3.6 bpm. The EX+LBNP group had almost no change in blood volume or plasma angiotensin II from pre-bed rest to HDT60, while both the CON and NUT groups had larger increases in plasma volume and almost double concentrations of angiotensin II. These data show a positive effect in the EX+LBNP group on the heart rate response as well as an unexpected possible benefit in the NUT group. Further studies are required to confirm possible cardiovascular benefits of the protein supplement.

Implementation of the NASA AG-Bed Rest Pilot

NASA Technical Reports Server (NTRS)

Warren, L. E.; Paloski, W. H.; Young, L. R.

2007-01-01

To examine the efficacy of artificial gravity (AG) as a countermeasure to spaceflight deconditioning, intermittent AG produced by a horizontal short-radius centrifuge (SRC) was utilized on human test subjects deconditioned by bed rest. This poster will present the subject screening, study design, logistics, and implementation of the 41 day pilot study conducted at the University of Texas Medical Branch, Galveston, TX bed rest facility. An extensive screening process was employed to exclude subjects that were dissimilar to the U.S. astronaut population. Candidates underwent a modified U.S. Air Force Class III physical and tests of bone density, cardiovascular fitness, vestibular system function, psychological fitness and centrifuge tolerance. 15 subjects completed the study; 7 control and 8 AG treatment. All provided written consent to volunteer after the nature of the study and its hazards were clearly explained to them. Standard conditions were strictly regulated; Ta = 72 +/- 2 F, humidity = 70 +/- 5%, light/dark cycle 16h:8h. All fluid intake (minimum 28.5 ml/kg body weight/day) and urine output was monitored. Caloric intake was adjusted as necessary to maintain body weight. Carbohydrate, fat and protein were provided in a ratio of 55:30:15. Phosphorus intake was 1400 mg/d, sodium intake was 2 mmol/kg/d, potassium intake was 1.3 mmol/kg/d, and dietary calcium intake was 1000 mg/d. A physician examined each subject daily. During the first 11 days of the study protocol, subjects were ambulatory, but confined to the facility. Subjects participated in multiple baseline tests of bone, muscle, cardiovascular, sensory-motor, immunological, and psychological function. On the 12th day, subjects entered the bed rest phase of the study, during which they were confined to strict 6? head down tilt bed rest for 21 days. Beginning 24 hrs into this period, treatment subjects received 1 hour daily exposures to artificial gravity which was produced by spinning the subjects on a 3.0 m radius SRC. They were oriented radially in the supine position so that the centrifugal force was aligned with their long body axis, and while spinning, they #stood# on a force plate, supporting the centrifugal loading (2.5 g at the feet, 1.0 g at the heart). The subject station allowed free translation over approximately 10 cm to ensure full loading of the lower extremities and to allow for anti-orthostatic muscle contractions. Control subjects were positioned on the centrifuge but did not spin. Following the bed rest phase, subjects were allowed to ambulate again, but remained within the facility for an additional 9 days and participated in multiple follow-up tests of physiological function.

Downsizing of acute inpatient beds associated with private finance initiative: Scotland's case study.

PubMed

Dunnigan, Matthew G; Pollock, Allyson M

2003-04-26

To evaluate whether the projected 24% reduction in acute bed numbers in Lothian hospitals, which formed part of the private finance initiative (PFI) plans for the replacement Royal Infirmary of Edinburgh, is being compensated for by improvements in efficiency and greater use of community facilities, and to ascertain whether there is an independent PFI effect by comparing clinical activity and performance in acute specialties in Lothian hospitals with other NHS hospitals in Scotland. Comparison of projected and actual trends in acute bed capacity and inpatient and day case admissions in the first five years (1995-6 to 2000-1) of Lothian Health Board's integrated healthcare plan. Population study of trends in bed rate, hospital activity, length of stay, and throughput in Lothian hospitals compared with the rest of Scotland from 1990-1 to 2000-1. Staffed bed rates, admission rates, mean lengths of stay, occupancy, and throughput in four adult acute specialty groups in 1990-1, 1995-6, and 2000-1. By 2000-1, rates for inpatient admission in all acute, medical, surgical, and intensive therapy specialties in Lothian hospitals were respectively 20%, 6%, 28%, and 38% below those in the rest of Scotland. Day case rates in all acute and acute surgical specialties were 13% and 33% lower. The proportion of delayed discharges in staffed acute and post-acute NHS beds in Lothian hospitals exceeded the Scottish average (15% and 12% respectively; P<0.001). The planning targets and increase in clinical activity in acute specialties in Lothian hospitals associated with PFI had not been achieved by 2000-1. The effect on clinical activity has been a steeper decline in the number of acute beds and rates of admission in Lothian hospitals compared with the rest of Scotland between 1995-6 and 2000-1.

Executive function on the 16-day of bed rest in young healthy men

NASA Astrophysics Data System (ADS)

Ishizaki, Yuko; Fukuoka, Hideoki; Tanaka, Hidetaka; Ishizaki, Tatsuro; Fujii, Yuri; Hattori-Uchida, Yuko; Nakamura, Minako; Ohkawa, Kaoru; Kobayashi, Hodaka; Taniuchi, Shoichiro; Kaneko, Kazunari

2009-05-01

Microgravity due to prolonged bed rest may cause changes in cerebral circulation, which is related to brain function. We evaluate the effect of simulated microgravity due to a 6° head-down tilt bed rest experiment on executive function among 12 healthy young men. Four kinds of psychoneurological tests—the table tapping test, the trail making test, the pointing test and losing at rock-paper-scissors—were performed on the baseline and on day 16 of the experiment. There was no significant difference in the results between the baseline and day 16 on all tests, which indicated that executive function was not impaired by the 16-day 6° head-down tilting bed rest. However, we cannot conclude that microgravity did not affect executive function because of the possible contribution of the following factors: (1) the timing of tests, (2) the learning effect, or (3) changes in psychophysiology that were too small to affect higher brain function.

Alendronate as an Effective Countermeasure to Disuse Induced Bone loss

NASA Technical Reports Server (NTRS)

LeBlanc, Adrian D.; Driscol, Theda B.; Shackelford, Linda C.; Evans, Harlan J.; Rianon, Nahid J.; Smith, Scott M.; Lai, Dejian

2002-01-01

Microgravity, similar to diuse immobilization on earth, causes rapid bone loss. This loss is believed to be an adaptive response to the reduced musculoskelatal forces in space and occurs gradually enough that changes occurring during short duration space flight are not a concern. Bone loss, however, will be a major impediment for long duration missions if effective countermeasures are not developed and implemented. Bed rest is used to simulate the reduced mechanical forces in humans and was used to test the hypothesis that oral alendronate would reduce the effects of long duration (17 weeks) inactivity on bone. Eight male subjects were given daily oral doses of alendronate during 17 weeks of horizontal bed rest and compared with 13 male control subjects not given the drug. Efficacy was evaluated based on measurements of bone markers, calcium balance and bone density performed before, during and after the bed rest. The results show that oral alendronate attenuates most of the characteristic changes associated with long duration bed rest and presumably space flight.

Exercise thermoregulation with bed rest, confinement, and immersion deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1997-01-01

Altered thermoregulation following exposure to prolonged (12-14 days) of bed rest and 6 hr of head-down thermoneutral water immersion in humans, and cage confinement (8 weeks) in male, mongrel dogs resulted in occasional increased core temperature (Tcore) at rest, but consistent "excessive" increase in Tcore during submaximal exercise. This excessive increase in Tcore in nonexercising and exercising subjects was independent of the mode (isometric or isotonic) of exercise training during bed rest, and was associated with the consistent hypovolemia in men but not in women taking estrogen supplementation (1.25 mg premarin/ day) which restored plasma volume during bed rest to ambulatory control levels. Post-bed rest exercise sweating (evaporative heat loss) was unchanged or higher than control levels; however, calculated tissue heat conductance was significantly lower in men, and forearm venoconstriction was greater (venous volume was reduced) in women during exercise after bed rest. Because sweating appeared proportional to the increased level of Tcore, these findings suggest that one major factor for the excessive hyperthermia is decreased core to periphery heat conduction. Exercising dogs respond like humans with excessive increase in both rectal (Tre) and exercising muscle temperatures (Tmu) after confinement and, after eight weeks of exercise training on a treadmill following confinement, they had an attenuated rate of increase of Tre even below ambulatory control levels. Intravenous infusion of glucose also attenuated not only the rise in Tre during exercise in normal dogs, but also the excessive rise in Tre and exercising Tmu after confinement. Oral glucose also appeared to reduce the rate of increase in excessive Tre in men after immersion deconditioning. There was a greater rate of rise in Tcore in two cosmonauts during supine submaximal exercise (65% VO2 max) on the fifth recovery day after the 115-day Mir 18 mission. Thus, the excessive rise in core temperature after deconditioning appears to be caused by decreased peripheral vasodilation in humans. Factors related to glucose metabolism may influence this mechanism.

Gender Differences in Isokinetic Strength after 60 and 90 d Bed Rest

NASA Technical Reports Server (NTRS)

English, K. L.; Ploutz-Snyder, R. J.; Cromwell, R. L.; Ploutz-Snyder, L. L.

2010-01-01

Recent reports suggest that changes in muscle strength following disuse may differ between males and females. PURPOSE: To examine potential gender differences in strength changes following 60 and 90 d of experimental bed rest. METHODS: Isokinetic extensor and flexor strength of the knee (60deg and 180deg/s, concentric only), ankle (30deg/s, concentric and eccentric), and trunk (60deg/s, concentric only) were measured following 60 d (males: n=4, 34.5+/-9.6 y; females: n=4, 35.5+/-8.2 y) and 90 d (males: n=10, 31.4+/-4.8 y; females: n=5, 37.6+/-9.9 y) of 6-degree head-down-tilt bed rest (BR; N=23). Subjects were fed a controlled diet (55%/15%/ 30%, CHO/PRO/FAT) that maintained body weight within 3% of the weight recorded on Day 3 of bed rest. After a familiarization session, testing was conducted 6 d before BR and 2 d after BR completion. Peak torque and total work were calculated for the tests performed. To allow us to combine data from both 60- and 90-d subjects, we used a mixed-model statistical analysis in which time and gender were fixed effects and bed rest duration was a random effect. Log-transformations of strength measures were utilized when necessary in order to meet statistical assumptions. RESULTS: Main effects were seen for both time and gender (p<0.05), showing decreased strength in response to bed rest for both males and females, and males stronger than females for most strength measures. Only one interaction effect was observed: females exhibited a greater loss of trunk extensor peak torque at 60 d versus pre-BR, relative to males (p=0.004). CONCLUSION: Sixty and 90 d of BR induced significant losses in isokinetic muscle strength of the locomotor and postural muscles of the knee, ankle, and trunk. Although males were stronger than females for most of the strength measures that we examined, only changes in trunk extensor peak torque were greater for females than males at day 60 of bed rest

Use it or lose it--the hazards of bed rest and inactivity.

PubMed Central

Corcoran, P. J.

1991-01-01

Professional experience and lay wisdom teach us the benefits of exercise and the hazards of idleness. Yet the myth persists that "bed rest is good for you" when ill or convalescing. Abundant scientific evidence in the past 50 years has demonstrated the specific damage done to each of the body's organ systems by inactivity. Both aging and inactivity lead to strikingly similar kinds of deterioration. I summarize the data from military and veterans' hospitals, rehabilitation experience, aerospace research, and gerontology and review the physiologic and metabolic changes of aging and inactivity, along with strategies to help prevent the iatrogenic complications of bed rest. PMID:1866946

Prolonged bed rest decreases skeletal muscle and whole body protein synthesis

NASA Technical Reports Server (NTRS)

Ferrando, A. A.; Lane, H. W.; Stuart, C. A.; Davis-Street, J.; Wolfe, R. R.

1996-01-01

We sought to determine the extent to which the loss of lean body mass and nitrogen during inactivity was due to alterations in skeletal muscle protein metabolism. Six male subjects were studied during 7 days of diet stabilization and after 14 days of stimulated microgravity (-6 degrees bed rest). Nitrogen balance became more negative (P < 0.03) during the 2nd wk of bed rest. Leg and whole body lean mass decreased after bed rest (P < 0.05). Serum cortisol, insulin, insulin-like growth factor I, and testosterone values did not change. Arteriovenous model calculations based on the infusion of L-[ring-13C6]-phenylalanine in five subjects revealed a 50% decrease in muscle protein synthesis (PS; P < 0.03). Fractional PS by tracer incorporation into muscle protein also decreased by 46% (P < 0.05). The decrease in PS was related to a corresponding decrease in the sum of intracellular amino acid appearance from protein breakdown and inward transport. Whole body protein synthesis determined by [15N]alanine ingestion on six subjects also revealed a 14% decrease (P < 0.01). Neither model-derived nor whole body values for protein breakdown change significantly. These results indicate that the loss of body protein with inactivity is predominantly due to a decrease in muscle PS and that this decrease is reflected in both whole body and skeletal muscle measures.

Performance and mood-state parameters during 30-day 6 deg head-down bed rest with exercise training

NASA Technical Reports Server (NTRS)

Deroshia, Charles W.; Greenleaf, J. E.

1993-01-01

A study aimed at determining if the performance and mood impairments occur in bed-rested subjects, and if different exercise-training regimens modify or prevent them is presented. Eighteen healthy men were divided into three groups performing no exercise, isotonic exercise, and isokinetic exercise. Few deleterious changes occurred in performance and mood of the three groups which did not exceed baseline ambulatory levels. It is concluded that mood and performance did not deteriorate in response to prolonged bedrest and were not altered by exercise training.

A Forty-Year Follow-Up of the Dallas Bed Rest and Training Study: The Effect of Age on the Cardiovascular Response to Exercise in Men

PubMed Central

McGavock, Jonathan M.; Hastings, Jeffrey L.; Snell, Peter G.; McGuire, Darren K.; Pacini, Eric L.; Mitchell, Jere H.

2009-01-01

Background In 1966, five 20-year-old men underwent a comprehensive physiological evaluation of the capacity for adaptation of the cardiovascular system in response to 3 weeks of bed rest and 8 weeks of heavy endurance training; these same participants were reevaluated before and after training at the age of 50. The aim of the present study was to reexamine these same men 40 years following the original assessments. Methods and Results In all three studies, minute ventilation and expired gases were analyzed during exercise testing with Douglas bag collection. Cardiac output (CO) was determined using the acetylene rebreathing technique. Compared with the original 30-year interval, the decline in maximal oxygen uptake (VO2max) (−11% vs −25%), maximal CO (+6% vs −11%), and maximal stroke volume (+10% vs −10%) were greater between 50 and 60 years of age. The annualized decline in VO2max (55 mL/min/y) between ages 50 and 60 was approximately fourfold higher than the decline between 20 and 50 years (12 mL/min/y). Conclusions In the original five participants of the Dallas Bed Rest and Training Study, VO2max declined after 40 years of living due to a balanced decrease in central and peripheral determinants of oxygen uptake. The rate of decline in VO2max and its components accelerated after the age of 50 years secondary to age and clinical comorbidities. The net proportional decline in VO2max for a period of 40 years of life was comparable with that experienced after 3 weeks of strict bed rest at the age of 20 (27% vs 26%, respectively). PMID:19196908

New onset of constipation during long-term physical inactivity: a proof-of-concept study on the immobility-induced bowel changes.

PubMed

Iovino, Paola; Chiarioni, Giuseppe; Bilancio, Giancarlo; Cirillo, Massimo; Mekjavic, Igor B; Pisot, Rado; Ciacci, Carolina

2013-01-01

The pathophysiological mechanisms underlining constipation are incompletely understood, but prolonged bed rest is commonly considered a relevant determinant. Our primary aim was to study the effect of long-term physical inactivity on determining a new onset of constipation. Secondary aim were the evaluation of changes in stool frequency, bowel function and symptoms induced by this prolonged physical inactivity. Ten healthy men underwent a 7-day run-in followed by 35-day study of experimentally-controlled bed rest. The study was sponsored by the Italian Space Agency. The onset of constipation was evaluated according to Rome III criteria for functional constipation. Abdominal bloating, flatulence, pain and urgency were assessed by a 100mm Visual Analog Scales and bowel function by adjectival scales (Bristol Stool Form Scale, ease of passage of stool and sense of incomplete evacuation). Daily measurements of bowel movements was summarized on a weekly score. Pre and post bed rest Quality of Life (SF-36), general health (Goldberg's General Health) and depression mood (Zung scale) questionnaires were administered. New onset of functional constipation fulfilling Rome III criteria was found in 60% (6/10) of participants (p=0.03). The score of flatulence significantly increased whilst the stool frequency significantly decreased during the week-by-week comparisons period (repeated-measures ANOVA, p=0.02 and p=0.001, respectively). Stool consistency and bowel symptoms were not influenced by prolonged physical inactivity. In addition, no significant changes were observed in general health, in mood state and in quality of life at the end of bed rest. Our results provide evidence that prolonged physical inactivity is relevant etiology in functional constipation in healthy individuals. The common clinical suggestion of early mobilization in bedridden patients is supported as well.

Multi-System Effects of Daily Artificial Gravity Exposures in Humans Deconditioned by Bed Rest

NASA Technical Reports Server (NTRS)

Paloski, William H.

2007-01-01

We have begun to explore the utility of intermittent artificial gravity (AG) as a multi-system countermeasure to the untoward health and performance effects of adaptation to decreased gravity during prolonged space flight. The first study in this exploration was jointly designed by an international, multi-disciplinary team of scientists interested in standardizing an approach so that comparable data could be obtained from follow-on studies performed in multiple international locations. Fifteen rigorously screened male volunteers participated in the study after providing written informed consent. All were subjected to 21 days of 6deg head-down-tilt (HDT) bed rest. Eight were treated with daily 1hr AG exposures (2.5g at the feet decreasing to 1.0g at the heart) aboard a short radius (3m) centrifuge, while the other seven served as controls. Multiple observations were made of dependent measures in the bone, muscle, cardiovascular, sensory-motor, immune, and behavioral systems during a 10 day acclimatization period prior to HDT bed rest and again during an 8 day recovery period after the bed rest period. Comparisons between the treatment and control subjects demonstrated salutary effects of the AG exposure on aspects of the muscle and cardiovascular systems, with no untoward effects on the vestibular system, the immune system, or cognitive function. Bone deconditioning was similar between the treatment and control groups, suggesting that the loading provided by this specific AG paradigm was insufficient to protect that system from deconditioning. Future work will be devoted to varying the loading duty cycle and/or coupling the AG loading with exercise to provide maximum physiological protection across all systems. Testing will also be extended to female subjects. The results of this study suggest that intermittent AG could be an effective multi-system countermeasure.

Immune Response and Function: Exercise Conditioning Versus Bed-Rest and Spaceflight Deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Jackson, C. G. R.; Lawless, D.

1994-01-01

Immune responses measured at rest immediately or some hours after exercise training (some with and some without increase in maximal oxygen uptake) gave variable and sometimes conflicting results; therefore, no general conclusions can be drawn. On the other hand, most immune responses were either unchanged (immunoglobulin, T cells, CD4+, and natural killer activity) or decreased (blood properdin, neutrophil phagocytic activity, salivary lysozymes, brain immunoglobulin A and G, and liver B lymphocytes and phytohemagglutinin activity) during prolonged bed rest. Some data suggested that exercise training during bed rest may partially ameliorate the decreased functioning of the immune system. Exercise and change in body position, especially during prolonged bed rest with plasma fluid shifts and diuresis, may induce a change in plasma protein concentration and content, which can influence drug metabolism as well as immune function. Leukocytosis, accompanied by lymphopenia and a depressed lymphocyte response, occurs in astronauts on return to Earth from spaceflight; recovery may depend on time of exposure to microgravity. It is clear that the effect of drugs and exercise used as countermeasures for microgravity deconditioning should be evaluated for their effect on an astronaut's immune system to assure optimal health and performance on long-duration space missions.

Bed Rest Affects Ventricular and Arterial Elastances in Monkeys: Implications for Humans

DTIC Science & Technology

2004-01-01

Eart may provide insight into adaptation and compromise of cardiovascular function induced by exposure to microgravity or confinement to bed rest...control treatments in our animals in order for Ees to increase in a similar magnitude across LBNP. Although we did not measure cardiac baroreflex function ...treatments. Sunagawa and co-workers have proposed that the integrity of cardiovascular function during rest and exercise is dependent on a mechanical

Six-Degree Head-Down Tilt Bed Rest: Forty Years of Development as a Physiological Analog for Weightlessness

NASA Technical Reports Server (NTRS)

Smith, Jeffrey D.; Cromwell, Ronita L.; Kundrot, Craig E.; Charles, John B.

2011-01-01

Early on, bed rest was recognized as a method for inducing many of the physiological changes experienced by spaceflight. Head-down tilt (HDT) bed rest was first introduced as an analog for spaceflight by a Soviet team led by Genin and Kakurin. Their study was performed in 1970 (at -4 degrees) and lasted for 30 days; results were reported in the Russian Journal of Space Biology (Kosmicheskaya Biol. 1972; 6(4): 26-28 & 45-109). The goal was to test physiological countermeasures for cosmonauts who would soon begin month-long missions to the Salyut space station. HDT was chosen to produce a similar sensation of blood flow to the head reported by Soyuz cosmonauts. Over the next decade, other tilt angles were studied and comparisons with spaceflight were made, showing that HDT greater than 4 degrees was superior to horizontal bed rest for modeling acute physiological changes observed in space; but, at higher angles, subjects experienced greater discomfort without clearly improving the physiological comparison to spaceflight. A joint study performed by US and Soviet investigators, in 1979, set the goal of standardization of baseline conditions and chose 6-degrees HDT. This effectively established 6-degree HDT bed rest as the internationally-preferred analog for weightlessness and, since 1990, nearly all further studies have been conducted at 6-degrees HDT. A thorough literature review (1970-2010) revealed 534 primary scientific journal articles which reported results from using HDT as a physiological analog for spaceflight. These studies have ranged from as little as 10 minutes to the longest duration of 370 days. Long-term studies lasting four weeks or more have resulted in over 170 primary research articles. Today, the 6-degree HDT model provides a consistent, thoroughly-tested, ground-based analog for spaceflight and allows the proper scientific controls for rigorous testing of physiological countermeasures; however, all models have their strengths and limits. The 6-degrees HDT model must continue to be scrutinized, re-examined, validated and compared to other analog environments whenever possible. Only by understanding the strengths and limits of this model, will it continue to serve as a critical physiological analog to spaceflight for many more years to come.

Effect of artificial gravity with exercise load by using a short-arm centrifuge with bicycle ergometer as a countermeasure against disused osteoporosis

NASA Astrophysics Data System (ADS)

Shiozawa, Youke; Iwase, Satoshi; Kamiya, Atsunori; Takada, Hiroki; Michikami, Daisaku; Hiriayanagi, Kaname; Watanabe, Yoriko; Sugenoya, Jun-ichi; Mano, Tada-aki; Yajima, Kazuyoshi

2005-08-01

To evaluate the effectiveness of centrifuge-induced artificial gravity with ergometric exercise to disused osteoporosis, 9 young healthy men were exposed to -6° head-down bed-rest for 14 days. Four out of nine subjects were loaded by intermittent artificial gravity with ergometric workload. The rest of subjects were the control group. The concentrations of urine deoxy-pyridinoline were examined in each subject before and after the bed-rests. The rate of increase of urine deoxy-pyridinoline of the countermeasure group was significantly more suppressed than the control group. This countermeasure can definitely suppress the bone absorption which is caused by 14 days head-down bed-rest; however the effectiveness is still insufficient. More gravitational load or exercise load is still required.

The Functional Task Test: Results from the One-Year Mission

NASA Technical Reports Server (NTRS)

Bloomberg, J. J; Batson, C. D.; Buxton, R. E.; Feiveson, A. H.; Kofman, I. S.; Laurie, S.; Lee, S. M. C.; Miller, C. A.; Mulavara, A. P.; Peters, B. T.;

Evaluation of the occurrence and diagnose definitions for Nocturnal Polyuria in Spinal Cord Injured patients during rehabilitation.

PubMed

Viaene, Annick; Denys, Marie-Astrid; Goessaert, An-Sofie; Claeys, Jana; Raes, Ann; Roggeman, Saskia; Everaert, Karel

2017-11-03

Little is known about the occurrence of nocturnal polyuria in spinal cord injured (SCI) patients and the definitions which are preferable in this population. To determine the occurrence of nocturnal polyuria (NP) in spinal cord injured patients during in-patient rehabilitation in the Ghent University Hospital. To study the influence of different time periods (daytime, bed rest and sleep) on the accuracy of the existing diagnose definitions for NP specifically for this type of patients. Retrospective study using patient records. SCI patients during hospital based rehabilitation between 2011 and 2014. Seventy-four SCI patients were selected and their records of frequency-volume charts were examined, after exclusion of unreliable data, forty-seven patients were retained for the current study. Retrospective study using data from frequency-volume charts of either two or three days from patients with SCI. Nocturnal urine production (NUP) and nocturnal polyuria index (NPi) were calculated. There was a significant increase in diuresis, calculated as urine production, between day time and bed rest (p=0.008) and between day time and sleep (p=0.001). All patients showed nocturnal polyuria during a 12-hour night time period (including both bed rest and sleep) and 39 patients showed nocturnal polyuria during the 8 hour period of sleep. There was no significant difference in mean urine production between bed rest and sleep. Prevalence of NP did not significantly differ between the complete or incomplete SCI patients or between patients with higher and lower SCI levels. This study showed that the occurrence of nocturnal polyuria in patients with SCI is high and that it is important to consider which definitions of NP are used for diagnosis. Increase in diuresis is observed during bed rest and sleep and the diagnose is correctly estimated when nocturnal urine production definitions are used in both time periods. In accordance with what was expected, diagnose of NP was overestimated when nocturnal polyuria index type definitions were used. It is important to be aware of the frequent occurrence of nocturnal polyuria in spinal cord injury patients and the impact of their daily routine to the accuracy of the diagnosis of NP. More knowledge about this topic can help to avoid incontinence caused by nocturnal polyuria.

Effects of space flight and -6 degrees bed rest on the neuroendocrine response to metabolic stress in physically fit subjects.

PubMed

Ksinantová, Lucia; Koska, Juraj; Martinkovic, Miroslav; Vigas, Milan; Macho, Ladislav; Kvetnansky, Richard

2004-06-01

The aim of this study was to evaluate the association of plasma epinephrine (EPI) and norepinephrine (NE) responses to insulin-induced hypoglycemia (ITT) 3 weeks before the space flight (SF), on the fifth day of SF, on days 2 and 16 after landing in the first Slovak astronaut, and before and on the fifth day of prolonged bed rest (BR) in 15 military aircraft pilots, aged 33.5 +/- 1.4 years, body mass index (BMI) 26.5 +/- 0.7 kg/m(2), maximal oxygen uptake (VO(2max)) 55.2 +/- 2.4 mL/kg/min, who volunteered for the study. ITT was induced by i.v. administrations of 0.1 IU/kg body weight insulin (Actrapid HM) in a bolus. Insulin administration led to a comparable hypoglycemia in preflight, actual flight conditions, and before and after bed rest. ITT led to a pronounced increase in EPI levels and moderate increase in NE in preflight studies. However, an evidently reduced plasma elevation of EPI was found after insulin administration during SF and during BR. Thus, during the real microgravity in SF and simulated microgravity in BR, ITT activates the adrenomedullary system to less extent that at conditions of the Earth's gravitation. Post-flight changes in EPI and NE did not differ from those of preflight values, since SF was relatively short (8 days) and the readaptation to Earth's gravitation was fast. It seems that an increased blood flow in brain might be responsible for the reduced EPI response to insulin. Responses to ITT in physically fit subjects indicate the stimulus specificity of the deconditioning effect of 5 days of bed rest on the stress response.

Fuel utilization during exercise after 7 days of bed rest

NASA Technical Reports Server (NTRS)

Barrows, Linda H.; Harris, Bernard A.; Moore, Alan D.; Siconolfi, Steven F.

1992-01-01

Energy yield from carbohydrate, fat, and protein during physical activity is partially dependent on an individual's fitness level. Prolonged exposure to microgravity causes musculoskeletal and cardiovascular deconditioning; these adaptations may alter fuel utilization during space flight. Carbohydrate and fat metabolism during exercise were analyzed before and after 7 days of horizontal bed rest.

The prevalence of short cervix between 20 and 24 weeks of gestation and vaginal progesterone for prolonging of gestation.

PubMed

Maerdan, Malipati; Shi, Chunyan; Zhang, Xiaoxiao; Fan, Lixin

2017-07-01

The objective of this study is to understand the prevalence of short cervical length between 20 and 24 weeks gestation in China and to evaluate the efficacy of micronized progesterone for prolonging gestation in nulliparous patients with a short cervix. From May 2010 to May 2015, a total of 25 328 asymptomatic women with singleton pregnancies at Peking University First Hospital had their cervical length routinely measured between 20 and 24 weeks of gestation. A cervical length of 25 mm or less was defined as a shortened cervical length. The therapies prescribed include vaginal micronized progesterone capsules (200 mg each night) or bed rest from 20 to 34 weeks of gestation. The primary outcome was spontaneous delivery before 33 weeks. (1) One hundred fourteen women had a cervical length of ≤25 mm (0.45%). (2) Twenty-nine of which with previous spontaneous preterm delivery or late pregnancy loss had cervical cerclage, the remaining 85 women by the use of vaginal progesterone or simply resting activity restriction to prevent preterm birth. (3) In 85 nulliparous women treated by progesterone or bed rest, progesterone use in cervical length between 10 and 20 mm was associated with a statistically significant reduction in the incidence of preterm birth at <33 weeks of gestation (9.5% versus 45.5%, p = 0.02) compared with bed rest. There were no significant differences in cervical length between 20 and 25 mm in their rates of spontaneous preterm delivery at <33 (5.3% versus 3.2%, p = 0.72), <37 (33.3% versus 54.5%, p = 0.25), or <35 weeks (14.3% versus 45.5, p = 0.06) of gestation between vaginal progesterone and bed rest. The rate of short cervical length was less than expected. Vaginal progesterone is efficacious for the prolonging of gestation in women with a cervical length of 10-20 mm in the mid-trimester for a singleton gestation and nulliparous women. For a cervical length of 20-25 mm in the mid trimester, vaginal progesterone compared with bed rest did not prolong pregnancy.

Leucine partially protects muscle mass and function during bed rest in middle-aged adults1,2

PubMed Central

English, Kirk L; Mettler, Joni A; Ellison, Jennifer B; Mamerow, Madonna M; Arentson-Lantz, Emily; Pattarini, James M; Ploutz-Snyder, Robert; Sheffield-Moore, Melinda; Paddon-Jones, Douglas

2016-01-01

Background: Physical inactivity triggers a rapid loss of muscle mass and function in older adults. Middle-aged adults show few phenotypic signs of aging yet may be more susceptible to inactivity than younger adults. Objective: The aim was to determine whether leucine, a stimulator of translation initiation and skeletal muscle protein synthesis (MPS), can protect skeletal muscle health during bed rest. Design: We used a randomized, double-blind, placebo-controlled trial to assess changes in skeletal MPS, cellular signaling, body composition, and skeletal muscle function in middle-aged adults (n = 19; age ± SEM: 52 ± 1 y) in response to leucine supplementation (LEU group: 0.06 g ∙ kg−1 ∙ meal−1) or an alanine control (CON group) during 14 d of bed rest. Results: Bed rest decreased postabsorptive MPS by 30% ± 9% (CON group) and by 10% ± 10% (LEU group) (main effect for time, P < 0.05), but no differences between groups with respect to pre-post changes (group × time interactions) were detected for MPS or cell signaling. Leucine protected knee extensor peak torque (CON compared with LEU group: −15% ± 2% and −7% ± 3%; group × time interaction, P < 0.05) and endurance (CON compared with LEU: −14% ± 3% and −2% ± 4%; group × time interaction, P < 0.05), prevented an increase in body fat percentage (group × time interaction, P < 0.05), and reduced whole-body lean mass loss after 7 d (CON compared with LEU: −1.5 ± 0.3 and −0.8 ± 0.3 kg; group × time interaction, P < 0.05) but not 14 d (CON compared with LEU: −1.5 ± 0.3 and −1.0 ± 0.3 kg) of bed rest. Leucine also maintained muscle quality (peak torque/kg leg lean mass) after 14 d of bed-rest inactivity (CON compared with LEU: −9% ± 2% and +1% ± 3%; group × time interaction, P < 0.05). Conclusions: Bed rest has a profoundly negative effect on muscle metabolism, mass, and function in middle-aged adults. Leucine supplementation may partially protect muscle health during relatively brief periods of physical inactivity. This trial was registered at clinicaltrials.gov as NCT00968344. PMID:26718415

Effect of leg exercise training on vascular volumes during 30 days of 6 deg head-down bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Vernikos, J.; Wade, C. E.; Barnes, P. R.

1992-01-01

In order to investigate the effects of leg exercise training on vascular volumes during 30 d of 6-deg head-down bed rest, plasma and red cell volumes, body density, and water balance were measured in 19 men confined to bed rest (BR). One group had no exercise training (NOE), another near-maximal variable-intensity isotonic exercise (ITE) for 60 min/d, and the third near-maximal intermittent isokinetic exercise (IKE) for 60 min/d. Mean energy costs for the NOE, IKE, and ITE regimens were determined. Body densities within groups and mean urine volumes between groups were unchanged during BR. Changes in red cell volume followed changes in plasma volume. There was close coupling between resting plasma volume and plasma protein and osmotic content. It is argued that the ITE training protocol is better than the IKE protocol for maintaining plasma volume during prolonged exposure to BR.

Bone mineral loss and recovery after 17 weeks of bed rest

NASA Technical Reports Server (NTRS)

Leblanc, A. D.; Schneider, V. S.; Evans, H. J.; Engelbretson, D. A.; Krebs, J. M.; LaBlanc, A. D. (Principal Investigator)

1990-01-01

The purpose of this work was to determine the rate and extent of bone loss and recovery from long-term disuse and in particular from disuse after exposure to weightlessness. For this purpose, bed rest is used to simulate the reduced stress and strain on the skeleton. This study reports on the bone loss and recovery after 17 weeks of continuous bed rest and 6 months of reambulation in six normal male volunteers. Bone regions measured were the lumbar spine, hip, tibia, forearm, calcaneus, total body, and segmental regions from the total-body scan. The total body, lumbar spine, femoral neck, trochanter, tibia, and calcaneus demonstrated significant loss, p less than 0.05. Expressed as the percentage change from baseline, these were 1.4, 3.9, 3.6, 4.6, 2.2, and 10.4, respectively. Although several areas showed positive slopes during reambulation, only the calcaneus was significant (p less than 0.05), with nearly 100% recovery. Segmental analysis of the total-body scans showed significant loss (p less than 0.05) in the lumbar spine, total spine, pelvis, trunk, and legs. During reambulation, the majority of the regions demonstrated positive slopes, although only the pelvis and trunk were significant (p less than 0.05). Potential redistribution of bone mineral was observed: during bed rest the bone mineral increased in the skull of all subjects. The change in total BMD and calcium from calcium balance were significantly (p less than 0.05) correlated, R = 0.88.

Submaximal exercise VO2 and Qc during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Ertl, A. C.; Bernauer, E. M.

1996-01-01

BACKGROUND: Maintaining intermediary metabolism is necessary for the health and well-being of astronauts on long-duration spaceflights. While peak oxygen uptake (VO2) is consistently decreased during prolonged bed rest, submaximal VO2 is either unchanged or decreased. METHODS: Submaximal exercise metabolism (61 +/- 3% peak VO2) was measured during ambulation (AMB day-2) and on bed rest days 4, 11, and 25 in 19 healthy men (32-42 yr) allocated into no exercise (NOE, N = 5) control, and isotonic exercise (ITE, N = 7) and isokinetic exercise (IKE, N = 7) training groups. Exercise training was conducted supine for two 30-min periods per day for 6 d per week: ITE training was intermittent at 60-90% peak VO2; IKE training was 10 sets of 5 repetitions of peak knee flexion-extension force at a velocity of 100 degrees s-1. Cardiac output was measured with the indirect Fick CO2 method, and plasma volume with Evans blue dye dilution. RESULTS: Supine submaximal exercise VO2 decreased significantly (*p < 0.05) by 10.3%* with ITE and by 7.3%* with IKE; similar to the submaximal cardiac output decrease of 14.5%* (ITE) and 20.3%* (IKE), but different from change in peak VO2 (+1.4% with ITE and -10.2%* with IKE) and decrease in plasma volume of -3.7% (ITE) and -18.0%* (IKE). Reduction of submaximal VO2 during bed rest correlated 0.79 (p < 0.01) with submaximal Qc, but was not related to change in peak VO2 or plasma volume. CONCLUSION: Reduction in submaximal oxygen uptake during prolonged bed rest is related to decrease in exercise but not resting cardiac output; perturbations in active skeletal muscle metabolism may be involved.

Effect of prolonged LBNP and saline ingestion on plasma volume and orthostatic responses during bed rest

NASA Technical Reports Server (NTRS)

Fortney, Suzanne M.; Dussack, Larry; Rehbein, Tracy; Wood, Margie; Steinmann, Laura

1991-01-01

Orthostatic intolerance remains a significant problem following space flight despite frequent use of the saline fluid-loading countermeasure and volitional use of an anti-gravity suite during reentry and landing. The purpose of this project is to examine the plasma volume (PV), endocrine, and orthostatic responses of bedrested subjects following 2-hr and 4-hr treatments of lower body negative pressure (LBNP) and saline ingestion. Ten healthy men were randomly assigned into 2 groups. Group A underwent a 4-hr LBNP/saline treatment on best rest day 5 and the 2-hr treatment on day 11. Group B underwent the 2-hr treatment on day 6 and the 4-hr treatment on day 10. Blood volume was determined before and after bed rest using radiolabelling. Changes in PV between measurements were calculated from changes in hematocrit and estimated red cell volume. Urinary excretion of anti-diuretic hormone (ADH) and aldosterone (ALD) were measured each day during the study. Orthostatic responses were measured using a ramp LBNP protocol before bed rest, before each treatment, and 24 hours after each treatment. Both 2-hr and 4-hr treatments resulted in a restoration of PV to pre-bed rest levels which persisted at least 24 hours. This increase in PV was associated with significant increases in urinary excretion of ADH and ALD. Twenty-four hours after the 4-hr treatment, the heart rate and pulse pressure response to LBNP were significantly lower and stroke volumes during LBNP were increased. Twenty-four hours after the 2-hr treatment, there was no evidence of improvement in orthostatic responses. These results suggest that a countermeasure which simply restores PV during space flight may not be sufficient for restoring orthostatic responses.

Assessment of Immune Status, Latent Viral Reactivation and Stress during Long Duration Bed Rest as an Analog for Spaceflight

NASA Technical Reports Server (NTRS)

Crucian, Brian E.; Stowe, Raymond P.; Mehta, Satish K.; Yetman, Deborah L.; Leaf, Melanie J.; Pierson, Duane L.; Sams, Clarence F.

2007-01-01

As logistical access for in-flight space research becomes more limited, the use of ground based spaceflight analogs for life science studies will increase. These studies are particularly important as NASA progresses towards the Lunar and eventually Mars missions outlined in the 2005 Vision for Space Exploration. Countermeasures must be developed to mitigate the clinical risks associated with exploration class space missions. In an effort to coordinate studies across multiple disciplines, NASA has selected 90-day bed rest as the analog of choice, and initiated the Flight Analogs Project to implement research studies with or without the evaluation of countermeasures. Although bed rest is not the analog of choice to evaluate spaceflight-associated immune dysfunction, a standard Immune Assessment was developed for subjects participating in the 90-day bed best studies. The Immune Assessment consists of: leukocyte subset distribution, T cell functional responses, intracellular cytokine production profiles, latent viral reactivation, virus specific T cell levels, virus specific T cell function, stress hormone levels and a behavioral assessment using stress questionnaires. The purpose of the assessment during the initial studies (without countermeasure) is to establish control data against which future studies (with countermeasure) will be evaluated. It is believed that some of the countermeasures planned to be evaluated in future studies, such as exercise, pharmacologic intervention or nutritional supplementation, have the ability to impact immune function. Therefore immunity will likely be monitored during those studies. The data generated during the first three control studies showed that the subjects in general did not display altered peripheral leukocyte subsets, constitutive immune activation, significant latent viral reactivation (EBV, VZV) or altered T cell function. Interestingly, for some subjects the level of constitutively activated T cells (CD8+/CD69+) and virus-specific T cells (CMV and EBV) both decreased during the studies. This likely reflects the isolation of the subjects (from an immunological perspective) and absence of everyday subclinical challenges to the immune system. Cortisol levels (plasma and saliva) did not vary significantly during the studies. This probably reflects a lack of physiological stress during the study and the stress of readaptation to the 1xG environment at R+1. These data demonstrate the absence of significant immune alteration during 90-day bed rest, and establish control data against which future studies (including countermeasures) may be compared.

