User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-4714392-20130929143726/@comment-6050823-20130930023742

Its actually an ability recently found on Rajangs, atleast the ones in MH4's Region(I'm sure this may have some connection with the Red Rajang of Frontier). Anyway, it increases the strength and power in Rajang's arms allowing for it to do more damage and also allowing it lift up heavier objects. The only two downsides to this ability is that puts alot stress on the Rajang's body causing it tire easily and also lowering down its defense, letting hunters do more damage.

Sources: Trinfo and Famitsu