The ones you can balance on while doing weights? ?They look like an exercise ball that's been cut in half and it has a flat rubber/plastic side you can stand on or put flat on the floor. ?
I used them when i worked w/ a trainer and it make a huge difference to balance on it while I was doing weights. ?She also made me do push ups and jump ups with it---the b*tch. ?;-)?
Re: what are those 1/2 exercise balls called?
Bosu balls.
I take a Bosu Ball class on the weekends and feel like I want to die every time. It is brutal.