Weightlessness SimulationVIVALDI 3NCT06777329
A Comparison Study Between 10 Days of Dry Immersion Versus 10 Days of Head-down Bedrest on 20 Healthy Male Volunteers
A study testing 10 days of dry immersion and 10 days of Head Down Bed Rest in people with Weightlessness Simulation, run by Centre National d'Etudes Spatiales at 1 site in France.
Trial summary
The space agencies are actively engaged in studying the physiological adaptation to space environment through studies on board the International Space Station (ISS) but also on the ground. Read more about this study
- Who is it for?
- Ages 20 to 40 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Weightlessness Simulation
- What is being tested?
- 10 days of dry immersion and 10 days of Head Down Bed Rest
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 1 siteFrance
- Study dates
- 9 Dec 2024to 23 Apr 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 20 to 40 years
- Men only
- Healthy volunteers accepted
- Adult
Who may be able to join
None listed.
Who cannot join
- Any history or presence of clinically relevant cardiovascular, neurological or ENT (especially orthostatic hypotension and vestibular disorders), any chronic disease; any acute infectious disease. Particularly:
- Symptomatic orthostatic hypotension whatever the decrease in blood pressure, or asymptomatic postural hypotension defined by a decrease in SBP equal to or greater than 20 mmHg within 3 minutes when changing from the supine to the standing position,
- Cardiac rhythm disorders,
- Hypertension,
- Chronic back pains,
- Vertebral fracture, scoliosis or herniated disc,
Show all 37Show fewer
- Glaucoma,
- Self-reported hearing problems,
- History of migraines,
- History of hiatus hernia or gastro-esophageal reflux,
- History of thyroid dysfunction, renal stones, diabetes,
- History of head trauma,
- History of genetic muscle and bone diseases of any kind,
- Past records of thrombophlebitis, family history of thrombosis or positive response in thrombosis screening procedure (anti thrombin III, S-protein, C-protein, factor V Leiden mutation and the mutation 20210 of the prothrombin gene),
- Signs of venous insufficiency, varicose veins, or telangiectasia
- Bone mineral density: T-score ≤ -1.5,
- Poor tolerance to blood sampling,
- Having given whole blood (more than 7ml/kg) in a period of 8 weeks or less before the start of the experiment, or having given whole blood more than 5 times in the past 12 months,
- Significant history of allergy, especially no dermatological allergy,
- History of food allergy,
- Significant anomaly detected in the biological analysis,
- Positive reaction to any of the following tests: HVA IgM (hepatitis A), HBs antigen (hepatitis B), anti-HVC antibodies (hepatitis C), anti-HIV1+2 antibodies,
- Vegetarian or vegan,
- Refusal to give permission to contact his general practitioner,
- Subject who, in the judgment of the investigator, is likely to be non-compliant during the study, or unable to cooperate because of a language problem or poor mental development,
- Subject already participating or in the exclusion period of a clinical research,
- Subject who has received more than 6000 Euros within 12 months for being a research subject,
- MRI contraindications:
- History or active claustrophobia,
- Osteosynthesis material, presence of metallic implants or any other contra-indication for MRI,
- Allergy to Gadolinium.
- Vulnerable persons according to law "Code de la Santé Publique" (L1121-5 to L1121-8) :
- Persons deprived of their liberty by an administrative or judicial decision,
- Persons under involuntary psychiatric care,
- Persons admitted in a health or social establishment for purposes other than research,
- Minors,
- Adults subject to legal protection (subject under guardianship or trusteeship) or unable to express their consent.
Trial locations and contacts
1 site in 1 country.
France1 site
Medes-Institut de Médecine et de Physiologie Spatiale
Toulouse, France, 31400
About this study
Official title: Standardization of the Dry Immersion Model Used as a Ground-based Model to Mimic Weightlessness. Part 3: a Comparison Study Between 10 Days of Dry Immersion vs. 10 Days of Head-down Bedrest on 20 Healthy Male Volunteers (VIVALDI 3)
The space agencies are actively engaged in studying the physiological adaptation to space environment through studies on board the International Space Station (ISS) but also on the ground. Different methods are used to simulate weightlessness on Earth, including cellular models, animal models using hind-limb unloading, or on humans with unilateral lower limb suspension. However, two approaches, -6° head-down bed rest (HDBR) and dry immersion (DI) have provided possibilities for long-term exposures with findings closest to those seen with a weightless state. They produce changes in body composition (including body fluid redistribution), cardiovascular and skeletal muscle characteristics that resemble the effects of microgravity.
The common physiological denominator is the combination of a cephalad shift of body fluids and reduced physical activity. Being similar in their effects on the human body, these models, however, differ in their specifics and acting factors.
Read more
The Head-down Bedrest (HDBR) model has been widely used for this purpose and is considered one of the references for reproducing the physiological effects of weightlessness on Earth. During HDBR, subjects are lying down with an angle of -6° between the feet and head, on their side, their back or their front, but must keep one shoulder in contact with the mattress. All daily activities and tests are performed in this position.
