EDEN PRAIRIE, Minn. (AP) - Russ Paine had never met anyone like Adrian Peterson.

Paine has done decades of work with professional athletes, and Peterson's return to the Minnesota backfield about 8 1/2 months after reconstructive surgery on his left knee still left him amazed.

This guy is in the top half of one percent of the human bodies in the world,'' said Paine, a longtime physical therapist in Houston who supervised much of Peterson's rehabilitation.He's just an unbelievable physical specimen. Those guys tend to recover quicker, but I've had some guys who just weren't tough enough to do it. So you've got to suck it up.''

Peterson also suffered a complete rupture of the medial collateral ligament, slightly delaying his ability to begin putting weight on the leg after the surgery, making restoration of his knee's range of motion more challenging. But, Paine said, Peterson had that movement back in no time.

Peterson's unwavering prediction that he'd play for the Vikings in their season opener after the injury last Christmas Eve proved to be an honest belief, not a competition-driven delusion.

I hope that I inspire a lot of people. Just to change their mentality, I think that's the biggest part,'' said Peterson, who rushed for 84 yards and two touchdowns on 17 carries last Sunday in Minnesota's overtime win over Jacksonville. He added:I understood that if I kept doing my therapy and kept working hard that it would be OK.''

Peterson was referred to Paine by Dr. James Andrews, who performed his operation. At Memorial Hermann sports medicine clinic, where Paine works, about 80 patients per day come through the doors.

Just an unbelievable smile. It's infectious. He'd talk to everybody,'' Paine said.Some of them didn't know who he was, believe it or not, but he'd just ask them how things were going.''

At the beginning, Peterson's visits with Paine lasted about 90 minutes before he left to hit the weights. As the strength in his quadriceps muscle began to come back - one of the biggest hurdles for an ACL patient - Peterson stayed three hours at a time with Paine working on the range of motion, rebuilding strength and balance and moving onto football-specific skills. He made occasional returns to Minnesota to work with Vikings athletic trainer Eric Sugarman and his staff before returning to his offseason home in Houston.

There were psychological barriers, too, but Peterson's combination of confidence in his own healing power and reliance on his Christian faith helped him overcome those.

For all his accomplishments, from that 296-yard game as a rookie in 2007 to those endless clips of him running over a potential tackler during a romp down the field, Peterson might've drawn more praise this week than ever for the way he stepped right in at full strength.

I have to sit back and kind of think, 'Wow, God has truly blessed me with this caliber of talent,''' Peterson said.These guys are in the same league that I'm in, the best of the best.''

The Vikings remain cautious about his workload. Coach Leslie Frazier said this week he's not yet ready to clear Peterson for 20 to 25 carries. But as conservative as they tried to be this summer, once they saw Peterson moving around on the field last month they realized even giving him a few plays in an exhibition game was useless.

We saw him doing things in practice that told us he was well on his way to being ready for the regular season. We could see he was coming at a rate where we didn't have to play him in the preseason,'' Frazier said.It was maybe a week ago or two weeks ago, we knew he was on his way.''

One University of Pennsylvania study, published in the American Journal of Sports Medicine in 2006, analyzed a group of 31 NFL running backs and 33 NFL wide receivers who had anterior cruciate ligament tears between 1998-2002. They came back in an average of nine to 12 months. One in five didn't return to game action at all, though draft slot and experience level always weigh heavily into whether a team brings back the injured player.

But with a formula using total yards and touchdowns in the three years before and after the injury, the authors also determined that statistical performance is reduced by about one-third.

Another study in 2010 in the same publication, conducted by Andrews and some of his colleagues in Texas and Alabama, tracked 49 NFL players covering all positions who underwent primary ACL reconstruction surgeries at their clinic from 2001-06. Only 31 of them, or 63 percent, returned to game action. The average time was a little more than 10 1/2 months after the operation.

So maybe this is not quite a medical marvel, but Peterson's return has raised a lot of eyebrows around the world of sports.

Surgical techniques and post-operation rehabilitation programs have improved drastically over the past few decades, sure, but that magic pill a player can take to start sprinting the day after surgery has not yet been invented.

``It still takes time to heal,'' said Dr. Michael Stuart, an orthopedist at the Mayo Clinic in Rochester, Minn., who also serves as chief medical officer for USA Hockey.

Stuart watched the Vikings play on TV last weekend and, like most other people, found Peterson's performance uplifting.

He definitely is an inspiration for everybody,'' Stuart said.We always have to individualize treatment and make sure we don't pair each patient to someone else. There are all kinds of different factors that can affect an athlete's recovery. But on the other hand, here's someone who is in the limelight and able to return to play at the highest level.''

Paine spoke to Peterson about the risks and reminded him of Hall of Fame wide receiver Jerry Rice, whose too-soon return from his own ACL injury led to a cracked kneecap. Rice was one of the vocal skeptics of Peterson's rapid recovery this summer. But Peterson was too busy with his own rehab to worry about proving people wrong.

``It really doesn't matter. Hopefully they look at things differently. Hopefully it was an eye opener for them. During the process it really didn't matter what everyone else had to say. I had my vision, I knew what I wanted to do, and that's all that matters,'' Peterson said.

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