The sports world is once again buzzing about how far athletes are willing to go to win after a report from Al Jazeera named several top athletes as being involved in using banned performance enhancing substances, such as human growth hormone or HGH.

The highest-profile name in the report is Denver Broncos quarterback Peyton Manning.

The allegations come from an Al Jazeera America investigation called "The Dark Side: The Secret World of Sports Doping." Peyton Manning has denied the allegations, telling Sports Illustrated that the allegation is "a total fabrication." The Denver Broncos have also said they they support Manning "100 percent."

For more, we're joined by Courtney Brunious, associate director at the Sports Business Institute at the University of Southern California.