As most people know, a microgravity environment is devastating on the body when it comes to muscle and bone-density loss. This has been a big problem for astronauts on long missions on the International Space Station. NASA has, in the past, come up with a few implements to help this problem. Unfortunately, they weren't machines that were suited best for muscle building. The end result is that for most of spaceflight, exercise in space has consisted of running on a treadmill or using an exercise bike. I thought it would be a great idea to use S&P principles and come up with an exercise machine that specifically recreates the big three (squats, deadlifts, and bench press). So I tried to contact NASA officials to see if this could be done. It turns out, they've already begun producing a machine that does this as of 2006. Took them long enough, but it seems like even NASA agrees that deadlifts and squats are the best way to reverse muscle loss (per an interview with Beth Shepherd, NASA trainer). Here are some pics of the Advanced Resistive Exercise Device (ARED) that was just shuttled to the ISS. 
Unfortunately, it's more like a Smith Machine but it's probably the closest to simulating free weight barbell in space that you can get.
Unfortunately, it's more like a Smith Machine but it's probably the closest to simulating free weight barbell in space that you can get.
I personally don't like those lifts, they are way too prone to cause injury... lunges are good enough (on earth) and increasing the strength of the lower back beyond just doing yardwork seems nonbeneficial compared to the risks.
