Belts come in handy here for improvising a dodge-ball training target
This mitchmen team have a very efficient way of testing the resilience of new recruits.
Its' no good going in for contact sports if you can't take the knocks!
I love this picture, the simple arm and wrist restraint is so effective both visually and practically and the sense of unexpected combination of helplessness and bizarre threat in a gym of all places is superb. It's hard to credit that it's from Kink.com.
Image of Adam Knox, from Bound In Public, Arrogant Gym Rat punished (incl video clip)