Minnesota Vikings running back Adrian Peterson appears to be in the best shape of his life, which is good considering that he's a 31-year-old rusher with six 300-plus touch seasons under his belt. The veteran joined the team for the start of OTAs on Monday and once again began to impress during practice this week. Afterward, he spoke about his conditioning and how he feels right now.

A reporter pressed Peterson to describe the shape that he's in at the moment.

"Here we go with the shape question again," Peterson joked. "Yeah, I'll say that [I'm in the best shape I've been]. I feel good."

Peterson's work ethic has never been in question, and his conditioning has always been top notch throughout his career. What's more important to the ball-carrier is his promise to improve following Minnesota's post-season defeat at the hands of the Seattle Seahawks. Head coach Mike Zimmer pointed to this promise earlier this offseason, saying that the offense would demand more versatility from him.

Specifically, Peterson wants to become a better receiver.

"It's really focusing on running the route tree, just being more agile in running routes and not as stiff," he said. "You get out and you run routes. Whether it's after the workout, you get 10 routes in each - whether it's a flat, or whether it's an option route - we just kind of go through it. We just kind of pinpoint being patient, depending on what route in the concept is going to be called."

Peterson was only targeted 36 times in 2015, and he was normally replaced by Jerick McKinnon or Matt Asiata on third downs. In 2016, Peterson wants to remain on the field during passing downs, which means being more effective in the shotgun formation.

"I thought I was being patient, but I felt myself kind of being a little too fast. The pace was too fast on it...On that play, there was a little more penetration, so that kind of sparked me to speed it up. But even in that instance, I still have to be a little more patient than I was."

If anyone can make this transition work, it's Peterson. Last year, he became the first 30-something running back to win a rushing title in more than a decade. He's used to defying the odds.