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Physical inactivity increases cardiometabolic risk through a variety of mechanisms, among which alterations of immunological, metabolic, and autonomic control systems may play a pivotal role. Physical inactivity is frequently associated with other factors that may further worsen prognosis. The association between physical inactivity and hypoxia is particularly interesting and characterizes several conditions—whether physiological (e.g., residing or trekking at high altitude and space flights) or pathological (e.g., chronic cardiopulmonary diseases and COVID-19). In this randomized intervention study, we investigated the combined effects of physical inactivity and hypoxia on autonomic control in eleven healthy and physically active male volunteers, both at baseline (ambulatory) conditions and, in a randomized order, hypoxic ambulatory, hypoxic bedrest, and normoxic bedrest (i.e., a simple experimental model of physical inactivity). Autoregressive spectral analysis of cardiovascular variabilities was employed to assess cardiac autonomic control. Notably, we found hypoxia to be associated with an impairment of cardiac autonomic control, especially when combined with bedrest. In particular, we observed an impairment of indices of baroreflex control, a reduction in the marker of prevalent vagal control to the SA node, and an increase in the marker of sympathetic control to vasculature.

International audience; Physical inactivity, i.e., not reaching the recommended level of physical activity (PA) and sedentary behaviors (SB), i.e., sitting time have been associated with increased risk for common metabolic diseases. Recent epidemiological data suggest that high volumes of SB are detrimental for metabolic health, even in the presence of regular exercise, i.e., moderate/vigorous (MVPA). This suggests that the health effects of SB are independent from those of exercise. However, experimentally testing this hypothesis is complicated because of the difficulty in disassociating SB from PA. Bedrest studies, a traditional space science model, can offer new insights. In some bedrest studies, an exercise training protocol has been used to counteract the harmful effects of inactivity. While bedrest induces an inactive and sedentary state, exercise with bedrest represents a unique model of sedentary yet physically active people. Here, we review bedrest studies with and without exercise training. Although exercise training prevents the loss of muscle mass and function, even large volumes of exercise are not sufficient to fully counteract the negative metabolic adaptations triggered by inactivity. This observation supports the existence of independent adverse health effects of SB, but also the potential benefits of non‐exercise activity, i.e., daily living light‐intensity activities (LPA). We gathered available data to examine the complex relationships between exercise, non‐exercise activity, SB and health outcomes. Given the large amount of SB in modern societies, the sole promotion of exercise, i.e., MVPA may be insufficient, and promotion of LPA may be a complimentary approach to improve health.

Exposure to actual or simulated microgravity results in alterations of renal function, fluid redistribution, and bone loss, which is coupled to a rise of urinary calcium excretion. We provided evidence that high calcium delivery to the collecting duct reduces local Aquaporin 2 (AQP2)-mediated water reabsorption under vasopressin action, thus limiting the maximal urinary concentration to reduce calcium saturation. To investigate early renal adaptation into simulated microgravity, we investigated the effects of 10 days of strict bedrest in 10 healthy volunteers. We report here that 10 days of inactivity are associated with a transient, significant decrease (day 5) in vasopressin (copeptin) paralleled by a decrease in AQP2 excretion, consistent with an increased central volume to the heart, resulting in reduced water reabsorption. Moreover, bedrest caused a significant increase in calciuria secondary to bone demineralization paralleled by a decrease in PTH. Urinary osteopontin, a glycoprotein exerting a protective effect on stone formation, was significantly reduced during bedrest. Moreover, a significant increase in adrenomedullin (day 5), a peptide with vasodepressor properties, was observed at day 5, which may contribute to the known reduced orthostatic capacity post-bedrest. We conclude that renal function is altered in simulated microgravity and is associated with an early increase in the risk of stone formation and reduced orthostatic capacity post-bedrest within a few days of inactivity.

