Crossfit began as an exercise routine to help firefighters, SWAT teams and other first responders stay in shape. Now the aggressive, no-frills workout is sweeping through Houston with special gyms popping up all over town.

KPRC Local 2 anchor Lauren Freeman tried it out and even brought her husband along.

The warm-up began with pushups.

"If I hadn't been working out with a trainer for the last couple of weeks, I would already be beyond tired," Lauren said.

The idea behind the Crossfit trend is to ditch machines and go "old school."

"It is every day movements. We don't use machines," said Carlos Ibarra with Crossfit Houston. "It is not that kind of gym. It is every day, doing something random, a functional movement."

"It is sort of something you love to hate," client Adrienne Scott said.

A 15-minute circuit is called the workout of the day.

Lauren called it torture.

"I thought I was in better shape than this, really I did, but I am not," she said.

"Glad that is over. It was the longest 15 minutes ever," said Forest, Lauren's husband. "Before I knew what was happening, I was perspiring and gasping for air, watching the clock."

"This is ridiculously hard," Lauren said.

It's almost hard to believe how popular Crossfit has become in the Houston area and not with just your typical gym rat.

"We have a pilot here. We have doctors, lawyers, nurses. We have teachers," Scott said.

It took about a year for Carlos and Lisa Ibarra to ditch their garage gym and move their clients to an open warehouse in south Houston.

"Now everyone knows Crossfit. Somebody is doing it somewhere -- a friend of a friend all know about it," Carlos Ibarra said.

The personalized exercises and constant supervision give participants the feeling of sharing a personal training session with friends.

People post their fit numbers every day, which results in a lot of competition among friends.

That rush and push to power through to beat the "other guy" also has some fitness experts cringing. They said the dangerous mixture of exhaustion and extremes can sometimes lead to serious injuries.

Doctors say it is not for casual exercisers or weekend warriors.

"That's the reason we are here -- to make sure the form and technique is not lost through it," Lisa Ibarra said.

She said they have never had a serious injury. The worst problem has been a few asthma attacks.

Carlos Ibarra said all of the exercises can be modified to any fitness level. But staying safe heavily depends on the trainers of the class because at that exhaustion level, it's hard for most people to always do the moves correctly.

For more information on Crossfit Houston, visit www.crossfithouston.com.