I have to think that the other end of the blue rod we see in pic 1 is connected to his hood and pulling up. This means he can't lower his head without pulling on his arms and this in turn puts more strain on his arms in that position, although his hood could be connected to something we can't yet see and is equally pulling it up. He can't move his legs as they are tied and his balls are connected to that rachet pulley, so he can't pull back on that either. He can be left in this position as long as you decide as he'll only ache a lot, no real danger of anything much.  I do think a cane to the ass is called for though. 