Backstreet Boys star A.J. McLean was left doubled over in pain after allowing his bandmate Nick Carter to hit him in the testicles with a baseball bat for a bizarre stunt.

The I Want It That Way hitmakers were taking part in a photo project for celebrity snapper Tyler Shields recently when MCLean took a smack to his groin - although the purpose of the brave prank is not clear.

Video footage of the encounter has since been posted online, depicting MCLean bracing himself for the hit by pleading, "Not in the nuts dude!", before relenting and saying, "Ok, just do it quick!"

After Carter strikes him in the privates, the camera pans to fellow Backstreet Boy Kevin Richardson, who quips, "He's got balls of steel!"