The indoor football field at UPMC Sports Medicine is where the Steelers and Panthers practice. I've been here a few times when the Pittsburgh Marathon and Steel City Road Runners hosted training runs. Due to the large number in attendance, Porta Johns are placed in the parking lot.
It's a great facility and parking fills up quickly during the runing events. The Southside trail is right next to the complex and you're walking distance from Southside Works and other businesses.