The negative effect of hypokinesia involving injury and preventive measures

NASA Technical Reports Server (NTRS)

Izakson, K. A.

1981-01-01

The optimum length of bed rest for athletes suffering from broken bones is considered. Negative effects of hypokinesia induced by bed rest include general weakness and deconditioning of the muscles as well as sleeplessness, headaches, muscle pain, constipation, unstable pulse and arterial pressure, and changes in reflexes. This is considered to be the result of a vegetative dysfunction induced by the decreased flow of nerve impulses and a decrease in interoceptive and exteroceptive signals. The briefest possible period of bed rest, followed by an increase in motor activity, the prescription of a large quantity of LFK, and an active program of physical therapy are recommended. The symptomology associated with hypokinesia disappears after one month of free motor activity.

Integrated Resistance and Aerobic Training Maintains Cardiovascular and Skeletal Muscle Fitness During 14 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Ploutz-Snyder, Lori; Goetchius, Elizabeth; Crowell, Brent; Hackney, Kyle; Wickwire, Jason; Ploutz-Snyder, Robert; Snyder, Scott

2012-01-01

Background: Known incompatibilities exist between resistance and aerobic training. Of particular importance are findings that concurrent resistance and aerobic training reduces the effectiveness of the resistance training and limits skeletal muscle adaptations (example: Dudley & Djamil, 1985). Numerous unloading studies have documented the effectiveness of resistance training alone for the maintenance of skeletal muscle size and strength. However the practical applications of those studies are limited because long ]duration crew members perform both aerobic and resistance exercise throughout missions/spaceflight. To date, such integrated training on the International Space Station (ISS) has not been fully effective in the maintenance of skeletal muscle function. Purpose: The purpose of this study was to evaluate the efficacy of high intensity concurrent resistance and aerobic training for the maintenance of cardiovascular fitness and skeletal muscle strength, power and endurance over 14 days of strict bed rest. Methods: 9 subjects (8 male and 1 female; 34.5 +/- 8.2 years) underwent 14 days of bed rest with concurrent training. Resistance and aerobic training were integrated as shown in table 1. Days that included 2 exercise sessions had a 4-8 hour rest between exercise bouts. The resistance training consisted of 3 sets of 12 repetitions of squat, heel raise, leg press and hamstring curl exercise. Aerobic exercise consisted of periodized interval training that included 30 sec, 2 min and 4 min intervals alternating by day with continuous aerobic exercise.

Changes in prevalence of subjective fatigue during 14-day 6° head-down bed rest

NASA Astrophysics Data System (ADS)

Hirayanagi, Kaname; Natsuno, Toyoki; Shiozawa, Tomoki; Yamaguchi, Nobuhisa; Watanabe, Yoriko; Suzuki, Satomi; Iwase, Satoshi; Mano, Tadaaki; Yajima, Kazuyoshi

2009-06-01

The present study examines the prevalence of subjective fatigue in young healthy males during 14 days of 6° head-down bed rest (HDBR) by using a multidimensional questionnaire. Forty-one subjects completed the Subjective Fatigue Scale questionnaire to assess the fatigue-related complaints and symptoms. The questionnaire is composed of three sections, with 10 items each. The sections measured drowsiness and dullness (Section 1), difficulty in concentration (Section 2), and the projection of physical disintegration (Section 3). The subjects answered simple questions between 1400 and 1700 on 6 measurement days before and during the HDBR period. The prevalence rate of low back pain was markedly high (80.5%) on the second day and more than 50% in the first half of the HDBR period, and any complaints related to either a lack of sleep or a deterioration in the quality of sleep continued until the end of the HDBR period. Our findings may be useful in developing preventive strategies against physical and mental fatigue associated with prolonged HDBR, horizontal bed rest, and microgravity environments.

Tensiomygraphic Measurement of Atrophy Related Processes During Bed Rest and Recovery

NASA Astrophysics Data System (ADS)

Simunic, B. ostjan; Degens, Hans; Rittweger, Jorn; Narici, Marcco; Pisot, Venceslav; Mekjavic, Igor B.; Pisot, Rado

2013-02-01

Tensiomyographic (TMG) parameters were recently proposed for a non-invasive estimation of MHC distribution in human vastus lateralis muscle. However, TMG potential is even higher, offers additional insight into the skeletal muscle physiology, especially in the field of atrophy and hypertrophy. The purpose of this study is in developing time dynamics of TMG-measured contraction time (Tc) and maximal response amplitude (Dm), together with muscle belly thickness, measure thoroughly during 35-day bed rest and followed in 30-day recovery (N = 10 males; age 24.3 ± 2.6 years). Measurements were performed in two postural muscles (vastus medialis and lateralis) and one non-postural muscle (biceps femoris). During bed rest period we found different dynamics of muscle thickness decrease and Dm increase. Tc was unchanged in postural muscles, but in non-postural muscle increased significantly and stayed as such even at the end of recovery. We could conclude that TMG related parameters are more sensitive in measuring muscle atrophic and hypertrophic processes than biomedical imaging technique. However, a mechanism that regulates Dm still needs to be identified.

Disproportionate loss of thin filaments in human soleus muscle after 17-day bed rest

NASA Technical Reports Server (NTRS)

Riley, D. A.; Bain, J. L.; Thompson, J. L.; Fitts, R. H.; Widrick, J. J.; Trappe, S. W.; Trappe, T. A.; Costill, D. L.

1998-01-01

Previously we reported that, after 17-day bed rest unloading of 8 humans, soleus slow fibers atrophied and exhibited increased velocity of shortening without fast myosin expression. The present ultrastructural study examined fibers from the same muscle biopsies to determine whether decreased myofilament packing density accounted for the observed speeding. Quantitation was by computer-assisted morphometry of electron micrographs. Filament densities were normalized for sarcomere length, because density depends directly on length. Thick filament density was unchanged by bed rest. Thin filaments/microm2 decreased 16-23%. Glycogen filled the I band sites vacated by filaments. The percentage decrease in thin filaments (Y) correlated significantly (P < 0.05) with the percentage increase in velocity (X), (Y = 0.1X + 20%, R2 = 0.62). An interpretation is that fewer filaments increases thick to thin filament spacing and causes earlier cross-bridge detachment and faster cycling. Increased velocity helps maintain power (force x velocity) as atrophy lowers force. Atrophic muscles may be prone to sarcomere reloading damage because force/microm2 was near normal, and force per thin filament increased an estimated 30%.

Postural responses of head and foot cutaneous microvascular flow and their sensitivity to bed rest

NASA Technical Reports Server (NTRS)

Aratow, Michael; Hargens, Alan R.; Meyer, J.-UWE; Arnaud, Sara B.

1991-01-01

To explore the mechanism for facial puffiness, headache, and nasal congestion associated with microgravity and cephalad fluid shifts, the postural responses of the cutaneous microcirculation (CMC) in the forehead and dorsum of the foot of eight healthy men were studied by changing body position on a tilt table and measuring blood flows with a laser Doppler flowmeter. Increasing arterial pressure in the feet by moving from a -6-deg head-down tilt to a 60-deg head-up posture decreased foot CMC by 46.5 + or - 12.0 percent. Raising arterial pressure in the head increased forehead CMC by 25.5 + or - 0.7 percent (p less than 0.05). To investigate the possibility that these opposite responses could be modified by simulated microgravity, tilt test were repeated after 7 d of -6-deg head-down-tilt bed rest. The responses were not significantly different from those recorded before bed rest. Therefore, CMC in the feet is well regulated to prevent edema when shifting to an upright position, whereas there is less regulation in the head CMC.

Effects Of Exercise During Prolonged Bed Rest

NASA Technical Reports Server (NTRS)

Arnaud, S.; Berry, P; Cohen, M.; Danelis, J.; Deroshia, C.; Greenleaf, J.; Harris, B.; Keil, L.; Bernauer, E.; Bond, M.;

Cardiovascular Differences after 4 Hours of Head-Down Bed Rest (HDBR) in Men and Women

NASA Astrophysics Data System (ADS)

Edgell, Heather; Grinberg, Anna; Beavers, Keith; Gagne, Nathalie; Geaves, Danielle; Hughson, Richard

2008-06-01

In both sexes, orthostatic responses are impaired by spaceflight or head-down bed-rest (HDBR), with a greater impact in women. We measured heart rate (HR), mean arterial blood pressure (MAP), cardiac output (Q), stroke volume (SV), central venous pressure (CVP), and total peripheral resistance (TPR) in response to lower body negative pressure (LBNP) in men (n=6) and women (n=6; day 8-11 after menstruation) before and after 4-hr HDBR or seated control (SEAT). Women exhibit lower MAP and TPR with higher SV and Q than men (normalized for body size). LBNP increased HR, decreased CVP, decreased SV, increased TPR and decreased Q. In women 4-hr SEAT results in lower CVP (P=0.015). After 4 hr HDBR men and women exhibit: 1) higher HR response (P<0.001), 2) lower resting CVP (P=0.001), 3) a tendency for higher resting Q (p=0.061). Our results indicate that inactivity and/or circadian rhythm may be important factors to consider when studying women.

Neuro-Motor Responses to Daily Centrifugation in Bed-Rested Subjects

NASA Technical Reports Server (NTRS)

Reschke, Millard F.; Somers, Jeffery T.; Krnavek, Jody; Fisher, Elizibeth; Ford, George; Paloski, William H.

2007-01-01

It is well known from numerous space flight studies that exposure to micro-g produces both morphological and neural adaptations in the major postural muscles. However, the characteristics and mechanism of these changes, particularly when it may involve the central nervous system are not defined. Furthermore, it is not known what role unloading of the muscular system may have on central changes in sensorimotor function or if centrifugation along the +Gz direction (long body axis) can mitigate both the peripheral changes in muscle function and modification of the central changes in sensorimotor adaptation to the near weightless environment of space flight. The purpose of this specific effort was, therefore, to investigate the efficacy of artificial gravity (AG) as a method for maintaining sensorimotor function in micro-g. Eight male subjects were exposed to daily 1 hr centrifugation during a 21 day 6 degree head-down bed rest study. Seven controls were placed on the centrifuge without rotation. The radius and angular velocity of the centrifuge were adjusted such that each subject experienced a centripetal acceleration of 2.5g at the feet, and approximately 1.0g at the heart. Both the tendon (MSR) and functional stretch reflexes (FSR) were collected using an 80 lb. ft. servomotor controlled via position feedback to provide a dorsiflexion step input to elicit the MSR, and the same step input with a built in 3 sec hold to evoke the FSR. EMG data were obtained from the triceps surae. Supplementary torque, velocity and position data were collected with the EMG responses. All data were digitized and sampled at 4 kHz. Only the MSR data has been analyzed at this time, and preliminary results suggest that those subjects exposed to active centrifugation (treatment group) show only minor changes in MSR peak latency times, either as a function of time spent in bed rest or exposure to centrifugation, while the control subjects show delays in the MSR peak latencies that are typical of bed rested subjects. There also appears to be a trend in the treatment group where centrifugation results in peak latencies that are shorter than the control group. This trend is supported by the observation that peak reflex amplitudes are larger (up to 40% in magnitude)than those of the control subjects. Furthermore, centrifugation tends, by day 21 of bed rest, to normalize the peak amplitudes to the amplitudes observed prior to bed rest or centrifugation. From a preliminary point of view, centrifugation appears to have a positive effect on the sensorimotor system, and specifically on those muscles that provide anti-gravity and postural support.

New Onset of Constipation during Long-Term Physical Inactivity: A Proof-of-Concept Study on the Immobility-Induced Bowel Changes

PubMed Central

Iovino, Paola; Chiarioni, Giuseppe; Bilancio, Giancarlo; Cirillo, Massimo; Mekjavic, Igor B.; Pisot, Rado; Ciacci, Carolina

2013-01-01

Background The pathophysiological mechanisms underlining constipation are incompletely understood, but prolonged bed rest is commonly considered a relevant determinant. Aims Our primary aim was to study the effect of long-term physical inactivity on determining a new onset of constipation. Secondary aim were the evaluation of changes in stool frequency, bowel function and symptoms induced by this prolonged physical inactivity. Methods Ten healthy men underwent a 7-day run-in followed by 35-day study of experimentally-controlled bed rest. The study was sponsored by the Italian Space Agency. The onset of constipation was evaluated according to Rome III criteria for functional constipation. Abdominal bloating, flatulence, pain and urgency were assessed by a 100mm Visual Analog Scales and bowel function by adjectival scales (Bristol Stool Form Scale, ease of passage of stool and sense of incomplete evacuation). Daily measurements of bowel movements was summarized on a weekly score. Pre and post bed rest Quality of Life (SF-36), general health (Goldberg’s General Health) and depression mood (Zung scale) questionnaires were administered. Results New onset of functional constipation fulfilling Rome III criteria was found in 60% (6/10) of participants (p=0.03). The score of flatulence significantly increased whilst the stool frequency significantly decreased during the week-by-week comparisons period (repeated-measures ANOVA, p=0.02 and p=0.001, respectively). Stool consistency and bowel symptoms were not influenced by prolonged physical inactivity. In addition, no significant changes were observed in general health, in mood state and in quality of life at the end of bed rest Conclusions Our results provide evidence that prolonged physical inactivity is relevant etiology in functional constipation in healthy individuals. The common clinical suggestion of early mobilization in bedridden patients is supported as well. PMID:23977327

Using the Abitibi Greenstone Belt to Understand Martian Hydrothermal Systems and the Potential for Biosignature Preservation in High Temperature Aqueous Environments

NASA Technical Reports Server (NTRS)

Hurowitz, J.; Abelson, J.; Allwood, A.; Anderson, R.; Atkinson, B.; Beaty, D.; Bristow, T.; Ehlmann, B.; Eigenbrode, J.; Grotzinger, J.;

Proceedings of the 1972 Lyndon B. Johnson Space Center Endocrine Program Conference

NASA Technical Reports Server (NTRS)

1974-01-01

Subjects covered during the Endocrine Program Conference include the following: (1) endocrine/metabolic studies on the Apollo 16 crewmen; (2) changes in glucose, insulin, and growth hormone levels associated with bed rest; (3) circadian rhythms of heart rate and body temperature during 56 days of bed rest; (4) stress-induced changes in corticosteroid metabolism in man; (5) present status of physiological studies on parathyroid hormone and vitamin D; (6) antagonistic effect of lithium on antidiuretic hormone action; (7) proposed Skylab body-fluid volumes study; (8) daily rhythmic changes in serotonin content in areas of the mouse brain and norepinephrine content in areas of the hamster brain; (9) studies of sodium homeostasis during simulated weightlessness; and (10) application of the water immersion model to man.

Stochastic analysis of particle movement over a dune bed

USGS Publications Warehouse

Lee, Baum K.; Jobson, Harvey E.

1977-01-01

Stochastic models are available that can be used to predict the transport and dispersion of bed-material sediment particles in an alluvial channel. These models are based on the proposition that the movement of a single bed-material sediment particle consists of a series of steps of random length separated by rest periods of random duration and, therefore, application of the models requires a knowledge of the probability distributions of the step lengths, the rest periods, the elevation of particle deposition, and the elevation of particle erosion. The procedure was tested by determining distributions from bed profiles formed in a large laboratory flume with a coarse sand as the bed material. The elevation of particle deposition and the elevation of particle erosion can be considered to be identically distributed, and their distribution can be described by either a ' truncated Gaussian ' or a ' triangular ' density function. The conditional probability distribution of the rest period given the elevation of particle deposition closely followed the two-parameter gamma distribution. The conditional probability distribution of the step length given the elevation of particle erosion and the elevation of particle deposition also closely followed the two-parameter gamma density function. For a given flow, the scale and shape parameters describing the gamma probability distributions can be expressed as functions of bed-elevation. (Woodard-USGS)

Perception of Human-Derived Risk Influences Choice at Top of the Food Chain

PubMed Central

Cristescu, Bogdan; Stenhouse, Gordon B.; Boyce, Mark S.

2013-01-01

On human-used landscapes, animal behavior is a trade-off between maximizing fitness and minimizing human-derived risk. Understanding risk perception in wildlife can allow mitigation of anthropogenic risk, with benefits to long-term animal fitness. Areas where animals choose to rest should minimize risk from predators, which for large carnivores typically equate to humans. We hypothesize that high human activity leads to selection for habitat security, whereas low activity enables trading security for forage. We investigated selection of resting (bedding) sites by GPS radiocollared adult grizzly bears (n = 10) in a low density population on a multiple-use landscape in Canada. We compared security and foods at resting and random locations while accounting for land use, season, and time of day. On reclaimed mines with low human access, bears selected high horizontal cover far from trails, but did not avoid open (herbaceous) areas, resting primarily at night. In protected areas bears also bedded at night, in areas with berry shrubs and Hedysarum spp., with horizontal cover selected in the summer, during high human access. On public lands with substantial human recreation, bears bedded at day, selected resting sites with high horizontal cover in the summer and habitat edges, with bedding associated with herbaceous foods. These spatial and temporal patterns of selection suggest that bears perceive human-related risk differentially in relation to human activity level, season and time of day, and employ a security-food trade-off strategy. Although grizzly bears are presently not hunted in Alberta, their perceived risks associated with humans influence resting-site selection. PMID:24367549

Complications of immobilization and bed rest. Part 1: Musculoskeletal and cardiovascular complications.

PubMed Central

Dittmer, D. K.; Teasell, R.

1993-01-01

Prolonged bed rest and immobilization inevitably lead to complications. Such complications are much easier to prevent than to treat. Musculoskeletal complications include loss of muscle strength and endurance, contractures and soft tissue changes, disuse osteoporosis, and degenerative joint disease. Cardiovascular complications include an increased heart rate, decreased cardiac reserve, orthostatic hypotension, and venous thromboembolism. Images Figures 1-2 Figures 3-4 PMID:8324411

Effects of rehydration on +Gz tolerance after 14-days' bed rest.

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Van Beaumont, W.; Bernauer, E. M.; Haines, R. F.; Sandler, H.; Staley, R. W.; Young, H. L.; Yusken, J. W.

1973-01-01

Investigation of the magnitude of reduction in human tolerance to centrifugation following 2 weeks of bed rest with moderate daily exercise. The degree of hypovolemia associated with these exposures is assessed, and the possibility to improve or to return to control levels the tolerance to acceleration forces acting in the head-to-foot direction through rehydration prior to acceleration is explored.

Vitamin K Status in Spaceflight and Ground-Based Models of Spaceflight

PubMed Central

Zwart, Sara R; Booth, Sarah L; Peterson, James W; Wang, Zuwei; Smith, Scott M

2011-01-01

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. © 2011 American Society for Bone and Mineral Research. PMID:21541997

WISE-2005: Integrative Cardiovascular Responses with LBNP during 60-Day Bed Rest in Women

NASA Technical Reports Server (NTRS)

Hughson, R. L.; Kerbeci, P.; Arbeille, Ph.; Mattar, L.; Shoemaker, J. K.

2005-01-01

During 2005, 24 women will take part in the Women International Space-simulation for Exploration (WISE). In this paper we report on the first phase that studied 4 Exercise (EX+LBNP), 4 nutrition (NUT), and 4 no countermeasure control (CON) subjects. The EX+LBNP group completed regular exercise on a treadmill inside LBNP, flywheel resistive exercise and static periods of LBNP, and had recovery days. The NUT group received daily protein supplements. Integrative cardiovascular responses were obtained and here we report data for heart rate during LBNP, blood volume and angiotensin 11. LBNP was applied at 0, -10, -20 and -30 mmHg for 2-minutes for each stage. Blood was sampled prebed rest and on HDT-60. After 60-days head down bed rest, HR in the CON group increased by 6.1+/-2.8 bpm at rest and by 20.7+/-5.0 bpm at -30 mmHg LBNP. The EX+LBNP group had increases of 3.6+/-5.6 and 11.6+/-5.4 bpm, while the NUT group HR increased 2.6+/-3.1 and 9.4+/-3.6 bpm. The EX+LBNP group had almost no change in blood volume or plasma angiotensin II from pre-bed rest to HDT60, while both the CON and NUT groups had larger increases in plasma volume and almost double concentrations of angiotensin II. These data show a positive effect in the EX+LBNP group on the heart rate response as well as an unexpected possible benefit in the NUT group. Further studies are required to confirm possible cardiovascular benefits of the protein supplement.

Artificial Gravity as a Multi-System Countermeasure to Bed Rest Deconditioning: Pilot Study Overview

NASA Technical Reports Server (NTRS)

Paloski, William H.; Young, L. R.

2007-01-01

Efficient, effective, multi-system countermeasures will likely be required to protect the health, safety, and performance of crews aboard planned exploration-class space flight missions to Mars and beyond. To that end, NASA, DLR, and IMBP initiated a multi-center international project to begin systematically exploring the utility of artificial gravity (AG) as a multi-system countermeasure in ground based venues using test subjects deconditioned by bed rest. The goal of this project is to explore the efficacy of short-radius, intermittent AG as a countermeasure to bone, muscle, cardiovascular, and sensory-motor adaptations to hypogravity. This session reports the results from a pilot study commissioned to validate a standardized protocol to be used by all centers involved in the project. Subject selection criteria, medical monitoring requirements, medical care procedures, experiment control procedures, and standardized dependent measures were established jointly. Testing was performed on 15 rigorously screened male volunteers subjected to 21 days of 6deg HDT bed rest. (All provided written consent to volunteer after the nature of the study and its hazards were clearly explained to them.) Eight were treated with daily 1hr AG exposures (2.5g at the feet decreasing to 1.0g at the heart) aboard a short radius (3m) centrifuge, while the other seven served as controls. Multiple tests of multiple dependent measures were made in each of the primary physiological systems of interest during a 10 day acclimatization period prior to HDT bed rest and again during an 8 day recovery period after the bed rest period was complete. Analyses of these data (presented in other papers in this session) suggest the AG prescription had salutary effects on aspects of the bone, muscle, and cardiovascular systems, with no untoward effects on the vestibular system, the immune system, or cognitive function. Furthermore, treatment subjects were able to tolerate 153/160 centrifuge sessions over the 21 day deconditioning protocol, suggesting that tolerance was unaffected by deconditioning. These positive results set the stage for full implementation of the planned multi-center international AG project. Future work will be devoted to developing optimization techniques for AG prescriptions (likely supplemented by exercise) to provide maximum physiological protection across all systems subject to space flight deconditioning in both men and women with minimum time and/or side effects. While a continuous AG solution (rotating vehicle) would likely be more efficient, this study suggests that intermittent AG could be an effective multi-system countermeasure.

Treadmill exercise within lower-body negative pressure attenuates simulated spaceflight-induced reductions of balance abilities in men but not women

PubMed Central

Macaulay, Timothy R; Macias, Brandon R; Lee, Stuart MC; Boda, Wanda L; Watenpaugh, Donald E; Hargens, Alan R

2016-01-01

Spaceflight causes sensorimotor adaptations that result in balance deficiencies on return to a gravitational environment. Treadmill exercise within lower-body negative pressure (LBNP) helps protect physiological function during microgravity as simulated by bed rest. Therefore, we hypothesized that treadmill exercise within LBNP would prevent balance losses in both male and female identical twins during 30 days of 6° head-down tilt bed rest. Fifteen (seven female and eight male) identical twin sets participated in this simulation of microgravity. Within each twin pair, one twin was randomly assigned to an exercise group that performed 40 min of supine treadmill exercise within LBNP set to generate 1.0–1.2 body weight, followed by 5 min of static feet-supported LBNP, 6 days per week. Their identical sibling was assigned to a non-exercise control group with all other bed rest conditions equivalent. Before and immediately after bed rest, subjects completed standing and walking rail balance tests with eyes open and eyes closed. In control subjects, standing rail balance times (men: −42%, women: −40%), rail walk distances (men: −44%, women: −32%) and rail walk times (men: −34%, women: −31%) significantly decreased after bed rest. Compared with controls, treadmill exercise within LBNP significantly attenuated losses of standing rail balance time by 63% in men, but the 41% attenuation in women was not significant. Treadmill exercise within LBNP did not affect rail walk abilities in men or women. Treadmill exercise within LBNP during simulated spaceflight attenuates loss of balance control in men but not in women. PMID:28725733

Effect of aerobic capacity on Lower Body Negative Pressure (LBNP) tolerance in females

NASA Technical Reports Server (NTRS)

Moore, Alan D., Jr.; Fortney, Suzanne M.; Siconolfi, Steven F.

1993-01-01

This investigation determined whether a relationship exists in females between: (1) aerobic capacity and Lower Body Negative Pressure (LBNP); and (2) aerobic capacity and change in LBNP tolerance induced by bed rest. Nine females, age 27-47 (34.6 plus or minus 6.0 (Mean plus or minus SD)), completed a treadmill-graded exercise test to establish aerobic capacity. A presyncopal-limited LBNP test was performed prior to and after 13 days of bed rest at a 6 deg head-down tilt. LBNP tolerance was quantified as: (1) the absolute level of negative pressure (NP) tolerated for greater than or equal to 60 sec; and (2) Luft's Cumulative Stress Index (CSI). Aerobic capacity was 33.3 plus or minus 5.0 mL/kg/min and ranged from 25.7 to 38.7. Bed rest was associated with a decrease in NP tolerance (-9.04 1.6 kPa(-67.8 plus or minus 12.0 mmHg) versus -7.7 1.1 kPa(-57.8 plus or minus 8.33 mmHg); p = 0.028) and in CSI (99.4 27.4 kPa min(745.7 plus or minus 205.4 mmHg min) versus 77.0 16.9 kPa min (577.3 plus or minus mmHg min); p = 0.008). The correlation between aerobic capacity and absolute NP or CSI pre-bed rest did not differ significantly from zero (r = -0.56, p = 0.11 for NP; and r = -0.52, p = 0.16 for CSI). Also, no significant correlation was observed between aerobic and pre- to post-rest change for absolute NP tolerance (r = -0.35, p = 0.35) or CSI (r = -0.32, p = 0.40). Therefore, a significant relationship does not exist between aerobic capacity and orthostatic function or change in orthostatic function induced by bed rest.

Misting and fan cooling of the rest area in a dairy barn.

PubMed

Calegari, Ferdinando; Calamari, Luigi; Frazzi, Ermes

2012-03-01

This summer study aimed to evaluate the effect on dairy cows, kept in a free stall barn equipped with fans and sprinklers in the feeding area, of the delivery rate of misters in a cooling system in rest areas with different bedding materials. Thirty cows were divided into two homogenous groups according to milk yield and kept in two pens: one had beds with sand (SAMM) while the other had straw (STLM). Each pen was equipped with 2 fans (Ø 70 cm, 0.50 kW) and 2 misters (delivery rate of 11.2 and 22.5 L/h in STLM and SAMM, respectively) in the rest area. Microclimatic parameters, rectal temperature (RT), breathing rate (BR), milk yield, and some milk traits were recorded. Behavioural routines of the cows (standing and lying) were also continuously recorded during the hotter days. During the trial, two mild-moderate heat waves were observed. During these hotter periods, the daily maximum temperature recorded in the rest areas was 28.9 in SAMM and 31.2 in STLM, and the daily maximum THI was 78.2 in SAMM and 81.5 in STLM. In these periods, the cows in SAMM compared with those in STLM showed lower BR (P < 0.05) and greater rest time (10.2 and 7.8 h/day in SAMM and STLM, respectively). The RT did not differ (38.89 ± 0.29 and 38.88 ± 0.33°C in STLM and SAMM r,espectively). In conclusion, our research suggests that the cooling system using fans plus misters with mild wetting in rest areas with sand as bedding materials reduces heat stress and improves cow comfort.

Misting and fan cooling of the rest area in a dairy barn

NASA Astrophysics Data System (ADS)

Calegari, Ferdinando; Calamari, Luigi; Frazzi, Ermes

2012-03-01

This summer study aimed to evaluate the effect on dairy cows, kept in a free stall barn equipped with fans and sprinklers in the feeding area, of the delivery rate of misters in a cooling system in rest areas with different bedding materials. Thirty cows were divided into two homogenous groups according to milk yield and kept in two pens: one had beds with sand (SAMM) while the other had straw (STLM). Each pen was equipped with 2 fans (Ø 70 cm, 0.50 kW) and 2 misters (delivery rate of 11.2 and 22.5 L/h in STLM and SAMM, respectively) in the rest area. Microclimatic parameters, rectal temperature (RT), breathing rate (BR), milk yield, and some milk traits were recorded. Behavioural routines of the cows (standing and lying) were also continuously recorded during the hotter days. During the trial, two mild-moderate heat waves were observed. During these hotter periods, the daily maximum temperature recorded in the rest areas was 28.9 in SAMM and 31.2 in STLM, and the daily maximum THI was 78.2 in SAMM and 81.5 in STLM. In these periods, the cows in SAMM compared with those in STLM showed lower BR ( P < 0.05) and greater rest time (10.2 and 7.8 h/day in SAMM and STLM, respectively). The RT did not differ (38.89 ± 0.29 and 38.88 ± 0.33°C in STLM and SAMM r,espectively). In conclusion, our research suggests that the cooling system using fans plus misters with mild wetting in rest areas with sand as bedding materials reduces heat stress and improves cow comfort.

Long-term effects of antepartum bed rest on offspring.

PubMed

Bellieni, Carlo Valerio; Bagnoli, Franco; Perrone, Serafina; Caparelli, Ninetta; Cordelli, Duccio Maria; Melissa, Bernardino; Buonocore, Giuseppe

2003-01-01

We studied the children of mothers who were confined to bed during pregnancy for more than 15 consecutive days (mean 3.69 months) in the years 1986-1990 (bed rest offspring; BRO). We studied 86 children: 43 BRO and 43 control children. Data were obtained by means of a 20-item questionnaire filled in by the mothers. The BRO group differed from the control group in incidence of allergies (p = 0.005), motion sickness (p = 0.03), and need to be rocked to fall asleep (p = 0.01). More BRO born at term than controls played musical instruments later in life. Two possible explanations for more allergies among the BRO group are the use of beta-stimulating drugs against premature delivery and the effects of prolonged stress on the developing immune system. Understimulation of the developing vestibular system during gestation may affect some aspects of its development and may explain the higher incidence of motion sickness and need for vigorous rocking in BRO. Copyright 2003 S. Karger AG, Basel

Contributions of MSNA and stroke volume to orthostatic intolerance following bed rest

NASA Technical Reports Server (NTRS)

Shoemaker, J. K.; Hogeman, C. S.; Sinoway, L. I.

1999-01-01

We examined whether the altered orthostatic tolerance following 14 days of head-down tilt bed rest (HDBR) was related to inadequate sympathetic outflow or to excessive reductions in cardiac output during a 10- to 15-min head-up tilt (HUT) test. Heart rate, blood pressure (BP, Finapres), muscle sympathetic nerve activity (MSNA, microneurography), and stroke volume blood velocity (SVV, Doppler ultrasound) were assessed during supine 30 degrees (5 min) and 60 degrees (5-10 min) HUT positions in 15 individuals who successfully completed the pre-HDBR test without evidence of orthostatic intolerance. Subjects were classified as being orthostatically tolerant (OT, n = 9) or intolerant (OI, n = 6) following the post-HDBR test. MSNA, BP, and SVV during supine and HUT postures were not altered in the OT group. Hypotension during 60 degrees HUT in the post-bed rest test for the OI group (P < 0.05) was associated with a blunted increase in MSNA (P < 0.05). SVV was reduced following HDBR in the OI group (main effect of HDBR, P < 0.02). The data support the hypothesis that bed rest-induced orthostatic intolerance is related to an inadequate increase in sympathetic discharge that cannot compensate for a greater postural reduction in stroke volume.

The relationship between physical activity level and completion rate of small bowel examination in patients undergoing capsule endoscopy.

PubMed

Shibuya, Tomoyoshi; Mori, Hiroki; Takeda, Tsutomu; Konishi, Masae; Fukuo, Yuka; Matsumoto, Kenshi; Beppu, Kazuko; Sakamoto, Naoto; Osada, Taro; Nagahara, Akihito; Otaka, Michiro; Ogihara, Tatsuo; Watanabe, Sumio

2012-01-01

Capsule endoscopy (CE) allows direct examination of the small bowel in a safe, noninvasive and well-tolerated manner. Nonetheless, experience indicates failure to reach the cecum in 20-30% of patients within the 8 hour battery life. Attempts to improve the completion rate (CR) as defined by reaching the cecum have been unsuccessful. This study was to investigate the relationship between patients' physical activity and CR. Between January 2009 and January 2010, 76 patients (44 men, 32 women; median age 64.5 yr) underwent CE for the diagnosis of small intestinal disorders. Indications for CE were obscure gastrointestinal bleeding/anemia (62 cases), others (14 cases). Patients were divided into an outpatient group (n=23), mild bed rest group (n=35) and strict bed rest group (n=18). For all patients, the average gastric transit time was 65.5 minutes, small bowel transit time was 301.4 minutes and the CR was 86.8%. However, the CR was 100% (23/23) in the outpatient group, an 85.7% (30/35) in the mild bed rest group, and 72.2% (13/18) in the strict bed rest group. The CR increased with physical activity of patients by Cochran-Armitage Trend Test (p=0.009). In multivariate logistic regression analyses, low physical activity was a significant risk factor for failure to reach the cecum during CE examination; adjusted OR: 3.39, 95% CI: 1.01-11.42 (p=0.048). Our observations suggested that increasing physical activity would increase the likelihood of a complete bowel examination by CE. Further, for CE, inconvenient bowel preparations like the use of polyethylene glycol may be avoided.

Deterioration of left ventricular chamber performance after bed rest : "cardiovascular deconditioning" or hypovolemia?

NASA Technical Reports Server (NTRS)

Perhonen, M. A.; Zuckerman, J. H.; Levine, B. D.; Blomqvist, C. G. (Principal Investigator)

2001-01-01

BACKGROUND: Orthostatic intolerance after bed rest is characterized by hypovolemia and an excessive reduction in stroke volume (SV) in the upright position. We studied whether the reduction in SV is due to a specific adaptation of the heart to head-down tilt bed rest (HDTBR) or acute hypovolemia alone. METHODS AND RESULTS: We constructed left ventricular (LV) pressure-volume curves from pulmonary capillary wedge pressure and LV end-diastolic volume and Starling curves from pulmonary capillary wedge pressure and SV during lower body negative pressure and saline loading in 7 men (25+/-2 years) before and after 2 weeks of -6 degrees HDTBR and after the acute administration of intravenous furosemide. Both HDTBR and hypovolemia led to a similar reduction in plasma volume. However, baseline LV end-diastolic volume decreased by 20+/-4% after HDTBR and by 7+/-2% after hypovolemia (interaction P<0.001). Moreover, SV was reduced more and the Starling curve was steeper during orthostatic stress after HDTBR than after hypovolemia. The pressure-volume curve showed a leftward shift and the equilibrium volume of the left ventricle was decreased after HDTBR; however, after hypovolemia alone, the curve was identical, with no change in equilibrium volume. Lower body negative pressure tolerance was reduced after both conditions; it decreased by 27+/-7% (P<0.05) after HDTBR and by 18+/-8% (P<0.05) after hypovolemia. CONCLUSIONS: Chronic HDTBR leads to ventricular remodeling, which is not seen with equivalent degrees of acute hypovolemia. This remodeling leads to a greater decrease in SV during orthostatic stress after bed rest than hypovolemia alone, potentially contributing to orthostatic intolerance.

Whey protein with potassium bicarbonate supplement attenuates the reduction in muscle oxidative capacity during 19 days of bed rest.

PubMed

Bosutti, Alessandra; Salanova, Michele; Blottner, Dieter; Buehlmeier, Judith; Mulder, Edwin; Rittweger, Jörn; Yap, Moi Hoon; Ganse, Bergita; Degens, Hans

2016-10-01

The effectiveness of whey protein plus potassium bicarbonate-enriched diet (WP+KHCO 3 ) 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+KHCO 3 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 (V̇o 2 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 V̇o 2 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+KHCO 3 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+KHCO 3 appears to attenuate disuse-induced reductions in fiber oxidative capacity. Copyright © 2016 the American Physiological Society.

Physiology of Fluid and Electrolyte Responses During Inactivity: Water Immersion and Bed Rest

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1984-01-01

This manuscript emphasizes the physiology of fluid-electrolyte-hormonal responses during the prolonged inactivity of bed rest and water immersion. An understanding of the total mechanism of adaptation (deconditioning) should provide more insight into the conditioning process. Findings that need to be confirmed during bed rest and immersion are: (1) the volume and tissues of origin of fluid shifted to the thorax and head; (2) interstitial fluid pressure changes in muscle and subcutaneous tissue, particularly during immersion; and (3) the composition of the incoming presumably interstitial fluid that contributes to the early hypervolemia. Better resolution of the time course and source of the diuretic fluid is needed. Important data will be forthcoming when hypotheses are tested involving the probable action of the emerging diuretic and natriuretic hormones, between themselves and among vasopressin and aldosterone, on diuresis and blood pressure control.

Study protocol to examine the effects of spaceflight and a spaceflight analog on neurocognitive performance: extent, longevity, and neural bases.

PubMed

Koppelmans, Vincent; Erdeniz, Burak; De Dios, Yiri E; Wood, Scott J; Reuter-Lorenz, Patricia A; Kofman, Igor; Bloomberg, Jacob J; Mulavara, Ajitkumar P; Seidler, Rachael D

2013-12-18

Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether spaceflight also affects other central nervous system functions such as cognition is yet largely unknown, but of importance in consideration of the health and performance of crewmembers both in- and post-flight. We are therefore conducting a controlled prospective longitudinal study to investigate the effects of spaceflight on the extent, longevity and neural bases of sensorimotor and cognitive performance changes. Here we present the protocol of our study. This study includes three groups (astronauts, bed rest subjects, ground-based control subjects) for which each the design is single group with repeated measures. The effects of spaceflight on the brain will be investigated in astronauts who will be assessed at two time points pre-, at three time points during-, and at four time points following a spaceflight mission of six months. To parse out the effect of microgravity from the overall effects of spaceflight, we investigate the effects of seventy days head-down tilted bed rest. Bed rest subjects will be assessed at two time points before-, two time points during-, and three time points post-bed rest. A third group of ground based controls will be measured at four time points to assess reliability of our measures over time. For all participants and at all time points, except in flight, measures of neurocognitive performance, fine motor control, gait, balance, structural MRI (T1, DTI), task fMRI, and functional connectivity MRI will be obtained. In flight, astronauts will complete some of the tasks that they complete pre- and post flight, including tasks measuring spatial working memory, sensorimotor adaptation, and fine motor performance. Potential changes over time and associations between cognition, motor-behavior, and brain structure and function will be analyzed. This study explores how spaceflight induced brain changes impact functional performance. This understanding could aid in the design of targeted countermeasures to mitigate the negative effects of long-duration spaceflight.

Dietary acid load and bone turnover during long-duration spaceflight and bed rest.

PubMed

Zwart, Sara R; Rice, Barbara L; Dlouhy, Holly; Shackelford, Linda C; Heer, Martina; Koslovsky, Matthew D; Smith, Scott M

2018-05-01

Bed rest studies document that a lower dietary acid load is associated with lower bone resorption. We tested the effect of dietary acid load on bone metabolism during spaceflight. Controlled 4-d diets with a high or low animal protein-to-potassium (APro:K) ratio (High and Low diets, respectively) were given to 17 astronauts before and during spaceflight. Each astronaut had 1 High and 1 Low diet session before flight and 2 High and 2 Low sessions during flight, in addition to a 4-d session around flight day 30 (FD30), when crew members were to consume their typical in-flight intake. At the end of each session, blood and urine samples were collected. Calcium, total protein, energy, and sodium were maintained in each crew member's preflight and in-flight controlled diets. Relative to preflight values, N-telopeptide (NTX) and urinary calcium were higher during flight, and bone-specific alkaline phosphatase (BSAP) was higher toward the end of flight. The High and Low diets did not affect NTX, BSAP, or urinary calcium. Dietary sulfur and age were significantly associated with changes in NTX. Dietary sodium and flight day were significantly associated with urinary calcium during flight. The net endogenous acid production (NEAP) estimated from the typical dietary intake at FD30 was associated with loss of bone mineral content in the lumbar spine after the mission. The results were compared with data from a 70-d bed rest study, in which control (but not exercising) subjects' APro:K was associated with higher NTX during bed rest. Long-term lowering of NEAP by increasing vegetable and fruit intake may protect against changes in loss of bone mineral content during spaceflight when adequate calcium is consumed, particularly if resistive exercise is not being performed. This trial was registered at clinicaltrials.gov as NCT01713634.

