At the end of a recent practice inside Albuquerque’s Jackson-Winkeljohn gym, UFC light heavyweight champion Jon Jones could be found with his arms draped over the shoulders of his teammates, gathered in a large, sweaty circle of pro fighters all doing their best to jump up and down in something resembling unison.

Trust me, it’s harder than it sounds, which is kind of the point.

At first glance it seems like a conditioning exercise, and it is, in a way. It’s just not strictly for the body. Most of these guys have separate coaches in separate facilities who handle that, after all. This is more about mental conditioning. So too, Jackson insists, are those sand dune sprints he puts his team through in the barren New Mexico desert.

“Toughness is a skill,” Jackson told MMAjunkie. “You learn it.”

That might surprise some people. When you hear fans talk about toughness inside the cage, it often takes on a different feel. It’s as if we sometimes assume that toughness is a trait, something in a fighter’s genetic material, like speed or size. But according to Jackson, who’s seen plenty of tough guys and girls come through his doors, it doesn’t work that way – not for the special brand of toughness that fighters need, the kind that will help people like UFC heavyweight Travis Browne push through broken bones in a losing effort.

“Nobody comes in here born that tough,” Jackson said. “That’s why we do stuff like those sand-dune runs. It’s a very conscious thing we do, and it’s to take people out of their comfort zones, break them down, and positively build them a structure that will help them when the times are rough.”

To hear retired UFC fighter Brian Stann tell it, it works, too. After his time in the Naval Academy and then as a U.S. Marine serving in Iraq, he’d had his toughness tested plenty of times, and with the highest possible stakes. But that kind of grit and resiliency isn’t something you gain once and then keep in your back pocket for the rest of your life, he said.

“I think it’s something you build, but I also think it’s something you maintain,” Stann said. “I’ve seen guys who were really tough at certain points in their lives, like while they’re in the military. But then they transition out, get a civilian job, and it’s like the movie ‘Young Guns II,’ where Emilio Estevez has this line about how if you don’t test yourself every day, you get slow. I definitely think that’s the truth. I know I live that way.”

Even in retirement, Stann said, he still forces himself to do some unpleasant things just to make sure he doesn’t lose that edge. Some of it takes place in the gym during his workouts. Some of it is as simple as proving to himself that he can still operate on little to no sleep, even when he doesn’t need to, just like he did during his time in the military.

“Part of the reason I do it is because, hey, I used to be able to do this in my 20s,” Stann said. “In combat I’d go a couple days without sleeping all the time. If I don’t test myself, I may lose my ability to do that.”

Mental conditioning was as vital to him during his career as it was to any other fighter, Stann said, though it’s not always the kind of thing that shows up on a fighter’s record. For instance, take Stann’s unanimous decision loss to Phil Davis at UFC 109.

“I had nothing for him that night,” Stann said. “My skill set at the time, just athletically, he was a completely superior fighter. When I was underneath him, there was nothing I was going to be able to do to get him off of me. In the second round, I knew I could cover up and let the ref stop it for me, or maybe I’ll let him sneak in one of these chokes he keeps going for. Or, the best I could do that night, is just take everything he has and maybe, just maybe, I’ll create a miracle. That’s a choice you make.”

According to UFC light heavyweight and former U.S. Olympic wrestling team captain Daniel Cormier, it’s also a choice you make in practice. While some people think that grueling fights reveal some essential truth about a fighter’s personality or nature, what they really reveal, Cormier said, is what choices that fighter has made in the weeks and months leading up to that moment.

“Every day you’re given opportunities to work on your mental toughness,” Cormier said. “When you’re in there training with someone like Luke Rockhold or Cain Velasquez, and you’re tired and they’re getting the better of you, there’s your chance. You can check out, or you can get through that day and work on your mental toughness even when you’re not at your best physically.”

That toughness can also sometimes masquerade as a physical trait, Cormier said, as it often does with the UFC heavyweight champ Velasquez. People talk about his speed and his pace as if they’re inherent physical attributes he brings to the cage. Instead, Cormier said, they’re more an expression of his will.

“It’s not that he doesn’t get tired,” Cormier said. “It’s that he’s built himself to the point where, when he’s exhausted and fatigued, he knows you’re a lot further along that path than he is. He understands that, so he’s willing to go there, because he knows you’re going to break first. And it really is mental. It’s not physical.”

The thing about that sort of toughness, however, is that the people who possess it often never let you see it. That’s part of the skill to it, in fact. In Velasquez’s rematch with Junior Dos Santos, Cormier said, he appeared to be dominating with ease. What people didn’t realize is the extent to which he was being tested even while seemingly running away with the fight down the stretch.

“He told me that between the third and fourth round, walking back to his corner, he thought, ‘Well, I’m going to pass out.’ He literally thought he was going to faint right there, he was so exhausted,” Cormier said. “Then he went and sat on the stool and a minute later he got up and fought at the same exact pace. Nothing changed. That’s mental toughness.”

Those moments in the fight are sometimes as valuable as the training that gets fighters there. According to Alliance MMA coach Eric Del Fierro, sometimes it’s just a matter of finding yourself in the fire before you realize how tough you are.

“Like building soldiers for war, once we confront their fears and weaknesses, they will grow tougher,” Del Fierro said. “Once they realize what their mind and body are capable of, mental toughness increases.”

That’s sort of how it was for both Jones and his most recent challenger, Alexander Gustafsson. Their brutal five-round battle in September forced both men to dig deeper than they ever had before. That’s why the fight that landed him in the hospital was “actually really inspiring” for him, according to Jones.

It was inspiring to other fighters, too, Stann said.

“That’s a different level of toughness,” he said of the Jones-Gustafsson bout. “I don’t know if both those guys knew they had that in them. There’s a choice that they made somewhere in that third or fourth round, and they both had to make it. It’s that moment where you decide to either push through it or quit.”

Even Cormier, who hasn’t been Jones’ biggest fan of late, had to admit that it was something special. What he’ll be watching very closely to see at UFC 172 on Saturday in Baltimore, where Jones defends his title against Glover Teixeira, is whether it was a one-time thing.

“You saw that Jon Jones is pretty mentally tough because he got through that,” Cormier said. “He was getting tested like never before, getting beat up, looking like he was going to lose the fight. Was he mentally tough going in, or was he forced to become mentally tough in that instant? Is he OK with knowing he may have to go there again? We don’t know. That’s one of the things we may find out this weekend.”

For more on UFC 172, stay tuned to the UFC Rumors section of the site.