Confinement study while in the present one despite the subjects reduced slightly their physical activity and changed their salt intake no body weight nor water content loss was reported. Thus the vessel wall change Forsythin measured during MARS 500 could not be related to Ganoderic-acid-F significant hemodynamic changes. No significant change in the portal vein size supports the hypothesis that long term confinement did not induce any splanchnic flow volume change. Conversely during a 60 day bedrest where the subject lived in a confined area and remained in an anti-orthostatic position 24 h a day, a significant decrease in the portal vein area was measured in control subjects. this observation suggests that the changes in portal vein area during head down bedrest were mainly related to the head wards fluid shift and absence of exercise which reduce plasma volume. The femoral and tibial vein diameter did not increase which means that there was no abnormal blood pooling in the legs veins. On 
the other hand the jugular vein was not enlarged like in microgravity or head down bedrest, thus there was no venous stagnation at the cephalic level too. No sign of orthostatic intolerance was observed at the end of the experiment, thus we can consider that the sympathetic and the distal neuro-vascular response to acute fluidshift were not affected as it is the case after a space flight or a bedrest. Carotid and femoral IMT were found significantly increased during the whole confinement period and remained elevated at +2 days after the end of the confinement while it returned to basal level 6 months later. Simulated microgravity on rats induced a cerebral artery wall thickness and cross-sectional area increase, whereas it induced a decrease in cross sectional area and vessel wall thickness at the mesenteric artery level. Moreover daily 1-h �C hyper gravity fully prevented these changes in both kinds of arteries. During tail suspension the animal was submitted to fluid shift towards the head and various stress related to the confinement, and the constraints due to the abnormal position. During MARS 500 only IMT was increased, while the subject was submitted to confinement stress induced but not to any gravitational change nor fluid shift. Conversely in simulated microgravity the animal was submitted to stress plus head ward fluid shift and both diameter and IMT increased. One may suggest that IMT and diameter increase should be related to different factors in these 2 cases. Patients with cardiovascular risk factors and increased IMT have a higher risk to have cardiovascular events than those with normal IMT. Thus IMT increase is considered as a risk factor or a marker of aging at the vascular level like the increase in distal vascular resistance or hypertension. Nevertheless despite an increased IMT is considered as a risk factor associated with atheromatous lesion, no correlation was found between elevated IMT and presence of high degree of stenosis. In diabetes patient with increased IMT the phosphodiesterase inhibitor cilostazol was found to reduce the IMT, while the IMT remained increased in patients not treated. But in the MARS 500 study the subjects had a nutritional regime well calibrated which could not reasonably induce any metabolic disorder. Stable arterial hypertension in young men was associated with signs of remodeling of common carotid artery walls and increase of their rigidity. Such population was closer to the MARS 500 one, than general cardiac patient as the subjects had no multiple cardiovascular risk factor or significant cardiovascular disease but the MARS 500 population did not show any increase in blood pressure. In a normal population, the carotid IMT was found to increase with age and its determinants associated with age and gender.