Cardiovascular Deconditioning in Humans: Alteration in Cardiovascular Regulation and Function During Simulated Microgravity

NASA Technical Reports Server (NTRS)

Cohen, Richard

1999-01-01

Alterations in cardiovascular regulation and function that occur during and after space flight have been reported. These alterations are manifested, for example, by reduced orthostatic tolerance upon reentry to the earth's gravity from space. However, the precise physiologic mechanisms responsible for these alterations remain to be fully elucidated. Perhaps, as a result, effective countermeasures have yet to be developed. In this project we apply a powerful, new method - cardiovascular system identification (CSI) - for the study of the effects of space flight on the cardiovascular system so that effective countermeasures can be developed. CSI involves the mathematical analysis of second-to-second fluctuations in non-invasively measured heart rate, arterial blood pressure (ABP), and instantaneous lung volume (ILV - respiratory activity) in order to characterize quantitatively the physiologic mechanisms responsible for the couplings between these signals. Through the characterization of all the physiologic mechanisms coupling these signals, CSI provides a model of the closed-loop cardiovascular regulatory state in an individual subject. The model includes quantitative descriptions of the heart rate baroreflex, autonomic function, as well as other important physiologic mechanisms. We are in the process of incorporating beat-to-beat fluctuations of stroke volume into the CSI technique in order to quantify additional physiologic mechanisms such as those involved in control of peripheral vascular resistance and alterations in cardiac contractility. We apply CSI in conjunction with the two general protocols of the Human Studies Core project. The first protocol involves ground-based, human head down tilt bed rest to simulate microgravity and acute stressors - upright tilt, standing and bicycle exercise - to provide orthostatic and exercise challenges. The second protocol is intended to be the same as the first but with the addition of sleep deprivation to determine whether this contributes to cardiovascular alterations. In these studies, we focus on the basic physiologic mechanisms responsible for the alterations in cardiovascular regulation and function during the simulated microgravity in order to formulate hypotheses regarding what countermeasures are likely to be most effective. Compared to our original proposal, the protocol we are using has been slightly modified to lengthen the bed rest period to 16 days and streamline the data collection. These modifications provide us data on a longer bed rest period and have enabled us to increase our subject throughput. Based on review of our preliminary data we have decided to test a countermeasure which is applied the very end of the bed rest period. We will use the same bed rest protocol to test this countermeasure. We anticipate completing the baseline data collection in our first protocol plus testing of the countermeasure in an additional eight subjects, at which time we plan to initiate the second protocol which includes sleep deprivation. In future studies, we plan to apply CSI to test other potential countermeasures in conjunction with the same bed rest, sleep deprivation and acute stressor models. We also anticipate applying CSI for studying astronauts before and after space flight and ultimately, during space flight. The application of CSI is providing information relevant to the development and evaluation of effective countermeasures allowing humans to adapt appropriately upon re-exposure to a gravity field, and to live and work for longer periods of time in microgravity.

High Protein Intake Improves Insulin Sensitivity but Exacerbates Bone Resorption in Immobility (WISE Study)

NASA Technical Reports Server (NTRS)

Heer, Martina; Smith, Scott M.; Frings-Meuthen, Petra; Zwart, Sara R.; Baecker, Natalie

2012-01-01

Inactivity, like bed rest (BR), causes insulin resistance (IR) and bone loss even in healthy subjects. High protein intake seems to mitigate this IR but might exacerbate bone loss. We hypothesized that high protein intake (animal:vegetable protein ratio: 60:40), isocaloric, compared to the control group plus high potassium intake would prevent IR without affecting bone turnover. After a 20-day ambulatory adaptation to controlled confinement and diet, 16 women participated in a 60-day, 6 deg head-down-tilt BR and were assigned randomly to one of the two groups. Control subjects (CON, n=8) received 1g/kg body mass/d dietary protein. Nutrition subjects (NUT, n=8) received 1.45g/kg body mass/d dietary protein plus 7.2g branched chain amino acids per day during BR. All subjects received 1670 kcal/d. Bed rest decreased glucose disposal by 35% (p<0.05) in CON. Isocaloric high protein intake prevented insulin resistance, but exacerbated bed rest induced increase in bone resorption markers C-telopeptide (> 30%) and Ntelopeptide (>20%) (both: p<0.001). Bone formation markers were unaffected by high protein intake. We conclude from these results that high protein intake might positively affect glucose tolerance, but might also foster bone loss. Further long-duration studies are mandatory before high protein intake for diabetic patients, who have an increased fracture risk, might be recommended.

Effects of 17 days of head-down bed rest on hydro-electrolytic regulation in men

NASA Technical Reports Server (NTRS)

Millet, C.; Custaud, M. A.; Allevard, A. M.; Zaouali-Ajina, M.; Monk, T. H.; Arnaud, S. B.; Gharib, C.; Gauquelin-Koch, G.

2001-01-01

Prolonged periods of head-down bed rest (HDBR) are commonly used to mimic the effects of microgravity. HDBR has been shown to produce, as in space, a cephalad redistribution of circulating blood volume with an increase in central blood volume which induces the early adaptations in blood volume regulating hormones. Changes in atrial natriuretic peptide (ANP), arginine vasopressin (AVP), renin activity and aldosterone have been observed. Many reports describe these endocrine adaptations but few investigations of rhythms are in the literature. We proposed to evaluate the circadian rhythms of the hormones and electrolytes involved in the hydro-electrolytic regulation during a HDBR study which was designed to simulate a 17-day spaceflight (Life and Microgravity Spacelab experiment, LMS, NASA).

Heat Acclimation and Water-Immersion Deconditioning: Responses to Exercise

NASA Technical Reports Server (NTRS)

Shvartz, E.; Bhattacharya, A.; Sperinde, S. J.; Brock, P. J.; Sciaraffa, D.; Haines, R. F.; Greenleaf, J. E.

1977-01-01

Simulated subgravity conditions, such as bed rest and water immersion, cause a decrease in a acceleration tolerance (3, 4), tilt tolerance (3, 9, 10), work capacity (5, 7), and plasma volume (1, 8-10). Moderate exercise training performed during bed rest (4) and prior to water immersion (5) provides some protection against the adverse effects of deconditioning, but the relationship between exercise and changes due to deconditioning remains unclear. Heat acclimation increases plasma and interstitial volumes, total body water, stroke volume (11), and tilt tolerance (6) and may, therefore, be a more efficient method of ameliorating deconditioning than physical training alone. The present study was undertaken to determine the effects of heat acclimation and moderate physical training, performed in cool conditions, on water-immersion deconditioning.

Once-Yearly Zoledronic Acid and Days of Disability, Bed Rest, and Back Pain: Randomized, Controlled HORIZON Pivotal Fracture Trial

PubMed Central

Cauley, Jane A.; Black, Dennis; Boonen, Steven; Cummings, Steven R.; Mesenbrink, Peter; Palermo, Lisa; Man, Zulema; Hadji, Peyman; Reid, Ian R.

2016-01-01

The objective of this study was to determine the effect of once-yearly zoledronic acid on the number of days of back pain and the number of days of disability (ie, limited activity and bed rest) owing to back pain or fracture in postmenopausal women with osteoporosis. This was a multicenter, randomized, double-blind, placebo-controlled trial in 240 clinical centers in 27 countries. Participants included 7736 postmenopausal women with osteoporosis. Patients were randomized to receive either a single 15-minute intravenous infusion of zoledronic acid (5 mg) or placebo at baseline, 12 months, and 24 months. The main outcome measures were self-reported number of days with back pain and the number of days of limited activity and bed rest owing to back pain or a fracture, and this was assessed every 3 months over a 3-year period. Our results show that although the incidence of back pain was high in both randomized groups, women randomized to zoledronic acid experienced, on average, 18 fewer days of back pain compared with placebo over the course of the trial (p = .0092). The back pain among women randomized to zoledronic acid versus placebo resulted in 11 fewer days of limited activity (p = .0017). In Cox proportional-hazards models, women randomized to zoledronic acid were about 6% less likely to experience 7 or more days of back pain [relative risk (RR) = 0.94, 95% confidence interval (CI) 0.90–0.99] or limited activity owing to back pain (RR = 0.94, 95% CI 0.87–1.00). Women randomized to zoledronic acid were significantly less likely to experience 7 or more bed-rest days owing to a fracture (RR = 0.58, 95% CI 0.47–0.72) and 7 or more limited-activity days owing to a fracture (RR = 0.67, 95% CI 0.58–0.78). Reductions in back pain with zoledronic acid were independent of incident fracture. Our conclusion is that in women with postmenopausal osteoporosis, a once-yearly infusion with zoledronic acid over a 3-year period significantly reduced the number of days that patients reported back pain, limited activity owing to back pain, and limited activity and bed rest owing to a fracture. PMID:21542001

Staying in bed to benefit ESA's astronauts and Europe's citizens.

PubMed

Elmann-Larsen, Benny; Schmitt, Didier

2003-02-01

Since Yuri Gagarin's historic first flight into space in April 1961, it has quickly become evident that the space environment influences the human body in many different ways and causes it to adapt in ways that can lead to problems when returning to Earth's gravity. Much research has been performed in the meantime and our understanding of what happens to our bodies in space improved considerably during the Mir space station and Space Shuttle/Spacelab era. However, many questions, particularly regarding how to counteract those changes that we now know take place, still need to be addressed through studies on the International Space Station (ISS) and through simulations on the ground. As we enter an era in which crews will spend longer periods in space on the ISS and of longer term plans by almost every space-faring nation for missions to Mars, it is clear that much more knowledge is needed, and quickly. Although a few hundred men and women have already travelled into space, the operating environment severely limits the amount of systematic research that can be performed--a situation that is unlikely to change. Other avenues for addressing specific scientific questions in a controlled research environment must therefore be found. One of these complementary alternatives is head-down-tilt bed-rest studies in which volunteers are confined to beds that are tilted -6 deg below the horizontal at the head end. Every activity, including eating, reading, showering, etc., is performed in this position for the duration of the study. This leads to changes in the human body that are very similar to those seen during spaceflight, such as bone-mass and muscle-mass loss, cardiovascular and neuro-sensory deconditioning. The controlled bed-rest setting therefore allows meaningful research into the bodily consequences of spaceflight and possible countermeasures. It also gives the scientific community interested in space-related medical research more ready access to a clinical model. The benefits of these studies go far beyond their space application. Patients bed-ridden because of illness or accidents suffer the same symptoms and can thus also profit from the studies. As a clear indication of this link, the clinicians and researchers involved in the bed-rest campaigns typically spend the majority of their time exploring "terrestrial" problems.

Reduction of Dietary Acid Load as a Potential Countermeasure for Bone Loss Associated with Spaceflight

NASA Technical Reports Server (NTRS)

Zwart, S. R.; Watts, S. M.; Sams, C. F.; Whitson, P. A.; Smith, S. M.

2006-01-01

In several studies we tested the concepts that diet can alter acid-base balance and that reducing the dietary acid load has a positive effect on maintenance of bone. In study 1, (n = 11, 60-90 d bed rest), the renal acid load of the diet was estimated from its chemical composition, and was positively correlated with urinary markers of bone resorption (P less than 0.05); that is, the greater the acid load, the greater the excretion of bone resorption markers. In study 2, in males (n = 8, 30 d bed rest), an estimate of the ratio of nonvolatile acid precursors to base precursors in the diet was positively correlated (P less than 0.05) with markers of bone resorption. In study 3, for 28 d subjects received either a placebo (n = 6) or an essential amino acid supplement (n = 7) that included methionine, a known acid precursor. During bed rest (28 d), urinary calcium was greater than baseline levels in the supplemented group but not the control group (P less than 0.05), and in the supplemented group, urinary pH decreased (P less than 0.05). In study 4, less bone resorption occurred in space crew members who received potassium citrate (n = 6) during spaceflight of 4-6 months than in crew members who received placebo or were not in the study (n = 8) (P less than 0.05). Reducing acid load has the potential to mitigate increased bone resorption during spaceflight, and may serve as a bone loss countermeasure.

[A pilot study on pain assessment among elderly with severe dementia
in residential aged care facilities of Reggio Emilia district].

PubMed

Bargellini, Annalisa; Mastrangelo, Stefano; Cervi, Monica; Bagnasco, Michele; Reghizzi, Jlenia; Coriani, Sandra

2017-01-01

. A pilot study on pain assessment among elderly with severe dementia in residential aged care facilities of Reggio Emilia district. Despite the availability of pain assessment tools and best practice recommendations for the assessment and management of pain in people with severe dementia, pain in residential aged care facilities is still undetected or misinterpreted. To assess pain prevalence and analgesic load medication in people with severe cognitive impairment admitted to residential aged care facilities of Reggio Emilia (Italy) province. A pilot cross-sectional study was conducted on 84 elderly patients affected by severe dementia and resident in aged care facilities. Pain was assessed with the PAINAD observational scale, both at rest and during routine procedures: positioning in bed, from bed to standing position, from bed to chair or during the medication of a pressure sore (under challenge). 33.4% of patients had pain at rest, mainly mild, and 86.9 % under challenge. During routine interventions, in 64 patients (76.2%) pain increased compared to at rest condition (for 39, 2/3, moderate-severe); although 46 of them were prescribed as-required analgesic medication, none had received the drug. Also patients with analgesics on regular basis experienced more pain during routine procedures. Many patients experienced pain during routine procedures. The regular use of pain assessment tools and adequate training of all healthcare professionals are essential requirements for an effective pain control.

Physical performance tests after stroke: reliability and validity.

PubMed

Maeda, A; Yuasa, T; Nakamura, K; Higuchi, S; Motohashi, Y

2000-01-01

To evaluate the reliability and validity of the modified physical performance tests for stroke survivors who live in a community. The subjects included 40 stroke survivors and 40 apparently healthy independent elderly persons. The physical performance tests for the stroke survivors comprised two physical capacity evaluation tasks that represented physical abilities necessary to perform the main activities of daily living, e.g., standing-up ability (time needed to stand up from bed rest) and walking ability (time needed to walk 10 m). Regarding the reliability of tests, significant correlations were confirmed between test and retest of physical performance tests with both short and long intervals in individuals after stroke. Regarding the validity of tests, the authors studied the significant correlations between the maximum isometric strength of the quardriceps muscle and the time needed to walk 10 m, centimeters reached while sitting and reaching, and the time needed to stand up from bed rest. The authors confirmed that there were significant correlations between the instrumental activity of daily living and the time needed to stand up from bed rest, along with the time needed to walk 10 m for the stroke survivors. These physical performance tests are useful guides for evaluating a level of activity of daily living and physical frailty of stroke survivors living in a community.

The implementation of game in a 20-day head-down tilting bed rest experiment upon mood status and neurotic levels of rest subjects

NASA Astrophysics Data System (ADS)

Ishizaki, Yuko; Fukuoka, Hideoki; Ishizaki, Tatsuro; Tanaka, Hidetaka; Ishitobi, Hiromi

2004-12-01

This study evaluated the effect of the implementation of game on mental health among participants in a bed rest (BR) experiment. Subjects were 12 healthy males aged 20-26, who participated in a 20-day 6-degrees head-down tilting BR experiment. The participants were asked to complete psychometrical questionnaires before, during, and after the experiment. We entrusted the participants to manage their leisure time and they intended a game in which all of them could take part over the experiment period. The general conversation and light-hearted mood among the subjects continued during the experimental period. Longitudinal data analysis showed that levels of neurosis and mood status did not deteriorate during the experiment, while our previous experiments, which were performed under the same protocol as this study except for the implementation of the game showed a distinct deterioration in psychosocial status. We consider that the implementation of game autonomously contributes to the positive effects on the mental health among the participants.

Analysis by NASA's VESGEN Software of Retinal Blood Vessels in Human Subjects Undergoing Head-Down Tilt During 70-Day Bed Rest

NASA Technical Reports Server (NTRS)

Vyas, Ruchi J.; Murray, Matthew C.; Predovic, Marina; Lim, Shiyin; Askin, Kayleigh N.; Vizzeri, Gianmarco; Taibbi, Giovanni; Mason, Sara Stroble; Zanello, Susana B.; Young, Millenia;

Excercise Within LBNP as an Artificial Gravity Countermeasure

NASA Technical Reports Server (NTRS)

Hargens, A. R.; Watenpaugh, D. E.; Lee, S. M. C.; Meyer, R. S.; Macias, B.; Tanaka, K.; Kimura, S.; Steinbach, G.; Groppo, E.; Khalili, N.;

When Treatments Don't Work

EPA Pesticide Factsheets

Pesticide treatment to eliminate bed bugs may be unsuccessful if other resting areas such as hampers or furniture are missed, recommended label rates of application or timeframe are not followed, or bed bugs developing resistance to the chemical.

Effects of health insurance on non-working married women's medical care use and bed days at home.

PubMed

Lee, Changwoo; Shin, Euichul

2013-07-01

This study examines whether bed days are alternative methods to medical care use for treating a particular illness. If bed days at home are considered as an alternative to medical treatment, then medical care use and bed days at home should be influenced by an individual's health insurance status. This study uses data from the 2003 Medical Expenditure Panel Survey (MEPS) on medical care use and bed days at home for each contracted illness of non-working married women. The results suggest that the health insurance status of non-working married women has considerable influence on their choice between medical care use and bed days at home. In addition, those with health insurance are more likely to use medical care and less likely to use bed days at home, but they tend to avoid the simultaneous use of medical care and bed days at home. In contrast to previous studies' findings indicating that absences from work and medical care use among working males may be complements, this study's results for non-working married women without health insurance suggest that they use rest and medical treatment as substitutes, not complements.

Physiology of prolonged bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1988-01-01

Bed rest has been a normal procedure used by physicians for centuries in the treatment of injury and disease. Exposure of patients to prolonged bed rest in the horizontal position induces adaptive deconditioning responses. While deconditioning responses are appropriate for patients or test subjects in the horizontal position, they usually result in adverse physiological responses (fainting, muscular weakness) when the patient assume the upright posture. These deconditioning responses result from reduction in hydrostatic pressure within the cardiovascular system, virtual elimination of longitudinal pressure on the long bones, some decrease in total body metabolism, changes in diet, and perhaps psychological impact from the different environment. Almost every system in the body is affected. An early stimulus is the cephalic shift of fluid from the legs which increases atrial pressure and induces compensatory responses for fluid and electrolyte redistribution. Without countermeasures, deterioration in strength and muscle function occurs within 1 wk while increased calcium loss may continue for months. Research should also focus on drug and carbohydrate metabolism.

Space weightlessness and hormonal changes in human subjects and experimental animals

NASA Technical Reports Server (NTRS)

Grindeland, R. E.

1982-01-01

Data from spaceflight and bed rest studies are briefly described and the difficulties in interpreting these results are discussed. Growth hormone, prolactin, adrenocorticotropic hormone, cortisol, insulin, aldosterone, and other hormones are addressed.

Binge eating disorder and obesity: preliminary evidence for distinct cardiovascular and psychological phenotypes.

PubMed

Klatzkin, Rebecca R; Gaffney, Sierra; Cyrus, Kathryn; Bigus, Elizabeth; Brownley, Kimberly A

2015-04-01

This study investigated cardiovascular functioning, mood, and eating-related psychological factors at rest and in response to mental stress in three groups of women: 1) Obese women with binge eating disorder (BED; n=9); 2) obese non-BED women (n=15); and 3) normal weight (NW) non-BED women (n=15). Compared to both obese and NW non-BED women, obese women with BED showed heightened overall blood pressure and reported greater depression symptoms, perceived stress, and eating-related psychopathology. Additionally, obese women with BED reported greater overall negative affect and state anxiety compared to obese non-BED women. The heart rate response to stress was blunted in the obese BED group compared to the other groups, but this effect was no longer significant after controlling for baseline differences in depression. Correlational analyses revealed a positive association between stress-induced changes in hunger and cardiovascular measures only in obese women with BED. Longitudinal studies are needed to determine if stress dysregulation and stress-induced increases in hunger contribute to the onset and/or maintenance of BED. In particular, studies utilizing an additional NW BED control group are warranted in order to further examine the impact of BED above and beyond the impact of obesity on psychophysiological functioning and to inform the growing literature regarding stress-related factors that distinguish the BED and obesity phenotypes. Copyright © 2015 Elsevier Inc. All rights reserved.

Fluid shifts and endocrine responses during chair rest and water immersion in man

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Shvartz, E.; Kravik, S.; Keil, L. C.

1980-01-01

The effects of external water pressure on intercompartmental fluid volume shifts and endocrine responses in man are investigated. Extracellular fluid volumes and plasma and urine electrolyte and endocrine responses of four male subjects were measured during eight hours of head-out water immersion and 16 hours of recovery bed rest and compared to responses obtained during eight hours of chair rest and 16 hours of bed rest without external hydrostatic pressure obtained in the same subjects five months later. Immersion is found to result in a substantial diuresis with respect to chair rest, accounted for by decreases in extracellular volume. A negative water balance during immersion and a positive water balance during chair rest were observed to be accompanied by a shift of extracellular volume to the intracellular compartment, as well as the suppression of plasma arginine vasopressin and renin activities in both regimes. The vasopressin and renin activity decreases are attributed to the increased central blood volume, and half of the plasma loss in immersed subjects is attributed to the effects of external water pressure.

Physiological Observations and Omics to Develop Personalized Sensormotor Adaptability Countermeasures Using Bed Rest and Space Flight Data

NASA Technical Reports Server (NTRS)

Mulavara, A. P.; Seidler, R. D.; Feiveson, A.; Oddsson, L.; Zanello, S.; Oman, C. M.; Ploutz-Snyder, L.; Peters, B.; Cohen, H. S.; Reschke, M.;

Energy and thermal regulation during bed rest and spaceflight

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1989-01-01

This paper presents data available from bed-rest and flight studies on the energy metabolism and thermoregulatory parameters and their changes during long-duration space missions which may influence requirements of astronauts for food and water. It is calculated, on the basis of 3100 kcal and 2.2 l water a day, with 1 h/day moderate exercise, that the requirements for a 2-yr flight would be 2,263,000 kcal and 1606 l water for each astronaut. One daily 5-h-long extravehicular sortie would require an additional 529,250 kcal and 1,095 l of water per year. Changes in the efficiency of work or metabolism would affect these nutritional requirements for long spaceflights. Factors that would increase food and water requirements are discussed.

Study protocol to examine the effects of spaceflight and a spaceflight analog on neurocognitive performance: extent, longevity, and neural bases

PubMed Central

2013-01-01

Background Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether spaceflight also affects other central nervous system functions such as cognition is yet largely unknown, but of importance in consideration of the health and performance of crewmembers both in- and post-flight. We are therefore conducting a controlled prospective longitudinal study to investigate the effects of spaceflight on the extent, longevity and neural bases of sensorimotor and cognitive performance changes. Here we present the protocol of our study. Methods/design This study includes three groups (astronauts, bed rest subjects, ground-based control subjects) for which each the design is single group with repeated measures. The effects of spaceflight on the brain will be investigated in astronauts who will be assessed at two time points pre-, at three time points during-, and at four time points following a spaceflight mission of six months. To parse out the effect of microgravity from the overall effects of spaceflight, we investigate the effects of seventy days head-down tilted bed rest. Bed rest subjects will be assessed at two time points before-, two time points during-, and three time points post-bed rest. A third group of ground based controls will be measured at four time points to assess reliability of our measures over time. For all participants and at all time points, except in flight, measures of neurocognitive performance, fine motor control, gait, balance, structural MRI (T1, DTI), task fMRI, and functional connectivity MRI will be obtained. In flight, astronauts will complete some of the tasks that they complete pre- and post flight, including tasks measuring spatial working memory, sensorimotor adaptation, and fine motor performance. Potential changes over time and associations between cognition, motor-behavior, and brain structure and function will be analyzed. Discussion This study explores how spaceflight induced brain changes impact functional performance. This understanding could aid in the design of targeted countermeasures to mitigate the negative effects of long-duration spaceflight. PMID:24350728

Behavioral Responses of the Bed Bug to Permethrin-Impregnated ActiveGuard™ Fabric.

PubMed

Jones, Susan C; Bryant, Joshua L; Harrison, Scott A

2013-06-07

ActiveGuard™ Mattress Liners have been used to control house dust mites, and they also are commercially available as an integrated pest management tool for use against bed bugs (Cimex lectularius). The aim of our study was to evaluate responses of numerous populations of the bed bug to the permethrin-impregnated fabric, with particular regard to contact toxicity, repellency, and feeding inhibition. Continuous exposure to ActiveGuard fabric resulted in rapid intoxication for three of four populations, with 87 to 100% of moderately pyrethroid-resistant and susceptible bed bugs succumbing by 1 d. In comparison, a highly resistant population reached 22% mortality at 10 d. Video data revealed that bed bugs readily traversed ActiveGuard fabric and spent a considerable amount of time moving about and resting on it during a 12-h period. ActiveGuard fabric was non-repellent to bed bugs from five tested populations. Furthermore, significantly fewer bed bugs successfully fed to repletion through ActiveGuard fabric than through blank fabric for the five populations. With just 30 min of feeding exposure, mortality ranged from 4% to 83%, depending upon the bed bug strain. These laboratory studies indicate that ActiveGuard liners adversely affected bed bugs from diverse populations.

Exercise countermeasures for bed rest deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, John (Editor)

1989-01-01

The major objectives were to evaluate the efficiency of different modes of exercise (isotonic and isokinetic) for countering the effects of bed rest deconditioning on work capacity (peak oxygen uptake), muscular strength, orthostatic tolerance, posture, equilibrium and gait; and to collect additional data of a more fundamental nature to help understand how these deconditioning responses occur. These data will be used for writing prescriptions for exercise to be utilized by astronauts for maintaining work capacity and well-being on Freedom Station, and to determine what exercise devices should be place in the station.

Placenta previa

MedlinePlus

... bleeding. This can be deadly to both the mother and baby. If the placenta is near or covering part of the cervix, your provider may recommend: Reducing your activities Bed rest Pelvic rest, which means no sex, no tampons, and no douching Nothing should be ...

Measurement of a MMP-2 degraded Titin fragment in serum reflects changes in muscle turnover induced by atrophy.

PubMed

Sun, S; Henriksen, K; Karsdal, M A; Armbrecht, G; Belavý, D L; Felsenberg, D; Rittweger, J; Wang, Y; Zheng, Q; Nedergaard, A F

2014-10-01

In this study we sought to determine whether a Titin peptide fragment can serve as a clinical biomarker for changes in muscle mass. Mass spectrometry was used to identify Titin fragment in urine. An antibody against this Titin sequence was raised and used to develop a competitive ELISA assay for measurement in serum. Rat tissue extractions in the presence or absence of a series of proteases of interest were used to identify its enzymatic origin. A rat model of dexamethasone (DEX) induced muscle atrophy and a human 56-day bed rest study with and without vibration therapy were used to assess biological and clinical relevance. A technically robust ELISA measuring the Titin fragment was developed against a Titin peptide fragment identified in human urine. The fragment was shown to be produced primarily by MMP-2 cleavage of Titin. In the rat muscle DEX induced atrophy model, Titin-MMP2 fragment was decreased in the beginning of DEX treatment, and then significantly increased later on during DEX administration. In the human bed rest study, the Titin-MMP2 fragment was initially decreased 11.9 (±3.7) % after 1day of bed rest, and then gradually increased ending up at a 16.4 (±4.6) % increase at day 47. We developed a robust ELISA measuring a muscle derived MMP-2 generated Titin degradation fragment in rat and human serum. Importantly, the fragment can be measured in serum and that these levels are related to induction of skeletal muscle atrophy. Copyright © 2014 Elsevier Inc. All rights reserved.

Surveillance of Ocular Parameters and Visual Function in Bed Rest Subjects

NASA Technical Reports Server (NTRS)

Cromwell, Ronita L.

2011-01-01

Recent visual changes in astronauts have raised concern about ocular health during long duration spaceflight. Seven cases have been documented in astronauts who spent 6 months aboard the International Space Station. These astronauts were male ranging in age from 45 to 55 years old. All astronauts exhibited pre- to post flight refractive changes. Decreased intraocular pressure (IOP) post flight was observed in 3 cases. Fundoscopic exams revealed post flight findings of choroidal folds in 4 cases, optic disc edema in 5 cases and the presence of cotton wool spots in 3 cases. Optical coherence tomography (OCT) confirmed findings of choroidal folds and disc edema, and also documented retinal nerve fiber layer thickening (5 cases). Findings from MRI examinations showed posterior globe flattening (5 cases), optic nerve sheath distention (6 cases) and torturous optic nerves (2 cases). Of the 7 cases, intracranial pressure was measured on 4 astronauts. These 4 showed elevated ICP post-flight that remained elevated for as long as 19 months in one case. While the etiology remains unknown, hypotheses speculate that venous insufficiency or hypertension in the brain caused by cephalad fluid shifts during spaceflight are possible mechanisms for ocular changes seen in astronauts. Head-down tilt bed rest is a spaceflight analog that induces cephalad fluid shifts. This study is designed to provide ocular monitoring of bed rest subjects and determine whether clinically relevant changes are found. Ocular Changes

Sympathetic activity and early mobilization in patients in intensive and intermediate care with severe brain injuries: a preliminary prospective randomized study.

PubMed

Rocca, A; Pignat, J-M; Berney, L; Jöhr, J; Van de Ville, D; Daniel, R T; Levivier, M; Hirt, L; Luft, A R; Grouzmann, E; Diserens, K

2016-09-13

Patients who experience severe brain injuries are at risk of secondary brain damage, because of delayed vasospasm and edema. Traditionally, many of these patients are kept on prolonged bed rest in order to maintain adequate cerebral blood flow, especially in the case of subarachnoid hemorrhage. On the other hand, prolonged bed rest carries important morbidity. There may be a clinical benefit in early mobilization and our hypothesis is that early gradual mobilization is safe in these patients. The aim of this study was to observe and quantify the changes in sympathetic activity, mainly related to stress, and blood pressure in gradual postural changes by the verticalization robot (Erigo®) and after training by a lower body ergometer (MOTOmed-letto®), after prolonged bed rest of minimum 7 days. Thirty patients with severe neurological injuries were randomized into 3 groups with different protocols of mobilization: Standard, MOTOmed-letto® or Erigo® protocol. We measured plasma catecholamines, metanephrines and blood pressure before, during and after mobilization. Blood pressure does not show any significant difference between the 3 groups. The analysis of the catecholamines suggests a significant increase in catecholamine production during Standard mobilization with physiotherapists and with MOTOmed-letto® and no changes with Erigo®. This preliminary prospective randomized study shows that the mobilization of patients with severe brain injuries by means of Erigo® does not increase the production of catecholamines. It means that Erigo® is a well-tolerated method of mobilization and can be considered a safe system of early mobilization of these patients. Further studies are required to validate our conclusions. The study was registered in the ISRCTN registry with the trial registration number ISRCTN56402432 . Date of registration: 08.03.2016. Retrospectively registered.

Advice to stay active as a single treatment for low back pain and sciatica.

PubMed

Hilde, G; Hagen, K B; Jamtvedt, G; Winnem, M

2002-01-01

Low back pain is one of the most common conditions managed in primary care. Restricted activity, rest, and symptomatic analgesics are the most commonly prescribed treatment for low back pain and sciatica. To assess the effects of advice to stay active as single treatment for patients with low back pain. Computerised searches in MEDLINE, EMBASE, Sport, The Cochrane Controlled Trials Register, Musculoskeletal Group's Trials Register and Scisearch, and scanning of reference lists from relevant articles were undertaken. Relevant studies were also traced by contacting authors. Date of the most recent searches: December 1998. We included all randomised trials or quasi-randomised trials where the study population consisted of adult patients with low back pain or sciatica, in which one comparison group was advised to stay active. The main outcomes of interest were pain, functional status, recovery and return to work. Two reviewers independently selected trials for inclusion, assessed the validity of included trials and extracted data. Investigators were contacted to collect missing data or for clarification when needed. Four trials, with a total of 491 patients, were included. Advice to stay active was compared to advice to rest in bed in all trials. Two trials were assessed to have low risk of bias and two to have moderate to high risk of bias. The results were heterogeneous. Results from one high quality trial of patients with acute simple LBP found small differences in functional status [Weighted Mean Difference (on a 0-100 scale) 6.0 (95% CI: 1.5, 10.5)] and length of sick leave [WMD 3.4 days (95% CI: 1.6, 5.2)] in favour of staying active compared to advice to stay in bed for two days. The other high quality trial compared advice to stay active with advice to rest in bed for 14 days for patients with sciatic syndrome, and found no differences between the groups. One of the high quality trials also compared advice to stay active with exercises for patients with acute simple LBP, and found improvement in functional status and reduction in sick leave in favour of advice to stay active. The best available evidence suggests that advice to stay active alone has small beneficial effects for patients with acute simple low back pain, and little or no effect for patients with sciatica. There is no evidence that advice to stay active is harmful for either acute low back pain or sciatica. If there is no major difference between advice to stay active and advice to rest in bed, and there is potential harmful effects of prolonged bed rest, then it is reasonable to advise people with acute low back pain and sciatica to stay active. These conclusions are based on single trials.

WITHDRAWN: Advice to stay active as a single treatment for low-back pain and sciatica.

PubMed

Hilde, G; Hagen, K B; Jamtvedt, G; Winnem, M

2007-07-18

Low back pain is one of the most common conditions managed in primary care. Restricted activity, rest, and symptomatic analgesics are the most commonly prescribed treatment for low back pain and sciatica. To assess the effects of advice to stay active as single treatment for patients with low back pain. Computerised searches in MEDLINE, EMBASE, Sport, The Cochrane Controlled Trials Register, Musculoskeletal Group's Trials Register and Scisearch, and scanning of reference lists from relevant articles were undertaken. Relevant studies were also traced by contacting authors. Date of the most recent searches: December 1998. We included all randomised trials or quasi-randomised trials where the study population consisted of adult patients with low back pain or sciatica, in which one comparison group was advised to stay active. The main outcomes of interest were pain, functional status, recovery and return to work. Two reviewers independently selected trials for inclusion, assessed the validity of included trials and extracted data. Investigators were contacted to collect missing data or for clarification when needed. Four trials, with a total of 491 patients, were included. Advice to stay active was compared to advice to rest in bed in all trials. Two trials were assessed to have low risk of bias and two to have moderate to high risk of bias. The results were heterogeneous. Results from one high quality trial of patients with acute simple LBP found small differences in functional status [Weighted Mean Difference (on a 0-100 scale) 6.0 (95% CI: 1.5, 10.5)] and length of sick leave [WMD 3.4 days (95% CI: 1.6, 5.2)] in favour of staying active compared to advice to stay in bed for two days. The other high quality trial compared advice to stay active with advice to rest in bed for 14 days for patients with sciatic syndrome, and found no differences between the groups. One of the high quality trials also compared advice to stay active with exercises for patients with acute simple LBP, and found improvement in functional status and reduction in sick leave in favour of advice to stay active. The best available evidence suggests that advice to stay active alone has small beneficial effects for patients with acute simple low back pain, and little or no effect for patients with sciatica. There is no evidence that advice to stay active is harmful for either acute low back pain or sciatica. If there is no major difference between advice to stay active and advice to rest in bed, and there is potential harmful effects of prolonged bed rest, then it is reasonable to advise people with acute low back pain and sciatica to stay active. These conclusions are based on single trials.

WISE 2005: Aerobic and resistive countermeasures prevent paraspinal muscle deconditioning during 60-day bed rest in women.

PubMed

Holt, Jacquelyn A; Macias, Brandon R; Schneider, Suzanne M; Watenpaugh, Donald E; Lee, Stuart M C; Chang, Douglas G; Hargens, Alan R

2016-05-15

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.

Postural Instability Caused by Extended Bed Rest Is Alleviated by Brief Daily Exposure to Low Magnitude Mechanical Signals

PubMed Central

Muir, Jesse; Judex, Stefan; Qin, Yi-Xian; Rubin, Clinton

2011-01-01

Loss of postural stability, as exacerbated by chronic bed rest, aging, neuromuscular injury or disease, results in a marked increase in the risk of falls, potentiating severe injury and even death. To investigate the capacity of low magnitude mechanical signals (LMMS) to retain postural stability under conditions conducive to its decline, twenty-nine healthy adult subjects underwent 90 days of 6-degree head down tilt bed-rest. Treated subjects underwent a daily 10 minute regimen of 30 Hz LMMS at either a 0.3g-force (n=12) or 0.5g force (n=5). Control subjects (n=13) received no LMMS treatment. Postural stability, quantified by dispersions of the plantar-based center of pressure, deteriorated significantly from baseline in control subjects, with displacement and velocity at 60d increasing 98.7% and 193% respectively, while the LMMS group increased only 26.7% and 6.4%, reflecting a 73% and 97% relative retention in stability as compared to control. Increasing LMMS magnitude from 0.3 to 0.5g had no significant influence on outcomes. LMMS failed to spare loss of muscle extension strength, but helped to retain flexion strength (e.g., 46.2% improved retention of baseline concentric flexion strength vs. untreated controls; p=0.01). These data suggest the potential of extremely small mechanical signals as a non-invasive means of preserving postural control under the challenge of chronic bed rest, and may ultimately represent non-pharmacologic means of reducing the risk of debilitating falls in elderly and infirm. PMID:21273076

[Electromechanical registration of the resting behavior of fattening pigs].

PubMed

Heuser, H; Plonait, H

1977-10-05

The resting behaviour of four weanling pigs has been continuously recorded by an electromechanical apparatus for 8 weeks. The duration of different postures: standing, ventral recumbency, lateral recumbency and frequency of standing periods were recorded as influenced by different environmental factors. 1. Floor with and without bedding at 21 degrees C. 2. Floor without bedding at 27 degrees C environmental temperature. 3. Feeding once daily versus twice. Duration of recumbency periods was increases at 21 degrees C if bedding was provided. This also improved daily gain. At elevated environmental temperatures the animals preferred the lying posture on concrete floor. Feeding twice increased the duration of recumbency. The same was the case as the animals grew older. Disturbance by caretaking activities in neighbouring dens increased the duration of standing.

Hormonal changes during 17 days of head-down bed-rest

NASA Technical Reports Server (NTRS)

Custaud, Marc-Antoine; Arnaud, Sara B.; Monk, Timothy H.; Claustrat, Bruno; Gharib, Claude; Gauquelin-Koch, Guillemette

2003-01-01

We investigated in six men the impact of 17 days of head-down bed rest (HDBR) on the daily rhythms of the hormones involved in hydroelectrolytic regulation. This HDBR study was designed to mimic a real space flight. Urine samples were collected at each voiding before, during and after HDBR. Urinary excretion of Growth Hormone (GH), Cortisol, 6 Sulfatoxymelatonin, Normetadrenaline (NMN) and Metadrenaline (NM) was determined. A decrease in urinary cortisol excretion during the night of HDBR was noted. For GH, a rhythm was found before and during HDBR. The rhythm of melatonin, evaluated with the urine excretion of 6 Sulfatoxymelatonin (aMT6S), the main hepatic metabolite, persisted throughout the experiment without any modification to the level of phase. A decrease during the night was noted for normetadrenaline urinary derivates, but only during the HDBR.

Effects of health insurance on non-working married women’s medical care use and bed days at home

PubMed Central

2013-01-01

Background This study examines whether bed days are alternative methods to medical care use for treating a particular illness. If bed days at home are considered as an alternative to medical treatment, then medical care use and bed days at home should be influenced by an individual’s health insurance status. Method This study uses data from the 2003 Medical Expenditure Panel Survey (MEPS) on medical care use and bed days at home for each contracted illness of non-working married women. Results The results suggest that the health insurance status of non-working married women has considerable influence on their choice between medical care use and bed days at home. In addition, those with health insurance are more likely to use medical care and less likely to use bed days at home, but they tend to avoid the simultaneous use of medical care and bed days at home. Conclusions In contrast to previous studies’ findings indicating that absences from work and medical care use among working males may be complements, this study’s results for non-working married women without health insurance suggest that they use rest and medical treatment as substitutes, not complements. PMID:23816313

Fluid and electrolyte shifts in women during +Gz acceleration after 15 days' bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Stinnett, H. O.; Davis, G. L.; Kollias, J.; Bernauer, E. M.

