Effects of three days of dry immersion on muscle sympathetic nerve activity and arterial blood pressure in humans

A sedentary lifestyle has adverse effects on the cardiovascular system, including impaired endothelial functions. Subjecting healthy men to 7 days of dry immersion (DI) presented a unique opportunity to analyze the specific effects of enhanced inactivity on the endothelium. We investigated endothelial properties before, during, and after 7 days of DI involving eight subjects. Microcirculatory functions were assessed with laser Doppler in the skin of the calf. We studied basal blood flow and endotheliumdependent and -independent vasodilation. We also measured plasma levels of microparticles, a sign of cellular dysfunction, and soluble endothelial factors, reflecting the endothelial state. Basal flow and endothelium-dependent vasodilation were reduced by DI (22 Ϯ 4 vs. 15 Ϯ 2 arbitrary units and 29 Ϯ 6% vs. 12 Ϯ 6%, respectively, P Ͻ 0.05), and this was accompanied by an increase in circulating endothelial microparticles (EMPs), which was significant on day 3 (42 Ϯ 8 vs. 65 Ϯ 10 EMPs/l, P Ͻ 0.05), whereas microparticles from other cell origins remained unchanged. Plasma soluble VEGF decreased significantly during DI, whereas VEGF receptor 1 and soluble CD62E were unchanged, indicating that the increase in EMPs was associated with a change in antiapoptotic tone rather than endothelial activation. Our study showed that extreme physical inactivity in humans induced by 7 days of DI causes microvascular impairment with a disturbance of endothelial functions, associated with a selective increase in EMPs. Microcirculatory endothelial dysfunction might contribute to cardiovascular deconditioning as well as to hypodynamia-associated pathologies. In conclusion, the endothelium should be the focus of special care in situations of acute limitation of physical activity. dry immersion; weightlessness; microcirculation; endothelial dysfunction; soluble endothelial markers THE VASCULAR ENDOTHELIUM is a key element in the control of local blood flow (12,46). It is now widely recognized that alterations of endothelial integrity and physiological functions represent pivotal mechanisms in the initiation and development of vascular diseases. A decrease in endothelial vasomotor function (endothelium-dependent vasodilation), which correlates with a risk of cardiovascular events, has been demonstrated in patients with atherosclerosis, hypertension, and peripheral vascular diseases (49). Physical inactivity and a sedentary lifestyle are known to cause cardiovascular deconditioning and increase the risk of cardiovascular disease (5). Endothelial dysfunction seems to be intimately linked to this deconditioning. A chronic decrease in shear stress forces during physical inactivity, especially significant in small vessels of the microcirculatory bed (8), may impair endothelial functions.Experimental physical inactivity of varying duration and intensity in healthy humans can be achieved through confinement (altitude chambers), partial immobilization, bedrest, and "dry" water immersion (33, 34). Dry immersion (DI) induces extreme physical inac...

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“…DI involves immersing the subject into thermoneutral water covered with a special elastic waterproof fabric film (30,33,43) (Fig. 1).…”

Section: Methodsmentioning

confidence: 99%

Enforced physical inactivity increases endothelial microparticle levels in healthy volunteers

Navasiolava

Dignat-George

Sabatier

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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“…Furthermore, most authors have not found significant changes in resting heart rate ( Fig. 9) or resting blood pressure at the end of 3-7 days of dry immersion (Bravyi et al 2008;Eshmanova 2009;Iwase et al 2000;Mikhailov et al 1995;Navasiolava et al 2010a, b;Vil'-Viliams and Shul'zhenko 1978). Some authors found a 15-20% increase in diastolic pressure after 7 days (Vil'-Vil'iams and Shul'zhenko 1980) and 10 days (Panferova 1976) of immersion.…”

