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first, your legs first, then stand up, make sure you’ve got your balance back. The balance is the one thing that you just don’t have. Again, the brain hasn’t been utilizing the inner ear or senses of where the pressure is on the bottom of feet, for instance, to use as cues to balance itself against gravity. It hasn’t done that for a week. So you’ve got to carefully start through all that and consciously think about balance and consciously think about standing up, and we very consciously do that, because the last thing you want to do, in front of hundreds of millions of people watching on television, is to fall down the ramp leaving the orbiter.
    Normally, on Earth, the body works hard to make sure the brain is adequately provided with blood. From a circulatory perspective, the brain, the part of the body that most needs blood, is located inconveniently at the top of the body, so the heart has to pump blood against gravity to get it there. In orbit, on the other hand, blood flows much more easily to the head, but it doesn’t fill the legs the same way without gravity pulling blood into them. Astronauts develop bloated heads and “chicken legs” due to the body’s confusion over how to distribute blood without gravity. The body takes the increased fluid flow to the head as a sign that it is overly hydrated and begins to shed what it sees as excess fluid. After the return to Earth, fluid redistributes again, which can cause problems.
    “The body adapts by, among other things, letting go of a lot of fluid, about a liter of liquid, which makes you clinically dehydrated while you’re in space, except the whole condition of the body is different up there, so you’re really not dehydrated in that environment,” Walker said.
But if you come back without replacing that liter of fluid, then you are dehydrated. You try to stand up with not so much fluid to go to the head, and so you literally could pass out. Nobody did that, but I know I had sensations of lightheadedness for the first few minutes until I just literally worked at getting my balance back and focusing attention, and the body was adapting all that time, too. But leaving the spacecraft, I was holding onto the handrail as I went down the stairway. Got to the bottom of the stairs, and I was walking like a duck, because I was trying to keep my balance.
    Once they’ve adjusted enough to walk, crew members board the Astrovan, which takes them to the medical quarters for postflight medical exams and a shower. Walker said it felt good to take a shower after days without one.
Every sensation for the next many hours, normal sensations of water running over you in a shower, [felt] strange. Because again, here this water’s hitting you, and it’s running down. And hours later, I found that I still could at any moment just think about the sensations in my body, and it was odd to feel this pull down toward the surface of the Earth, to be stuck to the surface of the Earth. [When I flew], it was still fairly new to hear comics or some wag note that this or that “sucks.” [Coming back] the astronauts were saying, “Well, the Earth really does suck.” So it keeps me drawn right down to the surface. Gravity is really real, and it stands out in your mind to, again, the freedom of weightlessness when you’ve had that opportunity. And that was just very much on my mind. I remember even a day, two days later, probably like a day later at a meal, I was sitting down, and I could not easily figure out whether I should sit back against the back of the seat or lean forward, because my head was telling me I was leaning forward at an angle, and, in fact, I was sitting almost straight up and down. So the inner ear is still adapting to its own senses and the body’s cues to orient itself and still doesn’t have itself figured out completely yet.
    Even if an astronaut spends only a few days in orbit after a lifetime of living in the gravity of Earth, habits developed during those