Effect of antiorthostatic bed rest on the human body

Head-down (-4 degrees) bedrest brings about a more rapid development of changes in haemodynamics, fluid displacement and nervous tone than traditional recumbent bed rest. Changes occurring during head-down hypokinesia have much in common with the changes typical of real weightlessness. They are characterized by phasic changes in the vascular tone. Under these conditions changes in the tone and blood-filling of the brain are important for the functional state of the vestibular apparatus.