1977-01-01

Experiments were conducted on twelve women aged 23-34 yr - a bed rest (BR) group of eight subjects and an ambulatory (AMB) group of four subjects - to determine the effect of bed rest on shifts in plasma volume, electrolytes, and erythrocyte volume during +Gz acceleration on a centrifuge. The BR group underwent the +Gz acceleration during a two-week ambulatory control period, after 15 days of a 17-day BR period, and on the third day of ambulatory recovery. The AMB group underwent the same experimental procedures, but continued their normal daily routine during the BR period without additional prescribed physical exercise. Major conclusions are that (1) the higher the mean control tolerance, the greater the tolerance decline after BR; (2) relative confinement and reduced activity contribute as much to reduction in tolerance as does the horizontal body position during BR; (3) BR deconditioning has no effect on the erythrocyte volume during +3.0 Gz; and (4) about one-half the loss in tolerance after BR can be attributed to plasma volume and electrolyte shifts.

Submaximal Exercise VO2 and Q During 30-Day 6 degree Head-Down Bed Rest with Isotonic and Isokinetic Exercise Training

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Bernauer, E. M.; Erti, A. C.

1995-01-01

Submaximal exercise (61+3% peak VO2) metabolism was measured before (AC day-2) and on bed rest day 4, 11, and 25 in 19 healthy men (32-42 yr) allocated into no exercise (NOE, N=5) control, and isotonic exercise (ITE, N=7)and isokinetic exercise (IKE, N=7) training groups. Training was conducting supine for two 30-min periods/d for 6 d/wk: ITE was 60-90% peak VO2: IKE was peak knee flexion-extension at 100 deg/s. Supine submaximal exercise 102 decreased significantly (*p<0.05) by 10.3%, with ITE and by 7.3%* with IKE; similar to the submaximal cardiac output (Q) change of -14.5%* (ITE) and -203%* (IKE), but different from change in peak VO2 (+1.4% with ITE and - 10.2%, with IKE) and plasma volume of -3.7% (ITE) and - 18.0% * (IKE). Thus, reduction of submaximal V02 during prolonged bed rest appears to respond to submaximal Q but is not related to change in peak VO2 or plasma volume.

Gas composition of sludge residue profiles in a sludge treatment reed bed between loadings.

PubMed

Larsen, Julie D; Nielsen, Steen M; Scheutz, Charlotte

2017-11-01

Treatment of sludge in sludge treatment reed bed systems includes dewatering and mineralization. The mineralization process, which is driven by microorganisms, produces different gas species as by-products. The pore space composition of the gas species provides useful information on the biological processes occurring in the sludge residue. In this study, we measured the change in composition of gas species in the pore space at different depth levels in vertical sludge residue profiles during a resting period of 32 days. The gas composition of the pore space in the sludge residue changed during the resting period. As the resting period proceeded, atmospheric air re-entered the pore space at all depth levels. The methane (CH 4 ) concentration was at its highest during the first part of the resting period, and then declined as the sludge residue became more dewatered and thereby aerated. In the pore space, the concentration of CH 4 often exceeded the concentration of carbon dioxide (CO 2 ). However, the total emission of CO 2 from the surface of the sludge residue exceeded the total emission of CH 4 , suggesting that CO 2 was mainly produced in the layer of newly applied sludge and/or that CO 2 was emitted from the sludge residue more readily compared to CH 4 .

Downsizing of acute inpatient beds associated with private finance initiative: Scotland's case study

PubMed Central

Dunnigan, Matthew G; Pollock, Allyson M

2003-01-01

Objectives To evaluate whether the projected 24% reduction in acute bed numbers in Lothian hospitals, which formed part of the private finance initiative (PFI) plans for the replacement Royal Infirmary of Edinburgh, is being compensated for by improvements in efficiency and greater use of community facilities, and to ascertain whether there is an independent PFI effect by comparing clinical activity and performance in acute specialties in Lothian hospitals with other NHS hospitals in Scotland. Design Comparison of projected and actual trends in acute bed capacity and inpatient and day case admissions in the first five years (1995-6 to 2000-1) of Lothian Health Board's integrated healthcare plan. Population study of trends in bed rate, hospital activity, length of stay, and throughput in Lothian hospitals compared with the rest of Scotland from 1990-1 to 2000-1. Main outcome measures Staffed bed rates, admission rates, mean lengths of stay, occupancy, and throughput in four adult acute specialty groups in 1990-1, 1995-6, and 2000-1. Results By 2000-1, rates for inpatient admission in all acute, medical, surgical, and intensive therapy specialties in Lothian hospitals were respectively 20%, 6%, 28%, and 38% below those in the rest of Scotland. Day case rates in all acute and acute surgical specialties were 13% and 33% lower. The proportion of delayed discharges in staffed acute and post-acute NHS beds in Lothian hospitals exceeded the Scottish average (15% and 12% respectively; P<0.001). Conclusion The planning targets and increase in clinical activity in acute specialties in Lothian hospitals associated with PFI had not been achieved by 2000-1. The effect on clinical activity has been a steeper decline in the number of acute beds and rates of admission in Lothian hospitals compared with the rest of Scotland between 1995-6 and 2000-1. What is already known on this topicThe full business cases for the 15 first wave private finance initiative (PFI) hospitals in England and Scotland projected reductions in acute beds of about 30% in the five years before the opening of the new replacement hospitalsThe new PFI Royal Infirmary of Edinburgh, which will fully open in 2003, is the cornerstone of Lothian Health Board's healthcare plan for its acute hospitalsWhat this study addsCompared with other Scottish NHS hospitals, service delivery has been reduced across Lothian associated with PFI developmentThe planning targets and increase in clinical activity in acute specialties in Lothian hospitals had not been achieved by 2000-1There is evidence of an independent “PFI effect” on hospital downsizing and bed reductions, which in Lothian has resulted in severe capacity constraints across all acute specialties with a need for immediate expansion in acute and community provisionFurther hospital and community service downsizing may be required to meet the financial deficit, which is principally due to the high costs of PFI PMID:12714469

Analysis of Arterial Mechanics During Head-down Tilt Bed Rest

NASA Technical Reports Server (NTRS)

Elliot, Morgan; Martin, David S.; Westby, Christian M.; Stenger, Michael B.; Platts, Steve

2014-01-01

Arterial health may be affected by microgravity or ground based analogs of spaceflight, as shown by an increase in thoracic aorta stiffness1. Head-down tilt bed rest (HDTBR) is often used as a ground-based simulation of spaceflight because it induces physiological changes similar to those that occur in space2, 3. This abstract details an analysis of arterial stiffness (a subclinical measure of atherosclerosis), the distensibility coefficient (DC), and the pressure-strain elastic modulus (PSE) of the arterial walls during HDTBR. This project may help determine how spaceflight differentially affects arterial function in the upper vs. lower body.

Changes in size and compliance of the calf after 30 days of simulated microgravity

NASA Technical Reports Server (NTRS)

Convertino, Victor A.; Doerr, Donald F.; Stein, Stewart L.

1989-01-01

The hypothesis that reducing muscle compartment by a long-term exposure to microgravity would cause increased leg venous compliance was tested in eight men who were assessed for vascular compliance and for serial circumferences of the calf before and after 30 days of continuous 6-deg head-down bed rest. It was found that head-down bed rest caused decreases in the calculated calf volume and the calf-muscle compartment, as well as increases in calf compliance. The percent increases in calf compliance correlated significantly with decreases in calf muscle compartment.

Forearm and upper-arm oscillometric blood pressure comparison in acutely ill adults.

PubMed

Schell, Kathleen; Morse, Kate; Waterhouse, Julie K

2010-04-01

When patients' upper arms are not accessible and/or when cuffs do not fit large upper arms, the forearm site is often used for blood pressure (BP) measurement. The purpose of this study is to compare forearm and upper-arm BPs in 70 acutely ill adults, admitted to a community hospital's 14-bed ICU. Using Philips oscillometric monitors, three repeated measures of forearm and upper-arm BPs are obtained with head of bed flat and with head of bed elevated at 30 degrees. Arms are resting on the bed. Paired t tests show statistically significant differences in systolic BPs, diastolic BPs, and mean arterial pressures in the supine and head-elevated positions. Bland-Altman analyses indicate that forearm and upper-arm oscillometric BPs are not interchangeable in acutely ill adults.

Antigravity Suits For Studies Of Weightlessness

NASA Technical Reports Server (NTRS)

Kravik, Stein E.; Greenleaf, John

1992-01-01

Report presents results of research on use of "antigravity" suit, one applying positive pressure to lower body to simulate some effects of microgravity. Research suggests lower-body positive pressure is alternative to bed rest or immersion in water in terrestrial studies of cardioregulatory, renal, electrolyte, and hormonal changes induced in humans by microgravity.

Natural calcium isotonic composition of urine as a marker of bone mineral balance

USGS Publications Warehouse

Skulan, J.; Bullen, T.; Anbar, A.D.; Puzas, J.E.; Shackelford, L.; LeBlanc, A.; Smith, S.M.

2007-01-01

Background: We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Methods: Calcium isotopic compositions are expressed as ??44Ca, or the difference in parts per thousand between the 44Ca/40Ca of a sample and the 44Ca/ 40Ca of a standard reference material. ??44Ca was measured in urine samples from 10 persons who participated in a study of the effectiveness of countermeasures to bone loss in spaceflight, in which 17 weeks of bed rest was used to induce bone loss. Study participants were assigned to 1 of 3 treatment groups: controls received no treatment, one treatment group received alendronate, and another group performed resistive exercise. Measurements were made on urine samples collected before, at 2 or 3 points during, and after bed rest. Results: Urine ??44Ca values during bed rest were lower in controls than in individuals treated with alendronate (P <0.05, ANOVA) or exercise (P <0.05), and lower than the control group baseline (P <0.05, Mest). Results were consistent with the model and with biochemical and bone mineral density data. Conclusion: Results confirm the predicted relationship between bone mineral balance and calcium isotopes, suggesting that calcium isotopic analysis of urine might be refined into a clinical and research tool. ?? 2007 American Association for Clinical Chemistry.

Natural calcium isotopic composition of urine as a marker of bone mineral balance.

PubMed

Skulan, Joseph; Bullen, Thomas; Anbar, Ariel D; Puzas, J Edward; Shackelford, Linda; LeBlanc, Adrian; Smith, Scott M

2007-06-01

We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Calcium isotopic compositions are expressed as delta(44)Ca, or the difference in parts per thousand between the (44)Ca/(40)Ca of a sample and the (44)Ca/(40)Ca of a standard reference material. delta(44)Ca was measured in urine samples from 10 persons who participated in a study of the effectiveness of countermeasures to bone loss in spaceflight, in which 17 weeks of bed rest was used to induce bone loss. Study participants were assigned to 1 of 3 treatment groups: controls received no treatment, one treatment group received alendronate, and another group performed resistive exercise. Measurements were made on urine samples collected before, at 2 or 3 points during, and after bed rest. Urine delta(44)Ca values during bed rest were lower in controls than in individuals treated with alendronate (P <0.05, ANOVA) or exercise (P <0.05), and lower than the control group baseline (P <0.05, t-test). Results were consistent with the model and with biochemical and bone mineral density data. Results confirm the predicted relationship between bone mineral balance and calcium isotopes, suggesting that calcium isotopic analysis of urine might be refined into a clinical and research tool.

Immune response to 60-day head-down bed rest

NASA Astrophysics Data System (ADS)

Song, Jinping; Guo, Aihua; Zhong, Ping; Zhang, Hongyu; Wu, Feng; Wan, Yumin; Bai, Yanqiang; Chen, Shanguang; Li, Yinghui

Introduction: Exposure of humans to spaceflight has resulted in disregulation of the immune system. Head-down bed rest (HDBR) has been extensively used as an earth-bound analog to study physiologic effects mimicking those occurring in weightlessness during spaceflight. It is uncertain how a prolonged period of bed rest affect human immune responses. The objective of this study was to investigate the effects of 60-day HDBR on immune function and EB virus reactivation in seven male volunteers. Methods: There were seven healthy male volunteers who were subjected to HDBR for 60d. Immunological parameters including leukocyte subset distribution, lymphocyte proliferation to mitogens, secreted cytokine profiles and EB virus reactivation were monitored. Results: Total WBC conunts increased significantly 10d post-HDBR as compared with pre-HDBR. At the same time, the relative percentage of neutrophils was also higher than pre-HDBR but not significant. MFI of CD11b in neutrophils was reduced obviously at thd end of HDBR. T Lymphocyte proliferations to PHA reduced at HDBR 30, HDBR 60 and 10d post-HDBR while IL-2 production decreased significantly at the same time. IFN-and IL-4 production trended to decrease at HDBR 30 and HDBR 60. The relative percentage of T lymphocyte subset, B lymphocyte and NK cells were not altered. EBV EA (early antigen) were negative and EBV VCA titers had no changes through HDBR. Conclusion: The results indicate that several immunological parameters (mainly cellular immunity) are altered significantly by prolonged HDBR, and these changes were similar to those happened in spaceflight.

WISE-2005: Adrenergic Responses Before and After 60 Days of 6 Degree Head-Down Bed-Rest in Women

NASA Technical Reports Server (NTRS)

Edgell, H.; Dyson, K.; Shoemaker, J. K.; Custaud, M. A.; Arbeille, Ph.; Greaves, D.; Hughson, R. L.; Hughson, R. L.

2006-01-01

Sixteen women who participated in the WISE-2005 headdown bed rest (HDBR) were studied before and on day 56 of bed rest to test the hypothesis that chronic changes in circulating norepinephrine (NOR) would change the response to adrenergic receptor agonists. Five minute infusions of 2 doses of isoproterenol (ISO), and 2 doses of NOR were administered while heart rate (HR), mean arterial pressure (MAP) and total peripheral resistance (TPR) were measured. Before HDBR, the higher dose of ISO increased HR by 13 beats/min (P

Behavioral Responses of the Bed Bug to Permethrin-Impregnated ActiveGuard™ Fabric

PubMed Central

Jones, Susan C.; Bryant, Joshua L.; Harrison, Scott A.

2013-01-01

ActiveGuard™ Mattress Liners have been used to control house dust mites, and they also are commercially available as an integrated pest management tool for use against bed bugs (Cimex lectularius). The aim of our study was to evaluate responses of numerous populations of the bed bug to the permethrin-impregnated fabric, with particular regard to contact toxicity, repellency, and feeding inhibition. Continuous exposure to ActiveGuard fabric resulted in rapid intoxication for three of four populations, with 87 to 100% of moderately pyrethroid-resistant and susceptible bed bugs succumbing by 1 d. In comparison, a highly resistant population reached 22% mortality at 10 d. Video data revealed that bed bugs readily traversed ActiveGuard fabric and spent a considerable amount of time moving about and resting on it during a 12-h period. ActiveGuard fabric was non-repellent to bed bugs from five tested populations. Furthermore, significantly fewer bed bugs successfully fed to repletion through ActiveGuard fabric than through blank fabric for the five populations. With just 30 min of feeding exposure, mortality ranged from 4% to 83%, depending upon the bed bug strain. These laboratory studies indicate that ActiveGuard liners adversely affected bed bugs from diverse populations. PMID:26464388

Behavioral, Brain Imaging and Genomic Measures to Predict Functional Outcomes Post-Bed Rest and Space Flight

NASA Technical Reports Server (NTRS)

Mulavara, A. P.; Peters, B.; De Dios, Y. E.; Gadd, N. E.; Caldwell, E. E.; Batson, C. D.; Goel, R.; Oddsson, L.; Kreutzberg, G.; Zanello, S.;

Effects of 1-week head-down tilt bed rest on bone formation and the calcium endocrine system

NASA Technical Reports Server (NTRS)

Arnaud, Sara B.; Whalen, Robert T.; Fung, Paul; Sherrard, Donald J.; Maloney, Norma

1992-01-01

The -6-deg head-down tilt (HDT) is employed in the study of 8 subjects to determine early responses in human bone and calcium endocrines during spaceflight. The average rates of bone formation in the iliac crest are determined by means of a single-dose labeling schedule and are found to decrease in 6 of the subjects. The decrease varies directly with walking miles, and increased excretion of urinary Ca and Na are observed preceding increased levels of ionized serum calcium on a bed-rest day late in the week. Reduced phosphorous excretions are also followed by increased serum phosphorous on day six, and reductions are noted in parathyroid hormone and vitamin D by the end of the experiment. The data demonstrate the responsiveness of the skeletal system to biomechanical stimuli such as the HDT.

The time course of the adaptations of human muscle proteome to bed rest and the underlying mechanisms

PubMed Central

Brocca, Lorenza; Cannavino, Jessica; Coletto, Luisa; Biolo, Gianni; Sandri, Marco; Bottinelli, Roberto; Pellegrino, Maria Antonietta

2012-01-01

In order to get a comprehensive picture of the complex adaptations of human skeletal muscle to disuse and further the understanding of the underlying mechanisms, we participated in two bed rest campaigns, one lasting 35 days and one 24 days. In the first bed rest (BR) campaign, myofibrillar proteins, metabolic enzymes and antioxidant defence systems were found to be down-regulated both post-8 days and post-35 days BR by proteomic analysis of vastus lateralis muscle samples from nine subjects. Such profound alterations occurred early (post-8 days BR), before disuse atrophy developed, and persisted through BR (post-35 days BR). To understand the mechanisms underlying the protein adaptations observed, muscle biopsies from the second bed rest campaign (nine subjects) were used to evaluate the adaptations of master controllers of the balance between muscle protein breakdown and muscle protein synthesis (MuRF-1 and atrogin-1; Akt and p70S6K), of autophagy (Beclin-1, p62, LC3, bnip3, cathepsin-L), of expression of antioxidant defence systems (NRF2) and of energy metabolism (PGC-1α, SREBP-1, AMPK). The results indicate that: (i) redox imbalance and remodelling of muscle proteome occur early and persist through BR; (ii) impaired energy metabolism is an early and persistent phenomenon comprising both the oxidative and glycolytic one; (iii) although both major catabolic systems, ubiquitin proteasome and autophagy, could contribute to the progression of atrophy late into BR, a decreased protein synthesis cannot be ruled out; (iv) a decreased PGC-1α, with the concurrence of SREBP-1 up-regulation, is a likely trigger of metabolic impairment, whereas the AMPK pathway is unaltered. PMID:22848045

[Rehabilitation for the patients with low-back pain].

PubMed

Shirado, Osamu; Watanabe, Yasuyuki; Kawase, Masafumi

2005-03-01

The first choice for the treatment of low-back pain should be physical therapy, or rehabilitation. These are mainly divided into two modalities; passive and active modality. The former includes bed rest, hot pack, massage, and brace. The latter includes therapeutic exercise. The modality used should be dependent of the stages in each patient. Bed rest is indicated in the acute stage within a week after the occurrence low-back pain. The rest longer than a week is basically contraindicated, because of disuse syndrome such as muscle weakness, osteoporosis, and soft tissue contracture. Therapeutic exercise is the mainstay in the chronic stage. It includes trunk muscles strengthening exercise and stretching. Lumbar stabilization exercise has currently drawn attention for the treatment of low-back pain. Patient education such as back-school also plays an important role to manage low-back pain.

Parallels between astronauts and terrestrial patients - Taking physiotherapy rehabilitation "To infinity and beyond".

PubMed

Hides, Julie; Lambrecht, Gunda; Ramdharry, Gita; Cusack, Rebecca; Bloomberg, Jacob; Stokes, Maria

2017-01-01

Exposure to the microgravity environment induces physiological changes in the cardiovascular, musculoskeletal and sensorimotor systems in healthy astronauts. As space agencies prepare for extended duration missions, it is difficult to predict the extent of the effects that prolonged exposure to microgravity will have on astronauts. Prolonged bed rest is a model used by space agencies to simulate the effects of spaceflight on the human body, and bed rest studies have provided some insights into the effects of immobilisation and inactivity. Whilst microgravity exposure is confined to a relatively small population, on return to Earth, the physiological changes seen in astronauts parallel many changes routinely seen by physiotherapists on Earth in people with low back pain (LBP), muscle wasting diseases, exposure to prolonged bed rest, elite athletes and critically ill patients in intensive care. The medical operations team at the European Space Agency are currently involved in preparing astronauts for spaceflight, advising on exercises whilst astronauts are on the International Space Station, and reconditioning astronauts following their return. There are a number of parallels between this role and contemporary roles performed by physiotherapists working with elite athletes and muscle wasting conditions. This clinical commentary will draw parallels between changes which occur to the neuromuscular system in the absence of gravity and conditions which occur on Earth. Implications for physiotherapy management of astronauts and terrestrial patients will be discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metabolic consequences of physical inactivity.

PubMed

Biolo, Gianni; Ciocchi, Beniamino; Stulle, Manuela; Piccoli, Arianna; Lorenzon, Stefania; Dal Mas, Viviana; Barazzoni, Rocco; Zanetti, Michela; Guarnieri, Gianfranco

2005-01-01

Physical inactivity is associated with alteration of normal physiologic processes leading to muscle atrophy, reduced exercise capacity, insulin resistance, and altered energy balance. Bed rest studies in human beings using stable isotopes of amino acids indicate that muscle unloading decreases the turnover rates of muscle and whole-body proteins, with a prevailing inhibition of protein synthesis. In the fasting state, muscle and whole-body nitrogen loss was not accelerated during bed rest. In experimental postprandial states, the amino acid-mediated stimulation of protein synthesis was impaired, whereas the ability of combined insulin and glucose infusion to decrease whole-body proteolysis was not affected by muscle inactivity. Thus, an impaired ability of protein/amino acid feeding to stimulate body protein synthesis is the major catabolic mechanism for the effect of bed rest on protein metabolism. This suggests that a protein intake level greater than normal could be required to achieve the same postprandial anabolic effect during muscle inactivity. Metabolic adaptation to muscle inactivity also involves development of resistance to the glucoregulatory action of insulin, decreased energy requirements, and increased insulin and leptin secretion. These alterations may lead to the development of the metabolic syndrome that is defined as the association of hyperinsulinemia, dyslipidemia, hypertension, hyperglycemia, and abdominal obesity. This cluster of metabolic abnormalities is a risk factor for coronary artery disease and stroke. Evidence indicates that exercise training programs may counteract all of these abnormalities both in healthy sedentary subjects and in patients affected by a variety of chronic disease states.

Performance and mood-state parameters during 30-day 6 degrees head-down bed rest with exercise training

NASA Technical Reports Server (NTRS)

DeRoshia, C. W.; Greenleaf, J. E.

1993-01-01

The study was designed to determine if performance and mood impairments occur in bed-rested subjects, and if different exercise-training regimens modify or prevent them. Eighteen normal, healthy men were divided on the basis of age, peak oxygen uptake, and maximal isometric knee extension strength into three similar groups: no exercise (NOE), isotonic exercise (ITE), and isokinetic exercise (IKE). A 15-min battery of 10 performance tests and 8 mood and 2 sleep scales were administered daily during ambulatory control, 30 d of absolute bed rest (BR), and 4 d of ambulatory recovery. Performance test proficiency increased (p < 0.05) for all three groups during BR in 7 of 10 tests and there were no consistent significant differences between the three groups. However, during BR, the ITE group was distinguished from the other groups by a decline (p < 0.05) in the activation mood dimension and in two of its constituent scales (motivation and concentration), and by improvement (p < 0.05) in the trouble-falling-asleep and psychological-tension scales. Since few deleterious changes in performance and mood occurred in the three groups and did not exceed baseline ambulatory levels, we conclude that mood and performance did not deteriorate in response to prolonged BR and were not altered by exercise training. However, the decline in activation mood scales in the ITE group may reflect overtraining or excess total workload in this group.

Analysis by NASA's VESGEN Software of Retinal Blood Vessels Before and After 70-Day Bed Rest: A Retrospective Study

NASA Technical Reports Server (NTRS)

Raghunandan, Sneha; Vyas, Ruchi J.; Vizzeri, Gianmarco; Taibbi, Giovanni; Zanello, Susana B.; Ploutz-Snyder, Robert; Parsons-Wingerter, Patricia A.

2016-01-01

Significant risks for visual impairment associated with increased intracranial pressure (VIIP) are incurred by microgravity spaceflight, especially long-duration missions. Impairments include decreased near visual acuity, posterior globe flattening, choroidal folds, optic disc edema and cotton wool spots. We hypothesize that microgravity-induced fluid shifts result in pathological changes within the retinal blood vessels that precede development of visual and other ocular impairments. Potential contributions of retinal vascular remodeling to VIIP etiology are therefore being investigated by NASAs innovative VESsel GENeration Analysis (VESGEN) software for two studies: (1) head-down tilt in human subjects before and after 70 days of bed rest, and (2) U.S. crew members before and after ISS missions. VESGEN analysis in previous research supported by the US National Institutes of Health identified surprising new opportunities to regenerate retinal vessels during early-stage, potentially reversible progression of the visually impairing and blinding disease, diabetic retinopathy.

The reliability of melatonin synthesis as an indicator of the individual circadian phase position.

PubMed

Roemer, Hermann C; Griefahn, Barbara; Kuenemund, Christa; Blaszkewicz, Meinolf; Gerngross, Heinz

2003-08-01

Melatonin synthesis occurs earlier in the morning than in the evening types who strictly adhere to their individual time schedule. This study tested whether melatonin profiles still separate between diurnal types who vary their individual rhythm or who are submitted to prescribed time schedules. Male and female students were observed during a constant routine in the laboratory (24-26 hours bed rest, 20 degrees C, <30 lux, hourly isocaloric diet) and soldiers who spent several days in a military hospital were observed during 12 hours (bed rest, <30 lux, normal meals). Salivary melatonin levels were determined hourly. In both studies, melatonin profiles occurred earlier in the morning than in the evening types. The difference was smaller in soldiers, thus conditioning contributes to the actual phase position but does not mask morningness. As morningness is related to the ability to cope with shift work, the melatonin onset can be used as a criterion when assigning a person to shift work.

[Therapeutic effect and safety of microendoscopic discectomy versus conventional open discectomy for the treatment of lumbar disc herniation: a Meta analysis].

PubMed

Ying, Xiao-Ming; Jiang, Yong-Liang; Xu, Peng; Wang, Peng; Zhu, Bo; Guo, Shao-Qing

2016-08-25

To conduct a meta analysis of studies comparing theapeutic effect and safety of microendoscopic discectomy to conventional open discectomy in the treatment of lumbar disc herniation in China. A systematic literature retrieval was conducted in the Chinese Bio medicine Database, CNKI database, Chongqin VIP database and Wangfang database. The statistical analysis was performed using a RevMan 4.2 software. The comparison included excellent rate, operation times, blood loss, periods of bed rest and resuming daily activities, hospital stay or hospital stay after surgery, and complications of microendoscopic discectomy versus conventional open discectomy. The search yielded 20 reports, which included 2 957 cases treated by microendoscopic discectomy and 2 130 cases treated by conventional open discectomy. There were 12, 11, 7, 5, 4 and 4 reports which had comparison of operation times, blood loss, period of bed rest, periods of resuming daily activities, hospital stay and hospital stay after surgery respectively. Complications were mentioned in 10 reports. Compared to patients treated by open discectomy, patients treated by microendoscopic discectomy had a higher excellent rates [OR=1.29, 95%CI (1.03, 1.62)], less blood loss[OR=-63.67, 95%CI (-86.78, -40.55)], less period of bed rest[OR=-15.33, 95%CI (-17.76, -12.90)], less period of resumption of daily activities [OR=-24.41, 95%CI (-36.86, -11.96)], less hospital stay [OR=-5.00, 95%CI (-6.94, -3.06)] or hospital stay after surgery [OR=-7.47, 95%CI (-9.17, -5.77) respectively. However, incidence of complications and operation times were proved no significant different between microendoscopic discectomy and open discectomy. Microendoscopic discectomy and conventional open discectomy in treatment of lumbar disc herniation are both safe, effective; incidence of complications are nearly. Patients with lumbar disc herniation treated by microendoscopic discectomy have fewer blood loss, shorter periods of bed rest and hospital stay, and resume daily activities faster. Techniques are selected according to indications, microendoscopic discectomy should be carried out when conjunct indications occur.

Low-G simulation in mammalian research

NASA Technical Reports Server (NTRS)

Sandler, H.

1982-01-01

After a review of space-flight research concerning the effects of weightlessness on mammals, the paper reviews various methods of low-G simulation. Consideration is given to water immersion; bed rest, chair rest, and confinement; immobilization; and partial body-support systems. Countermeasures to offset the effects of weightlessness are also discussed.

Behavioral, Brain Imaging and Genomic Measures to Predict Functional Outcomes Post - Bed Rest and Spaceflight

NASA Technical Reports Server (NTRS)

Mulavara, A. P.; DeDios, Y. E.; Gadd, N. E.; Caldwell, E. E.; Batson, C. D.; Goel, R.; Seidler, R. D.; Oddsson, L.; Zanello, S.; Clarke, T.;

Replacement of daily load attenuates but does not prevent changes to the musculoskeletal system during bed rest.

PubMed

Cavanagh, Peter R; Rice, Andrea J; Novotny, Sara C; Genc, Kerim O; Englehaupt, Ricki K; Owings, Tammy M; Comstock, Bryan; Cardoso, Tamre; Ilaslan, Hakan; Smith, Scott M; Licata, Angelo A

2016-12-01

The dose-response effects of exercise in reduced gravity on musculoskeletal health have not been well documented. It is not known whether or not individualized exercise prescriptions can be effective in preventing the substantial loss in bone mineral density and muscle function that have been observed in space flight and in bed rest. In this study, typical daily loads to the lower extremities were quantified in free-living subjects who were then randomly assigned to control or exercise groups. Subjects were confined to 6-degree head-down bed rest for 84 days. The exercise group performed individually prescribed 1 g loaded locomotor exercise to replace their free-living daily load. Eleven subjects (5 exercise, 6 control) completed the protocol. Volumetric bone mineral density results from quantitative computed tomography demonstrated that control subjects lost significant amounts of bone in the intertrochanteric and total hip regions ( p  < 0.0125), whereas the exercise group showed no significant change from baseline in any region ( p  > 0.0125). Pre-and post-bed rest muscle volumes were calculated from analysis of magnetic resonance imaging data. The exercise group retained a larger percentage of their total quadriceps and gastrocnemius muscle volume (- 7.2% ± 5.9, - 13.8% ± 6.1, respectively) than their control counterparts (- 23.3% ± 5.9, - 33.0 ± 8.2, respectively; p  < 0.01). Both groups significantly lost strength in several measured activities ( p  < 0.05). The declines in peak torque during repeated exertions of knee flexion and knee extension were significantly less in the exercise group than in the control group ( p  < 0.05) but work done was not significantly different between groups ( p  > 0.05). The decline in VO 2max was 17% ± 18 in exercising subjects ( p  < 0.05) and 31% ± 13 in control subjects ( p  = 0.003; difference between groups was not significant p  = 0.26). Changes in blood and urine measures showed trends but no significant differences between groups ( p  > 0.05). In summary, the decline in a number of important measures of musculoskeletal and cardiovascular health was attenuated but not eliminated by a subject-specific program of locomotor exercise designed to replace daily load accumulated during free living. We conclude that single daily bouts of exposure to locomotor exercise can play a role in a countermeasures program during bed rest, and perhaps space flight, but are not sufficient in their own right to ensure musculoskeletal or cardiovascular health.

Research on the relationship between the structural properties of bedding layer in spring mattress and sleep quality.

PubMed

Shen, Liming; Chen, Yu-xia; Guo, Yong; Zhong, ShiLu; Fang, Fei; Zhao, Jing; Hu, Tian-Yi

2012-01-01

Mattress, as a sleep platform, its types and physical properties has an important effect on sleep quality and rest efficiency. In this paper, by subjective evaluations, analysis of sleeping behaviors and tests of depth of sleep, the relationship between characteristics of the bedding materials, the structure of mattress, sleep quality and sleep behaviors were studied. The results showed that: (1) Characteristics of the bedding materials and structure of spring mattress had a remarkable effect on sleep behaviors and sleep quality. An optimum combination of the bedding materials, the structure of mattress and its core could improve the overall comfort of mattress, thereby improving the depth of sleep and sleep quality. (2) Sleep behaviors had a close relationship with sleeping postures and sleep habits. The characteristics of sleep behaviors vary from person to person.

Effects of prolonged hypoxia and bed rest on appetite and appetite-related hormones.

PubMed

Debevec, Tadej; Simpson, Elizabeth J; Mekjavic, Igor B; Eiken, Ola; Macdonald, Ian A

2016-12-01

Environmental hypoxia and inactivity have both been shown to modulate appetite. To elucidate the independent and combined effects of hypoxia and bed rest-induced inactivity on appetite-related hormones and subjective appetite, eleven healthy, non-obese males underwent three experimental interventions in a cross-over and randomized fashion: 1) Hypoxic confinement combined with daily moderate-intensity exercise (HAMB, F i O 2  = 0.141 ± 0.004; P i O 2  = 90.0 ± 0.4 mmHg) 2) Bed rest in normoxia (NBR, F i O 2  = 0.209; P i O 2  = 133.1 ± 0.3 mmHg) and 3) Bed rest in hypoxia (HBR, F i O 2  = 0.141 ± 0.004; P i O 2  = 90.0 ± 0.4 mmHg). A mixed-meal tolerance test (MTT), followed by an ad libitum meal were performed before (Pre) and after 16-days (Post) of each intervention. Composite satiety scores (CSS) during the MTT were calculated from visual analogue scores, while fasting and postprandial concentrations of total ghrelin, peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and leptin were quantified from arterialized-venous samples. Postprandial CSS were significantly lower at Post compared to Pre in NBR only (P < 0.05) with no differences observed in ad libitum meal intakes. Postprandial concentrations and incremental area under the curve (AUC) for total ghrelin and PYY were unchanged following all interventions. Postprandial GLP-1 concentrations were only reduced at Post following HBR (P < 0.05) with resulting AUC changes being significantly lower compared to HAMB (P < 0.01). Fasting leptin was reduced following HAMB (P < 0.05) with no changes observed following NBR and HBR. These findings suggest that independently, 16-day of simulated altitude exposure (∼4000 m) and bed rest-induced inactivity do not significantly alter subjective appetite or ad libitum intakes. The measured appetite-related hormones following both HAMB and HBR point to a situation of hypoxia-induced appetite stimulation, although this did not reflect in higher ad libitum intakes. NCT02293772. Copyright © 2016 Elsevier Ltd. All rights reserved.

The influence of exercise on bone atrophy

NASA Technical Reports Server (NTRS)

1978-01-01

The relationship between the skeletal system, the muscular system, and exercise in bed rest studies are described. The regime of exercises performed, the mineral balance data derived, and the bone densitometric data obtained are discussed. A brief review of some of the histological results are also given.

An evaluation of the effects of bed rest, sleep deprivation and discontinuance of training on the physical fitness of highly trained young men

NASA Technical Reports Server (NTRS)

Olree, H. D.; Corbin, B.; Dugger, G.; Smith, C.

1973-01-01

This experiment was conducted to determine what physiological effects result when highly trained subjects are confined to bed, deprived of sleep, or allowed to discontinue training. Results indicated: (1) There was a moderate increase in strength variables due to the training in this experiment but the stress which the subjects received caused a negligible change in strength variables. (2) The training program resulted in highly significant changes in specific bicycle ergometer variables indicating good increases in cardiopulmonary fitness. Five days of bed rest or fifty hours of sleep deprivation caused comparable drastic decreases in cardiopulmonary fitness. Post stress the subjects reverted to a normal daily schedule and after two weeks they had recovered about half of what they lost. (3) Cardiac output remains relatively constant at a constant work load, but stroke volume increases with conditioning and decreases with deconditioning due to stress.

Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle?

PubMed

Tschakovsky, Michael E; Sujirattanawimol, Kittiphong; Ruble, Stephen B; Valic, Zoran; Joyner, Michael J

2002-06-01

Sympathetic vasoconstriction of muscle vascular beds is important in the regulation of systemic blood pressure. However, vasoconstriction during exercise can also compromise blood flow support of muscle metabolism. This study tested the hypothesis that local factors in exercising muscle blunt vessel responsiveness to sympathetic vasoconstriction. We performed selective infusions of three doses of tyramine into the brachial artery (n = 8) to evoke endogenous release of noradrenaline (norepinephrine) at rest and during moderate and heavy rhythmic handgrip exercise. In separate experiments, tyramine was administered during two doses of adenosine infusion (n = 7) and two doses of sodium nitroprusside (SNP) infusion (n = 8). Vasoconstrictor effectiveness across conditions was assessed as the percentage reduction in forearm vascular conductance (FVC), calculated from invasive blood pressure and non-invasive Doppler ultrasound blood flow measurements at the brachial artery. Tyramine evoked a similar dose-dependent vasoconstriction at rest in all three groups, with the highest dose resulting in a 42-46 % reduction in FVC. This vasoconstriction was blunted with increasing exercise intensity (e.g. tyramine high dose percentage reduction in FVC; rest -43.4 +/- 3.7 %, moderate exercise -27.5 +/- 2.3 %, heavy exercise -16.7 +/- 3.6 %; P < 0.05). In contrast, tyramine infusion resulted in a greater percentage reduction in FVC during both doses of adenosine vs. rest (P < 0.05). Finally, percentage change in FVC was greater during low dose SNP infusion vs. rest (P < 0.05), but not different from rest at the high dose of SNP infusion (P = 0.507). A blunted percentage reduction in FVC during endogenous noradrenaline release in exercise but not vasodilator infusion indicates that sympathetic vasoconstriction is blunted in exercising muscle. This blunting appears to be exercise intensity-dependent.

Analogs of microgravity: head-down tilt and water immersion.

PubMed

Watenpaugh, Donald E

2016-04-15

This article briefly reviews the fidelity of ground-based methods used to simulate human existence in weightlessness (spaceflight). These methods include horizontal bed rest (BR), head-down tilt bed rest (HDT), head-out water immersion (WI), and head-out dry immersion (DI; immersion with an impermeable elastic cloth barrier between subject and water). Among these, HDT has become by far the most commonly used method, especially for longer studies. DI is less common but well accepted for long-duration studies. Very few studies exist that attempt to validate a specific simulation mode against actual microgravity. Many fundamental physical, and thus physiological, differences exist between microgravity and our methods to simulate it, and between the different methods. Also, although weightlessness is the salient feature of spaceflight, several ancillary factors of space travel complicate Earth-based simulation. In spite of these discrepancies and complications, the analogs duplicate many responses to 0 G reasonably well. As we learn more about responses to microgravity and spaceflight, investigators will continue to fine-tune simulation methods to optimize accuracy and applicability. Copyright © 2016 the American Physiological Society.

ARC-1993-AC93-0230-25

NASA Image and Video Library

1993-05-05

Ann Hutchinson (as subject), Dr. Joan Vernikos (R), Dee O'Hara (L), J. Evans and E. Lowe pose for pictures in the NASA Magazine aritcle 'How it Feels to be a Human Test Subject' as they prepare for a bed rest study to simulate the efects of microgravity on the human body.

Evaluation of Efficacy of Preventive Measures under Hypokinesia.

ERIC Educational Resources Information Center

Zorbas, Yan G.; Matveyev, Ivan O.

1987-01-01

The study evaluated the efficacy of physical exercise alone and in combination with other preventive measures with 24 adult male subjects kept under a bed rest regime. It was concluded that physical exercise was the most reliable measure in counteracting neuromuscular system disorders under diminished muscular activity conditions. (Author/DB)

Glucocorticoid resorption and influence on the hypothalamic‐pituitary‐adrenal axis after intra‐articular treatment of the knee in resting and mobile patients

PubMed Central

Weitoft, T; Rönnblom, L

2006-01-01

Background Studies have shown that intra‐articular glucocorticoid injection treatment for knee synovitis has a better outcome in resting patients than in mobile patients. One reason for this observation might be that rest retards steroid resorption, causing an enhanced local treatment effect. Objectives To study drug resorption and the impact on hormone production in the hypothalamic‐pituitary‐adrenal axis after intra‐articular glucocorticoid administration, with and without postinjection rest. Methods Twenty patients with rheumatoid arthritis and knee synovitis were randomised to either 24 hour bed rest or normal activity after intra‐articular glucocorticoid treatment with 20 mg triamcinolone hexacetonide (THA). Serum levels of THA, cortisol, and adrenocorticotropic hormone (ACTH) were followed during 2 weeks. Results Short term and reversible decreases in serum cortisol and ACTH levels (p<0.001) were seen, without any significant differences between resting and mobile patients. The THA levels increased similarly in both groups, with the median serum peak seen after 8 hours. Conclusion Immobilisation does not appear to retard glucocorticoid resorption after intra‐articular administration. Further studies are therefore needed to clarify the mechanism behind the beneficial effects of rest after intra‐articular glucocorticoid treatment for knee synovitis. PMID:16769782

Effects of Long Duration Spaceflight on Venous and Arterial Compliance

NASA Technical Reports Server (NTRS)

Ribeiro, L. C.; Lee, S. M. C.; Martin, D. S.; Ploutz-Snyder, R.; Stenger, M. B.; Westby, C. M.; Platts, S. H.

