ST. CHARLES, Mo. — When it comes to comebacks, the most important ingredient is sweat.

But it's not the perspiration you notice when you meet Josh Eckhoff, it's the determination.

"He comes in every day with a positive mindset," his trainer Toma Ghattas explained.

Eckhoff was an athlete who played both basketball and football at Parkway South High School. And that past is pushing the present.

"I want to attain the level of athleticism I had before my injury," he said.

The truth is, this 33-year-old shouldn't be here. And I don't just mean the gym.

He joined the Missouri Army National Guard in 2003 after deferring his freshman year in college.

"I grew up around a lot of Vietnam era veterans," he said. "They taught me early on the importance of serving and what it meant to have the freedoms that we have in this country."

One morning during his second tour in Iraq, his unit was clearing a road of roadside bombs.

"The day of my injury we had cleared our route," he recalled.

It happened as they headed back to base.

"The first projectile came through the door of my vehicle. It concaved the kevlar helmet on my head into the right hemisphere of my brain," he calmly told us.

Eckhoff didn't wake up from a coma until he was stateside weeks later. Lying in his hospital bed, with a traumatic brain injury, a Lt. Colonel had given him a brochure of the latest in power wheelchairs.

"And the next time the Lt. Colonel came in, I said 'Ma'am, they're going to teach me how to walk again,'" he said with a smile.

It turned out that his first step was just a stepping stone.

Sergeant Eckhoff is now running as part of his training with the Disabled Athletes Sports Association.

"I get a sense of freedom when I'm running," he said. "And a feeling like I'm getting back to the man I was before the injury."

And though, instead of minutes, his stopwatch has ticked off years, quitting was never an option. And Josh recently completed a 5K.

"He's always trying to get better, be stronger," said Ghattas.

By now, you may be wondering what is it that motivates Josh Eckhoff. It's not a what, it's a who.

"He was the guy who taught me to be the leader I am in the Army. He was on my first tour with me, he was my team leader," Josh told us.

On that terrible day that he was injured, his dear friend Staff Sergeant Bradley Skelton was killed.

Every Memorial Day, Josh travels to Gordonville, Missouri, to pay his respects.

"I think it's not even sufficient for me to be there that day," Eckhoff said.

It's Sgt. Skelton that inspires Josh in the gym,

When he runs.

And when he went back to the University of Missouri St. Louis to complete his degree. He hopes his friend would be proud.

"I pray every day that that's true," he said. "I think that's motivated me to do things they said I'd never do again."

Bravery doesn't just happen on the battlefield.

"There's nothing he can't do. And I tell him that every day," Ghattas said.

It's clear that Sergeant Joshua Eckhoff will always be a man on a mission.