One of the advantages of the HDBR model is that it has now been used in a great number of studies internationally, and its effects have long been described and compared with those of microgravity and spaceflight. Long-term bedrest is the gold-standard method for studying the effects of weightlessness and to test countermeasures.
Dry immersion involves immersing the subject in water covered with an elastic waterproof fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains dry. Within a relatively short duration, the model can faithfully reproduce most physiological effects of actual microgravity, including centralization of body fluids, support unloading, and hypokinesia.
The objective of the present study is to compare the physiological adaptations to10 days of dry immersion versus 10 days of head-down bedrest in 20 healthy male subjects. A set of measurements will assess the changes in the cardiovascular, neuro-ophthalmological, hematological, metabolic, sensorimotor, immune, muscle and bone systems as a result of both models. The most likely outcome of this study will not be to show a clear superiority of one model over the other. Rather, we expect to show differences in kinetics and intensity of adaptations, that should vary from one system to another. This will help future researchers choose the best model depending on the system they are investigating and the rapidity or intensity of the effect they are exploring. The two models, instead of competing with one another, are probably complementary.
- Conditions
- Weightlessness Simulation
- Being tested
- 10 days of dry immersion, 10 days of Head Down Bed Rest
- Keywords
- Comparison of 2 weightlessness simulation models
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
10 days of dry immersionBehavioural
Also called Dry Immersion (DI)
The volunteers in this arm will be immersed up to the neck for 10 days in a specially designed bath filled with tap water.
10 days of Head Down Bed RestBehavioural
Also called Head Down Tilt (HDT)
The volunteers in this arm will spend 10 days in -6° head down bed rest.
| Study group | Role | What they receive |
|---|---|---|
| Dry Immersion arm | Experimental | 10 days of dry immersion Receives: Behavioral: 10 days of dry immersion |
| Bed rest arm | Experimental | 10 days of head down bed rest Receives: Behavioral: 10 days of Head Down Bed Rest |
What is being measured
The primary outcome is the main question the study is designed to answer.
Changes in orthostatic tolerance
Orthostatic tolerance (min) will be assessed during a progressive Lower Body Negative Pressure test (LBNP test)
Measured: At baseline and first day of recovery
Changes in peak aerobic power (VO2max test)
Exercise capacity (ml/kg/min) wil be assessed by graded cycling on sitting ergometer until exhaustion
Measured: At baseline and the first day of recovery
Change in plasma volume
Plasma volume (L) will be assessed by the carbon monoxide-rebreathing method
Measured: At baseline and 3 days after the end of the intervention
Change in plasma volume percentage
The percentage change in plasma volume versus baseline (%) will be assessed by the Dill and Costill method
Measured: At baseline and at day 1, day 3, day 7 and at the end of the intervention periods
Change in fluid shift distribution towards the cardiac and cephalic region
The consequences of the fluid shift on the cardiac and cephalic area will be assessed by quantifying the carotid and femoral diameters (mm), as well as the carotid intima media thickness (mm) by ultrasound.
Measured: At baseline, the first day to quantify the short term effect, the fifth day and the tenth day of interventions to quantify the long term effect of fluid shift
Change in body fluid compartments by bioelectrical impedance analysis
Extracellular, intracellular and total body water (L) will be estimated by bioimpedance
Measured: At baseline, during the ten days of intervention and until 3 days after the end of the intervention
Change in calf and thigh circumferences
Change in calf and thigh circumferences will be measured using a measuring tape (cm)
Measured: At baseline, during the intervention period and until 3 days after the intervention period
Change in fat and lean body mass measured by dual energy x-ray absorptiometry (DEXA)
Change in fat and lean body mass (g) measured by dual energy x-ray absorptiometry (DEXA)
Measured: At baseline, after 10 days of dry-immersion and 10 days of reovery
Change in Resting Metabolic Rate (RMR)
RMR (kcal/24h) will be measured by indirect calorimetry technique
Measured: At baseline, at day 3 and day 9 days of intervention periods
Change in nitrogen balance
Nitrogen balance is a measure of nitrogen input minus nitrogen output. Nitrogen intake (g) is calculated with a nutrition software. Total urinary nitrogen (g) in the 24-Hour urine collection estimates nitrogen output
Measured: At baseline, at day 3 and day 9 days of intervention periods
Change in glucose tolerance (Oral Glucose Tolerance Test)
Glucose (mmol/L) levels will be measured at baseline (fasting) and 30, 60, 90, 120 and 180 minutes after drinking within 5 min a water solution containing 75 g of glucose
Measured: At baseline, at day 3 and day 9 days of intervention periods
Change in serum bone formation marker (bone-specific Alkaline Phosphatase bAP)
Change in bone-specific Alkaline Phosphatase (bAP, µg/L) will be assessed by chemiluminescence immunoassay
Measured: At baseline and during the 10 days of interventions
Change in serum bone resorption marker (C-terminal cross-linked telopeptide of type I collagen CTx)
Change in C-terminal cross-linked telopeptide of type I collagen (CTx, pmol/L) will be assessed by chemiluminescence immunoassay will be assessed by enzyme-immmuno assay
Measured: At baseline and during the 10 days of interventions
Changes in bone density (by DEXA and High Resolution Peripheral Computed Tomography (HR-pQCT))
Bone density (g/cm2) is measured at lumbar and hip level with DEXA and at tibia and radius level with HR-pQCT. Additionally tibia mechanical properties will be estimated by cortical ultrasound propagation velocity (m/s) via intraosseous ultrasonography.