Background: Immobility in critically ill patients is conditioned by the condition of the disease or by the effect of drugs, but in both cases, it emerges as a problem from the perspective of functional recovery. The decrease in muscle mass and joint amplitude delay or hinder the processes of recovery from spontaneous ventilation and self-care. When bed rest is required, safe rehabilitation nursing care is a resource to mitigate the problems associated with immobility. Objective: Evaluate the results of rehabilitation nursing care after the application of a structured passive joint mobilization care intervention in critically ill patients. Methods: Qualitative study, case study type. The case of an adult person in a critical situation is presented and eight joint mobilization sessions were carried out by a rehabilitation nurse. Joint amplitude was evaluated using goniometry before and after the application of a rehabilitation program. Study approved by the ethics committee. Results: It was found that in 26 days of admission to the intensive care unit, the joint amplitude remained in the different segments and there were gains in the supination movements of the forearm, left hand extension and right knee flexion. Passive joint mobilization exercises did not interfere with the stability of physiological parameters or adaptation to the ventilatory prosthesis. Conclusion: The results reveal that there is no decrease in joint amplitude and are sensitive to rehabilitation nursing care, in a structured and regular mobilization plan. There were gains in health and the minimization of complications associated with immobility. Other studies should be carried out in order to parameterize not only the intervention plan but also the evidence of the results obtained.

25 p.-3 fig.-5 tab., Bioinformatics approaches have proven useful in understanding biological responses to spaceflight. Spaceflight experiments remain resource intensive and rare. One outstanding issue is how to maximize scientific output from a limited number of omics datasets from traditional animal models including nematodes, fruitfly, and rodents. The utility of omics data from invertebrate models in anticipating mammalian responses to spaceflight has not been fully explored. Hence, we performed comparative analyses of transcriptomes of soleus and extensor digitorum longus (EDL) in mice that underwent 37 days of spaceflight. Results indicate shared stress responses and altered circadian rhythm. EDL showed more robust growth signals and Pde2a downregulation, possibly underlying its resistance to atrophy versus soleus. Spaceflight and hindlimb unloading mice shared differential regulation of proliferation, circadian, and neuronal signaling. Shared gene regulation in muscles of humans on bedrest and space flown rodents suggest targets for mitigating muscle atrophy in space and on Earth. Spaceflight responses of C. elegans were more similar to EDL. Discrete life stages of D. melanogaster have distinct utility in anticipating EDL and soleus responses. In summary, spaceflight leads to shared and discrete molecular responses between muscle types and invertebrate models may augment mechanistic knowledge gained from rodent spaceflight and ground-based studies., T.C. was supported by the NI Department for the Economy (DfE) Research Studentship. H.C. is supported by the Horizon Centre for Doctoral Training at the University of Nottingham (UKRI grant no. EP/S023305/1). R.H. is supported by the Spanish Plan Estatal de Investigación Científica y Desarrollo Tecnológico Grant RTI2018-099309-B-I00. S.S.R. is supported by the NASA Ames Space Biology Program

Environmental and psychological stressors can adversely affect astronaut cognitive performance in space. This study used a 6° head-down tilt bed rest (HDBR) paradigm to simulate some of the physiologic changes induced by microgravity. Twenty-four participants (mean ± SD age 33.3 ± 9.2 years, N = 16 men) spent 60 consecutive days in strict HDBR. They were studied in three groups of eight subjects each. One group served as Control, whereas the other two groups received either a continuous or intermittent artificial gravity (AG) countermeasure of 30 min centrifugation daily (1 g acceleration at the center of mass and 2 g at the feet). Participants performed all 10 tests of NASA’s Cognition battery and a brief alertness and mood survey repeatedly before, during, and after the HDBR period. Test scores were adjusted for practice and stimulus set difficulty effects. A modest but statistically significant slowing across a range of cognitive domains was found in all three groups during HDBR compared to baseline, most consistently for sensorimotor speed, whereas accuracy was unaffected. These changes were observed early during HDBR and did not further worsen or improve with increasing time in HDBR, except for emotion recognition performance. With increasing time spent in HDBR, participants required longer time to decide which facial emotion was expressed. They were also more likely to select categories with negative valence over categories with neutral or positive valence. Except for workload, which was rated lower in the Control group, continuous or intermittent AG did not modify the effect of HDBR on cognitive performance or subjective responses. Participants expressed several negative survey responses during HDBR relative to baseline, and some of the responses further deteriorated during recovery, which highlights the importance of adequate medical and psychological support during extended duration HDBR studies. In conclusion, 60 days of HDBR were associated with moderate cognitive slowing and changes in emotion recognition performance, but these effects were not mitigated by either continuous or intermittent exposure to AG for 30 min daily.

