The reasoning behind this is unclear, but he did it a number of times throughout his match with Dean Ambrose so there has to be something in it at least. Maybe Harper showing off his muscles is a stab at Roman Reigns' bulges, and how that physique is part of the reason why Reigns is the perceived 'chosen one'. Or maybe Luke is just poking fun at Ambrose's guns, as they are smaller than the rest of the roster's. Whatever it meant, it will surely be made more clear before Bray, Luke, Dean and Roman face-off at SummerSlam.