Measured: At baseline and at day 10 of intervention periods
Change in serum cartilage synthesis biomarkers
Change in serum CP II and in human cartilage glycoprotein-39 (YKL-40) concentrations
Measured: At baseline, during the intervention period and until 3 days after the intervention period
Change in serum cartilage degradation biomarkers
Change in serum Cartilage Oligomeric Matrix Protein (COMP) and fragments or propeptide of type II collagen (C2C, C1,2C, Coll-2-1) concentrations
Measured: At baseline, during the intervention period and until 3 days after the intervention period
Change in muscle strength
Muscle strength will be assessed from single leg isometric maximal voluntary contraction on the knee extensors \& flexors, the plantarflexors and dorsiflexors. The Isometric Torque will be measured in Nm. The peak of the three maximal attempts will be recorded for strength measures
Measured: At baseline and after one day of recovery
Changes in jump performance
Jump performance will be assessed on a platform and height of the jump will be evaluated
Measured: At baseline and the first day of recovery
Change in contraction time
Contraction time will be assessed during a measurement using the tensiomyography method in the following muscles: vastus lateralis, Gastrocnemius medialis and Biceps femoris of dominant leg.
Measured: At baseline and at the end of the intervention periods
Change in standing balance
Standing balance (CoP velocity, mm/s) will be assessed by posturography eyes open and eyes closed on a platform covered with 12-cm thick medium density foam
Measured: At baseline and at day 1 and day 2 of recovery
Change in walking balance
Functional mobility test (such as sit and walk, heel to toe steps with eyes closed and open, Triangle Completion Task) will assess walking balance.
Measured: At baseline and after 10 days of intervention and day 1 after the end of the intervention
Change in height
Change in height (mm) measured in standing position
Measured: At baseline and at day 1, day 2 and day 3 of recovery
Change in mid cerebral artery (MCA) blow flow velocity
Mid cerebral artery (MCA) blow flow velocity will be measured by transcranial Doppler
Measured: At baseline and one day after the intervention period
Change in circadian rhythms of blood pressure
Continuous 24-h recording of systolic and diastolic blood pressure will be performed by a Non Invasive Blood Pressure system (SOMNOtouch™NIBP) designed for ambulatory continuous measurements
Measured: At baseline and during the ten days of the intervention periods
Change in mood
Change in mood is assessed using the Profile of Mood States (POMS) questionnaire, by calculation of total mood disturbance (scale from -32 to 200, a higher score indicates more severe mood disturbance)
Measured: At baseline, at day 5 of the intervention period and 3 days after the end of the intervention
Change in affective states
Positive and Negative Affect Schedule (PANAS) questionnaire will be used to assess the intensity of positive (range from 10 to 50, with higher scores representing higher levels of positive affect) and negative (range from 10 to 50, with lower scores representing lower levels of negative affects) affective states. PANAS self-report questionnaire consists of two 10-item scales to measure both positive and negative affects.
Measured: At baseline, at day 5 of the intervention period and 3 days after the end of the intervention
Change in sleep quality
Pittsburgh Sleep Dairy (PghSD) will be used to assess sleep perceived quality. The PghSD is an instrument with separate components to be completed at bedtime and waketime. The following parameters are registered or assessed:
Bedtime, waketime, sleep latency, wake after sleep onset, total sleep time, mode of awakening and ratings of sleep quality, mood, and alertness on wakening, as well as daytime information on naps, exercise, meals and caffeine, tobacco and medications use.
Measured: Daily from baseline to 10 days after the end of the intervention
Change in psychological state: mental health
ical well-being and capture distress
GHQ-28 gives an overall total score and 4 scores for 4 subscales:
Somatic symptoms, Anxiety/insomnia, Social dysfunction, Severe depression. Higher scores indicate higher levels of distress
Measured: At baseline, at day 5 of the intervention period and 4 days after the end of the intervention
Change in coping strategies
Brief Cope Questionnaire is designed to measure effective and ineffective ways to cope with a stressful life event, and will be used to assess coping strategies. The Brief Cope is a shortened form (28 items) of the Carver and Scheier COPE inventory.
There are 14 coping strategies. These strategies can be then gathered in two main categories : approach coping and avoidance coping.
Measured: At day 5 of the intervention and 2 days after the end of the intervention
Measurement of changes in subjective sleepiness
Changes in subjective level of sleepiness will be measured using the Karolinska sleepiness scale (KSS) two times per day, with a scale from 1 to 10 (higher scores reprensent higher sleepiness).
