YouTube friend rivest266 sent me a link to the "Google Newspapers" archives, where he had discovered this fascinating article about Bed Pilots published in the St. Petersburg Times on Wednesday, April 4, 1973. An early milestone in the attempt to understand the effects of weightlessness!
Interestingly, two of their volunteers were prison inmates, so apparently the whole "background check" part of the screening process came much later.
The overall drill was the same: micro-gravity simulation to examine changes in bone tissue production. They mention exercise and pressure suit trials, and rounds where some subjects were given calcium supplements and compared to a control group who got none. The biggest difference to the current studies was the lack of a -6 degree tilt to the bed, to mimic blood flow and plasma volume changes that occur in weightlessness. It's amazing to see how these studies have evolved over the years as we've tried to achieve greater accuracy and learned more about the body while trying different counter-measures!
The subjects were paid $200.00 every two weeks. That works out to about $970 in modern* dollars. Today's study pays $2150 every two weeks -- more than twice the going rate for medical guinea-pigging in the 70s!
* (Source of calculations: http://www.measuringworth.com/calculators using the Consumer Price Index)