My friend's Pit did it until he fell down the stairs at a motel and dislocated his knee, then he had to retire. He pulled some insane amount of weight, like 2200 pounds, or something like that. Not bad for an 80 pound dog. My old Beagle would have loved to do it, he used to love to drag me around the house by a sock. I weighed about 250 pounds, and he was 40 or so. He could get some decent speed built up, going backwards!