2014-01-01

The visual impairment and intracranial pressure syndrome (VIIP) is a newly described space flight-associated medical condition made up of a constellation of symptoms affecting at least 34% of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures, and is thought to be related to elevated intracranial pressure secondary to space flightinduced cephalad fluid shifts. Loss of visual acuity could be a significant threat to crew health and performance and may be suggestive of other adaptations with implications for years post-flight. Our primary objective is to determine whether vascular compliance is altered by space flight and whether such adaptations are related to the incidence of VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no space flight experience, in astronauts before, during, and after space flight, and in bed rest subjects with conditions similar to space flight. Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archive to determine which factors might be predictive of the development of VIIP. The project will be conducted in four separate but related parts. To understand the baseline condition of astronauts without any prior space flight experience, we will study 10 astronauts who have never flown in space by performing a comprehensive evaluation of the vasculature of the head, neck and eyes. Hemodynamic data (stroke volume and blood pressure), ocular (tonometry and ocular ultrasound), venous and arterial parameters will be acquired across a range of tilt angles (20, 10, 0, -10, -20 degrees). Vessels to be studied include the temporal, jugular, and vertebral veins and the cerebral, carotid and vertebral arteries. Ophthalmic data from the annual physical will be obtained through data sharing. To examine the relation between vascular compliance in the head and neck and the development of VIIP after a long duration space flight, we will study 10 astronauts before, during, and after long-duration ISS missions. Pre- and post-flight testing will be identical to that described above. During flight, images of the same vessels of interest will be obtained for later analysis. Ophthalmic data including VIIP scores will be obtained through data sharing from medically-required tests. To investigate the effects of age and elevated sodium intake, two potential contributors to VIIP, we will study 24 men (in two age groups: 25-35 and 45-55) during a 14 day 6deg head-down bed rest, a well-accepted analog of space flight. Standard NASA bed rest conditions will be maintained except for dietary sodium. Sodium intake will be similar to that of ISS astronauts, which is higher than consumed in previous bed rest studies. Pre- and post-bed rest testing procedures will be identical to the testing protocol described above for astronauts. Ophthalmic testing (optical coherence tomography, fundoscopy, and tonometry) will be conducted on the same day that vascular compliance measures are obtained. To identify parameters that may relate to an increase in an astronaut's susceptibility to developing VIIP, we will use data mining techniques to evaluate astronaut data obtained from the LSAH. Medical history, family history, space flight history and its related exposures, and history of high performance jet aircraft exposure will be examined for their potential relationship to ocular data. We hypothesize that the cephalad fluid shift induced by space flight will result in structural and functional adaptations in head and neck vessels leading to decreased vascular compliance and related to the development of VIIP symptoms. Further, although VIIP has not been observed in previous bed rest studies, we hypothesize that an elevated sodium intake will increase the incidence of VIIP symptoms in this space flight analog. Finally, we hypothesize that data mining analyses will reveal relationships between health history, previous exposures (including space flight and high performance aircraft), and the development of VIIP in the astronaut population.

On a criterion of incipient motion and entrainment into suspension of a particle from cuttings bed in shear flow of non-Newtonian fluid

NASA Astrophysics Data System (ADS)

Ignatenko, Yaroslav; Bocharov, Oleg; May, Roland

2017-10-01

Solids transport is a major issue in high angle wells. Bed-load forms by sediment while transport and accompanied by intermittent contact with stream-bed by rolling, sliding and bouncing. The study presents the results of a numerical simulation of a laminar steady-state flow around a particle at rest and in free motion in a shear flow of Herschel-Bulkley fluid. The simulation was performed using the OpenFOAM open-source CFD package. A criterion for particle incipient motion and entrainment into suspension from cuttings bed (Shields criteria) based on forces and torques balance is discussed. Deflection of the fluid parameters from the ones of Newtonian fluid leads to decreasing of the drag and lift forces and the hydrodynamic moment. Thus, the critical shear stress (Shields parameter) for the considered non-Newtonian fluid must be greater than the one for a Newtonian fluid.

Hardware Evaluation of the Horizontal Exercise Fixture with Weight Stack

NASA Technical Reports Server (NTRS)

Newby, Nate; Leach, Mark; Fincke, Renita; Sharp, Carwyn

2009-01-01

HEF with weight stack seems to be a very sturdy and reliable exercise device that should function well in a bed rest training setting. A few improvements should be made to both the hardware and software to improve usage efficiency, but largely, this evaluation has demonstrated HEF's robustness. The hardware offers loading to muscles, bones, and joints, potentially sufficient to mitigate the loss of muscle mass and bone mineral density during long-duration bed rest campaigns. With some minor modifications, the HEF with weight stack equipment provides the best currently available means of performing squat, heel raise, prone row, bench press, and hip flexion/extension exercise in a supine orientation.

Automated electroencephalography system and electroencephalographic correlates of space motion sickness, part 4

NASA Technical Reports Server (NTRS)

Frost, J. D., Jr.

1977-01-01

Comparative data for further assessments of the EEG alterations seen during Skylab are elaborated. The variability of alpha, beta, theta, and delta EEG characteristics was analyzed with quantitative computer techniques in a group of six normal individuals over a period of two months, and the EEG effects of a prolonged period of bed rest were evaluated in two subjects. The results confirm that the inflight EEG changes seen during Skylab are statistically significant, but the absolute values obtained for the various parameters do not exceed the maximal range expected in a normal population. Further, the EEG manifestations of extended bed rest do not appear similar to those of space flight.

Effects of listening to music on pain intensity and pain distress after surgery: an intervention.

PubMed

Vaajoki, Anne; Pietilä, Anna-Maija; Kankkunen, Päivi; Vehviläinen-Julkunen, Katri

2012-03-01

To evaluate the effects of music listening on pain intensity and pain distress on the first and second postoperative days in abdominal surgery patients and the long-term effects of music on the third postoperative day. Music has been found to relieve pain intensity in surgery patients. There are only a few studies on music intervention in abdominal surgery. Music intervention studies assessing multidimensional pain such as pain intensity and pain distress are also scarce. Prospective clinical study with two parallel groups. Patients undergoing elective abdominal surgery (n = 168) were divided into either a music group (n = 83) or a control group (n = 85). Patients assessed pain intensity and pain distress in bed rest, during deep breathing and in shifting position once in the evening of the operation day and on the first and second postoperative days in the morning, at noon and in the evening. On the third postoperative day, the patients assessed their pain intensity and pain distress only once. In the music group, the patients' pain intensity and pain distress in bed rest, during deep breathing and in shifting position were significantly lower on the second postoperative day compared with control group of patients. On the third postoperative day, when long-term effects of music on pain intensity and pain distress were assessed, there were no significant differences between music and control groups. This study demonstrates that the use of music alleviates pain intensity and pain distress in bed rest, during deep breathing and in shifting position after abdominal surgery on the second postoperative day. Music intervention is safe, inexpensive and easily used to improve the healing environment for abdominal surgery patients. Music intervention should be offered as an adjunct alternative to pharmacological pain relief after abdominal surgery in nursing practice. © 2011 Blackwell Publishing Ltd.

Effects of Various Interventions, Including Mass Trapping with Passive Pitfall Traps, on Low-Level Bed Bug Populations in Apartments.

PubMed

Cooper, Richard; Wang, Changlu; Singh, Narinderpal

2016-04-01

Two experiments were conducted to evaluate the effects of various interventions on low-level bed bug, Cimex lectularius L., populations in occupied apartments. The first experiment was conducted in occupied apartments under three intervention conditions: never treated (Group I), recently treated with no further treatment (Group II), and recently treated with continued treatment (Group III). Each apartment was monitored with pitfall-style traps (interceptors) installed at beds and upholstered furniture (sleeping and resting areas) along with ∼18 additional interceptors throughout the apartment. The traps were inspected every 2 wk. After 22 wk, bed bugs had been eliminated (zero trap catch for eight consecutive weeks and none detected in visual inspections) in 96, 87, and 100% of the apartments in Groups I, II, and III, respectively. The second experiment investigated the impact of interceptors as a control measure in apartments with low-level infestations. In the treatment group, interceptors were continuously installed at and away from sleeping and resting areas and were inspected every 2 wk for 16 wk. In the control group, interceptors were placed in a similar fashion as the treatment group but were only placed during 6–8 and 14–16 wk to obtain bed bug counts. Bed bug counts were significantly lower at 8 wk in the treatment group than in the control group. At 16 wk, bed bugs were eliminated in 50% of the apartments in the treatment group. The implications of our results in the development of bed bug management strategies and monitoring protocols are discussed.

Management of Nail Bed Injuries Associated with Fingertip Injuries.

PubMed

George, Alexander; Alexander, Reena; Manju, C

2017-01-01

Management of nail injuries can often be a challenging experience, especially in presence of complex fingertips' injuries that include soft tissue loss and distal phalanx injury. Most studies found in the literature focus on individual injuries and describe methods to tackle those injuries, notwithstanding the fact that the nail, nailbed, distal phalanx, soft tissue and skin of the finger tip form a complex and often more than one element of this complex is injured. This retrospective study therefore focuses on the management of nail bed injuries as a part of the complex finger tip injury and outlines the surgical principles and techniques that were used in their management. Two hundred and forty patients from a tertiary care center in different clinical settings where a wide variety of cases involving the nail bed injuries were included in this study. Patients comprised of 192 (80%) males and 48 (20%) females with the average male age of 37.3 years (range 1-66 years) and average female age of 29 years (range 1-59 years). 210 patients had single finger involment, 30 patients had two finger involvement (total fingers involved- 270). The middle finger was most commonly involved while the index finger was the second most commonest finger involved. In 198 (89.18%) patients local anaesthesia was used while in the rest: regional blocks [ n = 10 (4.5%)] and general anaesthesia [ n = 14 (6.3%)] were used. In this retrospective study, out of the total of two hundred and forty patients, 222 (92.5%) patients underwent surgery, while the rest 18 (7.5%) were treated conservatively. Two hundred and ten patients who underwent surgery had complete healing over the course of treatment and followup, while four patients needed secondary interventional. Eight patients who had surgery were migrant workers were lost to follow up after surgery. Eight patients had postoperative complications that included infection, secondary necrosis, wound breakdown and non healing fractures. Accurate and timely diagnosis of nail bed injury and its meticulous repair is cardinal to the management of any nail bed injury. However all nail bed injuries must be seen in the context of associated injuries of the finger tip complex, namely skin, soft tissue and distal phalanx injuries. Fixation of associated bony injury which closely underlines the nail bed and provides physical support to the nail bed along with correction of soft tissue injuries in the form of flaps or grafts, compounded by the repair or replacement of nail plate in the first 24 hours.

Cardiovascular responses to hypogravic environments

NASA Technical Reports Server (NTRS)

Sandler, H.

1983-01-01

The cardiovascular deconditioning observed during and after space flight is characterized in a review of human space and simulation studies and animal simulations. The various simulation techniques (horizontal bed rest, head-down tilt, and water immersion in man, and immobilization of animals) are examined, and sample results are presented in graphs. Countermeasures such as exercise regimens, fluid replacement, drugs, venous pooling, G-suits, oscillating beds, electrostimulation of muscles, lower-body negative pressure, body-surface cooling, and hypoxia are reviewed and found to be generally ineffective or unreliable. The need for future space experimentation in both humans and animals is indicated.

Effect of 21-day head down bed rest on urine proteins related to endothelium: Correlations with changes in carbohydrate metabolism

NASA Astrophysics Data System (ADS)

Kashirina, D.; Pastushkova, L.; Custaud, M. A.; Dobrokhotov, I.; Brzhozovsky, A.; Navasiolava, N.; Nosovsky, A.; Kononikhin, A.; Nikolaev, E.; Larina, I.

2017-08-01

We performed liquid chromatography-mass spectrometric study of the urine proteome in 8 healthy volunteers aged between 20 and 44 y.o. who have completed 21-day head-down bed rest. ANDSystem software which builds associative networks was used to identify the urinary proteins functionally related to the endothelium. We identified 7 endothelium-related biological processes, directly linked to 13 urine proteins. We performed manual annotation of the proteins which were the most important in terms of endothelial functions. Analysis of the correlations with biochemical variables revealed a positive correlation between fasting blood glucose and the following urine proteins: albumin, CD44 antigen, endothelial protein C receptor, mucin-1, osteopontin, receptor tyrosine kinase. As well, we found a positive correlation between HOMA-insulin resistance index and the following urine proteins: endothelial protein C receptor and syndecan-4. These results might suggest the involvement of above-mentioned proteins in glucose metabolism and their participation in the response to changes in blood glucose level.

Bed-rest studies: Fluid and electrolyte responses

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1983-01-01

Confinement in the horizontal position for 2 to 3 weeks results in a chronic decrease in plasma volume, increased interstitial fluid volume, and unchanged or slightly increased extracellular fluid volume. Concentrations of blood electrolytes, glucose, and nitrogenous constituents remain within normal limits of variability when maintenance levels of isometric or isotonic exercise are performed for 1 hr/day. Hematocrit and plasma osmolality can be elevated significantly throughout bed rest (BR). Significant diuresis occurs on the first day, and increases in urine Na and Ca continue throughout BR, although voluntary fluid intake is unchanged. Urine Na and K are evaluated during the second week of BR in spite of stabilization of PV and extracellular volume. The initial diuresis probably arises from the extracellular fluid while subsequent urine loss above control levels must come from the intracellular fluid. Preservation of the extracellular volume takes precedance over maintenance of the intracellular fluid volume. The functioning of a natriuretic factor (hormone) to account for the continued increased loss of Na in the urine is suggested.

Alternative Compression Garments

NASA Technical Reports Server (NTRS)

Stenger, M. B.; Lee, S. M. C.; Ribeiro, L. C.; Brown, A. K.; Westby, C. M.; Platts, S. H.

2011-01-01

Orthostatic intolerance after spaceflight is still an issue for astronauts as no in-flight countermeasure has been 100% effective. Future anti-gravity suits (AGS) may be similar to the Shuttle era inflatable AGS or may be a mechanical compression device like the Russian Kentavr. We have evaluated the above garments as well as elastic, gradient compression garments of varying magnitude and determined that breast-high elastic compression garments may be a suitable replacement to the current AGS. This new garment should be more comfortable than the AGS, easy to don and doff, and as effective a countermeasure to orthostatic intolerance. Furthermore, these new compression garments could be worn for several days after space flight as necessary if symptoms persisted. We conducted two studies to evaluate elastic, gradient compression garments. The purpose of these studies was to evaluate the comfort and efficacy of an alternative compression garment (ACG) immediately after actual space flight and 6 degree head-down tilt bed rest as a model of space flight, and to determine if they would impact recovery if worn for up to three days after bed rest.

A novel lunar bed rest analogue.

PubMed

Cavanagh, Peter R; Rice, Andrea J; Licata, Angelo A; Kuklis, Matthew M; Novotny, Sara C; Genc, Kerim O; Englehaupt, Ricki K; Hanson, Andrea M

2013-11-01

Humans will eventually return to the Moon and thus there is a need for a ground-based analogue to enable the study of physiological adaptations to lunar gravity. An important unanswered question is whether or not living on the lunar surface will provide adequate loading of the musculoskeletal system to prevent or attenuate the bone loss that is seen in microgravity. Previous simulations have involved tilting subjects to an approximately 9.5 degrees angle to achieve a lunar gravity component parallel to the long-axis of the body. However, subjects in these earlier simulations were not weight-bearing, and thus these protocols did not provide an analogue for load on the musculoskeletal system. We present a novel analogue which includes the capability to simulate standing and sitting in a lunar loading environment. A bed oriented at a 9.5 degrees angle was mounted on six linear bearings and was free to travel with one degree of freedom along rails. This allowed approximately 1/6 body weight loading of the feet during standing. "Lunar" sitting was also successfully simulated. A feasibility study demonstrated that the analogue was tolerated by subjects for 6 d of continuous bed rest and that the reaction forces at the feet during periods of standing were a reasonable simulation of lunar standing. During the 6 d, mean change in the volume of the quadriceps muscles was -1.6% +/- 1.7%. The proposed analogue would appear to be an acceptable simulation of lunar gravity and deserves further exploration in studies of longer duration.

The pathology of innactivation in monkeys.

NASA Technical Reports Server (NTRS)

Bourne, G. H.; Golarz De Bourne, M. N.; Mcclure, H.; Keeling, M.

1973-01-01

Progress report on a long-term experiment using rhesus monkeys and designed to study the effects of isolation up to one year, as well as the effects of bed rest simulated by immobilization in a plaster cast for six months. The investigation includes histopathological and histochemical studies of these effects on various internal organs and tissues, and some of the preliminary results of these studies are presented and discussed.

Mechanical Vibrations Reduce the Intervertebral Disc Swelling and Muscle Atrophy from Bed Rest

NASA Technical Reports Server (NTRS)

Holguin, Nilsson; Muir, Jesse; Evans, Harlan J.; Qin, Yi-Xian; Rubin, Clinton; Wagshul, Mark; Judex, Stefan

2007-01-01

Loss of functional weight bearing, such as experienced during space flight or bed rest (BR), distorts intervertebral disc (IVD) and muscle morphology. IVDs are avascular structures consisting of cells that may derive their nutrition and waste removal from the load induced fluid flow into and out of the disc. A diurnal cycle is produced by forces related to weight bearing and muscular activity, and comprised of a supine and erect posture over a 24 hr period. A diurnal cycle will include a disc volume change of approx. 10-13%. However, in space there are little or no diurnal changes because of the microgravity, which removes the gravitational load and compressive forces to the back muscles. The BR model and the etiology of the disc swelling and muscle atrophy could provide insight into those subjects confined to bed for chronic disease/injury and aging. We hypothesize that extremely low-magnitude, high frequency mechanical vibrations will abate the disc degeneration and muscle loss associated with long-term BR.

Status of groundwater levels and storage volume in the Equus Beds aquifer near Wichita, Kansas, 2012 to 2014

USGS Publications Warehouse

Hansen, Cristi V.; Whisnant, Joshua A.; Lanning-Rush, Jennifer L.

2014-01-01

There was a larger percentage storage-volume increase since 1993 in the central part of the study area than in either the basin storage area or the entire study area. Storage-volume in the central part of the study area during winter 2012, summer 2013, winter 2013, and winter 2014 recovered about 46,300 acre-feet or more compared to the storage volume in 1993. In summer 2012 and winter 2013, the storage-volume increase since 1993 was larger in the central part of the study area than in the entire study area, indicating the storage-volume increases in the central part of the study area offset decreases in storage volume in the rest of the study area. The larger increase in storage volume in the central part of the study area than in the rest of the study area probably was because of the Integrated Local Water Supply Program strategy that reduced city pumpage from the Equus Beds aquifer by about 40 percent. The current (winter 2014) storage volumes in the entire study area and the central part of the study area are about 94 and 96 percent of their respective predevelopment storage volumes or about 3,067,000 and 962,000 acre-feet, respectively.

Changes in plasma volume during bed rest - Effects of menstrual cycle and estrogen administration

NASA Technical Reports Server (NTRS)

Fortney, S. M.; Beckett, W. S.; Carpenter, A. J.; Davis, J.; Drew, H.

1988-01-01

The effect of increased blood estrogen concentration, caused either during normal menstrual cycles or by exogenous administration of premarin, on the bed-rest (BR) induced decrease in plasma volume (PV) was investigated. In women who underwent duplicate 11-day BR without estrogen supplementation, the PV was found to decrease significantly, during the first 5 days of BR, to a lower level at which it remained for the rest of the BR period. In women who began BR in the periovulatory stage of the menstrual cycle, the loss of PV was delayed, while women who began BR during other stages of the cycle exhibited the usual trend of the PV decrease during the BR. In women who underwent a single 12-day BR period while taking premarin (1.25 mg/day), PV was found to decrease during the first 4-5 days of BR, but then returned toward the pre-BR level during the remainder of the BR, indicating that estrogens have a role in stabilizing body fluid volume.

Resistance exercise as a countermeasure to disuse-induced bone loss.

PubMed

Shackelford, L C; LeBlanc, A D; Driscoll, T B; Evans, H J; Rianon, N J; Smith, S M; Spector, E; Feeback, D L; Lai, D

2004-07-01

During spaceflight, skeletal unloading results in loss of bone mineral density (BMD). This occurs primarily in the spine and lower body regions. This loss of skeletal mass could prove hazardous to astronauts on flights of long duration. In this study, intense resistance exercise was used to test whether a training regimen would prevent the loss of BMD that accompanies disuse. Nine subjects (5 men, 4 women) participated in a supine maximal resistance exercise training program during 17 wk of horizontal bed rest. These subjects were compared with 18 control subjects (13 men, 5 women) who followed the same bed rest protocol without exercise. Determination of treatment effect was based on measures of BMD, bone metabolism markers, and calcium balance obtained before, during, and after bed rest. Exercisers and controls had significantly (P < 0.05) different means, represented by the respective following percent changes: lumbar spine BMD, +3% vs. -1%; total hip BMD, +1% vs. -3%; calcaneus BMD, +1% vs. -9%; pelvis BMD, -0.5% vs. -3%; total body BMD, 0% vs. -1%; bone-specific alkaline phosphatase, +64% vs. 0%; alkaline phosphatase, +31% vs. +5%; osteocalcin, +43% vs. +10%; 1,25 dihydroxyvitamin D, +12% vs. -15%; parathyroid hormone intact molecule, +18% vs. -25%; and serum and ionized calcium, -1% vs. +1%. The difference in net calcium balance was also significant (+21 mg/day vs. -199 mg/day, exercise vs. control). The gastrocnemius and soleus muscle volumes decreased significantly in the exercise group, but the loss was significantly less than observed in the control group. The results indicate that resistance exercise had a positive treatment effect and thus might be useful as a countermeasure to prevent the deleterious skeletal changes associated with long-duration spaceflight.

21 Days head-down bed rest induces weakening of cell-mediated immunity - Some spaceflight findings confirmed in a ground-based analog.

PubMed

Kelsen, Jens; Bartels, Lars Erik; Dige, Anders; Hvas, Christian Lodberg; Frings-Meuthen, Petra; Boehme, Gisela; Thomsen, Marianne Kragh; Fenger-Grøn, Morten; Dahlerup, Jens Frederik

2012-08-01

Several studies indicate a weakening of cell-mediated immunity (CMI) and reactivation of latent herpes viruses during spaceflight. We tested the hypothesis that head-down bed rest (HDBR), a ground-based analog of spaceflight, mimics the impact of microgravity on human immunity. Seven healthy young males underwent two periods of 3 weeks HDBR in the test facility of the German Aerospace Center. As a nutritional countermeasure aimed against bone demineralisation, 90 mmol potassium bicarbonate (KHCO(3)) was administered daily in a crossover design. Blood samples were drawn on five occasions. Whole blood was stimulated with antigen i.e. Candida albicans, purified protein derivative (PPD) tuberculin, tetanus toxoid and Cytomegalovirus (CMV) (CMV-QuantiFERON). Flow cytometric analysis included CD4(+)CD25(+)CD127(-)FOXP3(+) regulatory T cells (Tregs), γδ T cells, B cells, NK cells and dendritic cells. In one of the two bed rest periods, we observed a significant decrease in production of interleukin-2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) following phytohemagglutinin (PHA) stimulation, with a rapid normalization being observed after HDBR. The cytokine levels showed a V-shaped pattern that led to a relativeTh2-shift in cytokine balance. Only three individuals responded to the specific T cell antigens without showing signs of an altered response during HDBR, nor did we observe reactivation of CMV or Epstein-Barr virus (EBV). Of unknown significance, dietary supplementation with KHCO(3) counteracted the decrease in IL-2 levels during HDBR, while there was no impact on other immunological parameters. We conclude that discrete alterations in CMI may be induced by HDBR in selected individuals. Copyright © 2012 Elsevier Ltd. All rights reserved.

Twins Bed Rest Project: LBNP/Exercise Minimizes Changes in Lean Leg Mass, Strength and Endurance

NASA Technical Reports Server (NTRS)

Amorim, Fabiano T.; Schneider, Suzanne M.; Lee, Stuart M. C.; Boda, Wanda L.; Watenpaugh, Donald E.; Hargens, Alan R.

2006-01-01

Decreases in muscle strength and endurance frequently are observed in non-weightbearing conditions such as bed rest (BR), spaceflight or limb immobilization. Purpose: Ow purpose was to determine if supine treadmill exercise against simulated gravity, by application of lower body negative pressure (LBNP), prevents loss of lean leg mass, strength and endurance during 30 d of 6deg head-down bed rest (BR). Methods: Fifteen pairs of monozygous twins (8 male, 7 female pairs; 26+/-4 yrs; 170+/-12 cm; 62.6+/-11.3 kg; mean+/-SD) were subjects in the present study. One sibling of each pair of twins was randomly assigned to either an exercise (EX) or non-exercise (CON) group. The EX twin walked/jogged on a vertical treadmill within LBNP chamber 6 d/wk using a 40-min interval exercise protocol at 40-80% of pre-BR VO(sub 2peak). LBNP was adjusted individually for each subject such that footward force was between 1.0 and 1.2 times body weight (-53+/-5 mmHg LBNP). The CON twin performed no exercise during BR. Subjects performed isokinetic knee (60 and 120deg/s) and ankle (60deg/s) testing to assess strength and endurance (End) before and after BR. They also had their lean leg mass (L(sub mass)) evaluated by DEXA before and after BR. Results: Changes in peak torque (T(sub pk)) were smaller for flexion (flex) than for extension (ext) after BR and did not differ between groups. The CON group had larger decreases (P<0.05) in L(sub mass), knee and ankle ext T(sub pk), and knee ext End.

Orthostatic hypotension in patients, bed rest subjects, and astronauts

NASA Technical Reports Server (NTRS)

Lathers, C. M.; Charles, J. B.

1994-01-01

Orthostatic hypotension after even short space flights has affected a significant number of astronauts. Given the need for astronauts to function at a high level of efficiency during and after their return from space, the application of pharmacologic and other treatments is strongly indicated. This report addresses the clinical problem of orthostatic hypotension and its treatments to ascertain whether pharmacologic or physiologic treatment may be useful in the prevention of orthostatic hypotension associated with space flight. Treatment of orthostatic hypotension in patients now includes increasing intravascular volume with high sodium intake and mineralocorticoids, or increasing vascular resistance through the use of drugs to stimulate alpha or block beta vascular receptors. Earlier treatment used oral sympathomimetic ephedrine hydrochloride alone or with "head-up" bed rest. Then long-acting adrenocortical steroid desoxycorticosterone preparations with high-salt diets were used to expand volume. Fludrocortisone was shown to prevent the orthostatic drop in blood pressure. The combination of the sympathomimetic amine hydroxyamphetamine and a monoamine oxidase inhibitor tranylcypromine has been used, as has indomethacin alone. Davies et al. used mineralocorticoids at low doses concomitantly with alpha-agonists to increase vasoconstrictor action. Schirger et al used tranylcypromine and methylphenidate with or without a Jobst elastic leotard garment or the alpha-adrenergic agonist midodrine (which stimulates both arterial and venous systems without direct central nervous system or cardiac effects). Vernikos et al established that the combination of fludrocortisone, dextroamphetamine, and atropine exhibited a beneficial effect on orthostatic hypotension induced by 7-day 6 degrees head-down bed rest (a model used to simulate the weightlessness of space flight). Thus, there are numerous drugs that, in combination with mechanical techniques, including lower body negative pressure to elevate transmural pressure, could be studied to treat orthostatic hypotension after space flight.

Resistance exercise as a countermeasure to disuse-induced bone loss

NASA Technical Reports Server (NTRS)

Shackelford, L. C.; LeBlanc, A. D.; Driscoll, T. B.; Evans, H. J.; Rianon, N. J.; Smith, S. M.; Spector, E.; Feeback, D. L.; Lai, D.

2004-01-01

During spaceflight, skeletal unloading results in loss of bone mineral density (BMD). This occurs primarily in the spine and lower body regions. This loss of skeletal mass could prove hazardous to astronauts on flights of long duration. In this study, intense resistance exercise was used to test whether a training regimen would prevent the loss of BMD that accompanies disuse. Nine subjects (5 men, 4 women) participated in a supine maximal resistance exercise training program during 17 wk of horizontal bed rest. These subjects were compared with 18 control subjects (13 men, 5 women) who followed the same bed rest protocol without exercise. Determination of treatment effect was based on measures of BMD, bone metabolism markers, and calcium balance obtained before, during, and after bed rest. Exercisers and controls had significantly (P < 0.05) different means, represented by the respective following percent changes: lumbar spine BMD, +3% vs. -1%; total hip BMD, +1% vs. -3%; calcaneus BMD, +1% vs. -9%; pelvis BMD, -0.5% vs. -3%; total body BMD, 0% vs. -1%; bone-specific alkaline phosphatase, +64% vs. 0%; alkaline phosphatase, +31% vs. +5%; osteocalcin, +43% vs. +10%; 1,25 dihydroxyvitamin D, +12% vs. -15%; parathyroid hormone intact molecule, +18% vs. -25%; and serum and ionized calcium, -1% vs. +1%. The difference in net calcium balance was also significant (+21 mg/day vs. -199 mg/day, exercise vs. control). The gastrocnemius and soleus muscle volumes decreased significantly in the exercise group, but the loss was significantly less than observed in the control group. The results indicate that resistance exercise had a positive treatment effect and thus might be useful as a countermeasure to prevent the deleterious skeletal changes associated with long-duration spaceflight.

Stone Age hut in Israel yields world's oldest evidence of bedding.

PubMed

Nadel, Dani; Weiss, Ehud; Simchoni, Orit; Tsatskin, Alexander; Danin, Avinoam; Kislev, Mordechai

2004-04-27

The earliest archaeological remains of dwelling huts built by Homo sapiens were found in various European Upper Paleolithic open-air camps. Although floors of huts were found in a small number of cases, modern organization of the home space that includes defined resting areas and bedding remains was not discovered. We report here the earliest in situ bedding exposed on a brush hut floor. It has recently been found at the previously submerged, excellently preserved 23,000-year-old fisher-hunter-gatherers' camp of Ohalo II, situated in Israel on the shore of the Sea of Galilee. The grass bedding consists of bunches of partially charred Puccinellia confer convoluta stems and leaves, covered by a thin compact layer of clay. It is arranged in a repeated pattern, on the floor, around a central hearth. This study describes the bedding in its original context on a well preserved intentionally constructed floor. It also reconstructs on the basis of direct evidence (combined with ethnographic analogies) the Upper Paleolithic hut as a house with three major components: a hearth, specific working locales, and a comfortable sleeping area near the walls.

Effects of mechanical-bed massage on exercise-induced back fatigue in athletes.

PubMed

Zhong, Houyong; Eungpinichpong, Wichai; Wang, Xingze; Chatchawan, Uraiwon; Wanpen, Sawitri; Buranruk, Orawan

2018-03-01

[Purpose] The study aimed to preliminarily investigate the effects of mechanical-bed massage on exercise-induced back fatigue in athletes. [Subjects and Methods] Twelve male college athletes, randomly allocated to experimental or control groups, were instructed to perform reverse sit-up for 8 sessions until they became fatigued. The experimental group received a 20-min mechanical-bed massage session, while the control group rested on a bed for the same period of time. Visual Analogue Scale (VAS) on perceived back muscle fatigue, back muscle endurance, and Heart Rate Variability (HRV) parameters including stress index (SI), HRV index, SDNN, RMSSD, pNN50, LF, HF, and LF/HF were analyzed. [Results] Immediately and 24 hours after the intervention, the VAS significantly differed between the groups. Experimental group's HF was significantly higher immediately after the intervention than control group. Experimental group's LF and LF/HF were significantly lower immediately after the intervention than the control group. [Conclusion] Mechanical bed massage may help athletes overcome the subjective feelings of exercise-induced fatigue, modulate the automatic nervous system activity, especially for balancing sympathetic and parasympathetic activities. Therefore, mechanical bed massage may facilitate recovery from muscle and central fatigue after athlete training or competition.

Effects of mechanical-bed massage on exercise-induced back fatigue in athletes

PubMed Central

Zhong, Houyong; Eungpinichpong, Wichai; Wang, Xingze; Chatchawan, Uraiwon; Wanpen, Sawitri; Buranruk, Orawan

2018-01-01

[Purpose] The study aimed to preliminarily investigate the effects of mechanical-bed massage on exercise-induced back fatigue in athletes. [Subjects and Methods] Twelve male college athletes, randomly allocated to experimental or control groups, were instructed to perform reverse sit-up for 8 sessions until they became fatigued. The experimental group received a 20-min mechanical-bed massage session, while the control group rested on a bed for the same period of time. Visual Analogue Scale (VAS) on perceived back muscle fatigue, back muscle endurance, and Heart Rate Variability (HRV) parameters including stress index (SI), HRV index, SDNN, RMSSD, pNN50, LF, HF, and LF/HF were analyzed. [Results] Immediately and 24 hours after the intervention, the VAS significantly differed between the groups. Experimental group’s HF was significantly higher immediately after the intervention than control group. Experimental group’s LF and LF/HF were significantly lower immediately after the intervention than the control group. [Conclusion] Mechanical bed massage may help athletes overcome the subjective feelings of exercise-induced fatigue, modulate the automatic nervous system activity, especially for balancing sympathetic and parasympathetic activities. Therefore, mechanical bed massage may facilitate recovery from muscle and central fatigue after athlete training or competition. PMID:29581653

Economic assessment of conventional and conservation tillage practices in different wheat-based cropping systems of Punjab, Pakistan.

PubMed

Shahzad, Muhammad; Hussain, Mubshar; Farooq, Muhammad; Farooq, Shahid; Jabran, Khawar; Nawaz, Ahmad

2017-11-01

Wheat productivity and profitability is low under conventional tillage systems as they increase the production cost, soil compaction, and the weed infestation. Conservation tillage could be a pragmatic option to sustain the wheat productivity and enhance the profitability on long term basis. This study was aimed to evaluate the economics of different wheat-based cropping systems viz. fallow-wheat, rice-wheat, cotton-wheat, mung bean-wheat, and sorghum-wheat, with zero tillage, conventional tillage, deep tillage, bed sowing (60/30 cm beds and four rows), and bed sowing (90/45 cm beds and six rows). Results indicated that the bed sown wheat had the maximum production cost than other tillage systems. Although both bed sowing treatments incurred the highest production cost, they generated the highest net benefits and benefit: cost ratio (BCR). Rice-wheat cropping system with bed sown wheat (90/45 cm beds with six rows) had the highest net income (4129.7 US$ ha -1 ), BCR (2.87), and marginal rate of return compared with rest of the cropping systems. In contrast, fallow-wheat cropping system incurred the lowest input cost, but had the least economic return. In crux, rice-wheat cropping system with bed sown wheat (90/45 cm beds with six rows) was the best option for getting the higher economic returns. Moreover, double cropping systems within a year are more profitable than sole planting of wheat under all tillage practices.

Head-down-tilt bed rest alters forearm vasodilator and vasoconstrictor responses

NASA Technical Reports Server (NTRS)

Shoemaker, J. K.; Hogeman, C. S.; Silber, D. H.; Gray, K.; Herr, M.; Sinoway, L. I.

1998-01-01

To test the hypothesis that head-down-tilt bed rest (HDBR) for 14 days alters vascular reactivity to vasodilatory and vasoconstrictor stimuli, the reactive hyperemic forearm blood flow (RHBF, measured by venous occlusion plethysmography) and mean arterial pressure (MAP, measured by Finapres) responses after 10 min of circulatory arrest were measured in a control trial (n = 20) and when sympathetic discharge was increased by a cold pressor test (RHBF + cold pressor test; n = 10). Vascular conductance (VC) was calculated (VC = RHBF/MAP). In the control trial, peak RHBF at 5 s after circulatory arrest (34.1 +/- 2.5 vs. 48.9 +/- 4.3 ml . 100 ml-1 . min-1) and VC (0.34 +/- 0.02 vs. 0.53 +/- 0.05 ml . 100 ml-1 . min-1 . mmHg-1) were reduced in the post- compared with the pre-HDBR tests (P < 0. 05). Total excess RHBF over 3 min was diminished in the post- compared with the pre-HDBR trial (84.8 vs. 117 ml/100 ml, P < 0.002). The ability of the cold pressor test to lower forearm blood flow was less in the post- than in the pre-HDBR test (P < 0.05), despite similar increases in MAP. These data suggest that regulation of vascular dilation and the interaction between dilatory and constrictor influences were altered with bed rest.

Inflight Treadmill Exercise Can Serve as Multi-Disciplinary Countermeasure System

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Batson, C. D.; Buxton, R. E.; Feiveson, A. H.; Kofman, I. S.; Laurie, S.; Lee, S. M. C.; Miller, C. A.; Mulavara, A. P.; Peters, B. T.;

Fibroblast Growth Factor-23 in Bed Rest and Spaceflight

NASA Technical Reports Server (NTRS)

Bokhari, R.; Zwart, S. R; Fields, E.; Heer, M.; Sibonga, J.; Smith, S. M.

2014-01-01

Many nutritional factors influence bone, from the basics of calcium and vitamin D, to factors which influence bone through acid/base balance, including protein, sodium, and more. Fibroblast growth factor 23 (FGF23) is a recently identified factor, secreted from osteocytes, which is involved in classic (albeit complex) feedback loops controlling phosphorus homeostasis through both vitamin D and parathyroid hormone (PTH) (1, 2). As osteocytes are gravity sensing cells, it is important to determine if there are changes in FGF23 during spaceflight. In extreme cases, such as chronic kidney disease, FGF23 levels are highly elevated. FGF23 imbalances, secondary to dietary influences, may contribute to skeletal demineralization and kidney stone risk during spaceflight. Presented with an imbalanced dietary phosphorus to calcium ratio, increased secretion of FGF23 will inhibit renal phosphorus reabsorption, resulting in increased excretion and reduced circulating phosphorus. Increased intake and excretion of phosphorus is associated with increased kidney stone risk in both the terrestrial and microgravity environments. Highly processed foods and carbonated beverages are associated with higher phosphorus content. Ideally, the dietary calcium to phosphorus ratio should be at minimum 1:1. Nutritional requirements for spaceflight suggest that this ratio not be less than 0.67 (3), while the International Space Station (ISS) menu provides 1020 mg Ca and 1856 mg P, for a ratio of 0.55 (3). Subjects in NASA's bed rest studies, by design, have consumed intake ratios much closer to 1.0 (4). FGF23 also has an inhibitory influence on PTH secretion and 1(alpha)-hydroxylase, both of which are required for activating vitamin D with the conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. Decreased 1,25-dihydroxyvitamin D will result in decreased intestinal phosphorus absorption, and increased urinary phosphorus excretion (via decreased renal reabsorption). Should a decrease in 1,25- dihydroxyvitamin D be necessary to reduce intestinal phosphorus absorption, calcium absorption will also proportionally be reduced, potentially leading to skeletal demineralization. Demineralization of bone can increase kidney stone risk, a medical issue that could prove detrimental to mission success. Given the interrelationships described above, we sought to determine circulating FGF23 concentrations in spaceflight and ground analog studies to better understand the potential effects of dietary phosphorus on bone and calcium metabolism. We analyzed serum from ISS astronauts participating in studies of bone biochemistry, including the Nutrition SMO and Pro K experiments, and we also evaluated FGF23 during extended-duration bed rest. Serum intact FGF23 levels were determined using an ELISA kit from Kainos laboratories in Japan. While initial evaluation of the data showed no changes over time during flight or bed rest, evaluation continues of FGF23 data in light of dietary factors, PTH, vitamin D status, and other biochemical and endocrine factors.

Akterations/corrections to the BRASS Program

NASA Technical Reports Server (NTRS)

Brand, S. N.

1985-01-01

Corrections applied to statistical programs contained in two subroutines of the Bed Rest Analysis Software System (BRASS) are summarized. Two subroutines independently calculate significant values within the BRASS program.

