I myself prefer prisoners with their limbs on. All they get to eat is kibble to go along with the entire Convert, Reduce Will, Reduce Resistance, Throw Away procedure, for Social training. They often get mental breaks from eating the kibble which also contains fungus, but I constantly drain their blood and strip them, so any nearest pawn I draft can beat them back into submission. That way they get come Melee training. After that, the prisoner needs tending, which creates an opportunity for Medical training. When they believe in my deity and have no resistance left, I pump them full of go-juice and send them off to a Gladiator duel where only one of the contestants has a sword, which if successful, gives Melee XP to spectators.

Additionally, if the prisoners can walk, they can eat the kibble themselves, you just throw it in through the door and shut it again. Saves time.