It was another bit of collateral damage that Armstrong said he wasn't prepared to deal with.
"I saw my son defending me and saying, 'That's not true. What you're saying about my dad is not true,'" Armstrong recalled.
"That's when I knew I had to tell him."
Armstrong was near tears at that point, referring to 13-year-old Luke, the oldest of his five children. It came just past the midpoint of an hourlong broadcast, a day after the disgraced cycling champion admitted using performance-enhancing drugs
when he won seven straight Tour de France titles.
Critics said he hadn't been contrite enough in the first half of the interview, taped Monday, but Armstrong seemed to lose his composure when Winfrey zeroed in on the emotional drama involving his personal life.
"What did you say?" Winfrey asked.
"I said, 'Listen, there's been a lot of questions about your dad. My career. Whether I doped or did not dope. I've always denied that and I've always been ruthless and defiant about that. You guys have seen that. That's probably why you trusted me on it.' Which makes it even sicker," Armstrong said.
"And uh, I told Luke, I said," and here Armstrong paused for a long time to collect himself, "I said, 'Don't defend me anymore. Don't.'"
Lance Armstrong came clean to the American public on Thursday night when he admitted to Oprah Winfrey that he used performance enhancing drugs in each of his seven Tour de France wins. But was he really being truthful? After so many lies, its difficult to believe him now. And a host of body language experts have already examined Armstrongs non-verbal communication to make their own determinations.