Atelectasis

MedlinePlus

... Prolonged bed rest with few changes in position Shallow breathing (may be caused by painful breathing) Tumors ... chest to loosen mucus plugs in the airway. Deep breathing exercises (with the help of incentive spirometry ...

Self-reported sleep duration and time in bed as predictors of physical function decline: results from the InCHIANTI study.

PubMed

Stenholm, Sari; Kronholm, Erkki; Bandinelli, Stefania; Guralnik, Jack M; Ferrucci, Luigi

2011-11-01

To characterize elderly persons into sleep/rest groups based on their self-reported habitual total sleeping time (TST) and habitual time in bed (TIB) and to examine the prospective association between sleep/rest behavior on physical function decline. Population-based InCHIANTI study with 6 years follow-up (Tuscany, Italy). Community. Men and women aged ≥ 65 years (n = 751). At baseline, participants were categorized into 5 sleep/rest behavior groups according to their self-reported TST and TIB, computed from bedtime and wake-up time. Physical function was assessed at baseline and at 3- and 6-year follow-ups as walking speed, the Short Physical Performance Battery (SPPB), and self-reported mobility disability (ability to walk 400 m or climb one flight of stairs). Both long (≥ 9 h) TST and long TIB predicted accelerated decline in objectively measured physical performance and greater incidence in subjectively assessed mobility disability, but short (≤ 6 h) TST did not. After combining TST and TIB, long sleepers (TST and TIB ≥ 9 h) experienced the greatest decline in physical performance and had the highest risk for incident mobility disability in comparison to mid-range sleepers with 7-8 h TST and TIB. Subjective short sleepers reporting short (≤ 6 h) TST but long (≥ 9 h) TIB showed a greater decline in SPPB score and had a higher risk of incident mobility disability than true short sleepers with short (≤ 6 h) TST and TIB ≤ 8 hours. Extended time in bed as well as long total sleeping time is associated with greater physical function decline than mid-range or short sleep. TIB offers important additive information to the self-reported sleep duration when evaluating the consequences of sleep duration on health and functional status.

Effect of space flight and head-down bedrest on neuroendocrine response to metabolic stress in physically trained subjects.

PubMed

Kvetnanský, R; Ksinantová, L; Koska, J; Noskov, V B; Vigas, M; Grigoriev, A I; Macho, L

2004-07-01

The aim of this study was to evaluate the association of plasma epinephrine (EPI) and norepinephrine (NE) responses to insulin induced hypoglycemia (ITT) 3 weeks before the space flight (SF), on the 5th day of SF, on the 2nd and 16th days after the landing in the first Slovak astronaut, and before and on the 5th day of prolonged subsequent head-down (-6 degrees) bed rest (BR) in 15 military aircraft pilots. Blood samples during the test were collected via cannula inserted into cubital vein, centrifuged in the special appliance Plasma-03, frozen in Kryogem-03, and at the end of the 8-day space flight transferred to Earth in special container for hormonal analysis. Insulin hypoglycemia was induced by i.v. administration of 0.1 IU/kg BW insulin (Actrapid HM) in bolus. Insulin administration led to a comparable hypoglycemia in pre-flight, in-flight conditions and before and after bed rest. ITT led to a pronounced increase in EPI levels and moderate increase in NE in pre-flight studies. However, an evidently reduced EPI response was found after insulin administration during SF and during BR. Thus, during the real microgravity in SF and simulated microgravity in BR, insulin-induced hypoglycemia activates the adrenomedullary system to less extent than at conditions of the Earth gravitation. Post-flight changes in EPI and NE levels did not significantly differ from those of pre-flight since SF was relatively short (8 days) and the readaptation to Earth gravitation was fast. It seems, that an increased blood flow in brain might be responsible for the reduced EPI response to insulin. Responses to ITT in physically fit subjects indicate the stimulus specificity of deconditioning effect of 5 days bed rest on stress response. Thus, the data indicate that catecholamine responses to ITT are reduced after exposure to real as well as simulated microgravity.

Capacity of omega-3 fatty acids or eicosapentaenoic acid to counteract weightlessness-induced bone loss by inhibiting NF-kappaB activation: from cells to bed rest to astronauts.

PubMed

Zwart, Sara R; Pierson, Duane; Mehta, Satish; Gonda, Steve; Smith, Scott M

2010-05-01

NF-kappaB is a transcriptional activator of many genes, including some that lead to muscle atrophy and bone resorption-significant concerns for astronauts. NF-kappaB activation is inhibited by eicosapentaenoic acid (EPA), but the influence of this omega-3 fatty acid on the effects of weightlessness are unknown. We report here cellular, ground analogue, and spaceflight findings. We investigated the effects of EPA on differentiation of RAW264.7 monocyte/macrophage cells induced by receptor activator of NF-kappaB ligand (RANKL) and on activation of NF-kappaB by tumor necrosis factor alpha (TNF-alpha) or exposure to modeled weightlessness. EPA (50 microM for 24 hours) inhibited RANKL-induced differentiation and decreased activation of NF-kappaB induced by 0.2 microg/mL of TNF-alpha for 30 minutes or by modeled weightlessness for 24 hours (p < .05). In human studies, we evaluated whether NF-kappaB activation was altered after short-duration spaceflight and determined the relationship between intake of omega-3 fatty acids and markers of bone resorption during bed rest and the relationship between fish intake and bone mineral density after long-duration spaceflight. NF-kappaB was elevated in crew members after short-duration spaceflight, and higher consumption of fish (a rich source of omega-3 fatty acids) was associated with reduced loss of bone mineral density after flight (p < .05). Also supporting the cell study findings, a higher intake of omega-3 fatty acids was associated with less N-telopeptide excretion during bed rest (Pearson r = -0.62, p < .05). Together these data provide mechanistic cellular and preliminary human evidence of the potential for EPA to counteract bone loss associated with spaceflight. (c) 2010 American Society for Bone and Mineral Research.

Efficacy of three different steamers for control of bed bugs (Cimex lectularius L.).

PubMed

Wang, Desen; Wang, Changlu; Wang, Guohong; Zha, Chen; Eiden, Amanda L; Cooper, Richard

2018-04-15

Bed bugs, Cimex lectularius L., have become one of the most difficult urban pests to control. Steam treatment is reported to be an effective method to kill bed bugs and is considered to be an important component of bed bug integrated pest management (IPM). We evaluated and compared the efficacy of two affordable consumer-grade commercial steamers to a commonly used professional-grade steamer for killing bed bugs. In laboratory experiments, the consumer-grade steamer at an affordable price achieved the same high control efficacy as the professional-grade steamer for treating bed bugs exposed on mattresses (100% bed bug mortality), located beneath a fabric cover (>89% bed bug mortality), or hiding in cracks (100% bed bug mortality). Bed bugs located behind a leather cover did not suffer significant mortality from steam treatment regardless of the type of steamers used and treatment duration. Proper use of steamers can kill all life stages of bed bugs. Affordable consumer-grade steamers are as effective as professional-grade steam machines for eliminating bed bugs resting on mattresses, hiding behind fabric materials, or in cracks. This article is protected by copyright. All rights reserved.

Mechanisms of Orthostatic Intolerance During Real and Simulated Microgravity

NASA Technical Reports Server (NTRS)

1997-01-01

Session MP1 includes short reports on: (1) Orthostatic Tests after 42 Days of Simulated Weightlessness; (2) Effects of 12 Days Exposure to Simulated Microgravity on Central Circulatory Hemodynamics in the Rhesus Monkey; (3) Increased Sensitivity and Resetting of Baroflex Control of Exercise Heart Rate After Prolonged Bed-Rest; (4) Complex Cardiovascular Dynamics and Deconditioning During Head-down Bed Rest; (5) The Cardiovascular Effects of 6 Hours of Head-down Tilt Upon Athletes and Non-athletes; (6) Individual Susceptibility to Post-spaceflight Orthostatic Intolerance: Contributions of Gender-related and Microgravity-related Factors; (7) Cassiopee Mission 1996: Comparison of Cardiovascular Alteration after Short and Long-term Spaceflights; (8) Cerebral and Femoral Flow Response to LBNP during 6 Month MIR Spaceflights (93-95); and (9) Cerebrovascular Changes due to Spaceflight and Postflight Presyncope.

Ann Hutchinson (as subject), Dr. Joan Vernikos (R), Dee O'Hara (L), J. Evans and E. Lowe pose for

NASA Technical Reports Server (NTRS)

1993-01-01

Ann Hutchinson (as subject), Dr. Joan Vernikos (R), Dee O'Hara (L), J. Evans and E. Lowe pose for pictures in the NASA Magazine aritcle 'How it Feels to be a Human Test Subject' as they prepare for a bed rest study to simulate the efects of microgravity on the human body.

Recovery After Prolonged Bed-Rest Deconditioning

NASA Technical Reports Server (NTRS)

Greenleaf, John E.; Quach, David T.

2003-01-01

Recovery data were analyzed from normal healthy test subjects maintained in the horizontal or head-down body position in well-controlled bed rest (BR) studies in which adherence to the well-designed protocol was monitored. Because recovery data were almost always of secondary importance to the data collected during the BR period, there was little consistency in the recovery experimental designs regarding control factors (e.g., diet or exercise), duration, or timing of data collection. Thus, only about half of the BR studies that provided appropriate data were analyzed here. These recovery data were sorted into two groups: those from BR protocols of less than 37 days, and those from protocols greater than 36 days. There was great disparity in the unchanged responses at the end of BR in these two groups. Likewise with the variables that required more than 40 days for recovery; for example, some immune variables required more than 180 days. Knowledge of the recovery process after BR in healthy people should assist rehabilitation workers in differentiating "healthy" BR recovery responses from those of the infirmity of sick or injured patients; this should result in more appropriate and efficient health care.

Effects of long-term bed rest on H-reflex and motor evoked potential in lower leg muscles during standing.

PubMed

Yamanaka, K; Yamamoto, S; Nakazawa, K; Yano, H; Suzuki, Y; Fukunaga, T

1999-07-01

Maximal H-reflex amplitude (Hmax) compared with maximal M-response (Mmax) has been generally used to assess the efficacy of the monosynaptic transmission from Ia afferents to alpha motoneurons in spinal cord. In previous studies, it has been demonstrated that H-reflex in soleus muscle (SOL) is inhibited during free standing due to an increase in presynaptic inhibition of the Ia afferent terminals to SOL motoneurones (Katz et al. 1988, Koceja et al. 1993). Transcranial magnetic stimulation (TMS) of human motor cortex excites the corticospinal system monosynapticaly connecting to spinal alpha motoneurones. However, it is not clear whether or not the motor evoked potentials (MEPs) in SOL and tibialis anterior (TA) muscles induced by TMS are modulated during standing (Ackermann et al. 1991, Lavoie et al. 1995). Considering that postural control functions change with exposure to weightlessness, we supposed that the excitability of SOL and TA spinal motoneurons from Ia afferents and/or corticospinal tracts during free standing would change after long-term bed rest (BR). The aim of this study was to investigate the effect of BR on H-reflex and MEP in SOL and TA during free standing.

Mapping Bone Mineral Density Obtained by Quantitative Computed Tomography to Bone Volume Fraction

NASA Technical Reports Server (NTRS)

Pennline, James A.; Mulugeta, Lealem

2017-01-01

Methods for relating or mapping estimates of volumetric Bone Mineral Density (vBMD) obtained by Quantitative Computed Tomography to Bone Volume Fraction (BVF) are outlined mathematically. The methods are based on definitions of bone properties, cited experimental studies and regression relations derived from them for trabecular bone in the proximal femur. Using an experimental range of values in the intertrochanteric region obtained from male and female human subjects, age 18 to 49, the BVF values calculated from four different methods were compared to the experimental average and numerical range. The BVF values computed from the conversion method used data from two sources. One source provided pre bed rest vBMD values in the intertrochanteric region from 24 bed rest subject who participated in a 70 day study. Another source contained preflight vBMD values from 18 astronauts who spent 4 to 6 months on the ISS. To aid the use of a mapping from BMD to BVF, the discussion includes how to formulate them for purpose of computational modeling. An application of the conversions would be used to aid in modeling of time varying changes in vBMD as it relates to changes in BVF via bone remodeling and/or modeling.

[Remodeling simulation of human femur under bed rest and spaceflight circumstances based on three dimensional finite element analysis].

PubMed

Yang, Wenting; Wang, Dongmei; Lei, Zhoujixin; Wang, Chunhui; Chen, Shanguang

2017-12-01

Astronauts who are exposed to weightless environment in long-term spaceflight might encounter bone density and mass loss for the mechanical stimulus is smaller than normal value. This study built a three dimensional model of human femur to simulate the remodeling process of human femur during bed rest experiment based on finite element analysis (FEA). The remodeling parameters of this finite element model was validated after comparing experimental and numerical results. Then, the remodeling process of human femur in weightless environment was simulated, and the remodeling function of time was derived. The loading magnitude and loading cycle on human femur during weightless environment were increased to simulate the exercise against bone loss. Simulation results showed that increasing loading magnitude is more effective in diminishing bone loss than increasing loading cycles, which demonstrated that exercise of certain intensity could help resist bone loss during long-term spaceflight. At the end, this study simulated the bone recovery process after spaceflight. It was found that the bone absorption rate is larger than bone formation rate. We advise that astronauts should take exercise during spaceflight to resist bone loss.

Parathyroid hormone, calcitonin, and vitamin D 1974: Present status of physiological studies and analysis of calcium homeostasis

NASA Technical Reports Server (NTRS)

Potts, J. T., Jr.; Swenson, K. G.

1975-01-01

The role of parathyroid hormone, calcitonin, and vitamin D in the control of calcium and bone metabolism was studied. Particular emphasis was placed on the physiological adaptation to weightlessness and, as a potential model for this purpose, on the immobilization characteristic of space flight or prolonged bed rest. The biosynthesis, control of secretion, and metabolism of these hormonal agents is considered.

Midodrine prevents orthostatic intolerance associated with simulated spaceflight

NASA Technical Reports Server (NTRS)

Ramsdell, C. D.; Mullen, T. J.; Sundby, G. H.; Rostoft, S.; Sheynberg, N.; Aljuri, N.; Maa, M.; Mukkamala, R.; Sherman, D.; Toska, K.;

Personality, social support and affective states during simulated microgravity in healthy women

NASA Astrophysics Data System (ADS)

Nicolas, Michel

2009-12-01

This study investigated the time-course of stress and recovery states and their relations to social support and personality traits in healthy women during a long-term head-down tilt bed rest. Personality, social support and affective states were assessed in 16 women exposed to simulated microgravity for a 60-day duration involving three stages: a 20-day baseline control period (BDC), a 60-day head-down tilt bed rest (HDT) and a 20-day post-HDT ambulatory recovery period (R+). Participants were divided into two groups: an exercise (Exe, n = 8) and a control group (Ctl, n = 8). All the participants experienced significantly more stress during the HDT period. But exercise did not improve the impaired effects of simulated microgravity. The Exe group perceived more stress and less recovery than the Ctl group during the HDT period. Among the five major personality factors, only Neuroticism was related to both social and affective variables. Neuroticism was positively associated with stress and negatively associated with recovery and social support (S-SSQ). Practical implications in psychological countermeasures for better dealing with the key human factor in spaceflights are discussed.

Midodrine prevents orthostatic intolerance associated with simulated spaceflight.

PubMed

Ramsdell, C D; Mullen, T J; Sundby, G H; Rostoft, S; Sheynberg, N; Aljuri, N; Maa, M; Mukkamala, R; Sherman, D; Toska, K; Yelle, J; Bloomfield, D; Williams, G H; Cohen, R J

2001-06-01

Many astronauts after being weightless in space become hypotensive and presyncopal when they assume an upright position. This phenomenon, known as orthostatic intolerance, may interfere with astronaut function during reentry and after spaceflight and may limit the ability of an astronaut to exit a landed spacecraft unaided during an emergency. Orthostatic intolerance is more pronounced after long-term spaceflight and is a major concern with respect to the extended flights expected aboard the International Space Station and for interplanetary exploration class missions, such as a human mission to Mars. Fully effective countermeasures to this problem have not yet been developed. To test the hypothesis that alpha-adrenergic stimulation might provide an effective countermeasure, we conducted a 16-day head-down-tilt bed-rest study (an analog of weightlessness) using normal human volunteers and administered the alpha(1)-agonist drug midodrine at the end of the bed-rest period. Midodrine was found to significantly ameliorate excessive decreases in blood pressure and presyncope during a provocative tilt test. We conclude that midodrine may be an effective countermeasure for the prevention of orthostatic intolerance following spaceflight.

Bed-rest studies - Fluid and electrolyte responses

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1983-01-01

Confinement in the horizontal position for 2 to 3 weeks results in a chronic decrease in plasma volume, increased interstitial fluid volume, and unchanged or slightly increased extracellular fluid volume. Concentrations of blood electrolytes, glucose, and nitrogenous constituents remain within normal limits of variability when maintenance levels of isometric or isotonic exercise are performed for 1 hr/day. Hematocrit and plasma osmolality can be elevated significantly throughout bed rest (BR). Significant diuresis occurs on the first day, and increases in urine Na and Ca continue throughout BR, although voluntary fluid intake is unchanged. Urine Na and K are evaluated during the second week of BR in spite of stabilization of PV and extracellular volume. The initial diuresis probably arises from extracellular fluid while subsequent urine loss above control levels must come from the intracellular fluid. Preservation of the extracellular volume takes precedance over maintenance of the intracellular fluid volume. The functioning of a natriuretic factor (hormone) to account for the continued increased loss of Na in the urine is suggested. Previously announced in STAR as N83-24160

Aneurysm in the brain

MedlinePlus

... ruptured: Clipping is done during open brain surgery (craniotomy) . Endovascular repair is most often done. It usually ... unit (ICU) Complete bed rest and activity restrictions Drainage of blood from the brain area (cerebral ventricular ...

Pregnancy care

MedlinePlus

... have few or mild symptoms during pregnancy. Many women work their full term and travel while they are pregnant. Others may have to cut back on their hours or stop working. Some women require bed rest ...

Orthostatic Hypotension (Postural Hypotension)

MedlinePlus

... is usually caused by something obvious, such as dehydration or lengthy bed rest, and is easily treated. ... lightheadedness may be fairly minor — triggered by mild dehydration, low blood sugar or overheating. Dizziness or lightheadedness ...

Role for Lower Extremity Interstitial Fluid Volume Changes in the Development of Orthostasis after Simulated Microgravity

NASA Technical Reports Server (NTRS)

Platts, Steven H.; Summers, Richard L.; Martin, David S.; Meck, Janice V.; Coleman, Thomas G.

2007-01-01

Reentry orthostasis after exposure to the conditions of spaceflight is a persistent problem among astronauts. In a previous study, a computer model systems analysis was used to examine the physiologic mechanisms involved in this phenomenon. In this analysis, it was determined that an augmented capacitance of lower extremity veins due to a fluid volume contracture of the surrounding interstitial spaces during spaceflight results in an increase in sequestered blood volume upon standing and appears to be the initiating mechanism responsible for reentry orthostasis. In this study, we attempt to validate the central premise of this hypothesis using a ground-based spaceflight analog. 10 healthy subjects were placed at bed rest in a 6 head down tilt position for 60 days of bed rest. The impact of adaptations in interstitial fluid volume and venous capacitance in the lower extremities were then observed during a standard tilt test protocol performed before and after the confinement period. The interstitial thickness superficial to the calcaneous immediately below the lateral malleolus was measured using ultrasound with a 17-5 MHz linear array transducer. Measurements of the changes in anterior tibial vein diameter during tilt were obtained by similar methods. The measurements were taken while the subjects were supine and then during upright tilt (80') for thirty minutes, or until the subject had signs of presyncope. Additional measurements of the superficial left tibia interstitial thickness and stroke volume by standard echocardiographic methods were also recorded. In addition, calf compliance was measured over a pressure range of 10-60 mmHg, using plethysmography, in a subset of these subjects (n = 5). There was a average of 6% diminution in the size of the lower extremity interstitial space as compared to measurements acquired prior to bed rest. This contracture of the interstitial space coincided with a subsequent relative increase in the percentage change in tibial vein diameter and stroke volume upon tilting in contrast to the observations made before bed rest (54 vs 23% respectively). Compliance in the calf increased by an average of 36% by day 27 of bedrest. A systems analysis using a computer model of cardiovascular physiology suggests that microgravity induced interstitial volume depletion results in an accentuation of venous blood volume sequestration and is the initiating event in reentry orthostasis. This hypothesis was tested in volunteer subjects using a ground-based spaceflight analog model that simulated the body fluid redistribution induced by microgravity exposure. Measurements of changes in the interstitial spaces and observed responses of the anterior tibial vein with tilt, together with the increase in calf compliance, were consistent with our proposed mechanism for the initiation of postflight orthostasis often seen in astronauts.

Bed rest during pregnancy

MedlinePlus

... SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies . 7th ed. Philadelphia, PA: ... SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies . 7th ed. Philadelphia, PA: ...

9 CFR 3.3 - Sheltered housing facilities.

Code of Federal Regulations, 2012 CFR

2012-01-01

... attending veterinarian. Dry bedding, solid resting boards, or other methods of conserving body heat must be... wire, wood, metal, or concrete; and (iii) All walls, boxes, houses, dens, and other surfaces in contact...

9 CFR 3.3 - Sheltered housing facilities.

Code of Federal Regulations, 2013 CFR

2013-01-01

... attending veterinarian. Dry bedding, solid resting boards, or other methods of conserving body heat must be... wire, wood, metal, or concrete; and (iii) All walls, boxes, houses, dens, and other surfaces in contact...

9 CFR 3.3 - Sheltered housing facilities.

Code of Federal Regulations, 2014 CFR

2014-01-01

... attending veterinarian. Dry bedding, solid resting boards, or other methods of conserving body heat must be... wire, wood, metal, or concrete; and (iii) All walls, boxes, houses, dens, and other surfaces in contact...

Self-Monitoring vs. Implementation Intentions: a Comparison of Behaviour Change Techniques to Improve Sleep Hygiene and Sleep Outcomes in Students.

PubMed

Mairs, Lucinda; Mullan, Barbara

2015-10-01

This study seeks to investigate and compare the efficacy of self-monitoring and implementation intentions-two post-intentional behaviour change techniques-for improving sleep hygiene behaviours and sleep outcomes in university students. Seventy-two undergraduate students completed baseline measures of four sleep hygiene behaviours (making the sleep environment restful, avoiding going to bed hungry/thirsty, avoiding stress/anxiety-provoking activities near bed time and avoiding caffeine in the evening), as well as the Pittsburgh sleep quality index (PSQI) and the insomnia severity index (ISI). Participants were randomly assigned to an active-control diary-keeping, self-monitoring condition or completed implementation intentions for each behaviour. Post-intervention measurement was completed 2 weeks after baseline. Repeated measures analyses of variance found significant main effects of time for improvements in making the sleep environment restful and avoiding going to bed hungry or thirsty, as well as PSQI and ISI scores. Non-significant interactions suggested no group differences on any variable, except for increasing avoidance of stress and anxiety-provoking activities before bed time, for which only implementation intentions were found to be effective. Attrition was higher amongst self-monitoring participants. Both self-monitoring and implementation intentions appear to be promising behaviour change techniques for improving sleep hygiene and sleep. Future research should examine the acceptability of the two behaviour change techniques and the relationship with differential attrition, as well as effect size variations according to behaviour and technique. Researchers should investigate potential additive or interactive effects of the techniques, as they could be utilised in a complementary manner to target different processes in effecting behaviour change.

Body fluid alterations during head-down bed rest in men at moderate altitude

NASA Technical Reports Server (NTRS)

Loeppky, J. A.; Roach, R. C.; Selland, M. A.; Scotto, P.; Luft, F. C.; Luft, U. C.

1993-01-01

To determine the effects of hypoxia on fluid balance responses to simulated zero-gravity, measurements were made in six subjects before and during -5 deg continuous head-down bed rest (HDBR) over 8 d at 10,678 ft. The same subjects were studied again at this altitude without HDBR as a control (CON) using a cross-over design. During this time, they maintained normal upright day-time activities, sleeping in the horizontal position at night. Fluid balance changes during HDBR in hypoxia were more pronounced than similar measurements previously reported from HDBR studies at sea level. Plasma volume loss was slightly greater and the diuresis and natriuresis were doubled in magnitude as compared to previous studies in normoxia and sustained for 4 d during hypoxia. These changes were associated with an immediate but transient rise in plasma atrial natriuretic peptide (ANP) to day 4 of 140 percent in HDBR and 41 percent in CON (p less than 0.005), followed by a decline towards baseline. Differences were less striking between HDBR and CON for plasma antidiuretic hormone and aldosterone, which were transiently reduced by HDBR. Plasma catecholamines showed a similar pattern to ANP in both HDBR and CON, suggesting that elevated ANP and catecholamines together accounted for the enhanced fluid shifts with HDBR during hypoxia.

Rescue cerclage when foetal membranes prolapse into the vagina.

PubMed

Bayrak, Mehmet; Gul, Ahmet; Goynumer, Gokhan

2017-05-01

A cross-sectional study was conducted to evaluate the efficacy of rescue cerclage in patients with a dilated cervix and prolapsed foetal membranes. Thirty-five patients presenting with cervical dilatation and prolapsed foetal membranes were included in the study. A McDonald cerclage was placed in 27 patients. The duration of pregnancy prolongation and the number of deliveries after 28 weeks were evaluated. The median prolongation of pregnancy after cerclage placement differed significantly between the cerclage and bed-rest groups (64 days versus 13.5 days). Of the 27 patients who had cerclage, 17 (63%) delivered after 28 weeks of gestation, whereas all patients in the bed-rest group delivered before 28 weeks of gestation. The take-home baby rate was 63% in the cerclage group. When pregnancies were complicated by cervical dilatation with membrane prolapse into the vagina, placement of a McDonald cerclage in appropriately selected patients can be a beneficial therapeutic option. Impact statement Although the effectiveness and safety of rescue cerclage is controversial, our study provides strong support for the notion that cervical cerclage accompanied by long-term broad-spectrum antibiotics improves the perinatal outcomes in singleton gestations with membrane prolapsed into the vagina. Further prospective randomised trial is required to prove these findings.

Stone Age hut in Israel yields world's oldest evidence of bedding

PubMed Central

Nadel, Dani; Weiss, Ehud; Simchoni, Orit; Tsatskin, Alexander; Danin, Avinoam; Kislev, Mordechai

2004-01-01

The earliest archaeological remains of dwelling huts built by Homo sapiens were found in various European Upper Paleolithic open-air camps. Although floors of huts were found in a small number of cases, modern organization of the home space that includes defined resting areas and bedding remains was not discovered. We report here the earliest in situ bedding exposed on a brush hut floor. It has recently been found at the previously submerged, excellently preserved 23,000-year-old fisher-hunter-gatherers' camp of Ohalo II, situated in Israel on the shore of the Sea of Galilee. The grass bedding consists of bunches of partially charred Puccinellia confer convoluta stems and leaves, covered by a thin compact layer of clay. It is arranged in a repeated pattern, on the floor, around a central hearth. This study describes the bedding in its original context on a well preserved intentionally constructed floor. It also reconstructs on the basis of direct evidence (combined with ethnographic analogies) the Upper Paleolithic hut as a house with three major components: a hearth, specific working locales, and a comfortable sleeping area near the walls. PMID:15090648

Bone Resorption Increases as Early as the Second Day in Head- Down Bed Rest

NASA Astrophysics Data System (ADS)

Heer, M.; Kamps, N.; Mika, C.; Boese, A.; Gerzer, R.

Long-term bed rest and space mission studies have shown that immobilization as well as microgravity induce increased bone resorption while bone formation tends to decrease. In order to analyze the kinetics of short-term changes in bone turnover we studied in a randomized, strictly controlled crossover design the effects of 6 days 6° head-down tilt bed rest (HDT) in 8 male healthy subjects (mean body weight (BW): 70.1 +/- 1.88 kg; mean age: 25.5 +/- 1.04 years) in our metabolic ward. Two days before arriving in the metabolic ward the subjects started with a diet consisting of an energy content of 10 MJ/d, 2000 mg Calcium/d, 400 i.U. Vitamin D, 200 mEq Na+ and 50 ml water/kg BW/d. The diet was continued in the metabolic ward. The metabolic ward period (11days) was divided into 3 parts: 4 ambulatory days, 6 days either HDT or control and 1 recovery day. Continuous urine collection started on the first day in the metabolic ward to analyze calcium excretion and bone resorption markers, namely C-telopeptide (CTX) and N-telopeptide (NTX). On the 2nd ambulatory day in the metabolic ward and on the 5th day in HDT or control blood was drawn to analyze serum calcium, parathyroid hormone, and bone formation markers (bone Alkaline Phosphatase (bAP), Procollagen-I-Propeptide (P-I-CP). Both study phases were identical with respect to environmental conditions, study protocol and diet. Urinary calcium excretion was as early as the first day in immobilization increased (p<0.01). CTX- and NTX-excretion stayed unchanged the first 24 hours in HDT compared to the control. But, already on the 2nd day of immobilization both bone resorption markers significantly increased. NTX-excretion was increased by 28.7 +/- 14.0% (p<0.05), while CTX-excretion rose by 17.8 +/- 8.3% (p<0.01). Both, the CTX- excretion as well as the calcium excretion keep the significantly higher level during the HDT period, and even continued through the first day of recovery. However, NTX excretion, descended from day three until the end of HDT. But, the level of NTX excretion during HDT was always higher than during control. In contrast to the bone resorption markers, the formation marker P-I-CP tended to decrease as early as the fifth day of immobilization (p<0.10). Serum calcium-, parathyroid hormone-, as well as bAP concentrations were unchanged. We conclude from these results of a pronounced rise of bone resorption markers that already 24 hours of immobilization induce a significant rise in osteoclast activity in healthy subjects. Thus, it appears possible to use short-term bed rest studies for the development of countermeasures to immobilization osteoporosis and to avoid long-term studies, which presently impose major detectable changes on the health status of healthy human subjects. Further studies are mandatory to investigate the underlying mechanisms and respective countermeasures.

Local fluid shifts and edema in humans during simulated microgravity

NASA Technical Reports Server (NTRS)

Hargens, Alan R.

1991-01-01

Local fluid shifts and edema in humans during simulated microgravity is studied. Recent results and significance and future plans on the following research topics are discussed: mechanisms of headward edema formation during head-down tilt; postural responses of head and foot microcirculations and their sensitivity to bed rest; and transcapillary fluid transport associated with lower body negative pressure (LBNP) with and without saline ingestion.

Changes in Body Inertia During Bed Rest Studies

NASA Technical Reports Server (NTRS)

Todd, Beth A.

1999-01-01

Development of effective exercise countermeasures is crucial for long duration human space flight. To analyze the mechanical effects of a particular exercise on the musculoskeletal system, the inertial properties of segments of the body must be quantified. Since bone mineral density loss is related to the lack of mechanical stress and strain on the skeletal system, physical analysis can be very useful for countermeasure evaluation.

Development of an hypothesis for simulating anti-orthostatic bed rest

NASA Technical Reports Server (NTRS)

Leonard, J. I.; Grounds, D. J.; Fitzjerrell, D. G.

1978-01-01

The Guyton model, modified by the addition of leg compartments and the effect of the gravity vector, was used to evaluate hypotheses describing leg dehydration and fluid shifts. While the study is not complete, the basic approach was shown to be useful by identifying important mechanisms, identifying systems which need further experimental description and by assisting in the development of a general hypothesis.

Development of Human Muscle Protein Measurement with MRI

NASA Technical Reports Server (NTRS)

Lin, Chen; Evans, Harlan; Leblanc, Adrian D.

1997-01-01

It is known that micro-gravity has a strong influence on the human musculoskeletal system. A number of studies have shown that significant changes in skeletal muscles occur in both space flight and bedrest simulation. In our 5 week bedrest study, the cross-sectional area of soleus-gastrocnemius decreased about 12% while the cross-sectional area of anterior calf muscles decreased about 4%. Using volume measurements, these losses increased after 17 weeks to approximately 30% and 21% respectively. Significant muscle atrophy was also found on the SL-J crew members after only 8 days in space. It is important that these effects are fully understood so that countermeasures can be developed. The same knowledge might also be useful in preventing muscle atrophy related to other medical problems. A major problem with anatomical measurements of muscle during bed rest and microgravity is the influence of fluid shifts and water balance on the measurement of muscle volume, especially when the exposure duration is short and the atrophy is relatively small. Fluid shifts were documented in Skylab by visual observations of blood vessel distention, rapid changes in limb volume, center of mass measurements and subjective descriptions such as puffy faces and head fullness. It has been reported that the muscle water content of biopsied soleus muscles decreased following 8 hours of head down tilt bed rest. Three aspects of fluid shifts that can affect volume measurements are: first, the shift of fluid that occurs whenever there is a change from upright to a recumbent position and vice versa; second, the potential for fluid accumulation in the lower limbs resulting from muscle damage caused by overextending atrophied muscle or swelling caused by deconditioned precapillary sphincter muscles during reambulation; third, the net change of hydration level during and after bed rest or spaceflight. Because of these transitory fluid shifts, muscle protein is expected to represent muscle capacity better than does muscle volume. The purpose of this study is to test the feasibility of using MRI to quantify of muscle protein and water content changes in muscle.

The origin and distribution of HAPs elements in relation to maceral composition of the A1 lignite bed (Paleocene, Calvert Bluff Formation, Wilcox Group), Calvert mine area, east-central Texas

USGS Publications Warehouse

Crowley, Sharon S.; Warwick, Peter D.; Ruppert, Leslie F.; Pontolillo, James

1997-01-01

The origin and distribution of twelve potentially Hazardous Air Pollutants (HAPs; As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, and U) identified in the 1990 Clean Air Act Amendments were examined in relation to the maceral composition of the A1 bed (Paleocene, Calvert Bluff Formation, Wilcox Group) of the Calvert mine in east-central Texas. The 3.2 m-thick A1 bed was divided into nine incremental channel samples (7 lignite samples and 2 shaley coal samples) on the basis of megascopic characteristics. Results indicate that As, Cd, Cr, Ni, Pb, Sb, and U are strongly correlated with ash yield and are enriched in the shaley coal samples. We infer that these elements are associated with inorganic constituents in the coal bed and may be derived from a penecontemporaneous stream channel located several kilometers southeast of the mining block. Of the HAPs elements studied, Mn and Hg are the most poorly correlated to ash yield. We infer an organic association for Mn; Hg may be associated with pyrite. The rest of the trace elements (Be, Co, and Se) are weakly correlated with ash yield. Further analytical work is necessary to determine the mode of occurrence for these elements. Overall, concentrations of the HAPs elements are generally similar to or less than those reported in previous studies of lignites of the Wilcox Group, east-central region, Texas. Petrographic analysis indicates the following ranges in composition for the seven lignite samples: liptinites (5–8%), huminites (88–95%), and inertinites (trace amounts to 7%). Samples from the middle portion of the A1 bed contain abundant crypto-eugelinite compared to the rest of the samples; this relationship suggests that the degradation of plant material was an important process during the development of the peat mire. With the exception of Hg and Mn, relatively low levels of the HAPs elements studied are found in the samples containing abundant crypto-eugelinite. We infer that the peat-forming environment for this portion of the coal bed was very wet with minimal detrital input. Relatively high concentrations of crypto-humotelinite were found in samples from the top and base of the coal bed. The presence of abundant crypto-humotefinite in this part of the coal bed suggests the accumulation of wood-rich peat under conditions conducive to a high degree of tissue preservation in the peat mire. Although several of the trace elements (Be, Co, Ni, and Sb) exhibit enrichment in these samples, they are not necessarily chemically associated with humotelinite. We infer that these elements, with the exception of Be, are possibly associated with deposition of the roof and floor rock of the coal bed; however, further analytical work would be necessary to confirm this hypothesis. Beryllium may have an organic origin.

Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission.

PubMed

Gimnig, John E; Vulule, John M; Lo, Terrence Q; Kamau, Luna; Kolczak, Margarette S; Phillips-Howard, Penelope A; Mathenge, Evan M; ter Kuile, Feiko O; Nahlen, Bernard L; Hightower, Allen W; Hawley, William A

2003-04-01

The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P = 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of bed nets decreased if one or more residents did not sleep under a net or if bed nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if permethrin is reapplied at least biannually.

Preeclampsia - self-care

MedlinePlus

... preeclampsia is mild, you may be able to stay at home on bed rest. You will need to have ... and your baby if you develop preeclampsia: The mother can have kidney ... to detach from the uterus (abruption) and for stillbirth.

The Flu (For Kids)

MedlinePlus

... town. If your doctor says you have the flu, start taking these steps to feel better: Rest in bed or on the couch. Drink lots of liquids, like water, chicken broth, and other fluids. Take the medicine your ...

Repellency of Naturally Occurring or Related Compounds, DEET, and Para-Menthane-3,8-Diol to Bed Bugs (Hemiptera: Cimicidae).

PubMed

Anderson, John F; Ferrandino, Francis J; Vasil, Michael P; Bedoukian, Robert H; Maher, Marie; McKenzie, Karen

2018-05-04

Bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), have become a major health nuisance in the past 20 ysin cities and elsewhere throughout many areas of the world. Few studies have reported on repellent compounds that could reduce their transport in luggage. We evaluated the repellency of six naturally occurring or related compounds used in flavor/fragrance applications or structurally related compounds, para-menthane-3,8-diol, and N,N-diethyl-meta-toluamide (DEET) to bed bugs in a 183 × 183-cm arena . Repellency was assessed using soft-sided polyester lunch bags serving as surrogates of luggage and barrier cloth towels upon which rested untreated lunch bags. We report for the first time repellency of delta dodecalactone, 2-(3, 7-dimethyl-2, 6-nonadien-1-yl)-cyclopentanone (a.k.a. 'methyl apritone'), gamma dodecalactone, and para-menthane-3,8-diol to bed bugs. Propyl dihydrojasmonate, 3-methyl-5-hexyl-2-cyclohexenone, gamma methyl tridecalactone, and DEET are also documented to be repellent to bed bugs. These compounds provided relatively long-term protection. Propyl dihydrojasmonate prevented bed bugs from seeking refuge in treated lunch bags 27 d after treatment, and when applied to cloth towels repelled harborage-seeking bed bugs for 146 d. Methyl apritone blended with 3-methyl-5-hexyl-2-cyclohexenone and delta dodecalactone as an individual compound applied to cloth towels repelled bed bugs for 190 and 276 d, respectively. The above-mentioned compounds, either individually or as blends, may reduce risk of bed bugs seeking harborage in treated suitcases or towels upon which untreated luggage is placed.

Development of Countermeasures and Exercise Protocols to Reduce the Effects of Microgravity

NASA Technical Reports Server (NTRS)

Kulkarni, Pandurang M.

2000-01-01

I have helped scientists at NASA-JSC in analyzing data from many projects. Some of the major ones are: (1) cardiovascular responses to lower body negative pressure (LBNP) following bed rest, (2) the effects of dietary sodium, (3) in-flight cycle exercise mitigates reduced oxygen consumption at submaximal heart rates following space flight, (4) exercise thermoregulation after 13 days of head down bed rest, and (5) bed rest induced orthostatic intolerance. Many of the projects have now been completed and some of them are in the process of being published and others have been presented at national meetings. These projects have helped me be a true statistician and given me a real-life perspective of how interesting and complicated data can be. As a by-product of of these involvements I have been able to write and publish some methodological research that have applications in NASA and elsewhere. For instance, while I was at JSC, I happened to meet Dr. Al Feiveson and got into a discussion of the Space Shuttle Reliability. This led us to rethink about the way the data on the accelerated life testing of space shuttle pressure vessels had been analyzed. This has resulted in a major statistical paper and the paper has appeared in one of the top journals in the field of Statistics. A review of the paper by the editor of the journal was published in AmStatNews, a copy is attached with this report. I have presented these findings at the national/international statistics conference and at other places. I have also written another paper on reliability and a paper on calibration techniques that have applications in the engineering and the biomedical branches of NASA. Further, I am currently in the process of writing at least two more papers that have direct applications in NASA related studies.

Exercise as potential countermeasure for the effects of 70 days of bed rest on cognitive and sensorimotor performance

PubMed Central

Koppelmans, Vincent; Mulavara, Ajitkumar P.; Yuan, Peng; Cassady, Kaitlin E.; Cooke, Katherine A.; Wood, Scott J.; Reuter-Lorenz, Patricia A.; De Dios, Yiri E.; Stepanyan, Vahagn; Szecsy, Darcy L.; Gadd, Nichole E.; Kofman, Igor; Scott, Jessica M.; Downs, Meghan E.; Bloomberg, Jacob J.; Ploutz-Snyder, Lori; Seidler, Rachael D.

