Toby Gerhart's upper body looks as if it has been inflated with air. Barrel-chested with thick arms and shoulders, he looks as if he swallowed a keg.

"I've been the same weight since my senior year in high school," he said.

Come on. No way. He's never resembled a toothpick, but this is not how he looked last season.

"I think last year my weight was 233," he said. "This year they bumped my weight to 235."

That's it? Two measly pounds?

Weight gain or not, Gerhart sported a different appearance when he arrived for Vikings training camp. He transformed his body this offseason while maintaining his target weight, hoping the ripped muscle look would enable him to withstand more punishment as a featured running back in case Adrian Peterson's recovery from knee surgery hit a snag or unexpected delay.

Peterson's rehab remains on track and the Vikings intend to ramp up his workload in practice this week, but the team plans to hold him out the final two preseason games.

The Vikings continue to express cautious optimism with Peterson's timetable, careful to let the process play out, even as Peterson pushes the envelope to get back on the field. Peterson, of course, wants it to happen yesterday. He wants to feel the sensation of smashing into a defender, hitting a hole, getting tackled to the ground. He's ready to test his reconstructed knee to see how well it holds up.

The Vikings, however, must view his comeback and his career through a longer lens. They need him long-term, not only for Week 1. They won't do anything to jeopardize his future, or the $36 million in guaranteed money they invested in their franchise back.

Besides, they have a solid insurance policy in Gerhart, who is talented enough to be an NFL starter and has shown enough improvement to warrant a more prominent role in this offense, even with Peterson in the lineup.

We're not suggesting a 50-50 split or anything like that. Peterson is a special talent, and the guess here is that he will return to his normal self, or close to what he was pre-surgery, once he knocks some rust off.

But the Vikings certainly can and should lighten his workload, based on Gerhart's development at the end of 2011 and so far this preseason. Assuming Peterson returns for the season opener, it makes sense to have him and Gerhart share carries for a few games or however long it takes until Peterson feels strong enough to handle more. No need to rush things unnecessarily.

"With Adrian, all signs are point toward him being back and ready," Gerhart said. "At the same time, I don't know how big my role is going to be, but I'm going to be prepared to be the guy and be the starter."

Gerhart has rushed for 61 yards on 11 carries in the first two preseason games. He also had some nice moments in relief of Peterson last season. He has come a long way from his first training camp two years ago when veterans went out of their way to pound on the rookie, even in non-contact drills.

"I just feel much more confident and relaxed," he said, adding that a better understanding of the offensive system enables him to be more "instinctual."

His running style is pretty straightforward, literally. He's a true power back who relies on brawn more than speed. He's a load to bring down once he gets up to speed or in a rhythm. He becomes stronger the more carries he gets, but that's difficult in a backup role.

"Early on last year, I would get one in the first quarter, one in the third quarter," he said. "It's hard to get a feel for the game. When you get a couple back-to-back, that's when I'm at my best. I think that's any running back. You like to get a little sweat going."

Offensive coordinator Bill Musgrave said Gerhart is more assertive and "quicker to hit the hole" this season. That's largely a product of him having a full offseason and more familiarity with the scheme. But Gerhart also credits his offseason conditioning work, which included yoga in order to become more flexible.

"Tried to loosen up my hips a little bit so I'm not as stiff," he said.

Gerhart laughed at that thought. He knows he's always going to be more of a road grader than race car.

"I'm not going to be as fast as Adrian," he said. "This is what I was given."

His style works too. Hopefully, we'll get to see more of it. There should be plenty of room for him even when Peterson gets the green light.

Chip Scoggins • ascoggins@startribune.com