In a television interview with Oprah Winfrey broadcast on Friday morning, Armstrong revealed that he took drugs in all of his seven Tour de France victories between 1999 and 2005.
Tygart has revealed that Armstrong may be asked to once again testify under oath in a fresh investigation into the American's tarnished career.
"Tonight, Lance Armstrong finally acknowledged that his cycling career was built on a powerful combination of doping and deceit," Tygart said in a statement released on USADA's official website.
"His admission that he doped throughout his career is a small step in the right direction. But if he is sincere in his desire to correct his past mistakes, he will testify under oath about the full extent of his doping activities."
Despite admitting to doping, Armstrong claimed that taking the drugs did not feel like cheating.