Grandmaster Tu Jin-Sheng, best known for his Iron Crotch, attached himself not once, but twice, to a rental moving truck and pulled it several yards across a parking lot in Fremont. In lace-up leather boots and a black tank top, the 50-year-old tied a strip of blue fabric around the base of his penis and testicles and tugged to make sure it was on tight. An assistant kicked him hard between the legs before he lashed himself to the vehicle.
Here's the best part of the article:
Jin-Shengs performance drew a hearty applause (and only a few gasps) from the sparse crowd. He wrapped a piece of fabric around his waist to conceal his genitals from the crowd, but in the heat of the second truck pull, when he tied the cloth around his testicles only, it was pushed aside to reveal a ball of flesh that looked ready to burst.
Lovely. So apparently this sport doesn't involve muscle training, per se. It's more like hoping your skin and connective tissue don't rip apart as you lift (or pull) the weight. The description of the event sounds credible enough for me to categorize it as real.