The LBNP is a fabric cylinder like a sleeping bag which creates a partial vacuum around the lower body. The vacuum returns some of the fluids to the legs. The combination of fluid loading and the LBNP may alleviate some of the orthostatic intolerance problems. Vestibular function and equilibrium will also be studied. Extended stays in orbit appear to magnify an astronaut's perception of motion.
Sensory disorientation can occur when voluntary head motions are made.
The effect is especially important to understand because it can affect critical tasks, such as landing the Shuttle or making an emergency egress. One experiment will have crew members execute a variety of head movements with eyes both open and closed, and report on sensations of movement. Collection of cardiac dysrhythmia data during other non-EVA activities is incomplete. Consequently, it is not possible to tie dysrhythmias to a particular set of conditions, such as workload or exposure to pure oxygen at lower pressures inside spacesuits. To gather the data, crew members will wear cardiac monitoring devices for 24-hour periods and record ECGs during rest and exercise and after exercise.