2015-01-01

Background: Spaceflight has been associated with changes in gait and balance; it is unclear whether it affects cognition. Head down tilt bed rest (HDBR) is a microgravity analog that mimics cephalad fluid shifts and body unloading. In consideration of astronaut’s health and mission success, we investigated the effects of HDBR on cognition and sensorimotor function. Furthermore, we investigated if exercise mitigates any cognitive and sensorimotor sequelae of spaceflight. Method: We conducted a 70-day six-degree HDBR study in 10 male subjects who were randomly assigned to a HDBR supine exercise or a HDBR control group. Cognitive measures (i.e., processing speed, manual dexterity, psychomotor speed, visual dependency, and 2D and 3D mental rotation) and sensorimotor performance (functional mobility (FMT) and balance performance) were collected at 12 and 8 days pre-HDBR, at 7, 50, and 70 days in HDBR, and at 8 and 12 days post-HDBR. Exercise comprised resistance training, and continuous and high-intensity interval aerobic exercise. We also repeatedly assessed an outside-of-bed rest control group to examine metric stability. Results: Small practice effects were observed in the control group for some tasks; these were taken into account when analyzing effects of HDBR. No significant effects of HDBR on cognition were observed, although visual dependency during HDBR remained stable in HDBR controls whereas it decreased in HDBR exercise subjects. Furthermore, HDBR was associated with loss of FMT and standing balance performance, which were almost fully recovered 12 days post-HDBR. Aerobic and resistance exercise partially mitigated the effects of HDBR on FMT and accelerated the recovery time course post-HDBR. Discussion: HDBR did not significantly affect cognitive performance but did adversely affect FMT and standing balance performance. Exercise had some protective effects on the deterioration and recovery of FMT. PMID:26388746

Uncovering Physiologic Mechanisms of Circadian Rhythms and Sleep/Wake Regulation Through Mathematical Modeling

DTIC Science & Technology

2007-06-01

the effects of rest -activity-work schedules and interventions on neurobehavioral function. In a symposium titled “Modeling Human Neurobehavioral...physio- logic basis of Process S. The mutually inhibitory neu- ronal populations, together with the surrogate Process S, have the potential to serve...as a function of both ta and φ (Czeisler et al., 1999). Briefly, by imposing a cyclic pattern of bed rest and wake time at a period, T, sufficiently

Predictors for postpartum pelvic girdle pain in working women: the Mom@Work cohort study.

PubMed

Stomp-van den Berg, Suzanne G M; Hendriksen, Ingrid J M; Bruinvels, David J; Twisk, Jos W R; van Mechelen, Willem; van Poppel, Mireille N M

2012-12-01

The objective of this study was to examine which factors during pregnancy and postpartum predict pelvic girdle pain (PGP) at 12 weeks postpartum among working women. A total of 548 Dutch pregnant employees were recruited in 15 companies, mainly health care, child care, and supermarkets. The definition of PGP was any pain felt in the pelvic girdle region at 12 weeks postpartum. Participants received questionnaires at 30 weeks of pregnancy and at 6 and 12 weeks postpartum with demographic, work-related, pregnancy-related, fatigue, psychosocial, PGP-related and delivery-related questions. Univariate and multiple logistic regression analyses were performed. Almost half of the women experienced pain in their pelvic girdle at 12 weeks postpartum. However, the level of pain and the degree of disability due to postpartum PGP was low. Pregnancy-related predictors for PGP at 12 weeks were history of low back pain, higher somatisation, more than 8 hours of sleep or rest per day, and uncomfortable postures at work. The pregnancy and postpartum-related predictors were: more disability at 6 weeks, having PGP at 6 weeks, higher mean pain at 6 weeks, higher somatisation during pregnancy and at 6 weeks postpartum, higher birth weight of the baby, uncomfortable postures at work and number of days of bed rest. Based on these results, it is concluded that extra attention should be given to women who experience PGP during pregnancy to prevent serious PGP during late pregnancy and postpartum. More research is needed to confirm the roles of hours of sleep, somatisation, and bed rest in relation to PGP. Copyright © 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Catecholaminergic effects of prolonged head-down bed rest

NASA Technical Reports Server (NTRS)

Goldstein, D. S.; Vernikos, J.; Holmes, C.; Convertino, V. A.

1995-01-01

Prolonged head-down bed rest (HDBR) provides a model for examining responses to chronic weightlessness in humans. Eight healthy volunteers underwent HDBR for 2 wk. Antecubital venous blood was sampled for plasma levels of catechols [norepinephrine (NE), epinephrine, dopamine, dihydroxyphenylalanine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid] after supine rest on a control (C) day and after 4 h and 7 and 14 days of HDBR. Urine was collected after 2 h of supine rest during day C, 2 h before HDBR, and during the intervals 1-4, 4-24, 144-168 (day 7), and 312-336 h (day 14) of HDBR. All subjects had decreased plasma and blood volumes (mean 16%), atriopeptin levels (31%), and peripheral venous pressure (26%) after HDBR. NE excretion on day 14 of HDBR was decreased by 35% from that on day C, without further trends as HDBR continued, whereas plasma levels were only variably and nonsignificantly decreased. Excretion rates of dihydroxyphenylglycol and dihydroxyphenylalanine decreased slightly during HDBR; excretion rates of epinephrine, dopamine, and dihydroxyphenylacetic acid and plasma levels of catechols were unchanged. The results suggest that HDBR produces sustained inhibition of sympathoneural release, turnover, and synthesis of NE without affecting adrenomedullary secretion or renal dopamine production. Concurrent hypovolemia probably interferes with detection of sympathoinhibition by plasma levels of NE and other catechols in this setting. Sympathoinhibition, despite decreased blood volume, may help to explain orthostatic intolerance in astronauts returning from spaceflights.

Reducing bed rest time from five to three hours does not increase complications after cardiac catheterization: the THREE CATH Trial 1

PubMed Central

Matte, Roselene; Hilário, Thamires de Souza; Reich, Rejane; Aliti, Graziella Badin; Rabelo-Silva, Eneida Rejane

2016-01-01

Abstract Objective: to compare the incidence of vascular complications in patients undergoing transfemoral cardiac catheterization with a 6F introducer sheath followed by 3-hour versus 5-hour rest. Methods: randomized clinical trial. Subjects in the intervention group (IG) ambulated 3 hours after sheath removal, versus 5 hours in the control group (CG). All patients remained in the catheterization laboratory for 5 hours and were assessed hourly, and were contacted 24, 48, and 72 h after hospital discharge. Results: the sample comprised 367 patients in the IG and 363 in the GC. During cath lab stay, hematoma was the most common complication in both groups, occurring in 12 (3%) IG and 13 (4%) CG subjects (P=0.87). Bleeding occurred in 4 (1%) IG and 6 (2%) CG subjects (P=0.51), and vasovagal reaction in 5 (1.4%) IG and 4 (1.1%) CG subjects (P=0.75). At 24-h, 48-h, and 72-h bruising was the most commonly reported complication in both groups. None of the comparisons revealed any significant between-group differences. Conclusion: the results of this trial show that reducing bed rest time to 3 hours after elective cardiac catheterization is safe and does not increase complications as compared with a 5-hour rest. ClinicalTrials.gov Identifier: NCT-01740856 PMID:27463113

Investigation of Intermediary Metabolism and Energy Exchange Following Human Trauma.

DTIC Science & Technology

1979-07-01

effects of intravenous diets in the hypocaloric range. The present study indicates that in severely depleted patients, a moderate intake, averaging 65 g...the type of hypocaloric nutrition and of enforced bed rest on the "pattern of injury" which was found. It was formerly thought that the weakness and...regular house diet . Subsequent studies are then reported on patients under- going hip replacement and receiving either 70 g of amino acids/day as their

VIIP Bedrest Analog Roadmap

NASA Technical Reports Server (NTRS)

Villarreal, Jennifer D.

2014-01-01

The objective is to define successive bed rest campaigns leading to a potential VIIP (Vision Impairment and Intracranial Pressure) countermeasure. To determine if the analog is successful, changes need to occur in the following outcome measures (dependent variables): Intracranial pressure; Retinal nerve fiber layer; Choroidal engorgement; Globe flattening; Axial biometry; Optic nerve sheath diameter distention; Cycloplegic refraction; Visual acuity. Study parameters (independent variables) to include: CO2; Sodium; Exercise (resistive & aerobic); Strict tilt angle.

No effect of artificial gravity on lung function with exercise training during head-down bed rest

NASA Astrophysics Data System (ADS)

Su, Longxiang; Guo, Yinghua; Wang, Yajuan; Wang, Delong; Liu, Changting

2016-04-01

The aim of this study is to explore the effectiveness of microgravity simulated by head-down bed rest (HDBR) and artificial gravity (AG) with exercise on lung function. Twenty-four volunteers were randomly divided into control and exercise countermeasure (CM) groups for 96 h of 6° HDBR. Comparisons of pulse rate, pulse oxygen saturation (SpO2) and lung function were made between these two groups at 0, 24, 48, 72, 96 h. Compared with the sitting position, inspiratory capacity and respiratory reserve volume were significantly higher than before HDBR (0° position) (P < 0.05). Vital capacity, expiratory reserve volume, forced vital capacity, forced expiratory volume in 1 s, forced inspiratory vital capacity, forced inspiratory volume in 1 s, forced expiratory flow at 25, 50, and 75%, maximal mid-expiratory flow and peak expiratory flow were all significantly lower than those before HDBR (P < 0.05). Neither control nor CM groups showed significant differences in pulse rate, SpO2, pulmonary volume and pulmonary ventilation function over the HDBR observation time. Postural changes can lead to variation in lung volume and ventilation function, but a HDBR model induced no changes in pulmonary function and therefore should not be used to study AG countermeasures.

A critical benefit analysis of artificial gravity as a microgravity countermeasure

NASA Astrophysics Data System (ADS)

Kaderka, Justin; Young, Laurence R.; Paloski, William H.

2010-11-01

Deconditioning of astronauts during long duration spaceflight, especially with regard to the cardiovascular, musculo-skeletal, and neurological systems, is a well-recognized problem that has stimulated significant investments in countermeasure research over the past five decades. Because of its potential salutary effects on all of these systems, artificial gravity via centrifugation has been one of the most persistently discussed countermeasures; however, to date, few studies have tested its efficacy, particularly in comparison to other, system-specific countermeasures. This paper reports results of a meta-analysis we performed to compare previously published results from artificial gravity studies with those from studies utilizing traditional countermeasures, such as resistive exercise, aerobic exercise, lower body negative pressure (LBNP), or some variation of these countermeasures. Published and non-published literature involving human bed rest and immersion studies, human non-bed rest studies, and flight data were examined. Our analyses were confounded by differences in research design from study to study, including subject selection criteria, deconditioning paradigm, physiological systems assessed, and dependent measures employed. Nevertheless we were able to draw comparisons between studies that had some consistency across these variables. Results indicate that for prolonged spaceflight an artificial gravity-based countermeasure may provide benefits equivalent to traditional countermeasures for the cardiovascular system. Too few comparable studies have been performed to draw any conclusions for the musculo-skeletal system. Gaps in the current knowledge of artificial gravity are identified and provide the basis for a discussion of future topics for ground-based research using this countermeasure.

Comparative clinical effectiveness of management strategies for sciatica: systematic review and network meta-analyses.

PubMed

Lewis, Ruth A; Williams, Nefyn H; Sutton, Alex J; Burton, Kim; Din, Nafees Ud; Matar, Hosam E; Hendry, Maggie; Phillips, Ceri J; Nafees, Sadia; Fitzsimmons, Deborah; Rickard, Ian; Wilkinson, Clare

2015-06-01

There are numerous treatment approaches for sciatica. Previous systematic reviews have not compared all these strategies together. To compare the clinical effectiveness of different treatment strategies for sciatica simultaneously. Systematic review and network meta-analysis. We searched 28 electronic databases and online trial registries, along with bibliographies of previous reviews for comparative studies evaluating any intervention to treat sciatica in adults, with outcome data on global effect or pain intensity. Network meta-analysis methods were used to simultaneously compare all treatment strategies and allow indirect comparisons of treatments between studies. The study was funded by the UK National Institute for Health Research Health Technology Assessment program; there are no potential conflict of interests. We identified 122 relevant studies; 90 were randomized controlled trials (RCTs) or quasi-RCTs. Interventions were grouped into 21 treatment strategies. Internal and external validity of included studies was very low. For overall recovery as the outcome, compared with inactive control or conventional care, there was a statistically significant improvement following disc surgery, epidural injections, nonopioid analgesia, manipulation, and acupuncture. Traction, percutaneous discectomy, and exercise therapy were significantly inferior to epidural injections or surgery. For pain as the outcome, epidural injections and biological agents were significantly better than inactive control, but similar findings for disc surgery were not statistically significant. Biological agents were significantly better for pain reduction than bed rest, nonopioids, and opioids. Opioids, education/advice alone, bed rest, and percutaneous discectomy were inferior to most other treatment strategies; although these findings represented large effects, they were statistically equivocal. For the first time, many different treatment strategies for sciatica have been compared in the same systematic review and meta-analysis. This approach has provided new data to assist shared decision-making. The findings support the effectiveness of nonopioid medication, epidural injections, and disc surgery. They also suggest that spinal manipulation, acupuncture, and experimental treatments, such as anti-inflammatory biological agents, may be considered. The findings do not provide support for the effectiveness of opioid analgesia, bed rest, exercise therapy, education/advice (when used alone), percutaneous discectomy, or traction. The issue of how best to estimate the effectiveness of treatment approaches according to their order within a sequential treatment pathway remains an important challenge. Copyright © 2015 Elsevier Inc. All rights reserved.

Changes in the Diurnal Rhythms during a 45-Day Head-Down Bed Rest

PubMed Central

Liang, Xiaodi; Zhang, Lin; Wan, Yufeng; Yu, Xinyang; Guo, Yiming; Chen, Xiaoping; Tan, Cheng; Huang, Tianle; Shen, Hanjie; Chen, Xianyun; Li, Hongying; Lv, Ke; Sun, Fei; Chen, Shanguang; Guo, Jinhu

2012-01-01

In spaceflight human circadian rhythms and sleep patterns are likely subject to change, which consequently disturbs human physiology, cognitive abilities and performance efficiency. However, the influence of microgravity on sleep and circadian clock as well as the underlying mechanisms remain largely unknown. Placing volunteers in a prone position, whereby their heads rest at an angle of −6° below horizontal, mimics the microgravity environment in orbital flight. Such positioning is termed head-down bed rest (HDBR). In this work, we analysed the influence of a 45-day HDBR on physiological diurnal rhythms. We examined urinary electrolyte and hormone excretion, and the results show a dramatic elevation of cortisol levels during HDBR and recovery. Increased diuresis, melatonin and testosterone were observed at certain periods during HDBR. In addition, we investigated the changes in urination and defecation frequencies and found that the rhythmicity of urinary frequency during lights-off during and after HDBR was higher than control. The grouped defecation frequency data exhibits rhythmicity before and during HDBR but not after HDBR. Together, these data demonstrate that HDBR can alter a number of physiological processes associated with diurnal rhythms. PMID:23110150

Insulin and glucose responses during bed rest with isotonic and isometric exercise

NASA Technical Reports Server (NTRS)

Dolkas, C. B.; Greenleaf, J. E.

1977-01-01

The effects of daily intensive isotonic (68% maximum oxygen uptake) and isometric (21% maximum extension force) leg exercise on plasma insulin and glucose responses to an oral glucose tolerance test (OGTT) during 14-day bed-rest (BR) periods were investigated in seven young healthy men. The OGTT was given during ambulatory control and on day 10 of the no-exercise, isotonic, and isometric exercise BR periods during the 15-wk study. The subjects were placed on a controlled diet starting 10 days before each BR period. During BR, basal plasma glucose concentration remained unchanged with no exercise, but increased (P less 0.05) to 87-89 mg/100 ml with both exercise regimens on day 2, and then fell slightly below control levels on day 13. The fall in glucose content during BR was independent of the exercise regimen and was an adjustment for the loss of plasma volume. The intensity of the responses of insulin and glucose to the OGTT was inversely proportional to the total daily energy expenditure during BR. It was estimated that at least 1020 kcal/day must be provided by supplemental exercise to restore the hyperinsulinemia to control levels.

Physical activity for paediatric rheumatic diseases: standing up against old paradigms.

PubMed

Gualano, Bruno; Bonfa, Eloisa; Pereira, Rosa M R; Silva, Clovis A

2017-05-23

Over the past 50 years it has become clear that physical inactivity is associated with chronic disease risk. For several rheumatic diseases, bed rest was traditionally advocated as the best treatment, but several levels of evidence support the imminent paradigm shift from the prescription of bed rest to physical activity in individuals with paediatric rheumatic diseases, in particular juvenile systemic lupus erythematosus, juvenile idiopathic arthritis, juvenile fibromyalgia, and juvenile dermatomyositis. Increasing levels of physical activity can alleviate several symptoms experienced by patients with paediatric rheumatic diseases, such as low aerobic fitness, pain, fatigue, muscle weakness and poor health-related quality of life. Moreover, the propensity of patients with paediatric rheumatic diseases to be hypoactive - often due to social self-isolation, overprotection, and fear and/or ignorance on the part of parents, teachers and health practitioners - can be detrimental to general disease symptoms and function. In support of this rationale, a growing number of studies have demonstrated that the systemic benefits of exercise training clearly outweigh the risks in these diseases. In this sense, health professionals are advised to assess, track and fight against physical inactivity and sedentary behaviour on a routine basis, as they are invaluable health risk parameters in rheumatology.

Height increase, neuromuscular function, and back pain during 6 degrees head-down tilt with traction

NASA Technical Reports Server (NTRS)

Styf, J. R.; Ballard, R. E.; Fechner, K.; Watenpaugh, D. E.; Kahan, N. J.; Hargens, A. R.

1997-01-01

BACKGROUND: Spinal lengthening and back pain are commonly experienced by astronauts exposed to microgravity. METHODS: To develop a ground-based simulation for spinal adaptation to microgravity, we investigated height increase, neuromuscular function and back pain in 6 subjects all of whom underwent two forms of bed rest for 3 d. One form consisted of 6 degrees of head-down tilt (HDT) with balanced traction, while the other was horizontal bed rest (HBR). Subjects had a 2-week recovery period in between the studies. RESULTS: Total body and spinal length increased significantly more and the subjects had significantly more back pain during HDT with balanced traction compared to HBR. The distance between the lower endplate of L4 and upper endplate of S1, as measured by ultrasonography, increased significantly in both treatments to the same degree. Intramuscular pressures in the erector spinae muscles and ankle torque measurements during plantarflexion and dorsiflexion did not change significantly during either treatment. CONCLUSION: Compared to HBR, HDT with balanced traction may be a better method to simulate changes of total body and spinal lengths, as well as back pain seen in microgravity.

Effect of intermittent standing and walking on physiological changes induced by head-down bed rest

NASA Technical Reports Server (NTRS)

Vernikos, J.; Ludwig, D. A.; Ertl, A. C.; Wade, C. E.; Keil, L.; OHara, D.

1994-01-01

Continuous exposure to gravity may not be necessary to prevent compromised physiological function resulting from exposure to microgravity. However, minimum gravity (G) exposure requirements, effectiveness of passive Gz versus activity in a G field, and optimal G stimulus amplitude, duration, and frequency are unknown. To partially address these questions, a 4-day, 6 degree head-down bed rest (HDBR) study (one ambulatory control day, 4 full HDBR days, one recovery day) was conducted. Nine males, 30-50 yr, were subjected to four different +1 Gz (head-foot) exposure protocols (periodic standing or controlled walking for 2 or 4 h/day in 15 min doses), plus a continuous HDBR (0 Gz) control. Standing 4 h completely prevented and standing 2 h partially prevented post-HDBR orthostatic intolerance. Both walking conditions (2 h and 4 h) attenuated the decrease in peak VO2 and prevented the increased urinary Ca2+ excretion associated with HDBR. Both 4 h conditions (standing and walking) attenuated plasma volume loss during HDBR. It was concluded that various physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz and the duration (2 h vs. 4 h) of the stimulus may be an important moderating factor.

Mineral distribution in rat skeletons after exposure to a microgravity model

NASA Technical Reports Server (NTRS)

Arnaud, Sara B.; Harper, Jennifer S.; Navidi, Meena

1995-01-01

Exposure to space flight models induces changes in the distribution of bone mineral in the human skeleton that has the features of a gravitational gradient. Regional bone mineral measurements with dual energy x-ray absorptiometry (DEXA) in male adults exposed to head-down tilt bed rest for 30 days shown non-significant decrements in the pelvis and legs with 10% increases in the head region. Horizontal bed rest for 17 weeks reveals losses of bone mineral ranging from 2.2 to 10.4% from the lumbar spine to the calcaneus and an increase of 3.4% in the skull. Investigation of this phenomena would be most definitively carried out in an animal model. One candidate is the flight simulation model in the rat which removes body weight from the hind limbs and induces a cephalad fluid shift by suspending the animal by the tail. Weanling rats exposed to this model showed bone mineral to be lower in the hind limbs and higher in the skull after 3 weeks. These finds are similar in older 200 g animals after 2 weeks tail suspension. The purpose of this study was to determine the effect of age on the distribution of skeletal mineral in this model.

Daily Supine LBNP Treadmill Exercise Maintains Upright Exercise Capacity During 14 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Ertl, Andy C.; Watenpaugh, D. E.; Hargens, Alan R.; Fortney, S. M.; Lee, S. M. C.; Ballard, R. E.; William, J. M.

1996-01-01

Exposure to microgravity or bed rest reduces upright exercise capacity. Exercise modes, durations, and intensities which will effectively and efficiently counteract such deconditioning are presently unresolved. We that daily supine treadmill interval training with lower body negative pressure (LBNP) would prevent reduction in upright exercise capacity during 14 days of 6 deg. head-down bed rest (BR). Eight healthy male subjects underwent two 14 day BR protocols separated by 3 months. In a crossover design, subjects either remained at strict BR or performed 40 min of daily exercise consisting of supine walking and running at intensities varying from 40-80% of pre-BR upright peak oxygen uptake (VO2). LBNP during supine exercise was used to provide 1.0 to 1.2 times body weight of footward force. An incremental upright treadmill test to measure submaximal and peak exercise responses was given pre- and post-BR. In the non-exercise condition, peak VO2 and time to exhaustion were reduced 16 +/- 4% and 10 +/- 1% (p less than 0.05), respectively, from pre-BR. With LBNP exercise these variables were not significantly different (NS) from pre-BR. During submaximal treadmill speeds after BR, heart rate was higher (11 +/- 11 bpm, p less than 0.05) and respiratory exchange ratio was elevated (p less than 0.05) in the no exercise condition. Both were maintained at pre-BR levels in the LBNP exercise condition (NS from pre-BR). Since this supine treadmill interval training with addition of LBNP maintained upright exercise responses and capacity during BR, this countermeasure may also be effective during space flight.

Hoffmann-reflex is delayed during 6 degree head-down tilt with balanced traction

NASA Technical Reports Server (NTRS)

Haruna, Y.; Styf, J. R.; Kahan, N.; Hargens, A. R.

1999-01-01

BACKGROUND: Increased spinal height due to the lack of of axial compression on spinal structures in microgravity may stretch the spinal cord, cauda equina, nerve roots, and paraspinal tissues. HYPOTHESIS: Exposure to simulated microgravity causes dysfunction of nerve roots so that the synaptic portion of the Achilles tendon reflex is delayed. METHODS: Six healthy male subjects were randomly divided into two groups with three in each group. The subjects in the first group underwent horizontal bed rest (HBR) for three days. After a two week interval they underwent bed rest in a position of head-down tilt with balanced traction (HDT). So that each subject could serve as his own control, the second group was treated identically but in opposite order. Bilateral F waves and H-reflexes were measured daily (18:30-20:30) on all subjects placed in a prone position. RESULTS: By means of ANOVA, differences between HDT and HBR were observed only in M-latency and F-ratio, not in F-latency, central latency, and H-latency. Differences during the course of the bed rest were observed in M-latency and H-latency only. Tibial H latency was significantly lengthened in HDT group on day 2 and 3, although no significant difference between HDT and HBR was observed. CONCLUSION: The monosynaptic reflex assessed by H-reflex was delayed during 6 degree HDT with traction. The exact mechanism of this delay and whether the change was due to lengthening of the lower part of the vertebrae remain to be clarified.

Pregnancy-Induced Hypertension

MedlinePlus

... from work and rest in bed. In some cases, hospitalization may be necessary. A note about salt One way to control high blood pressure when you’ ... hypertensive, nonproteinuric, pregnancy, pregnancy-induced, pressure, ... ContentAllergy Shots: Could They Help Your Allergies?Read Article >>Allergy ...

Marginal bed load transport in a gravel bed stream, Sagehen Creek, California

USGS Publications Warehouse

Andrews, E.D.

1994-01-01

Marginal bed load transport describes the condition when relatively few bed particles are moving at any time. Bed particles resting in the shallowest bed pockets will move when the dimensionless shear stress т* exceeds a value of about 0.020. As т* increases, the number of bed particles moving increases. Significant motion of bed particles, i.e., when a substantial fraction of the bed particles are moving, occurs when т* exceeds a value of about 0.060. Thus marginal bed load transport occurs over the domain 0.020 < т* < 0.060. Marginal bed load transport rates and associated hydraulic characteristics of Sagehen Creek, a small mountain gravel bed stream, were measured on 55 days at discharges ranging from slightly less than one half of the bank-full discharge to more than 4 times the bank-full discharge. Dimensionless shear stress varied from 0.032 to 0.042, and bed particles as large as the 80th percentile of the bed surface were transported. The relation between reference dimensionless shear stress and relative particle protrusion for Sagehen Creek was determined by varying т*ri to obtain the best fit of the Parker bed load function to the measured transport rates. During the period of record (water years 1954–1991), the mean annual quantity of bed load transported past the Sagehen Creek gage was 24.7 tons. Forty-seven percent of all bed load transported during the 38 years of record occurred in just 6 years. During 10 of the 38 years of record, essentially no bed load was transported. The median diameter of bed load was 26 mm, compared to 58 mm in the surface bed material.

Comparison of cardiovascular function during the early hours of bed rest and space flight

NASA Technical Reports Server (NTRS)

Lathers, C. M.; Charles, J. B.

1994-01-01

This paper reviews the cardiovascular responses of six healthy male subjects to 6 hours in a 5 degrees head-down bed rest model of weightlessness, and compares these responses to those obtained when subjects were positioned in head-up tilts of 10 degrees, 20 degrees, and 42 degrees, simulating 1/6, 1/3, and 2/3 G, respectively. Thoracic fluid index, cardiac output, stroke volume, and peak flow were measured using impedance cardiography. Cardiac dimensions and volumes were determined from two-dimensional guided M-mode echocardiograms in the left lateral decubitus position at 0, 2, 4, and 6 hours. Cardiovascular response to a stand test were compared before and after bed rest. The impedance values were related to tilt angle for the first 2 hours of tilt; however, after 3 hours, at all four angles, values began to converge, indicating that cardiovascular homeostatic mechanisms seek a common adapted state, regardless of effective gravity level (tilt angle) up to 2/3 G. Echocardiography revealed that left ventricular end-diastolic and end-systolic volume, stroke volume, ejection fraction, heart rate, and cardiac output had returned to control values by hour 6 for all tilt angles. The lack of a significant immediate change in left ventricular end-diastolic volume, despite decrements in stroke volume (P < .05) and heart rate (not significant), indicates that multiple factors may play a role in the adaptation to simulated hypogravity. The echocardiography data indicated that no angle of tilt, whether head-down or head-up for 4 to 6 hours, mimicked exactly the changes in cardiovascular function recorded after 4 to 6 hours of space flight. Changes in left ventricular end-diastolic volume during space flight and tilt may be similar, but follow a different time course. Nevertheless, head-down tilt at 5 degrees for 6 hours mimics some (stroke volume, systolic and diastolic blood pressure, mean arterial blood pressure, and total resistance), but not all, of the changes occurring in an equivalent time of space flight. The magnitude of the change in the mean heart rate response to standing was greater after six hours of tilt at -5 degrees or 10 degrees. Thus, results from the stand test after 6 hours of bed rest at -5 degrees and 10 degrees, but not at 20 degrees or 42 degrees, are similar to those obtained after space flight.

Effects of Long Duration Spaceflight on Venous and Arterial Compliance in Astronants

NASA Technical Reports Server (NTRS)

Platts, Steven; Ribeiro, L. Christine

2014-01-01

1. Project Overview Visual impairment and intracranial pressure (VIIP) is a spaceflight-associated medical condition affecting at least a third of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures. In some astronauts, eye-related changes do not revert back to the preflight state upon return to Earth. Our team will study some of the possible causes for this syndrome. This will be achieved by reviewing previous astronaut data for factors that may predispose astronauts to higher rates of developing this syndrome or greater severity of symptoms. Additionally, we will conduct 3 separate experiments that will characterize vessels in the head and neck and measure the effects of the experimental conditions on ocular structures and function. 2. Technical Summary The primary objective of this study is to determine whether vascular compliance is altered by spaceflight and whether such adaptations are related to the incidence of the VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no spaceflight experience (Ground), in astronauts before, during, and after spaceflight (Flight), and in bed rest subjects with conditions similar to spaceflight (Bed Rest). Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archives to determine which factors might be predictive of the development of VIIP (Data Mining). The project will be conducted in four separate, but related parts. Hypothesis The central hypothesis of this proposal is that exposure to the spaceflight environment aboard the ISS may lead to development of the VIIP syndrome (increased intracranial pressure and impaired visual acuity) and that this may be related to alterations in venous and/or arterial compliance in the head and neck. Specific Aims 1. To determine whether noninvasive measures of venous and arterial compliance are altered by long-duration spaceflight exposure in ISS astronauts and whether these changes are related to the development of the VIIP syndrome. (Flight) 2. To determine whether previous spaceflight experience predispose astronauts to lower venous compliance and/or the development of the VIIP syndrome. (Ground + Flight) 3. To use a 14-day, 6deg head-down-tilt bed rest as a model of spaceflight, to evaluate the effect of aging on vascular compliance using a subject population similar to younger (25-35 yr) and older (45-55 yr) astronaut cohorts. (Bed Rest) 4. To determine what factors contribute to lower venous compliance and/or the development of the VIIP syndrome in astronauts. (Data Mining) 3. Earth Applications This research may inform the mechanisms that regulate blood/fluid flow in and out of the brain in the head and neck. This information may help with understanding of the mechanisms behind idiopathic intracranial hypertension. 4. Link to NASA Taskbook Entry Not Yet Available

Mineral and nitrogen balance study - Results of metabolic observations on Skylab II 28-day orbital mission

NASA Technical Reports Server (NTRS)

Whedon, G. D.; Lutwak, L.; Reid, J.; Rambaut, P.; Whittle, M.; Smith, M.; Leach, C.

1975-01-01

The prediction that various stresses of flight, particularly weightlessness, would bring about significant derangements in the metabolism of the musculoskeletal system has been based on various balance-study observations of long-term immobilized or inactive bed rest. The three astronauts of Skylab II consumed a planned dietary intake of major metabolic elements in mixed foods and beverages and provided virtually complete collections of excreta for 31 days preflight, 28 days inflight, and 17 days postflight. Analyses showed that, in varying degree among the crewmen, urinary calcium increased gradually during flight in a pattern similar to that observed in bed-rest studies. Fecal calcium excretion did not change significantly, but calcium balance, owing to the urinary calcium rise, became either negative or less positive than in preflight measurement. Increased excretion and negative nitrogen and phosphorus balances inflight indicated appreciable loss of muscle tissue in all three crewmen. Significant losses also occurred inflight in potassium, sodium, and magnesium. Based on the similarity in pattern and degree between these observations of calcium, phosphorus, and nitrogen loss, musculoskeletal integrity would not be threatened in space flights of up to at least 3 months. However, if similar changes occur in the planed Skylab flights for considerably more than 28 days, concern for capable musculoskeletal function should be serious for flights of very many months' duration.

Space exercise and Earth benefits.

PubMed

Macias, Brandon R; Groppo, Eli R; Eastlack, Robert K; Watenpaugh, Donald E; Lee, Stuart M C; Schneider, Suzanne M; Boda, Wanda L; Smith, Scott M; Cutuk, Adnan; Pedowitz, Robert A; Meyer, R Scott; Hargens, Alan R

2005-08-01

The detrimental impact of long duration space flight on physiological systems necessitates the development of exercise countermeasures to protect work capabilities in gravity fields of Earth, Moon and Mars. The respective rates of physiological deconditioning for different organ systems during space flight has been described as a result of data collected during and after missions on the Space Shuttle, International Space Station, Mir, and bed rest studies on Earth. An integrated countermeasure that simulates the body's hydrostatic pressure gradient, provides mechanical stress to the bones and muscles, and stimulates the neurovestibular system may be critical for maintaining health and well being of crew during long-duration space travel, such as a mission to Mars. Here we review the results of our studies to date of an integrated exercise countermeasure for space flight, lower body negative pressure (LBNP) treadmill exercise, and potential benefits of its application to athletic training on Earth. Additionally, we review the benefits of Lower Body Positive Pressure (LBPP) exercise for rehabilitation of postoperative patients. Presented first are preliminary data from a 30-day bed rest study evaluating the efficacy of LBNP exercise as an integrated exercise countermeasure for the deconditioning effects of microgravity. Next, we review upright LBNP exercise as a training modality for athletes by evaluating effects on the cardiovascular system and gait mechanics. Finally, LBPP exercise as a rehabilitation device is examined with reference to gait mechanics and safety in two groups of postoperative patients.

Bed Rest Muscular Atrophy

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

2000-01-01

A major debilitating response from prolonged bed rest (BR) is muscle atrophy, defined as a "decrease in size of a part of tissue after full development has been attained: a wasting away of tissue as from disuse, old age, injury or disease". Part of the complicated mechanism for the dizziness, increased body instability, and exaggerated gait in patients who arise immediately after BR may be a result of not only foot pain, but also of muscular atrophy and associated reduction in lower limb strength. Also, there seems to be a close association between muscle atrophy and bone atrophy. A discussion of many facets of the total BR homeostatic syndrome has been published. The old adage that use determines form which promotes function of bone (Wolff's law) also applies to those people exposed to prolonged BR (without exercise training) in whom muscle atrophy is a consistent finding. An extreme case involved a 16-year-old boy who was ordered to bed by his mother in 1932: after 50 years in bed he had "a lily-white frame with limbs as thin as the legs of a ladder-back chair". These findings emphasize the close relationship between muscle atrophy and bone atrophy. In addition to loss of muscle mass during deconditioning, there is a significant loss of muscle strength and a decrease in protein synthesis. Because the decreases in force (strength) are proportionately greater than those in fiber size or muscle cross-sectional area, other contributory factors must be involved; muscle fiber dehydration may be important.

Adaptation to prolonged bedrest in man: A compendium of research. [bibliographies on clinical medicine and human pathology

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Greenleaf, C. J.; Vanderveer, D.; Dorchak, K. J.

1976-01-01

A compilation of major studies that describe the clinical observations and elucidate the physiological mechanisms of the adaptive process of man undergoing prolonged bed rest is presented. Additional studies are included that provide background information in the form of reviews or summaries of the process. Wherever possible a detailed annotation is provided under the subheadings: (1) purpose, (2) procedure and methods, (3) results, and (4) conclusions. Additional references are provided in a selected bibliography.

Impact of insecticide-treated bed nets on malaria transmission indices on the south coast of Kenya

PubMed Central

2011-01-01

Background Besides significantly reducing malaria vector densities, prolonged usage of bed nets has been linked to decline of Anopheles gambiae s.s. relative to Anopheles arabiensis, changes in host feeding preference of malaria vectors, and behavioural shifts to exophagy (outdoor biting) for the two important malaria vectors in Africa, An. gambiae s.l. and Anopheles funestus. In southern coastal Kenya, bed net use was negligible in 1997-1998 when Anopheles funestus and An. gambiae s.s. were the primary malaria vectors, with An. arabiensis and Anopheles merus playing a secondary role. Since 2001, bed net use has increased progressively and reached high levels by 2009-2010 with corresponding decline in malaria transmission. Methods To evaluate the impact of the substantial increase in household bed net use within this area on vector density, vector composition, and human-vector contact, indoor and outdoor resting mosquitoes were collected in the same region during 2009-2010 using pyrethrum spray catches and clay pots for indoor and outdoor collections respectively. Information on bed net use per sleeping spaces and factors influencing mosquito density were determined in the same houses using Poisson regression analysis. Species distribution was determined, and number of mosquitoes per house, human-biting rates (HBR), and entomological inoculation rate (EIR) were compared to those reported for the same area during 1997-1998, when bed net coverage had been minimal. Results Compared to 1997-1998, a significant decline in the relative proportion of An. gambiae s.s. among collected mosquitoes was noted, coupled with a proportionate increase of An. arabiensis. Following > 5 years of 60-86% coverage with bed nets, the density, human biting rate and EIR of indoor resting mosquitoes were reduced by more than 92% for An. funestus and by 75% for An. gambiae s.l. In addition, the host feeding choice of both vectors shifted more toward non-human vertebrates. Besides bed net use, malaria vector abundance was also influenced by type of house construction and according to whether one sleeps on a bed or a mat (both of these are associated with household wealth). Mosquito density was positively associated with presence of domestic animals. Conclusions These entomological indices indicate a much reduced human biting rate and a diminishing role of An. gambiae s.s. in malaria transmission following high bed net coverage. While increasing bed net coverage beyond the current levels may not significantly reduce the transmission potential of An. arabiensis, it is anticipated that increasing or at least sustaining high bed net coverage will result in a diminished role for An. funestus in malaria transmission. PMID:22165904

Mineral and nitrogen metabolic studies, experiment M071

NASA Technical Reports Server (NTRS)

Whedon, G. D.; Lutwak, L.; Rambaut, P. C.; Whittle, M. W.; Smith, M. C., Jr.; Reid, J.; Leach, C. S.; Stadler, C. R.; Sanford, D. D.

1977-01-01

The similarity between bed rest test and space flight effects on human mineral and nitrogen metabolisms indicates impairment of capable musculoskeletal functions. A pattern of urinary calcium increases and total calcium shifts suggests that calcium losses continue with time. Significant losses of nitrogen and phosphorus are associated with reduction in muscle tissue. It is concluded that capable musculoskeletal function is likely to be impaired during space flights of 1 1/2 to 3 years duration.

Sparing of the Neural Stem Cell Compartment During Whole-Brain Radiation Therapy: A Dosimetric Study Using Helical Tomotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsh, James C., E-mail: james_marsh@rush.ed; Godbole, Rohit H.; Herskovic, Arnold M.

2010-11-01

Purpose: To assess the feasibility of dosimetrically sparing the hippocampus and neural stem cell (NSC) compartment during whole-brain radiotherapy (WBRT) and prophylactic cranial irradiation (PCI). Methods and Materials: We contoured the brain/brainstem on fused magnetic resonance /computed tomography images as the planning target volume (PTV) in 10 patients, excluding the hippocampus and NSC compartment as organs at risk. PCI and WBRT helical tomotherapy plans were prepared for each patient, with 1.0-cm field width, a pitch of 0.285, and a modulation factor of 2.5. We attempted to maximally spare the hippocampus and NSC compartment while treating the rest of the brainmore » to 30 Gy in 15 fractions (PCI) or 35 Gy in 14 fractions (WBRT) with a V{sub 100} of {>=}95%. Plan quality was assessed by calculating mean dose, equivalent uniform dose (EUD), and biologically equivalent dose (BED) for organs at risk and the percent volume of the PTV receiving the prescribed dose of V{sub 100}. Results: In the PCI plans, mean doses/EUD/BED for the hippocampus and NSC compartment were 11.5 Gy/13.1 Gy/15.7 Gy{sub 2} (BED assuming alpha/beta ratio of 2Gy) and 11.5 Gy/13.1 Gy/12.3 Gy{sub 10} (BED assuming alpha/beta ratio of 10Gy), respectively. In the WBRT plans, mean doses/EUD/BED for the hippocampus and NSC compartment were 11.8 Gy/14.8 Gy/16.8 Gy{sub 2} and 11.8 Gy/14.8 Gy/12.8 Gy{sub 10}, respectively. The mean V{sub 95} for the rest of the brain (PTV) was 96.9% for both the PCI and WBRT plans. Mean PCI and WBRT treatment times were 15.93 min (range, 14.28 min-17.50 min) and 20.18 min (range, 18.43 min-22.32 min), respectively. Conclusions: It is dosimetrically feasible to spare the hippocampus and NSC compartment using helical tomotherapy during the administration of whole-brain irradiation.« less

Diurnal time-activity budgets of redheads (Aythya americana) wintering in seagrass beds and coastal ponds in Louisiana and Texas

USGS Publications Warehouse

Michot, T.C.; Woodin, M.C.; Adair, S.E.; Moser, E.B.

