Often chanted after a close-up on HIRO's smiling, sweaty face, this phrase could be said to be the "theme song" of the group. It basically means "Boom, boom, boom! Sweaty sweaty!
The phrase often repeated after a close-up shot of HIRO's sweating face is considered the group's theme song.  It translates to "Boom, boom, boom! Sweaty sweaty!"