Originally, astronauts preparing for space first used sensory deprivation. In fact, NASA still trains their space personnel with these devices. While astronauts need to know how weightlessness will affect their bodies over time, floatation tanks focus on providing short-term benefits to users. Interestingly, when used as a therapy aid, floatation tank sessions have the exact opposite effect of long-term weightlessness in space.
In space, lack of gravity over time starts to shrink muscles and bone mass causing widespread pain and poor joint functionality. Muscle shrinkage also affects the heart’s ability to pump blood. In a zero gravity environment, blood flow does not fight moving towards the heart and head as it does on earth. The result is that blood flows more freely in peoples’ upper extremities and can cause puffiness in the face and eyes.