[Improvement of head-pelvis axis (+Gz) tolerance by increasing body hydration].

Experiments were performed to determine tolerance to head-to-feet (+Gz) acceleration in 62 test subjects aged 23 to 33 years. They were rotated in a human centrifuge before and after they consumed water and water-salt supplements under the conditions of normal activity or dry immersion simulating microgravity effects. During the centrifugation experiments the following parameters were recorded: stroke volume and cardiac output, arterial pressure by means of Korotkov sounds, electrolytes, total protein and hematocrit. Water and water-salt supplements were found to produce a beneficial effect on acceleration tolerance: tolerance threshold increased, stability of cardio-respiratory functions grew, cardiac arrhythmias developed less frequently. The efficacy of the methods increasing the hydration level was related to the amount of water consumed and retained in the body. It is recommended to use a differential approach to the development of procedures for increasing body hydration to be employed in aerospace medicine.