♪ ♪ >> greg: welcome back to "yarn in fun." sometimes the world needs jerks. for example, former olympian michael johnson is technically a jerk. he pointed out a legs in the olympics is troubling to him. south african paraolympian oscar is able-bodied this 400-meters, even though he runs on two carbon fiber legs. now when johnson was asked if oscar's inclusion made sense he said, "because we don't know for sure whether he gets an advantage from the prosthetics, it is unfair to the able-bodied competitors." scientists do suggest the gams could boost speed by up to 20%. maybe because he is l...