Wednesday night marks the premiere of “Man Vs. Bear” — or what happens when 21 brave-but-nervous athletes battle thousand-pound grizzlies in close proximity.

Each episode of the competition series, airing on Discovery (9 p.m.), features three athletic-minded contestants (men and women) engaging in five dangerous challenges against thousand-pound grizzly bears Tank, Honey Bump and her brother, Bart — famous for battling Jaime Lannister (Nikolaj Coster-Waldau) and Brienne of Tarth (Gwendoline Christie) in a Season 3 episode of “Game of Thrones.” The series is hosted by CBS Sports personality Brandon Tierney (“Tiki and Tierney”), who provides play-by-play (he’s joined by bear expert Casey Anderson).

“You’re going to see people testing the boundaries, not only of physical exertion, but of physical will and the potency of the mind,” says Tierney, who spent five weeks shooting the show in (of course) Bear Mountain, Utah near the sanctuary where Tank, Honey Bump and Bart live with their owners, Doug and Lynne Seus. “They have to be able to compartmentalize and process what’s in front of them — testing the limits and boundaries of life and unpredictable and frightening moments in something that has never been tried before.”

The contestants get fairly up-close-and-personal with the bears; no editing or camera tricks were used to separate the competitors in the five challenges: King of the Mountain (tug-of-war); Brute Force (log rolling); Apex Predator (humans and grizzlies chow down on bear food); Grizzly Heights (Honey Bump chases the contestants … up a tree); and Human Prey, in which the contestants, in a round ball steel cage, are rocked and rolled by Bart, the biggest and strongest of the grizzlies at 1,100 pounds.

“The bears are tame, but you can’t account for that small percentage of something going awry,” says Tierney. “In the tug-of-war competition everybody winds up in the water — you can’t outmuscle a grizzly bear and there were a lot of flailing limbs when people went into the water. In one case, the medical team went over and I tried to capture it in my call. No one knew what kind of condition that person was in and they sent in a diving team just in case.

“Every single day we shot somebody who entered the competition and they’re spirits were eventually clearly broken,” he says. “There was some dripping blood and black and blue marks.”

grizzly bear
Discovery Channel

Tierney says his sports announcing background came in handy when describing the action on “Man Vs. Bear.”

“Obviously I bring a 20-year sports background and I talk sports for a living. I’ve been in arenas and stadiums all my life,” he says. “You get verbal and non-verbal cues from athletes — are they fully engaged? Is there trepidation? Confidence? The challenge for me was to take that database and apply it to a completely unpredictable beast.

“I took my cues from the bears and had to be ready to explode into a call when the action happened without warning,” he says. “They’re calculating, cunning, cerebral and pretty awesome.”

Tierney says, that, believe it or not, some of the contestants trash-talked Honey Bump, Bart and Tank — much to their chagrin. “Some of them were loud and brazen and shouted at the bears trying to intimidate them,” he says. “They were deploying an intimidation tactic while others were more introverted and a little more cerebral, mentally going through it with a poker face.

“You wouldn’t think this would play in a competition series, but it does and they’ve captured it well,” he says. “It really does emit a good balance of the unknown, fear, sympathy and empathy.”