I tried attaching a backpack to the omnidirectional treadmill, because I was having stomach problems and was worried that the strap on the omnidirectional treadmill which wraps around your stomach to hold you in place was either aggravating or causing those stomach issues. The backpack allows me to use the omnidirectional treadmill without a strap putting pressure on my stomach. The backpack actually works pretty well. It feels a little unsafe to spin quickly or run quickly, because I’m attached to the treadmill higher up on my back and therefore my hips can move forward or to the side and mess with my balance and center of gravity a bit. But other than being a little careful about that, it seems to work OK. I was able to do a gaming workout without falling or hurting my shoulders or anything