International audience; The objective of the present study was to determine the effects of dry immersion, an innovative ground-based human model of simulated microgravity and extreme physical inactivity, on iron homeostasis and distribution. Twenty young healthy men were recruited and submitted to 5 days of dry immersion (DI). Fasting blood samples and MRI were performed before and after DI exposure to assess iron status, as well as hematological responses. DI increased spleen iron concentrations (SIC), whereas hepatic iron store (HIC) was not affected. Spleen iron sequestration could be due to the concomitant increase in serum hepcidin levels (P

Background: Pregnancy in a woman's life is a unique experience. But due to high risk pregnancy and the need to rest in bed, the women and her family are faced with different challenges and needs. The inability to manage these needs will result in crisis and understanding the needs of pregnant women during bed rest is essential to provide comprehensive health care for them. So this qualitative study was designed and conducted to examine the needs of women with high-risk pregnancy experience during bed rest to improve health in this group. Materials and Methods: This is a qualitative study conducted in 1393 using inductive qualitative content analysis. 32 individual semi-structured interviews were performed with 21 women with high-risk pregnancy and four members of their family (mother of a participant and husbands of three participants) and seven medical staff involved in their healthcare. Collected information was analyzed concurrently with information collecting. Results: Data analysis led to the emersion of the last category of need that was training and consultation. This main category has sub-categories such as: need for consultation on physical problems, psychological problems, marital problems, fear and the stresses caused by bed rest, common problem in pregnancy and childbirth and the need for help for planning various activities during bed rest. Conclusion: Conducting a comprehensive nursing and education services and counseling to women with high-risk pregnancy during bed rest leads to a reduction in their physical and psychosocial problems.

Filum terminale lipoma (FTL) causes various spinal symptoms known as tethered cord syndrome. The treatment for FTL is surgical untethering by sectioning the FTL, which can prevent symptom progression and often results in improvement of symptoms. This report describes a minimally invasive surgical strategy that we have introduced for FTL sectioning. The pediatric patients with FTL since 2007 were treated using this minimally invasive surgical strategy, which we refer to as an interlaminar approach (ILA). In summary, the surgical technique involves: minimal skin incision to expose the unilateral ligamentum flavum in the lower lumbar region; ligamentum flavum incision to expose the dural sac, and dural incision followed by identification and sectioning of the filum. Postoperatively, no bed rest was required. Prior to introducing ILA, we had used standard one level laminectomy/laminotomy (LL) with more than 1 week of postsurgical bed rest until 2007, providing an adequate control group for the benefit of the ILA. A total of 49 consecutive patients were treated using ILA. While 37 patients were treated using LL. Surgical complications that need surgery were seen only in one patient, who developed cerebrospinal fluid (CSF) leak in LL patients. No retethering or additional neurological symptoms were seen during follow-up. All patients complained of minimal postsurgical back pain, but no patients required postoperative bed rest in ILA patients, while LL patients need postsurgical bed rest because of back pain. The ILA strategy provides the advantage of a minimal tissue injury, associated with minimal postoperative pain, blood loss, and bed rest.

