 Costumes are regulation " posing trunks " ( bikini briefs ) for both men and women . Female bodybuilders in America are prohibited from wearing thongs or T @-@ back swimsuits in contests filmed for television , though they are allowed to do so by certain fitness organizations in closed events . For men , the dress code specifies " swim trunks only ( no shorts , cut @-@ off pants , or <unk> ) . " 
