I've been working with thisTRX strap going on two weeks (I have little balance apparently), and I was just pointed to this interesting link:
"It might be hard to imagine how someone with one arm trains with the TRX. It’s really very simple, explains Dustin. “We just attach the foot cradle to her left shoulder girdle. The TRX allows muscles to engage in the multiple planes of motion Bethany needs to restore balance in her frame and improve stability.”"