It is done quite successfully in North Korea. Prisoners are forced to work 15 hours a day, 364 days a year. And they're fed a bit of corn meal to beef up those muscles. If they're too sick to work, well just beat them into shape .. make them do 18 hours the next day. It's all done for rehabilitation.
Sounds like WalMart garment workers in Bangladesh only they don't get fed...........
Walmart refuses to join worker safety deal
Walmart refuses to join worker safety deal | Business | The Guardian