Measured: At baseline, at day 4 and 8 of the intervention period and 3 days after the end of the intervention
Change in circadian variations of heart rate
Difference between day-time and night-time heart rate (bpm) will be calculated
Measured: At baseline, at day 1, day 4, day 7 of intervention, and at first day of recovery
Change in daily body movements
Accelerometry-derived daily physical activity counts will be quantified using actigraph GT3X+
Measured: Continuously from baseline until 5 days after the intervention period
Dynamics of body fluids during the 4 first hours of exposure
Changes from pre to 240 min of exposure for plasma volume percentage versus baseline (%) assessed by the Dill and Costill method
Measured: The 4 first hours of Dry Immersion / Bed Rest
Lower limb vascular properties
Change in tibial intracortical blood flow velocity (mm/s), induced by physiological maneuvers (velocity of intracortical blood flow at medial tibia level and its responses to vascular occlusion will be assessed via Ultrasound Vector Flow Mapping)
Measured: At baseline, at day 10 of intervention periods, and day 3 of recovery
Myofiber atrophy
Biopsy sampling from m. vastus lateralis will be performed. Myofiber CSA related to fiber type (µm2) will be measured by morphometric analysis.
Measured: At baseline and at day 8 of intervention
Post-occlusive reactive hyperemia at great toe and thumb level
Blood flow (AU) will be assessed via Laser Doppler flowmetry. Post-occlusive reactive hyperemia index will be calculated.
Measured: At baseline and 4 days after the end of the intervention
Quantitative sensory testing at the dorsum of the foot (vibration detection threshold)
Vibration detection threshold (s) will be measured using graded tuning fork
Measured: At baseline, at day 7 of intervention periods, and day 2 of recovery
Whole-body MRI
Change in MRI-measured whole-body Lean mass (kg) and Fat mass (kg) will be estimated
Measured: At baseline, at day 9 of intervention periods
Vestibular health evaluation
Battery of tests routinely performed on astronauts will be used. Sit-to-stand time (s) will be quantified.
Measured: At baseline and the first day of recovery
Blood cytokines evolution
To characterize immune functions, the following blood cytokines (pg/ml) will be assessed: TPO, G-CSF, IL-1β, IL-1Ra, IL-4, IL-6, IL-8, IL-10, IFNy, TNF
Measured: At baseline, at day 3 & 10 of intervention periods, and day +10 of recovery
Salivary cortisol evolution
To characterize stress level, morning and evening salivary cortisol (ng/ml) will be assessed
Measured: At baseline, at day 1, 3 & 10 of intervention periods, and day +4 & +10 of recovery
Change in optic nerve sheath diameter (ONSD) considered as an indirect marker for intracranial pressure (ICP) estimation
The optic nerve sheath diameter (ONSD) variations will be measured by echography
Measured: From baseline to 1 day after the end of the intervention
Change in intraocular pressure (IOP)
IOP measured by applanation
Measured: From baseline to 1 day after the end of the intervention
Change in visual acuity
Far and near visual acuity are tested uncorrected, or if applicable with own correction with digital acuity system
Measured: At baseline and 2 days after the intervention period
Change in visual field
Visual field measured by standard automated perimetry
Measured: At baseline and 2 days after the intervention period
Change in the anatomical characteristics of the eye (optical biometry)
Optical biometry measured by partial coherence interferometry
Measured: At baseline and 2 days after the intervention period
Change in the central corneal thickness
Central corneal thickness on a single point on the cornea measured by Ultrasonic pachymetry
Measured: At baseline and 2 days after the intervention period
Change in the retina by non-mydriatic fundus retinography
Non-mydriatic fundus retinography allows a fundus photography to be taken and thus a color image of the papilla, retinal vessels and macula
Measured: At baseline and 2 days after the intervention period
Change in the cornea topography
Cornea topography measured by corneal topography equipment (like Pentacam). The elevation topography according to Scheimpflug principle allows the mapping of the anterior and posterior surface of the cornea.
Measured: At baseline and 2 days after the intervention period
Change in cerebral structures and in venous circulation of the brain by MRI
Visualization of cerebral structures and intracranial venous system will be performed by MRI coupled with injection of gadolinium
Measured: At baseline and at day 9 of intervention
Change in thrombotic and fibrinolytic processes
Thrombotic and fibrinolytic processes will be assessed by thromboelastometry (TEM, coagulation analyzer from Matel Medizintechnik, Graz, Austria), providing a kinetic analysis of the clot formation process and of clot dissolution by the fibrinolytic system. Clotting time (min) wil be measured.
Measured: At baseline, during the intervention and 2 days after the intervention period
Change in energy requirements
Change in energy requirements using the doubly labelled water
Measured: At baseline and at day 2 of the intervention period
Change in skin microcirculation
Indirect evaluation of cardiovascular and neurovascular change by performing deep inspiration. Blood flow (AU) at great toe will be assessed via Laser Doppler flowmetry. Inspiratory gasp vascular response (%) will be calculated.