Section: Resting Heart Rate and Blood Pressurementioning

confidence: 99%

“…Dry immersion was first developed and has been used mainly by Russian scientists (Grigor'ev et al 2004;Kozlovskaia 2008;Shulzhenko andVil-Vilyams 1975, 1976, and many other authors whose results are discussed below). Only a few non-Russian scientists have mentioned the specific model of dry immersion (Clement and Pavy-Le Traon 2004;Iwase et al 2000;Nicogossian et al 1993;Somody et al 1999;Watenpaugh and Hargens 1996). To our knowledge, apart from those performed in Russian facilities, dry immersion studies have only been conducted in India (Modak and Banerjee 2004) and Austria (Berger et al 2001;Saling et al 2002;Struhal et al 2002).…”

Section: Hydrostatic Compressionmentioning

confidence: 99%

“…In general, the subjects find dry immersion to be comfortable during the initial period (Atkov and Bednenko 1992;Iwase et al 2000;Nicogossian et al 1993;Shulzhenko and Vil-Vilyams 1976). Volunteers' comments have included: ''As if you were lying in thick jelly and didn't sink…''; ''It is like a soft feather bed or a slightly inflated rubber mattress…''.…”

Section: Tolerance and Subjective Sensationsmentioning

confidence: 99%

“…1 (Eshmanova 2009;Vinogradova et al 2002a). After 1.5-3 days of dry immersion, the figure is approximately one-sixth (Iwase et al 2000;Shul'zhenko et al 1984), and after 7 days of dry immersion, approximately one-third of the subjects are intolerant (Eshmanova 2009;Iarullin et al 1987). An increase in heart rate on orthostasis after dry immersion was shown by all the studies cited above.…”

Section: Orthostatic Tolerancementioning

confidence: 99%

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Long-term dry immersion: review and prospects

et al. 2010

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Dry immersion, which is a ground-based model of prolonged conditions of microgravity, is widely used in Russia but is less well known elsewhere. Dry immersion involves immersing the subject in thermoneutral water covered with an elastic waterproof fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains dry. For a relatively short duration, the model can faithfully reproduce most physiological effects of actual microgravity, including centralization of body fluids, support unloading, and hypokinesia. Unlike bed rest, dry immersion provides a unique opportunity to study the physiological effects of the lack of a supporting structure for the body (a phenomenon we call 'supportlessness'). In this review, we attempt to provide a detailed description of dry immersion. The main sections of the paper discuss the changes induced by long-term dry immersion in the neuromuscular and sensorimotor systems, fluid-electrolyte regulation, the cardiovascular system, metabolism, blood and immunity, respiration, and thermoregulation. The long-term effects of dry immersion are compared with those of bed rest and actual space flight. The actual and potential uses of dry immersion are discussed in the context of fundamental studies and applications for medical support during space flight and terrestrial health care.

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Space Physiology

Beckers

Verheyden

Aubert

2006

Wiley Encyclopedia of Biomedical Engineering

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Space exploration has been a dream of humankind ever since Baron von Münchausen, Jules Verne, Tsiolkovsky, Goddard, and many others. However, this intriguing environment is not without risks. The human body has developed over the past thousands of years in the constant presence of gravity. When this gravitational force is no longer acting on the body, changes occur. Some of these changes occur immediately; others progress only slowly. In the past 40 years of human space flight (first orbital flight by Yuri Gagarin in April 1961), several hazards for the human body have been identified. Bone mineral density is lost, and muscle atrophy and cardiovascular deconditioning occur. These changes in human physiology have to be reversed again when astronauts return to Earth. This reversal can cause adaptation problems, especially after long‐duration space flights. Also the reaction of the human physiology to radiation in space poses a huge risk at this moment. To make long‐duration space flight possible, we must understand the mechanisms of physiological adaptation. Only with this knowledge can effective countermeasures be developed.

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Effects of three days of dry immersion on muscle sympathetic nerve activity and arterial blood pressure in humans

Cited by 47 publications

References 25 publications

Enforced physical inactivity increases endothelial microparticle levels in healthy volunteers

Enforced physical inactivity increases endothelial microparticle levels in healthy volunteers

Long-term dry immersion: review and prospects

Space Physiology

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