The reality is, BJ Penn and Jens Pulver do not like each other.

That will be one of the main storylines on "The Ultimate Fighter 5" reality television series, which is scheduled to begin airing nationally on Spike TV Thursday.

Penn and Pulver are regarded as two of the best mixed martial arts competitors in the world. They will serve as opposing coaches for up-and-coming fighters on The Ultimate Fighter 5.

"I respect him — he's a world champion and I know he's dangerous," Penn said of Pulver. "But I just don't like him. That guy runs his mouth way too much."

Penn was raised in Hilo and still trains there. He is the first Hawai'i competitor to be selected as a coach for the popular reality show.

Previous coaches on the show included world champions Chuck Liddell, Randy Couture, Rich Franklin, Tito Ortiz and Ken Shamrock. The Ultimate Fighter was one of the most-watched shows on cable television for its first four seasons.

"This is definitely a huge promotion for me and my career, and for Hawai'i as well," said Penn, 28.

Pulver, 32, is from Iowa. When the television series concludes in June, Penn and Pulver will fight each other in Las Vegas, so the show will also provide months of hype for that bout.

"He's not a rival anymore, he's a straight nemesis," Pulver said of Penn. "He's a great fighter. He's a legend in the sport. But I really want to knock him out."

Penn said of Pulver: "I want to retire him."

Their rivalry can be traced to 2002, when Pulver upset Penn via decision for the world championship in the 155-pound class of the UFC organization.

The two fighters went their separate ways since then, but The "Ultimate Fighter 5" apparently ignited a hatred.

"I wouldn't do a show that had a WWE aspect to it, where we're faking things and getting in each other's face, pretending not to like each other," Pulver said. "But there are going to be times on the show where it happens, and I can tell you now, it's all real."

And according to Pulver, it is not part of a Spike TV plan to promote the show.

"I refused to be in the same room with (Penn) unless I had to be," Pulver said. "I can't be around him that long without my blood running."

The show has already concluded taping, but Penn and Pulver are not allowed to reveal details. The taping took place in Las Vegas over a six-week period.

Penn and Pulver will start the series with eight fighters on each team. The series focuses on the daily training and lifestyles of the fighters and coaches.

At the end of each episode, one fighter from each team will square off, with the loser eliminated from the show. By the end of the season, the best of the up-and-coming fighters will be awarded a contract with the UFC organization.

Andy Wang, a University of Hawai'i graduate, is one of the fighters on the show.

"Mentally, physically, emotionally, it was a drain," Penn said. "It was non-stop for six weeks, every day."

Penn trained daily with the fighters while recovering from an injury. In his last bout in September, Penn fractured a rib and tore muscles on his right torso in a loss to Matt Hughes.

"It still hurts when I lie on that side, but when I fight, I don't feel it," Penn said.

Until the June bout against Pulver, Penn said he will continue training in Hilo.

Both fighters said the weekly episodes of "The Ultimate Fighter 5" will serve as motivation. Although the taping has concluded, neither Penn nor Pulver knows what will air each week.

"If I'm ever feeling burnt out or tired, all I have to do is watch the show and it'll drive me to keep training," Pulver said. "I always wanted to fight BJ again before we started filming, but now it's all I think about."

Penn feels the same. At a recent press conference, Penn took a verbal shot at Pulver while promoting his Web site, www.bjpenn.com.

"You can watch me train at www.bjpenn.com and there's daily techniques," Penn said. "Jens Pulver should check it out."

Reach Dayton Morinaga at dmorinaga@honoluluadvertiser.com.