Hintergrund Eine Entlastung der Skelettmuskulatur, zum Beispiel durch Bettruhe, führt zu einem ausgeprägten Verlust der Muskelhistomorphometrie und –funktionalität, der durch Muskelaufbautraining als Gegenmaßnahme verhindert oder abgeschwächt werden kann. Ziele Ziel ist, den Einfluss von reaktiven Sprüngen in Rückenlage auf die Muskelhistomorphometrie und –funktionalität der Ober- und Unterschenkelmuskulatur von Probanden einer 60-tägigen Bettruhestudie zu quantifizieren. Methoden Die RSL-Studie wurde von der European Space Agency (ESA) organisiert und vom DLR in der Forschungseinrichtung :envihab in Köln von 2015 bis 2016 veranstaltet. Sie wurde in zwei Kampagnen, mit jeweils 12 Teilnehmern in einer Kontrollgruppe (BR-CTRL) und einer Trainingsgruppe (BR-Jump) durchgeführt, aus denen letztlich 22 Probanden zu den Muskelbiopsaten (VL, n=21; SOL, n=22) beigetragen haben. Die Muskelbiopsate (jeweils etwa 150 mg Feuchtgewicht) wurden aus dem VL und SOL beider Muskeln vor (pre), am Ende (post) und zehn Tage nach (rec) Bettruhe entnommen, in flüssigem Stickstoff schockgefroren, zur weiteren Analyse histomorphometrisch (Muskelfasergröße und –typenverteilung), enzymhistochemisch (Succinat-Dehydrogenase-Aktivitätsfärbung) und immunohistochemisch (Antikörper gegen schwere Ketten des Myosins I & II, PECAM) aufgearbeitet sowie mittels konventioneller und konfokaler Lasermikroskopie ausgewertet. Ergebnisse 60-tägige Bettruhe führt zu einer Verringerung der Querschnittsoberfläche der Muskelfasern (VL, p< 0,0001; SOL, p< 0,0001) und einer Muskelzelltypenverschiebung über einen Anstieg hybrider Zellen (VL, p=0,0131; SOL, p, Background Extended skeletal muscle inactivity (disuse) in bed rest results in considerable loss in muscle histomorphology with functional impairments that can be alleviated by physical exercise as countermeasure. Objectives To test the outcome of reactive jumps at supine position on human thigh and calf muscle histomorphology (myofibre size and type distribution) and other functional parameters (capillarity and oxygen consumption) in bed rest participants (60 days RSL study). Methods The RSL study was organized by the European Space Agency (ESA) and hosted by the DLR at the :envihab human physiology facility, Cologne, Germany in 2015-2016. The study ran in two campaigns, one bed rest (BR) control (BR-CTRL) and one exercise (BR-Jump) group, each (n=12), finally resulting in total n=22 study participants subjected to muscle biopsies (VL, n=21; SOL, n=22). In both groups, muscle biopsies (approximated 150 mg wet weight) were taken from the thigh and calf muscle before (pre), at the end (post), and during 10 days of recovery (rec), frozen in liquid nitrogen and further analyzed according to routine histomorphometry (myofibre size and type distribution), histochemistry (SDH stain), and immunohistochemistry (anti-myosin heavy chain, MyHC I and II, PECAM) using conventional and confocal laser microscopy. Results: 60 days of bed rest induced significant reductions in muscle cross sectional area (VL, p

This paper provides a general overview of key physiological consequences of microgravity experienced during spaceflight and of important parallels and connections to the physiology of aging. Microgravity during spaceflight influences cardiovascular function, cerebral autoregulation, musculoskeletal, and sensorimotor system performance. A great deal of research has been carried out to understand these influences and to provide countermeasures to reduce the observed negative consequences of microgravity on physiological function. Such research can inform and be informed by research related to physiological changes and the deterioration of physiological function due to aging. For example, head-down bedrest is used as a model to study effects of spaceflight deconditioning due to reduced gravity. As hospitalized older persons spend up to 80% of their time in bed, the deconditioning effects of bedrest confinement on physiological functions and parallels with spaceflight deconditioning can be exploited to understand and combat both variations of deconditioning. Deconditioning due to bed confinement in older persons can contribute to a downward spiral of increasing frailty, orthostatic intolerance, falls, and fall-related injury. As astronauts in space spend substantial amounts of time carrying out exercise training to counteract the microgravity-induced deconditioning and to counteract orthostatic intolerance on return to Earth, it is logical to suggest some of these interventions for bed-confined older persons. Synthesizing knowledge regarding deconditioning due to reduced gravitational stress in space and deconditioning during bed confinement allows for a more comprehensive approach that can incorporate aspects such as (mal-) nutrition, muscle strength and function, cardiovascular (de-) conditioning, and cardio-postural interactions. The impact of such integration can provide new insights and lead to methods of value for both space medicine and geriatrics (Geriatrics meets spaceflight!). In particular, such integration can lead to procedures that address the morbidity and the mortality associated with bedrest immobilization and in the rising health care costs associated with an aging population demographic.