Measured: At baseline and 3 days after the intervention period
Change in cardiovascular deconditioning and orthostatic tolerance (stand test)
This test continuously measures heart rate (bpm) via a Finapres device while subjects sit for 5 minutes, then stand for 5 minutes and then sit again for 5 minutes
Measured: At baseline and 2 days after the intervention period
Change in stress and mental load
This test assesses the effects of dry immersion and bed rest on cognitive tasks involving various executive functions (e.g., attention, memory, decision-making) by assessing both physiological (via the SOMNO HD system) and behavioral parameters (e.g., emotions, cognitive load) using the D2 test of attention. Pourcentage of errors (%) will be measured as a qualitative aspect of performance.
Measured: From baseline to 10 days after the end of the intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted15 Jan 2025
- Study start9 Dec 2024
- Primary completion23 Apr 2025
- Study completion23 Apr 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Weightlessness SimulationStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 20 participants (actual)
Sponsor and investigators
- Lead sponsor
- Centre National d'Etudes Spatiales
- Sponsor type
- Other government
- Responsible party
- Sponsor
- Investigators
- Marc-Antoine CUSTAUD, MD, PhD, Study director, University Hospital, Angers
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06777329
- Sponsor's protocol ID
- 24-336
- Other IDs
- 2024-A02109-38
- Acronym
- VIVALDI 3
- Status last verified
- May 2025
- First submitted
- 20 Dec 2024
- Last updated
- 6 May 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 6 May 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Standardization of the Dry Immersion Model Used as a Ground-based Model to Mimic Weightlessness. Part 3: a Comparison Study Between 10 Days of Dry Immersion vs. 10 Days of Head-down Bedrest on 20 Healthy Male Volunteers (VIVALDI 3)
- ClinicalTrials.gov ID
- NCT06777329
- Acronym / sponsor ID
- VIVALDI 3 / 24-336
- Conditions
- Weightlessness Simulation
- Keywords
- Comparison of 2 weightlessness simulation models
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 20 participants (actual)
- Lead sponsor
- Centre National d'Etudes SpatialesOther government
- Study start
- 9 Dec 2024 (actual)
- Primary completion
- 23 Apr 2025 (actual)
- Study completion
- 23 Apr 2025 (actual)
- First posted
- 15 Jan 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The space agencies are actively engaged in studying the physiological adaptation to space environment through studies on board the International Space Station (ISS) but also on the ground. Different methods are used to simulate weightlessness on Earth, including cellular models, animal models using hind-limb unloading, or on humans with unilateral lower limb suspension. However, two approaches, -6° head-down bed rest (HDBR) and dry immersion (DI) have provided possibilities for long-term exposures with findings closest to those seen with a weightless state. They produce changes in body composition (including body fluid redistribution), cardiovascular and skeletal muscle characteristics that resemble the effects of microgravity.
The common physiological denominator is the combination of a cephalad shift of body fluids and reduced physical activity. Being similar in their effects on the human body, these models, however, differ in their specifics and acting factors.
The Head-down Bedrest (HDBR) model has been widely used for this purpose and is considered one of the references for reproducing the physiological effects of weightlessness on Earth. During HDBR, subjects are lying down with an angle of -6° between the feet and head, on their side, their back or their front, but must keep one shoulder in contact with the mattress. All daily activities and tests are performed in this position.
One of the advantages of the HDBR model is that it has now been used in a great number of studies internationally, and its effects have long been described and compared with those of microgravity and spaceflight. Long-term bedrest is the gold-standard method for studying the effects of weightlessness and to test countermeasures.
Dry immersion involves immersing the subject in water covered with an elastic waterproof fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains dry. Within a relatively short duration, the model can faithfully reproduce most physiological effects of actual microgravity, including centralization of body fluids, support unloading, and hypokinesia.
