If you wanted to do astronaut training you might get devices that reverse the effects of gravity, flip you upside down, set you into blastoff position, evenly distribute your weight.  NASA developed materials and designs would be your template.

The first device our space cadet will use is an inversion table.  The inversion table pivots like a teeter totter and is adjusted to your body height and weight so that you can control the movement up and down by just moving your arms up and down.  Up above your head to go upside down and back down at your side to return to earth.
Inversion Table

There are foot clamps to hold your ankles and then you just go.  Here is a shot of me inverted.

Dave Inverted

Now I've been doing it slow and easy, but I suppose if you want the lightheaded, dizzy floating in space feeling you could go from upside down to upright quickly.

The next device in our space arsonal is the Anti Gravity chair.  This chair is a recliner that sits on a pivot. Similar to the inversion table it is balanced and you get it to recline back or forward by moving your arms up and down. You can move your legs as well for fine tuning. Then you can lock the chair into place.  The chair is supposedly designed on space shuttle seats so that it distributes your weight evenly along the spine for being able to handle multiple Gs of stress.  (In my case 1 G)  When reclined all the way back you are facing up into blast off position.

Chair computer station
Here is a shot of me using the chair.

Dave at Puter

OK, so I"m not going to get a natural shot unless someone else takes the picture.  Anyway I recline back with my keyboard across the armrests and set myself further back or up depending on how much spine stress I want to deal with.  This is a lot more comfortable than laying on the floor.  If I feel that I've been sitting too long in one position sometime I will release the locks and just let the chair swing down to a slightly inverted position and back up a little.  This should get the fluids moving along the spine.  I haven't used the massage features of this chair yet as currently am just enjoying it as a chair.

Other space materials.  I have also purchased a memory foam mattress topper.  Memory foam is another material developed by NASA.  It helps support the spine in whatever position you are sleeping in by filling in the spaces on your body and distributing your weight evenly.  Just as if you are sleeping in space.  (Memory foam has quite an odor.  They say to just air it out a couple of days, but still has quite an odor.  I'm referring to it as stink foam.)  You can buy entire mattresses made of memory foam.