Cardiovascular disease continues to be the leading cause of death in the United States. Coronary angiography is one of the most commonly used diagnostic tools in the identification of coronary artery disease, and it remains a prime treatment option for significant coronary artery stenosis. The widely used femoral approach to coronary angiography does not come without significant risk for access site complications, patient complaints of pain, and lengthy bedrest durations. With these concepts in mind came the evolution and implementation of multiple vascular closure devices. The purpose of this study was to compare complication rates after coronary angiography via the femoral approach between mechanical and manual closure techniques, the pain associated with each, and the duration of bedrest employed using a systematic review of the literature. Upon conclusion of the literature review, evidence has shown to provide significant data supporting the use of mechanical closure devices while reducing access site complications, pain, and lengthy bedrest durations when used in appropriate patients.

\( {{\dot{V}O}}_{2} , \)fH, \( \dot{Q}, \) SV, [Hb], CaO2, \( {{\dot{Q}}}_{\text{a}} \)O2, MAP and RP were measured in 10 young subjects at rest and during exercise at 50, 100 and 150 W before and after 14 days of head-down tilt bed rest (HDTBR) and of ambulatory (AMB) control period. fH was 18 and 8% higher after HDTBR and AMB, respectively. SV dropped by 15% both after HDTBR and AMB, whereas \( \dot{Q} \) did not change. After HDTBR, CaO2 decreased at rest (−8%) and at 50 W (−5%), whereas \( {{\dot{Q}}}_{\text{a}} \)O2 did not change; MAP was 14 and 6% lower at rest and at 100 W and RP decreased by 23% only at rest. Changes in fH and SV were larger after HDTBR than after AMB. These results show that, notwhistanding the drop of SV, moderate-intensity dynamic exercise elicited a normal pressure response after 14 days of HDTBR.

BackgroundBed-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.MethodsTwenty 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.ResultsBed-rest reduced plasma volume, weight, fat-free mass, and muscle mass (PConclusionsStudy results shows that urea is a marker of catabolic conditions secondary to hypokinetic conditions.

PLoS one 9(11), e112104 (2014). doi:10.1371/journal.pone.0112104, Published by PLoS [u.a.], Lawrence, Kan.

Bedrest produces decrements in the functioning of all physiological systems. Physiotherapists treat patients who are managed with Thomas splints following fractured femurs. The patients are generally compartmentally treated as orthopaedic patients. No attention is paid to the status of the respiratory system which can be the cause of morbidity in these patients. Since the ventilatory muscles play a major role in breathing and coughing the purpose of the present study was to determine the effect of a limited period of bedrest on the strength of the inspiratory and expiratory muscles.A sample of convenience consisting of 15 African male patients immobilized by Thomas’ Splint for fractured mid-shaft femurs participated in the study by voluntary consent. All patients had been confined to bed for at least 3 weeks. Maximal inspiratory pressures (PiMAX) and Maximal expiratory pressures (PeMAX) were recorded using a Boehringer Force Meter at functional residual capacity in the semi-recumbent position. The data were normalized and analyzed using the student t-test at the 0.05% level.The results showed a significant reduction in both PiMAX and PeMAX compared to age predicted normal values. The decrease in PeMAX was greater than that of PiMAX.We conclude that respiratory muscle strength decays with bedrest.

The present series of in vivo experiments in healthy subjects, were performed to investigate wall stiffness in peripheral vessels and how this modality adapts to iterative increments or sustained reductions in local intravascular pressures. Vascular stiffness was measured as changes in arterial and venous diameters, and in arterial flow, during graded increments in distending pressures in the vasculature of an arm or a lower leg. In addition, effects of intravascular pressure elevation on flow characteristics in veins, and on limb pain were elucidated. Arteries and veins were stiffer (i.e. pressure distension was less) in the lower leg than in the arm. The pressure-induced increase in arterial flow was substantially greater in the arm than in the lower leg, indicating a greater stiffness in the arterioles of the lower leg. Prolonged reduction of intravascular pressures in the lower body, induced by 5 wks of sustained horizontal bedrest (BR), decreased stiffness in the leg vasculature. BR increased pressure distension in the tibial artery threefold and in the tibial vein by 86 %. The pressure-induced increase in tibial artery flow was greater post bedrest, indicating reduced stiffness in the arterioles of the lower leg. Intermittent increases of intravascular pressures in one arm (pressure training; PT) during a 5-wk period decreased vascular stiffness. Pressure distension and pressure-induced flow in the brachial artery were reduced by about 50 % by PT. PT reduced pressure distension in arm veins by 30 to 50 %. High intravascular pressures changed venous flow to arterial-like pulsatile patterns, reflecting propagation of pulse waves from the arteries to the veins either via the capillary network or through arteriovenous anastomoses. High vascular pressures induced pain, which was aggravated by BR and attenuated by PT; the results suggest that the pain was predominantly caused by vascular overdistension. In conclusion, vascular wall stiffness constitutes a plastic modality that adapts to meet demands imposed by a change in the prevailing local intravascular pressure. That increased intravascular pressure leads to increased arteriolar wall stiffness supports the notion that local pressure load may serve as a “prime mover” in the development of vascular changes in hypertension. medicine doktorsexamen QC 20101109

