Tony Stewart shares details of ATV accident via Periscope

Giving a firsthand look at his rehabilitation from a back injury that will likely keep him sidelined for a large chunk of his final season, Tony Stewart conducted a question-and-answer Periscope session while walking on a treadmill Friday morning.

The three-time NASCAR champion, who announced his pending retirement last September, suffered a burst fracture of his L1 vertebra in a Jan. 31 all-terrain vehicle accident in the Southern California desert near the Arizona border.

For the first time since the incident, Stewart shared details of what happened during the live stream on the social media app, saying he's "never been hurt so bad running five miles an hour in my life." He underwent surgery three days following the crash, where doctors inserted two small rods and six screws in his back.

"I didn't hit the wrong dune," Stewart said, answering one question. "I just went over one and nose-planted into the bottom of it. It was about a 20-25 foot drop. I didn't think it was a straight drop on the other side."

Stewart was dune buggying with a group that included Jeff Gordon, Greg Biffle, Rusty Wallace, former NASCAR championship-winning crew chief Ray Evernham and NHRA legend Don Prudhomme when he became separated. Stewart said he was laying in the sand for 90 minutes and in great pain before he was rescued.

Stewart described his injury as "just another bump in the road" and that he's "been through a lot worse than this." Previous injuries he's incurred include a broken back during a wreck in a 1996 Indy car race and breaking his right leg in two places in 2013 when he crashed in a sprint car at an Iowa dirt track. At one point during the Q&A, Stewart lifted his T-shirt to show six scars and several bruises.

Doctors have advised Stewart to avoid sitting for any extended periods and he is supposed to either lay flat on his back or stand upright. He will only have to wear a back brace when he resumes driving, though there is no timetable for a return.

The setback will prevent Stewart from pursuing a first Daytona 500 victory (he's 0-for-17), one of the few races he hasn't won in a distinguished career spanning multiple disciplines. When asked if he would reconsider retirement and compete in NASCAR's marquee event, Stewart dismissed the idea.

"No, I'm not doing another season because this happened," he said. "I made my decision and that's it.

"I think this is just a missed deal with Daytona. You'll see us there next year, but in whole different roles."

The seemingly impromptu health update Stewart provided overlapped Stewart-Haas Racing, the team he co-owns, holding a press conference confirming Brian Vickers would drive Stewart's No. 14 car in the Sprint Unlimited exhibition Saturday night and in the Feb. 21 Daytona 500.

Stewart stepped off the treadmill to watch a portion of Vickers' media session at Daytona, even chuckling when SHR president Brett Frood provided a tongue-in-cheek response to a reporter's question. SHR did not name a driver beyond Daytona, with Frood describing the situation as "fluid."

Vickers has dealt with his own health issues recently. He missed significant time in 2010 and 2013 and raced just twice last season due to ongoing complications with blood clots. The 33-year-old sought a return to competition, but only wanted to do so with a team capable of winning, which SHR affords.

"It's nice to be able to take something negative on my side and be able to do something positive for somebody else with it," Stewart said. "I think he'll do a good job."