In "The Forever War", by Joe Haldeman, they used fluid compression to survive extreme acceleration in their starships. Most of the time was shirt-sleeves, but when they went into battle, it was "into the tank." He goes into a fair bit of gory detail about the discomforts of it. Frequently better science fiction authors will have some amount of research behind what they write, but I have no idea what research he might have done back in the mid-1970s when this was written.