The objective of the present study is to compare the physiological adaptations to10 days of dry immersion versus 10 days of head-down bedrest in 20 healthy male subjects. A set of measurements will assess the changes in the cardiovascular, neuro-ophthalmological, hematological, metabolic, sensorimotor, immune, muscle and bone systems as a result of both models. The most likely outcome of this study will not be to show a clear superiority of one model over the other. Rather, we expect to show differences in kinetics and intensity of adaptations, that should vary from one system to another. This will help future researchers choose the best model depending on the system they are investigating and the rapidity or intensity of the effect they are exploring. The two models, instead of competing with one another, are probably complementary.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Dry Immersion arm | Experimental | Behavioral: 10 days of dry immersion10 days of dry immersion |
| Bed rest arm | Experimental | Behavioral: 10 days of Head Down Bed Rest10 days of head down bed rest |
Who may qualify
- Ages
- 20 to 40 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (0 listed)
Key exclusion criteria (37 listed)
- Any history or presence of clinically relevant cardiovascular, neurological or ENT (especially orthostatic hypotension and vestibular disorders), any chronic disease; any acute infectious disease. Particularly:
- Symptomatic orthostatic hypotension whatever the decrease in blood pressure, or asymptomatic postural hypotension defined by a decrease in SBP equal to or greater than 20 mmHg within 3 minutes when changing from the supine to the standing position,
- Cardiac rhythm disorders,
- Hypertension,
- Chronic back pains,
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| 10 days of dry immersionAlso: Dry Immersion (DI)The volunteers in this arm will be immersed up to the neck for 10 days in a specially designed bath filled with tap water. | Behavioural | Dry Immersion arm |
| 10 days of Head Down Bed RestAlso: Head Down Tilt (HDT)The volunteers in this arm will spend 10 days in -6° head down bed rest. | Behavioural | Bed rest arm |
Primary outcome
Changes in orthostatic tolerance
Time frame: At baseline and first day of recovery
Orthostatic tolerance (min) will be assessed during a progressive Lower Body Negative Pressure test (LBNP test)
Changes in peak aerobic power (VO2max test)
Time frame: At baseline and the first day of recovery
Exercise capacity (ml/kg/min) wil be assessed by graded cycling on sitting ergometer until exhaustion
Change in plasma volume
Time frame: At baseline and 3 days after the end of the intervention
Plasma volume (L) will be assessed by the carbon monoxide-rebreathing method
Change in plasma volume percentage
Time frame: At baseline and at day 1, day 3, day 7 and at the end of the intervention periods
The percentage change in plasma volume versus baseline (%) will be assessed by the Dill and Costill method
Change in fluid shift distribution towards the cardiac and cephalic region
Time frame: At baseline, the first day to quantify the short term effect, the fifth day and the tenth day of interventions to quantify the long term effect of fluid shift
The consequences of the fluid shift on the cardiac and cephalic area will be assessed by quantifying the carotid and femoral diameters (mm), as well as the carotid intima media thickness (mm) by ultrasound.
Change in body fluid compartments by bioelectrical impedance analysis
Time frame: At baseline, during the ten days of intervention and until 3 days after the end of the intervention
Extracellular, intracellular and total body water (L) will be estimated by bioimpedance
Change in calf and thigh circumferences
Time frame: At baseline, during the intervention period and until 3 days after the intervention period
Change in calf and thigh circumferences will be measured using a measuring tape (cm)
Change in fat and lean body mass measured by dual energy x-ray absorptiometry (DEXA)
Time frame: At baseline, after 10 days of dry-immersion and 10 days of reovery
Change in fat and lean body mass (g) measured by dual energy x-ray absorptiometry (DEXA)
Change in Resting Metabolic Rate (RMR)
Time frame: At baseline, at day 3 and day 9 days of intervention periods
RMR (kcal/24h) will be measured by indirect calorimetry technique
Change in nitrogen balance
Time frame: At baseline, at day 3 and day 9 days of intervention periods
Nitrogen balance is a measure of nitrogen input minus nitrogen output. Nitrogen intake (g) is calculated with a nutrition software. Total urinary nitrogen (g) in the 24-Hour urine collection estimates nitrogen output
Change in glucose tolerance (Oral Glucose Tolerance Test)
Time frame: At baseline, at day 3 and day 9 days of intervention periods
Glucose (mmol/L) levels will be measured at baseline (fasting) and 30, 60, 90, 120 and 180 minutes after drinking within 5 min a water solution containing 75 g of glucose
Change in serum bone formation marker (bone-specific Alkaline Phosphatase bAP)
Time frame: At baseline and during the 10 days of interventions
Change in bone-specific Alkaline Phosphatase (bAP, µg/L) will be assessed by chemiluminescence immunoassay
Change in serum bone resorption marker (C-terminal cross-linked telopeptide of type I collagen CTx)
Time frame: At baseline and during the 10 days of interventions
Change in C-terminal cross-linked telopeptide of type I collagen (CTx, pmol/L) will be assessed by chemiluminescence immunoassay will be assessed by enzyme-immmuno assay
Changes in bone density (by DEXA and High Resolution Peripheral Computed Tomography (HR-pQCT))
Time frame: At baseline and at day 10 of intervention periods
Bone density (g/cm2) is measured at lumbar and hip level with DEXA and at tibia and radius level with HR-pQCT. Additionally tibia mechanical properties will be estimated by cortical ultrasound propagation velocity (m/s) via intraosseous ultrasonography.
Change in serum cartilage synthesis biomarkers
Time frame: At baseline, during the intervention period and until 3 days after the intervention period
Change in serum CP II and in human cartilage glycoprotein-39 (YKL-40) concentrations
Change in serum cartilage degradation biomarkers
Time frame: At baseline, during the intervention period and until 3 days after the intervention period
Change in serum Cartilage Oligomeric Matrix Protein (COMP) and fragments or propeptide of type II collagen (C2C, C1,2C, Coll-2-1) concentrations
Change in muscle strength
Time frame: At baseline and after one day of recovery
Muscle strength will be assessed from single leg isometric maximal voluntary contraction on the knee extensors \& flexors, the plantarflexors and dorsiflexors. The Isometric Torque will be measured in Nm. The peak of the three maximal attempts will be recorded for strength measures
Changes in jump performance
Time frame: At baseline and the first day of recovery
Jump performance will be assessed on a platform and height of the jump will be evaluated
Change in contraction time
Time frame: At baseline and at the end of the intervention periods
Contraction time will be assessed during a measurement using the tensiomyography method in the following muscles: vastus lateralis, Gastrocnemius medialis and Biceps femoris of dominant leg.
