The moment before the bullpen opens, adrenaline rises and the heart beats rapidly. A bull awaits release from the confinements of tight space while the rider anticipates a fierce eight-second battle after the gate opens.

This is the norm for professional bull riders who participate every weekend in what is dubbed the toughest sport on Earth. Professional Bull Riders Inc. stopped in Chicago at the home of the Bulls and Blackhawks, the United Center, 1901 W. Madison Ave., for the Chicago Invitational on March 5 and 6.

The Chicago Invitational is part of 28 events PBR holds in a yearly quest for one bull rider to win top prize in the World Finals, which conclude in Las Vegas. The Chronicle talks with bull rider Shane Procter.