Minnesota Vikings running back Adrian Peterson said Friday he is certain that NFL players have and are using HGH and is looking forward to the day when the league establishes a testing program to start "evening out the playing field."

Peterson also acknowledged social media speculation that he used the drug to aid his recovery last year from knee surgery and said he is eager to prove he is clean.

"You've got HGH something that doesn't show up on a test and you've got guys out there trying to provide for their families" Peterson said. "They're going to try to get that edge get that advantage especially if they're not worried about trying to get caught. Yeah it's being used."

Peterson said he heard from plenty of people on Twitter who were convinced his MVP performance last season -- which began less than nine months after major knee surgery -- was aided by HGH or another performance-enhancing drug. He specifically noted having seen the Twitter handle @HGHPeterson.