With the temperatures soaring in Nashville, the NASCAR Xfinity Series was tested today over the course of 250 miles. John Hunter Nemechek wanted to let the people know just how difficult racing on a day like today is. For those who don’t know, John Hunter Nemechek is an athlete beyond racing. He has trained and participated in Iron Man events and other triathlons. Nemechek pays close attention to his heart rate during races. Today in the media center after his win at Nashville Superspeedway, Nemechek explained how difficult racing in these conditions is for drivers. “I mean, I didn’t know it w…