With NFL training camps in full swing, "Survivor" survivor Jimmy Johnson offered an apt comparison in describing his experience doing the CBS reality show in Nicaragua.

He said it was tougher than three-a-days.

"At least if you're going through those practices, you get a good night's sleep and you have food in your stomach," Johnson said Tuesday. "We got no sleep, and there were days we were existing on less than 100 calories a day. It was extremely difficult."

The former coach of the Dallas Cowboys, Miami Dolphins and Miami Hurricanes spent more than a month this summer with "Survivor" as one of 20 castaways. The season premiere will air Sept. 15, and to preserve the suspense, Johnson didn't say how he fared.

But he laughed when asked if he was happy when he was done.

"I was happy when they handed me that first light beer," said Johnson, speaking by phone from his home in the Florida Keys. "People ask me did I enjoy it, and I have to hesitate. I can't say that I really enjoyed it, but I'm really glad I did it. It was just a great adventure, but it was at times miserable."

For one thing, the ex-coach known for his coiffure went without hairspray or a comb during Central America's rainy season. It was just as well he didn't have a mirror, either.

To prepare for the show, the 67-year-old Johnson built a shelter, started fires from scratch and tried to get physically fit. Once in Nicaragua, his experience as a Keys fisherman helped, but food was still hard to come by.

"It's a beautiful country, but it's a very harsh environment," Johnson said. "There was a lack of fruit. There was some fish. We had some interaction with howler monkeys, but we couldn't catch them.

"People watch it on television, sitting on the couch like I did, and say, `Hey, that's cool. I'd like to do that.' Well, it's a lot more difficult than what it looks."

Another fan of the show is the Dolphins' current coach, Tony Sparano, who visited with Johnson about being on "Survivor."

"I'm rooting for him," Sparano said with a grin. "I'm with him all the way. Better him than me, though."

Johnson has watched the show ever since it started in 2000. He said he first applied to be a contestant six or seven years ago and was turned down. He applied again in 2007 and was on the verge of landing a role.

"They flew me out to L.A., and I went through the physical with the doctors, and I was all set to go to Gabon, Africa," Johnson said. "The doctor for `Survivor' called me and said, `Coach, you've got one blocked artery and one 70-percent blocked, and we can't take you. You've got to see your cardiologist.'

"A week later I had an operation and a stent."

Undeterred, he applied for the show in Nicaragua.

"Even though I'm getting up there in years, I said, `I'm going to give it one more shot,"' he said.

This time Johnson made the cut. He was part of a team of 10 contestants over the age of 40 competing against a group 30 and under.

Johnson returned several weeks ago to the Keys -- or "heaven," as he called it. He's now preparing for another NFL season as a commentator for Fox.

"There was absolutely no contact with the outside world in Nicaragua," he said. "I'm catching up on the NFL now. I had to reintroduce myself to my wife when I came back. I found out who won the NBA championship, and I found out some college teams moved to a different conference."

Johnson's also catching up at the dinner table. He won't say how much weight he lost on the "Survivor" diet, but with a laugh he said, "I've gained about half of it back."