This is most likely the exercize that did his biceps in.
As Hong Kong Phooey would say, "could be!"
Just looking at that photo for a second... I seem to recall back when he was talking about the importance of this exercise to him, and how he suggested it was best executed, he said to keep the thumbs out of the grip to reduce the involvement of the biceps. Since he's clearly using a full grip here, perhaps it's because the poundage he was using for the shoot was higher than he'd normally use..? Can anyone tell if that's a Chris Lund shot..?