The aim of this study was to characterize the time course of maximal oxygen consumption (V'O2 max) changes during bed rests longer than 30 days,on the hypothesis that the decrease in _VO2 max tends to asymptote. On a total of 26 subjects who participated in one of three bedrest campaigns without countermeasures, lasting 14, 42 and 90 days, respectively, V'O2 max maximal cardiac output (Q'max) and maximal systemic O2 delivery (Q'aO2max) were measured. After all periods of HDT, V'O2 max; Q'max and Q'aO2max were significantly lower than before. The V'O2 max decreased less than Q'max after the two shortest bedrests, but its per cent decay was about 10% larger than that of Q'max after 90-day bedrest. The V'O2 max decrease after 90-day bedrest was larger than after 42- and 14-day bedrests, where it was similar. The Q'max and Q'aO2max declines after 90-day bedrest was equal to those after 14- and 42-day bedrest. The average daily rates of the V'O2 max; Q'max and Q'aO2max decay during bedrest were less if the bedrest duration were longer, with the exception of that of V'O2 max in the longest bedrest. The asymptotic V'O2 max decay demonstrates the possibility that humans could keep working effectively even after an extremely long time in microgravity. Two components in the V'O2 max decrease were identified, which we postulate were related to cardiovascular deconditioning and to impairment of peripheral gas exchanges due to a possible muscle function deterioration.

The aim of this study was to characterize the time course of maximal oxygen consumption VO2(max) changes during bedrests longer than 30 days, on the hypothesis that the decrease in VO2(max) tends to asymptote. On a total of 26 subjects who participated in one of three bedrest campaigns without countermeasures, lasting 14, 42 and 90 days, respectively, VO2(max) maximal cardiac output (Qmax) and maximal systemic O2 delivery (QaO2max) were measured. After all periods of HDT, VO2max, Qmax, and QaO2max were significantly lower than before. The VO2max decreased less than qmax after the two shortest bedrests, but its per cent decay was about 10% larger than that of Qmax after 90-day bedrest. The VO2max decrease after 90-day bedrest was larger than after 42- and 14-day bedrests, where it was similar. The Qmax and QaO2max declines after 90-day bedrest was equal to those after 14- and 42-day bedrest. The average daily rates of the VO2max, Qmax, and QaO2max decay during bedrest were less if the bedrest duration were longer, with the exception of that of VO2max in the longest bedrest. The asymptotic VO2max decay demonstrates the possibility that humans could keep working effectively even after an extremely long time in microgravity. Two components in the VO2max decrease were identified, which we postulate were related to cardiovascular deconditioning and to impairment of peripheral gas exchanges due to a possible muscle function deterioration.

To examine the effects of unweighting on the structural and metabolic adaptations of a non-postural muscle, deltoideus muscle biopsies were taken in seven male healthy subjects, before and after a 37 day bedrest. Myofibrillar ATPase histochemistry demonstrated no change in fibre type distributions (I, IIA, IIB), in fibre cross-sectional areas nor in capillary supply. No difference was noted in enzyme activities of oxidative metabolism (citrate synthase, 3-hydroxy-acyl-CoA dehydrogenase), and glycolysis (hexokinase, lactate dehydrogenase). Electron microscopy showed a decrease in the volume density of lipids but no change in mitochondrial volume density and distribution. The results indicate that bedrest induces no major morphological and biochemical changes in deltoideus muscle, contrary to what was previously reported in vastus lateralis muscle. This lack of changes is probably related to an unaltered deltoideus muscle use.