Lower Body Negative Pressure Test
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Function: 
The lower body negative pressure test places a stress on the cardiovascular system very similar to the one experienced when standing in Earth's gravity. 

Procedure: 
The crew member is placed in the lower body negative pressure device. The tube covers the astronaut from the feet to the waist and an airtight seal is made around the waist.  A pump then sucks air from the tube which creates a negative pressure inside the tube and hence around the legs of the subject. This in effect pulls blood from the upper part of the body to the legs. The pressure is lowered for about 50  minutes during which measurements are made.

Hardware: 
The lower body negative pressure device is a cylinder that encloses the lower abdomen and lower extremities to maintain a controlled pressure differential below ambient during periods of extended weightlessness.