Change in standing balance
Time frame: At baseline and at day 1 and day 2 of recovery
Standing balance (CoP velocity, mm/s) will be assessed by posturography eyes open and eyes closed on a platform covered with 12-cm thick medium density foam
Change in walking balance
Time frame: At baseline and after 10 days of intervention and day 1 after the end of the intervention
Functional mobility test (such as sit and walk, heel to toe steps with eyes closed and open, Triangle Completion Task) will assess walking balance.
Change in height
Time frame: At baseline and at day 1, day 2 and day 3 of recovery
Change in height (mm) measured in standing position
Change in mid cerebral artery (MCA) blow flow velocity
Time frame: At baseline and one day after the intervention period
Mid cerebral artery (MCA) blow flow velocity will be measured by transcranial Doppler
Change in circadian rhythms of blood pressure
Time frame: At baseline and during the ten days of the intervention periods
Continuous 24-h recording of systolic and diastolic blood pressure will be performed by a Non Invasive Blood Pressure system (SOMNOtouch™NIBP) designed for ambulatory continuous measurements
Change in mood
Time frame: At baseline, at day 5 of the intervention period and 3 days after the end of the intervention
Change in mood is assessed using the Profile of Mood States (POMS) questionnaire, by calculation of total mood disturbance (scale from -32 to 200, a higher score indicates more severe mood disturbance)
Change in affective states
Time frame: At baseline, at day 5 of the intervention period and 3 days after the end of the intervention
Positive and Negative Affect Schedule (PANAS) questionnaire will be used to assess the intensity of positive (range from 10 to 50, with higher scores representing higher levels of positive affect) and negative (range from 10 to 50, with lower scores representing lower levels of negative affects) affective states. PANAS self-report questionnaire consists of two 10-item scales to measure both positive and negative affects.
Change in sleep quality
Time frame: Daily from baseline to 10 days after the end of the intervention
Pittsburgh Sleep Dairy (PghSD) will be used to assess sleep perceived quality. The PghSD is an instrument with separate components to be completed at bedtime and waketime. The following parameters are registered or assessed: Bedtime, waketime, sleep latency, wake after sleep onset, total sleep time, mode of awakening and ratings of sleep quality, mood, and alertness on wakening, as well as daytime information on naps, exercise, meals and caffeine, tobacco and medications use.
Change in psychological state: mental health
Time frame: At baseline, at day 5 of the intervention period and 4 days after the end of the intervention
ical well-being and capture distress GHQ-28 gives an overall total score and 4 scores for 4 subscales: Somatic symptoms, Anxiety/insomnia, Social dysfunction, Severe depression. Higher scores indicate higher levels of distress
Change in coping strategies
Time frame: At day 5 of the intervention and 2 days after the end of the intervention
Brief Cope Questionnaire is designed to measure effective and ineffective ways to cope with a stressful life event, and will be used to assess coping strategies. The Brief Cope is a shortened form (28 items) of the Carver and Scheier COPE inventory. There are 14 coping strategies. These strategies can be then gathered in two main categories : approach coping and avoidance coping.
Measurement of changes in subjective sleepiness
Time frame: At baseline, at day 4 and 8 of the intervention period and 3 days after the end of the intervention
Changes in subjective level of sleepiness will be measured using the Karolinska sleepiness scale (KSS) two times per day, with a scale from 1 to 10 (higher scores reprensent higher sleepiness).
Change in circadian variations of heart rate
Time frame: At baseline, at day 1, day 4, day 7 of intervention, and at first day of recovery
Difference between day-time and night-time heart rate (bpm) will be calculated
Change in daily body movements
Time frame: Continuously from baseline until 5 days after the intervention period
Accelerometry-derived daily physical activity counts will be quantified using actigraph GT3X+
Dynamics of body fluids during the 4 first hours of exposure
Time frame: The 4 first hours of Dry Immersion / Bed Rest
Changes from pre to 240 min of exposure for plasma volume percentage versus baseline (%) assessed by the Dill and Costill method
Lower limb vascular properties
Time frame: At baseline, at day 10 of intervention periods, and day 3 of recovery
Change in tibial intracortical blood flow velocity (mm/s), induced by physiological maneuvers (velocity of intracortical blood flow at medial tibia level and its responses to vascular occlusion will be assessed via Ultrasound Vector Flow Mapping)
Myofiber atrophy
Time frame: At baseline and at day 8 of intervention
Biopsy sampling from m. vastus lateralis will be performed. Myofiber CSA related to fiber type (µm2) will be measured by morphometric analysis.