2006-01-01

Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid- to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations. ?? Springer 2006.

Forearm vasodilatation following release of venous congestion

PubMed Central

Caro, C. G.; Foley, T. H.; Sudlow, M. F.

1970-01-01

1. The volume rate of forearm blood flow was measured with a mercury-in-rubber strain gauge, or with a water-filled plethysmograph, from 1 sec after termination of a 2-3 min period of venous congestion. 2. When congesting pressure had been less than 18 mm Hg, average post-congestion flow (five subjects) was constant during approx. 10 sec and not significantly different from resting flow. 3. When congesting pressure had been 30 mm Hg, average post-congestion flow (eight subjects) was 26% higher than resting, during 3-4 sec after release of congestion, but rose to 273% of resting during 4-6 sec after release of congestion. 4. In other studies forearm vascular resistance had been found normal or increased during such venous congestion, and theoretical studies here indicated that passive mechanical factors could not account for the delayed occurrence of high post-congestion flow. 5. It appears, therefore, that the forearm vascular bed dilates actively shortly after release of substantial venous congestion. It would seem more likely that a myogenic mechanism, rather than a metabolic one, is responsible. PMID:5532541

Effects of Resistive Vibration Exercise Combined with Whey Protein and KHCO3 on Bone Tturnover Markers in Head-down Tilt Bed Rest (MTBR-MNX Study)

NASA Technical Reports Server (NTRS)

Graf, Sonja; Baecker, Natalie; Buehlmeier, Judith; Fischer, Annelie; Smith, Scott M.; Heer, Martina

2014-01-01

High protein intake further increases bone resorption markers in head-down tilt bed rest (HDBR), most likely induced by low-grade metabolic acidosis. Adding an alkaline salt to a diet with high protein content prevents this additional rise of bone resorption markers in HDBR. In addition, high protein intake, specifically whey protein, increases muscle protein synthesis and improves glucose tolerance, which both are affected by HDBR. Resistive vibration exercise (RVE) training counteracts the inactivity-induced bone resorption during HDBR. To test the hypothesis that WP plus alkaline salt (KHCO3) together with RVE during HDBR will improve bone turnover markers, we conducted a randomized, three-campaign crossover design study with 12 healthy, moderately fit male subjects (age 34+/-8 y, body mass [BM] 70 +/- 8 kg). All study campaigns consisted of a 7-d ambulatory period, 21days of -6 deg. head-down tilt bed rest (HDBR), and a 6-d recovery period. Diet was standardized and identical across phases. In the control (CON) campaign, subjects received no supplement or RVE. In the intervention campaigns, subjects received either RVE alone or combined with WP and KHCO3 (NEX). WP was applied in 3 doses per day of 0.6 g WP/kg BM together with 6 doses of 15 mmol KHCO3 per day. Eleven subjects completed the RVE and CON campaign, 8 subjects completed all three campaigns. On day 21 of HDBR excretion of the bone resorption marker C-telopeptide (CTX) was 80+/-28% (p<0.001) higher than baseline, serum calcium concentrations increased by 12 +/- 29% (p<0.001) and serum osteocalcin concentrations decreased by 6+/-12% (p=0.001). Urinary CTX excretion was 11+/- 25% (p=0.02) lower on day 21 of HDBR in the RVE- and tended to decrease by 3+/- 22% (p=0.06) in the NEX campaign compared to CON. Urinary calcium excretion was higher on day 21 in HDBR in the RVE and NEX (24+/- 43% p=0.01; 25+/- 37% p=0.03) compared to the CON campaign. We conclude that combination of RVE with WP/KHCO3 was not superior to RVE alone in any of these results.

A Hydrodynamic Characteristic of a Dual Fluidized Bed Gasification

NASA Astrophysics Data System (ADS)

Sung, Yeon Kyung; Song, Jae Hun; Bang, Byung Ryeul; Yu, Tae U.; Lee, Uen Do

A cold model dual fluidized bed (DFB) reactor, consisting of two parallel interconnected bubbling and fast fluidized beds, was designed for developing an auto-thermal biomass gasifier. The combustor of this system burns the rest char of the gasification process and provides heat to the gasifier by circulating solids inventory. To find an optimal mixing and circulation of heavy solid inventory and light biomass and char materials, we investigate two types of DFB reactors which have different configuration of distributor and way-out location of the solid inventory and char materials in the gasifier. To determine appropriate operating conditions, we measured minimum fluidization velocity, solid circulation rate, axial solid holdup and gas bypassing between the lower loop seal and the gasifier.

An international collaboration studying the physiological and anatomical cerebral effects of carbon dioxide during head-down tilt bed rest: the SPACECOT study.

PubMed

Marshall-Goebel, Karina; Mulder, Edwin; Donoviel, Dorit; Strangman, Gary; Suarez, Jose I; Venkatasubba Rao, Chethan; Frings-Meuthen, Petra; Limper, Ulrich; Rittweger, Jörn; Bershad, Eric M

2017-06-01

Exposure to the microgravity environment results in various adaptive and maladaptive physiological changes in the human body, with notable ophthalmic abnormalities developing during 6-mo missions on the International Space Station (ISS). These findings have led to the hypothesis that the loss of gravity induces a cephalad fluid shift, decreased cerebral venous outflow, and increased intracranial pressure, which may be further exacerbated by increased ambient carbon dioxide (CO 2 ) levels on the ISS. Here we describe the SPACECOT study (studying the physiological and anatomical cerebral effects of CO 2 during head-down tilt), a randomized, double-blind crossover design study with two conditions: 29 h of 12° head-down tilt (HDT) with ambient air and 29 h of 12° HDT with 0.5% CO 2 The internationally collaborative SPACECOT study utilized an innovative approach to study the effects of headward fluid shifting induced by 12° HDT and increased ambient CO 2 as well as their interaction with a focus on cerebral and ocular anatomy and physiology. Here we provide an in-depth overview of this new approach including the subjects, study design, and implementation, as well as the standardization plan for nutritional intake, environmental parameters, and bed rest procedures. NEW & NOTEWORTHY A new approach for investigating the combined effects of cephalad fluid shifting and increased ambient carbon dioxide (CO 2 ) is presented. This may be useful for studying the neuroophthalmic and cerebral effects of spaceflight where cephalad fluid shifts occur in an elevated CO 2 environment. Copyright © 2017 the American Physiological Society.

Cortisol, insulin and leptin during space flight and bed rest

NASA Technical Reports Server (NTRS)

Stein, T. P.; Schluter, M. D.; Leskiw, M. J.

1999-01-01

Most ground based models for studying muscle atrophy and bone loss show reasonable fidelity to the space flight situation. However there are some differences. Investigation of the reasons for these differences can provide useful information about humans during space flight and aid in the refinement of ground based models. This report discusses three such differences, the relationships between: (i) cortisol and the protein loss, (ii) cortisol and ACTH and (iii) leptin, insulin and food intake.

Electromyography-based analysis of human upper limbs during 45-day head-down bed-rest

NASA Astrophysics Data System (ADS)

Fu, Anshuang; Wang, Chunhui; Qi, Hongzhi; Li, Fan; Wang, Zheng; He, Feng; Zhou, Peng; Chen, Shanguang; Ming, Dong

2016-03-01

Muscle deconditioning occurs in response to simulated or actual microgravity. In spaceflight, astronauts become monkey-like for mainly using their upper limbs to control the operating system and to complete corresponding tasks. The changes of upper limbs' athletic ability will directly affect astronauts' working performance. This study investigated the variation trend of surface electromyography (sEMG) during prolonged simulated microgravity. Eight healthy males participating in this study performed strict 45-day head-down bed-rest (HDBR). On the 5th day of pre-HDBR, and the 15th, the 30th and the 45th days of HDBR, the subjects performed maximum pushing task and maximum pulling task, and sEMG was collected from upper limbs synchronously. Each subject's maximum volunteer contractions of both the tasks during these days were compared, showing no significant change. However, changes were detected by sEMG-based analysis. It was found that integrated EMG, root mean square, mean frequency, fuzzy entropy of deltoid, and fuzzy entropy of triceps brachii changed significantly when comparing pre-HDBR with HDBR. The variation trend showed a recovery tendency after significant decline, which is inconsistent with the monotonic variation of lower limbs that was proved by previous research. These findings suggest that EMG changes in upper limbs during prolonged simulated microgravity, but has different variation trend from lower limbs.

Postdural puncture headache

PubMed Central

2017-01-01

Postdural puncture headache (PDPH) is a common complication after inadvertent dural puncture. Risks factors include female sex, young age, pregnancy, vaginal delivery, low body mass index, and being a non-smoker. Needle size, design, and the technique used also affect the risk. Because PDPH can be incapacitating, prompt diagnosis and treatment are mandatory. A diagnostic hallmark of PDPH is a postural headache that worsens with sitting or standing, and improves with lying down. Conservative therapies such as bed rest, hydration, and caffeine are commonly used as prophylaxis and treatment for this condition; however, no substantial evidence supports routine bed rest and aggressive hydration. An epidural blood patch is the most effective treatment option for patients with unsuccessful conservative management. Various other prophylactic and treatment interventions have been suggested. However, due to a lack of conclusive evidence supporting their use, the potential benefits of such interventions should be weighed carefully against the risks. This article reviews the current literature on the diagnosis, risk factors, pathophysiology, prevention, and treatment of PDPH. PMID:28367283

Effects of 5-Days Head-Down Bed-Rest, with and without Artificial Gravity Countermeasure, on Left Ventricular Dimensions

NASA Astrophysics Data System (ADS)

Caiani, E. G.; Massabuau, P.; Weinert, L.; Lairez, O.; Berry, M.; Vaida, P.; Lang, R. M.

2013-02-01

Our aims were: 1) to assess the effects of 5-days of strict head-down (-6 degrees) bed-rest (BR) deconditioning on left ventricular (LV) size and mass by echocardiography; 2) to test the effectiveness of artificial gravity (AG) to prevent LV changes. Methods. Twelve healthy men (mean age 33±7) were enrolled in a cross-over design: each subject repeated the BR (MEDES, Toulouse) without countermeasures (CTRL), with AG applied daily for 30’ continuously (AG1), and for 30’ intermittently (AG2). Transthoracic echocardiography (iE33, Philips) was performed before (BCD-5), at the end of BR (R+0), and 3 days after (R+2). Two-way ANOVA with repeated measures was applied. Results. Despite the smaller changes in AG1 and AG2, no differences were found between groups and interactions. Cardiac adaptation to deconditioning affected LV mass and volumes, and AG countermeasure, when applied either continuously or intermittently, was not effective in preventing their loss.

The Gravity of LBNP Exercise: Lessons Learned from Identical Twins in Bed for 30 Days

NASA Technical Reports Server (NTRS)

Hargens, Alan R.; Groppo, Eli R.; Lee, Stuart M. C.; Watenpaugh, Donald; Schneider, Suzanne; O'Leary, Deborah; Smith, Scott M.; Steinbach, Gregory C.; Tanaka, Kunihiko; Kimura, Shinji;

Metabolic energy requirements for space flight

NASA Technical Reports Server (NTRS)

Lane, Helen W.

1992-01-01

The international space community, including the USSR, Japan, Germany, the European Space Agency, and the US, is preparing for extended stays in space. Much of the research planned for space will be tended by humans, thus, maintaining adequate nutritional status during long stays in space has lately become an issue of much interest. Historically, it appears that minimum nutritional requirements are being met during stays in space. Thus far, crewmembers have been able to consume food adequate for maintaining nominal performance in microgravity. The physiological data obtained from ground-based and flight research that may enable us to understand the biochemical alterations that effect energy utilization and performance. Focus is on energy utilization during the Apollo lunar missions, Skylab's extended space lab missions, and Space Shuttle flights. Available data includes those recorded during intra- and extravehicular activities as well as during microgravity simulation (bed rest). Data on metabolism during flight and during bed rest are discussed, with a follow-up on human gastrointestinal function.

Space Flight Effects on Intracellular Ions in Sublingual Cells of Non-Human Primates

NASA Technical Reports Server (NTRS)

Arnaud, Sara B.; Dotsenko, R.; Fung, P.; Navidi, M.; Silver, B.; Wade, Charles E. (Technical Monitor)

1994-01-01

We have used a novel technique that quantifies minerals and electrolytes from smears of sublingual cells by x-ray microanalysis to monitor metabolic changes in bed rest subjects. Increases in intracellular calcium (Ca), phosphorus (P), and potassium (K) were characteristic of subjects whose exercise regimen was inadequate to maintain calcium metabolism. To test the effects of space flight on intracellular ions, we analyzed cells from 2-4 kg Rhesus monkeys before and after 2 weeks in space or chair restraint (CR). There were increases in sublingual cell Ca, P and K after space flight which paralleled the clinical estimates of metabolic status of the animals and exceeded the levels found during CR on R+11. Increases after 2 weeks CR were 26% in Ca, 6% in P and 29% in K. Species similarity ill responses of intracellular ions to inactivity imposed by bed rest, restraint or microgravity suggest that this innovative non-invasive technique would be a useful in-flight monitor of exercise countermeasures directed toward maintaining calcium balance.

Alternative marine and fluvial models for the non-fossiliferous quartzitic sandstones of the Early Proterozoic Daspoort Formation, Transvaal Sequence of southern Africa

NASA Astrophysics Data System (ADS)

Eriksson, P. G.; Schreiber, U. M.; van der Neut, M.; Labuschagne, H.; Van Der Schyff, W.; Potgieter, G.

1993-04-01

This paper discusses some of the problems related to the palaeoenvironmental interpretation of non-fossiliferous, early Precambrian, recrystallised quartzitic sandstones, using the Early Proterozoic Daspoort Formation, Transvaal Sequence of southern Africa as a case study. These cross-bedded and planar stratified rocks have been interpreted previously as shallow marine deposits, based on limited studies of areas with well-exposed, relatively undeformed outcrops. This postulate rests largely on the apparently mature nature of the recrystallised sandstones and their thin bedding. Examination of outcrops throughout the preserved basin, including those which have been deformed and metamorphosed, reveals the presence of subordinate immature sandstones. Lateral facies relationships permit an alternative distal fan-fluvial braidplain model to be proposed. This is compatible with collected palaeocurrent data, thicknes trends and results of thin section petrography.

Effects of prolonged head-down bed rest on physiological responses to moderate hypoxia

NASA Technical Reports Server (NTRS)

Loeppky, J. A.; Roach, R. C.; Selland, M. A.; Scotto, P.; Greene, E. R.; Luft, U. C.

1993-01-01

To determine the effects of hypoxia on physiological responses to simulated zero-gravity cardiopulmonary and fluid balance measurements were made in 6 subjects before and during 5-degree head-down bed rest (HDBR) over 8 d at 10,678 ft and a second time at this altitude as controls (CON). The V-dot(O2)(max) increased by 9 percent after CON, but fell 3 percent after HDBR. This reduction in work capacity during HDBR could be accounted for by inactivity. The heart rate response to a head-up tilt was greatly enhanced following HDBR, while mean blood pressure was lower. No significant negative impact of HDBR was noted on the ability to acclimatize to hypoxia in terms of pulmonary mechanics, gas exchange, circulatory or mental function measurements. No evidence of pulmonary interstitial edema or congestion was noted during HDBR at the lower PIO2 and blood rheology properties were not negatively altered. Symptoms of altitude illness were more prevalent, but not marked, during HDBR and arterial blood gases and oxygenation were not seriously effected by simulated microgravity. Declines in base excess with altitude were similar in both conditions. The study demonstrated a minimal effect of HDBR on the ability to adjust to this level of hypoxia.

The relationship between dietary intake, exercise, energy balance and the space craft environment

NASA Technical Reports Server (NTRS)

Stein, T. P.

2000-01-01

Space flight is associated with the loss of skeletal muscle, principally from muscles with anti-gravity functions. Examination of data across different missions can permit a distinction to be made between true microgravity responses and what are mission-specific responses. Protein metabolism has been investigated on six missions, four short-term [Shuttle missions Space Life Sciences 1 (1991, SLSI), Space Life Sciences 2 (1993, SLS2), Deutsche-2 (1993, D2) and the Life and Microgravity Sciences (1996, LMS)] and two long-term missions (Skylab 1993 and NASA/MIR, 1996-1998). Measurements made include dietary intake (six missions), nitrogen balance (four missions), whole-body protein kinetics with [15N]glycine as the tracer (four missions) and cortisol excretion (three missions). Also available for comparison are bed rest studies with and without exercise. The purpose of this paper is to see what can be learnt about the muscle loss problem by comparing metabolic results across the six missions for which data are available and against bed rest. The analysis suggests that there is a linkage between the inability to maintain energy balance and exercise, and the connection is the decreased efficiency of removal of the metabolic by-products of exercise (heat, CO2) during space flight.

Reduction in nerve root compression by the nucleus pulposus after Feng's Spinal Manipulation☆

PubMed Central

Feng, Yu; Gao, Yan; Yang, Wendong; Feng, Tianyou

2013-01-01

Ninety-four patients with lumbar intervertebral disc herniation were enrolled in this study. Of these, 48 were treated with Feng's Spinal Manipulation, hot fomentation, and bed rest (treatment group). The remaining 46 patients were treated with hot fomentation and bed rest only (control group). After 3 weeks of treatment, clinical parameters including the angle of straight-leg raising, visual analogue scale pain score, and Japanese Orthopaedic Association score for low back pain were improved. The treatment group had significantly better improvement in scores than the control group. Magnetic resonance myelography three-dimensional reconstruction imaging of the vertebral canal demonstrated that filling of the compressed nerve root sleeve with cerebrospinal fluid increased significantly in the treatment group. The diameter of the nerve root sleeve was significantly larger in the treatment group than in the control group. However, the sagittal diameter index of the herniated nucleus pulposus and the angle between the nerve root sleeve and the thecal sac did not change significantly in either the treatment or control groups. The effectiveness of Feng's Spinal Manipulation for the treatment of symptoms associated with lumbar intervertebral disc herniation may be attributable to the relief of nerve root compression, without affecting the herniated nucleus pulposus or changing the morphology or position of the nerve root. PMID:25206408

Changes of Cytokines during a Spaceflight Analog - a 45-Day Head-Down Bed Rest

PubMed Central

Zhang, Shusong; Pang, Xuewen; Liu, Hongju; Li, Li; Sun, Xiuyuan; Zhang, Yu; Wu, Hounan; Chen, Xiaoping; Ge, Qing

2013-01-01

Spaceflight is associated with deregulation in the immune system. Head-down bed rest (HDBR) at -6° is believed to be the most practical model for examining multi-system responses to microgravity in humans during spaceflight. In the present study, a 45-day HDBR was performed to investigate the alterations in human immune cell distributions and their functions in response to various stimuli. The effect of countermeasure, Rhodiola rosea (RR) treatment, was also examined. A significant decrease of interferon-γ (IFN-γ) and interleukin-17 (IL-17) productions by activated T cells, increase of IL-1β and IL-18 by activated B and myeloid cells were observed during HDBR. The upregulation of serum cortisol was correlated with the changes of IL-1 family cytokines. In addition, a significant increase of memory T and B cell and regulatory T cells (Treg) were also detected. The uptake of RR further decreased IFN-γ level and slowed down the upregulation of IL-1 family cytokines. These data suggest that for prolonged HDBR and spaceflight, the decreased protective T cell immunity and enhanced proinflammatory cytokines should be closely monitored. The treatment with RR may play an important role in suppressing proinflammatory cytokines but not in boosting protective T cell immunity. PMID:24143230

Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest

PubMed Central

Aubert, André E.

2015-01-01

Spaceflight and head-down bed rest (HDBR) can induce the orthostatic intolerance (OI); the mechanisms remain to be clarified. The aim of this study was to determine whether or not OI after HDBR relates to the degree of autonomic cardiovascular adaptation. Fourteen volunteers were enrolled for 60 days of HDBR. A head-up tilt test (HUTT) was performed before and after HDBR. Our data revealed that, in all nonfainters, there was a progressive increase in heart rate over the course of HDBR, which remained higher until 12 days of recovery. The mean arterial pressure gradually increased until day 56 of HDBR and returned to baseline after 12 days of recovery. Respiratory sinus arrhythmia and baroreflex sensitivity decreased during HDBR and remained suppressed until 12 days of recovery. Low-frequency power of systolic arterial pressure increased during HDBR and remained elevated during recovery. Three subjects fainted during the HUTT after HDBR, in which systemic vascular resistance did not increase and remained lower until syncope. None of the circulatory patterns significantly differed between the fainters and the nonfainters at any time point. In conclusion, our data indicate that the impaired orthostatic tolerance after HDBR could not be distinguished by estimation of normal hemodynamic and/or neurocardiac data. PMID:26425559

Isokinetic strength and endurance during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Bernauer, E. M.; Ertl, A. C.; Bulbulian, R.; Bond, M.

1994-01-01

The purpose of our study was to determine if an intensive, intermittent, isokinetic, lower extremity exercise training program would attenuate or eliminate the decrease of muscular strength and endurance during prolonged bed rest (BR). The 19 male subjects (36 +/- 1 yr, 178 +/- 2 cm, 76.5 +/- 1.7 kg) were allocated into a no exercise (NOE) training group (N = 5), an isotonic (lower extremity cycle ergometer) exercise (ITE) training group (N = 7), and an isokinetic (isokinetic knee flexion-extension) exercise (IKE) training group (N = 7). Peak knee (flexion and extension) and shoulder (abduction-adduction) functions were measured weekly in all groups with one 5-repetition set. After BR, average knee extension total work decreased by 16% with NOE, increased by 27% with IKE, and was unchanged with ITE. Average knee flexion total work and peak torque (strength) responses were unchanged in all groups. Force production increased by 20% with IKE and was unchanged with NOE and ITE. Shoulder total work was unchanged in all groups, while gross average peak torque increased by 27% with ITE and by 22% with IKE, and was unchanged with NOE. Thus, while ITE training can maintain some isokinetic functions during BR, maximal intermittent IKE training can increase other functions above pre-BR control levels.

Isokinetic Strength and Endurance During 30-day 6 deg Head-Down Bed Rest with Isotonic and Isokinetic Exercise Training

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Bernauer, E. M.; Ertl, A. C.; Bond, M.; Bulbulian, R.

1994-01-01

The purpose of our study was to determine if an intensive, intermittent, isokinetic, lower extremity exercise training program would attenuate or eliminate the decrease of muscular strength and endurance during prolonged bed rest (BR). The 19 male subjects (36 +/- 1 yr, 178 +/- 2 cm, 76.5 +/- 1.7 kg) were allocated into a no exercise (NOE) training group (N = 5), an isotonic (lower extremity cycle orgometer) exercise (ITE) training group (N = 7), and an isokinetic (isokinetic knee flexion-extension) exercise (IKE) training group (N = 7). Peak knee (flexion and extension) and shoulder (abduction-adduction) functions were measured weekly in all groups with one 5-repetition set. After BR, average knee extension total work decreased by 16% with NOE, increased by 27% with IKE, and was unchanged with ITE. Average knee flexion total work and peak torque (strength) responses were unchanged in all groups. Force production increased by 20% with IKE and was unchanged with NOE and ITE. Shoulder total work was unchanged in all groups, while gross average peak torque increased by 27% with ITE and by 22% with IKE, and was unchanged with NOE. Thus, while ITE training can maintain some isokinetic functions during BR, maximal intermittent IKE training can increase other functions above pre-BR control levels.

Analysis and experiments for a system of two spacecraft paired by means of a flexible link

NASA Astrophysics Data System (ADS)

Sabatini, Marco; Palmerini, Giovanni B.; Gasbarri, Paolo

2016-11-01

A field of current interest in space technology is the on-orbit operation concept, often requiring that a chaser spacecraft captures a target spacecraft. The physical link connecting the two satellites is usually characterized by a high degree of flexibility, because of the special requirements imposed to the space systems, and specifically the constraints on the mass at launch. The focus of this paper is the study of an attitude control of the paired spacecraft system such that the elastic oscillations do not interfere with the attitude dynamics, and the final configuration is reached without residual vibrations. At the scope, a rest-to-rest techniques, that requires an accurate description of the dynamic model of the paired satellites as a flexible multibody setup, is applied. The results of this control are first tested by means of a numerical tool, simulating nominal and non-nominal scenarios. Then the identified control is proved in an experimental test-bed, consisting of two free-floating platforms connected by means of an elastic joint. The performance of the rest-to-rest technique is compared to other classical control laws aiming to minimally excite the system undesired dynamics, showing a promising superiority.

Water tribology on graphene.

PubMed

N'guessan, Hartmann E; Leh, Aisha; Cox, Paris; Bahadur, Prashant; Tadmor, Rafael; Patra, Prabir; Vajtai, Robert; Ajayan, Pulickel M; Wasnik, Priyanka

2012-01-01

Classical experiments show that the force required to slide liquid drops on surfaces increases with the resting time of the drop, t(rest), and reaches a plateau typically after several minutes. Here we use the centrifugal adhesion balance to show that the lateral force required to slide a water drop on a graphene surface is practically invariant with t(rest). In addition, the drop's three-phase contact line adopts a peculiar micrometric serrated form. These observations agree well with current theories that relate the time effect to deformation and molecular re-orientation of the substrate surface. Such molecular re-orientation is non-existent on graphene, which is chemically homogenous. Hence, graphene appears to provide a unique tribological surface test bed for a variety of liquid drop-surface interactions.

Assessing the benefits of napping and short rest breaks on processing speed in sleep-restricted adolescents.

PubMed

Lim, Julian; Lo, June C; Chee, Michael W L

2017-04-01

Achievement-oriented adolescents often study long hours under conditions of chronic sleep restriction, adversely affecting cognitive function. Here, we studied how napping and rest breaks (interleaved off-task periods) might ameliorate the negative effects of sleep restriction on processing speed. Fifty-seven healthy adolescents (26 female, age = 15-19 years) participated in a 15-day live-in protocol. All participants underwent sleep restriction (5 h time-in-bed), but were then randomized into two groups: one of these groups received a daily 1-h nap opportunity. Data from seven of the study days (sleep restriction days 1-5, and recovery days 1-2) are reported here. The Blocked Symbol Decoding Test, administered once a day, was used to assess time-on-task effects and the effects of rest breaks on processing speed. Controlling for baseline differences, participants who took a nap demonstrated faster speed of processing and greater benefit across testing sessions from practice. These participants were also affected significantly less by time-on-task effects. In contrast, participants who did not receive a nap benefited more from the rest breaks that were permitted between blocks of the test. Our results indicate that napping partially reverses the detrimental effects of sleep restriction on processing speed. However, rest breaks have a greater effect as a countermeasure against poor performance when sleep pressure is higher. These data add to the growing body of evidence showing the importance of sleep for good cognitive functioning in adolescents, and suggest that more frequent rest breaks might be important in situations where sleep loss is unavoidable. © 2017 European Sleep Research Society.

Oxidant damage during and after spaceflight

NASA Technical Reports Server (NTRS)

Stein, T. P.; Leskiw, M. J.

2000-01-01

The objectives of this study were to assess oxidant damage during and after spaceflight and to compare the results against bed rest with 6 degrees head-down tilt. We measured the urinary excretion of the F(2) isoprostane, 8-iso-prostaglandin (PG) F(2alpha), and 8-oxo-7,8-dihydro-2 deoxyguanosine (8-OH DG) before, during, and after long-duration spaceflight (4-9 mo) on the Russian space station MIR, short-duration spaceflight on the shuttle, and 17 days of bed rest. Sample collections on MIR were obtained between 88 and 186 days in orbit. 8-iso-PGF(2alpha) and 8-OH DG are markers for oxidative damage to membrane lipids and DNA, respectively. Data are mean +/- SE. On MIR, isoprostane levels were decreased inflight (96. 9 +/- 11.6 vs. 76.7 +/- 14.9 ng. kg(-1). day(-1), P < 0.05, n = 6) due to decreased dietary intake secondary to impaired thermoregulation. Isoprostane excretion was increased postflight (245.7 +/- 55.8 ng. kg(-1). day(-1), P < 0.01). 8-OH DG excretion was unchanged with spaceflight and increased postflight (269 +/- 84 vs 442 +/- 180 ng. kg(-1). day(-1), P < 0.05). On the shuttle, 8-OH DG excretion was unchanged in- and postflight, but 8-iso-PGF(2alpha) excretion was decreased inflight (15.6 +/- 4.3 vs 8.0 +/- 2.7 ng. kg(-1). day(-1), P < 0.05). No changes were found with bed rest, but 8-iso-PGF(2alpha) was increased during the recovery phase (48.9 +/- 23.0 vs 65.4 +/- 28.3 ng. kg(-1). day(-1), P < 0.05). The changes in isoprostane production were attributed to decreased production of oxygen radicals from the electron transport chain due to the reduced energy intake inflight. The postflight increases in the excretion of the products of oxidative damage were attributed to a combination of an increase in metabolic activity and the loss of some host antioxidant defenses inflight. We conclude that 1) oxidative damage was decreased inflight, and 2) oxidative damage was increased postflight.

A novel phytomyxean parasite associated with galls on the bull-kelp Durvillaea antarctica (Chamisso) Hariot.

PubMed

Goecke, Franz; Wiese, Jutta; Núñez, Alejandra; Labes, Antje; Imhoff, Johannes F; Neuhauser, Sigrid

2012-01-01

Durvillaea antarctica (Fucales, Phaeophyceae) is a large kelp of high ecological and economic significance in the Southern Hemisphere. In natural beds along the central coast of Chile (Pacific Ocean), abnormal growth characterized by evident gall development and discolorations of the fronds/thallus was observed. Analysing these galls by light microscopy and scanning electron microscopy revealed the presence of endophytic eukaryotes showing typical characteristics for phytomyxean parasites. The parasite developed within enlarged cells of the subcortical tissue of the host. Multinucleate plasmodia developed into many, single resting spores. The affiliation of this parasite to the Phytomyxea (Rhizaria) was supported by 18S rDNA data, placing it within the Phagomyxida. Similar microorganisms were already reported once 23 years ago, indicating that these parasites are persistent and widespread in D. antarctica beds for long times. The symptoms caused by this parasite are discussed along with the ecological and economic consequences. Phytomyxean parasites may play an important role in the marine ecosystem, but they remain understudied in this environment. Our results demonstrate for the first time the presence of resting spores in Phagomyxida, an order in which resting spores were thought to be absent making this the first record of a phagomyxean parasite with a complete life cycle so far, challenging the existing taxonomic concepts within the Phytomyxea. The importance of the here described resting spores for the survival and ecology of the phagomyxid parasite will be discussed together with the impact this parasite may have on 'the strongest seaweed of the world', which is an important habitat forming and economic resource from the Southern Hemisphere.

Measurement of the temporal progression of scour in a pool-riffle sequence in a gravel bed stream using an electronic scour monitor

NASA Astrophysics Data System (ADS)

Devries, Paul; Burges, Stephen J.; Daigneau, Julie; Stearns, Daniel

2001-11-01

A relatively inexpensive prototype monitor was designed and developed to record temporal variation in scour depth and was field-tested in a gravel bed stream. The device consists of plastic practice golf balls that are fitted internally with ring magnets and strung on a two-conductor cable enclosing a small reed switch. The balls are installed and oriented near-vertically in the streambed. As each ball is disturbed and released, it slides along the cable past the reed switch, and the time of circuit closure caused by passage of the magnet is recorded by a data logger. The device can be applied in arrays that span large areas of the streambed, including in wide channels that are inaccessible during a flood. Data obtained from 19 devices installed in an aggrading site described scouring processes in a pool-riffle interface during a bed load transport event. Substantial bed excavation occurred in the region of the pool edge during the rising stage, indicating existence of a local, temporally varying imbalance in bed load transport rate. Bed disturbance in the rest of the site prior to aggradation was limited to the surface and immediate subpavement layer.

Advection and dispersion of bed load tracers

NASA Astrophysics Data System (ADS)

Lajeunesse, Eric; Devauchelle, Olivier; James, François

2018-05-01

We use the erosion-deposition model introduced by Charru et al. (2004) to numerically simulate the evolution of a plume of bed load tracers entrained by a steady flow. In this model, the propagation of the plume results from the stochastic exchange of particles between the bed and the bed load layer. We find a transition between two asymptotic regimes. The tracers, initially at rest, are gradually set into motion by the flow. During this entrainment regime, the plume is strongly skewed in the direction of propagation and continuously accelerates while spreading nonlinearly. With time, the skewness of the plume eventually reaches a maximum value before decreasing. This marks the transition to an advection-diffusion regime in which the plume becomes increasingly symmetrical, spreads linearly, and advances at constant velocity. We analytically derive the expressions of the position, the variance, and the skewness of the plume and investigate their asymptotic regimes. Our model assumes steady state. In the field, however, bed load transport is intermittent. We show that the asymptotic regimes become insensitive to this intermittency when expressed in terms of the distance traveled by the plume. If this finding applies to the field, it might provide an estimate for the average bed load transport rate.

iss051e034105

NASA Image and Video Library

2017-05-02

iss051e034105 (May 2, 2017) --- Commander Peggy Whitson is working on the OsteoOmics bone cell study that utilizes the Microgravity Science Glovebox inside the U.S. Destiny laboratory. OsteoOmics investigates the molecular mechanisms that dictate bone loss in microgravity by examining osteoblasts, which form bone, and osteoclasts, which dissolves bone. This leads to better preventative care or therapeutic treatments for people suffering bone loss as a result of bone diseases like osteopenia and osteoporosis, or for patients on prolonged bed rest.

The Artificial Gravity Bed Rest Pilot Project: Effects on Knee Extensor and Plantar Flexor Muscle Groups

NASA Technical Reports Server (NTRS)

Caiozzo, V. J.; Haddad, F.; Lee, S.; Baker, M.; Baldwin, K. M.

2007-01-01

The goal of this project was to examine the effects of artificial gravity (2.5 g) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) control (C) group (N=7); and 2) an AG group (N=8), which was exposed to 21 days of bed-rest plus daily 1 hr exposures to AG (2.5 g). This particular experiment was part of an integrated AG Pilot Project sponsored by NASA/Johnson Space Center. The in vivo torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre and post treatment. Also, pre- and post treatment biopsy samples were obtained from both the vastus lateralis and soleus muscles and were used, in part, for a series of analyses on gene expression (mRNA abundance) of key factors implicated in the anabolic versus catabolic state of the muscle. Post/Pre toque-velocity determinations revealed greater decrements in knee extensor performance in the C versus AG group (P less than 0.04). The plantar flexor muscle group of the AG subjects actually demonstrated a net gain in torque-velocity relationship; whereas, in the C group the overall post/pre responses declined (AG vs C; P less than 0.001). Measurements of muscle fiber cross-sectional area (for both muscles) demonstrated a loss of approx. 20% in the C group while no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity (IGF-1, IGF-1 BP4, mechano growth factor, total RNA, and pro-collagen 3a) were higher in the AG group, whereas catabolic markers (myostatin and atrogen) were elevated in the C group. Importantly, these patterns were seen in both muscles. Based on these observations we conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading states. These findings also warrant further studies since it is likely that other robust paradigms of AG that employ various exercise strategies may be more effective in counteracting long duration unloading states as anticipated on the platforms of the Moon and Mars.

Disrupted resting-state brain network properties in obesity: decreased global and putaminal cortico-striatal network efficiency.

PubMed

Baek, K; Morris, L S; Kundu, P; Voon, V

2017-03-01

The efficient organization and communication of brain networks underlie cognitive processing and their disruption can lead to pathological behaviours. Few studies have focused on whole-brain networks in obesity and binge eating disorder (BED). Here we used multi-echo resting-state functional magnetic resonance imaging (rsfMRI) along with a data-driven graph theory approach to assess brain network characteristics in obesity and BED. Multi-echo rsfMRI scans were collected from 40 obese subjects (including 20 BED patients) and 40 healthy controls and denoised using multi-echo independent component analysis (ME-ICA). We constructed a whole-brain functional connectivity matrix with normalized correlation coefficients between regional mean blood oxygenation level-dependent (BOLD) signals from 90 brain regions in the Automated Anatomical Labeling atlas. We computed global and regional network properties in the binarized connectivity matrices with an edge density of 5%-25%. We also verified our findings using a separate parcellation, the Harvard-Oxford atlas parcellated into 470 regions. Obese subjects exhibited significantly reduced global and local network efficiency as well as decreased modularity compared with healthy controls, showing disruption in small-world and modular network structures. In regional metrics, the putamen, pallidum and thalamus exhibited significantly decreased nodal degree and efficiency in obese subjects. Obese subjects also showed decreased connectivity of cortico-striatal/cortico-thalamic networks associated with putaminal and cortical motor regions. These findings were significant with ME-ICA with limited group differences observed with conventional denoising or single-echo analysis. Using this data-driven analysis of multi-echo rsfMRI data, we found disruption in global network properties and motor cortico-striatal networks in obesity consistent with habit formation theories. Our findings highlight the role of network properties in pathological food misuse as possible biomarkers and therapeutic targets.

[A hospital stay without bedsores].

PubMed

Papas, Anne; Dérémience, Virginie; Tettiravou, Lucia; De Poix, Alix Tyrel

2013-10-01

A hospital stay without bedsores. The skin of elderly people is thin and fragile. After extended bed-rest, the skin's resources are rapidly depleted. The risk of bedsores becomes imminent. But a high-quality multi-disciplinary partnership can prevent bedsores in elderly patients with multiple illnesses. Example around a clinical case.

In vivo measurement of human body composition

NASA Technical Reports Server (NTRS)

Pace, N.

1974-01-01

The time course of physiological changes that occur during the first 21 days of continuous bed rest was examined. The test involved a total of 14 men in the age range of 25 to 36 years. The subjects were divided into groups and tested on a staggered schedule. Results are presented.

14 CFR 117.3 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... or physical performance capability resulting from lack of sleep or increased physical activity that... that provides a flightcrew member with a sleep opportunity. (1) Class 1 rest facility means a bunk or... ability to control light that provides a flightcrew member with the ability to sleep either in a bed, bunk...

Nutrient uptake by marshes and seagrasses: Ecosystem functions and spatial variability in the provision of this ecosystem servoce

EPA Science Inventory

Nitrogen entering coastal wetlands undergoes several important transformations involving oxidation and reduction; some ends up in the atmosphere, while much of it remains in the sediments of healthy marshes and seagrass beds – the rest passes into receiving waters. Variability i...

Bright Light Delights: Effects of Daily Light Exposure on Emotions, Restactivity Cycles, Sleep and Melatonin Secretion in Severely Demented Patients.

PubMed

Münch, Mirjam; Schmieder, Michael; Bieler, Katharina; Goldbach, Rolf; Fuhrmann, Timo; Zumstein, Naomi; Vonmoos, Petra; Scartezzini, Jean-Louis; Wirz-Justice, Anna; Cajochen, Christian

2017-01-01

We tested whether the effects of a dynamic lighting system are superior to conventional lighting on emotions, agitation behaviour, quality of life, melatonin secretion and circadian restactivity cycles in severely demented patients. As a comparison, an age matched control patient group was exposed to conventional lighting. For none of the output measures were significant differences between the two lighting conditions found during the 8 study weeks in fall/winter. Thus, we divided the patient cohort (n = 89) into two groups, solely based on the median of their daily individual light exposure. Patients with higher average daily light exposure (>417 lx) showed significantly longer emotional expressions of pleasure and alertness per daily observations than patients with lower daily light exposure. Moreover, they had a higher quality of life, spent less time in bed, went to bed later and initiated their sleep episodes later, even though the two groups did not differ with respect to age, severity of cognitive impairment and mobility. In general, men were more agitated, had shorter sleep with more wake episodes, had a lower circadian amplitude of relative rest-wake activity and interdaily circadian stability than women. In particular, lower daily light exposures significantly predicted lower circadian amplitudes of rest-activity cycles in men but not in women. This may indicate sex specific susceptibility to daily light exposures for rest-activity regulation in older demented patients. Our results provide evidence that a higher daily light exposure has beneficial effects on emotions and thus improved quality of life in a severely demented patient group. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.