Cyclist Tom Zirbel has been suspended for two years after testing positive for testosterone at the US Pro Road Championships last August, the US Anti-Doping Agency said Friday.

Zirbel, 31, finished second to David Zabriskie in the individual time trial at the championships, held in Greenville, South Carolina.

But his urine sample was positive for testosterone or its precursors, banned as an anabolic steroid.

Zirbel, who has denied doping, said in a blog in February that he was “walking away” from the sport rather than pursue an aggressive fight against the charge.

USADA said that Zirbel “accepted a two-year period of ineligibility which began on November 17, 2009, the day he accepted a provisional suspension.”

Zirbel’s results achieved at and subsequent to the meeting are forfeited.

In his blog on Friday, Zirbel wrote that he accepted the sanction in order to “gain a little credibility with USADA” but indicated he still didn’t know how the positive result came about.

“Even when my friends and family know that I am not a cheat, it still hurts to write this and it really hurt to send that fax today,” he wrote.

“Nothing has really changed: I will still continue to have testing done to try and figure out how this all happened in the first place and I still won’t be racing.”