Post-occlusive reactive hyperemia at great toe and thumb level
Time frame: At baseline and 4 days after the end of the intervention
Blood flow (AU) will be assessed via Laser Doppler flowmetry. Post-occlusive reactive hyperemia index will be calculated.
Quantitative sensory testing at the dorsum of the foot (vibration detection threshold)
Time frame: At baseline, at day 7 of intervention periods, and day 2 of recovery
Vibration detection threshold (s) will be measured using graded tuning fork
Whole-body MRI
Time frame: At baseline, at day 9 of intervention periods
Change in MRI-measured whole-body Lean mass (kg) and Fat mass (kg) will be estimated
Vestibular health evaluation
Time frame: At baseline and the first day of recovery
Battery of tests routinely performed on astronauts will be used. Sit-to-stand time (s) will be quantified.
Blood cytokines evolution
Time frame: At baseline, at day 3 & 10 of intervention periods, and day +10 of recovery
To characterize immune functions, the following blood cytokines (pg/ml) will be assessed: TPO, G-CSF, IL-1β, IL-1Ra, IL-4, IL-6, IL-8, IL-10, IFNy, TNF
Salivary cortisol evolution
Time frame: At baseline, at day 1, 3 & 10 of intervention periods, and day +4 & +10 of recovery
To characterize stress level, morning and evening salivary cortisol (ng/ml) will be assessed
Change in optic nerve sheath diameter (ONSD) considered as an indirect marker for intracranial pressure (ICP) estimation
Time frame: From baseline to 1 day after the end of the intervention
The optic nerve sheath diameter (ONSD) variations will be measured by echography
Change in intraocular pressure (IOP)
Time frame: From baseline to 1 day after the end of the intervention
IOP measured by applanation
Change in visual acuity
Time frame: At baseline and 2 days after the intervention period
Far and near visual acuity are tested uncorrected, or if applicable with own correction with digital acuity system
Change in visual field
Time frame: At baseline and 2 days after the intervention period
Visual field measured by standard automated perimetry
Change in the anatomical characteristics of the eye (optical biometry)
Time frame: At baseline and 2 days after the intervention period
Optical biometry measured by partial coherence interferometry
Change in the central corneal thickness
Time frame: At baseline and 2 days after the intervention period
Central corneal thickness on a single point on the cornea measured by Ultrasonic pachymetry
Change in the retina by non-mydriatic fundus retinography
Time frame: At baseline and 2 days after the intervention period
Non-mydriatic fundus retinography allows a fundus photography to be taken and thus a color image of the papilla, retinal vessels and macula
Change in the cornea topography
Time frame: At baseline and 2 days after the intervention period
Cornea topography measured by corneal topography equipment (like Pentacam). The elevation topography according to Scheimpflug principle allows the mapping of the anterior and posterior surface of the cornea.
Change in cerebral structures and in venous circulation of the brain by MRI
Time frame: At baseline and at day 9 of intervention
Visualization of cerebral structures and intracranial venous system will be performed by MRI coupled with injection of gadolinium
Change in thrombotic and fibrinolytic processes
Time frame: At baseline, during the intervention and 2 days after the intervention period
Thrombotic and fibrinolytic processes will be assessed by thromboelastometry (TEM, coagulation analyzer from Matel Medizintechnik, Graz, Austria), providing a kinetic analysis of the clot formation process and of clot dissolution by the fibrinolytic system. Clotting time (min) wil be measured.
Change in energy requirements
Time frame: At baseline and at day 2 of the intervention period
Change in energy requirements using the doubly labelled water
Change in skin microcirculation
Time frame: At baseline and 3 days after the intervention period
Indirect evaluation of cardiovascular and neurovascular change by performing deep inspiration. Blood flow (AU) at great toe will be assessed via Laser Doppler flowmetry. Inspiratory gasp vascular response (%) will be calculated.
Change in cardiovascular deconditioning and orthostatic tolerance (stand test)
Time frame: At baseline and 2 days after the intervention period
This test continuously measures heart rate (bpm) via a Finapres device while subjects sit for 5 minutes, then stand for 5 minutes and then sit again for 5 minutes
Change in stress and mental load
Time frame: From baseline to 10 days after the end of the intervention
This test assesses the effects of dry immersion and bed rest on cognitive tasks involving various executive functions (e.g., attention, memory, decision-making) by assessing both physiological (via the SOMNO HD system) and behavioral parameters (e.g., emotions, cognitive load) using the D2 test of attention. Pourcentage of errors (%) will be measured as a qualitative aspect of performance.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 6 May 2025.
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Marc-Antoine CUSTAUD, MD, PhD study director
University Hospital, Angers
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing 10 days of dry immersion and 10 days of Head Down Bed Rest in people with Weightlessness Simulation, run by Centre National d'Etudes Spatiales at 1 site in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 0 inclusion and 37 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 6 May 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Changes in orthostatic tolerance (time frame: At baseline and first day of recovery). The study lists 55 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 May 2025; AzTrials last refreshed its copy on 1 Nov 2026.