The class: Orange-theory fitness

Where: Orangetheory Fitness Tanglewood, 6415 San Felipe, near Voss; 713-952-9917; orangetheory

When: Classes are held weekdays starting at 5:30 a.m.; last class typically starts at 8 p.m. There also are classes Saturday and Sunday mornings.

The workout: I had been hearing buzz about Orangetheory since reading about the fitness franchise in the New York Times a few years ago. So I was eager to try it when Houston's first studio, Orangetheory Fitness Tanglewood, opened earlier this year. The workout is based on interval training, using a treadmill, indoor water rowing machine, free weights and core-strengthening suspension straps. Upon entering, you'll notice the facility is awash in the color orange, from the walls to the interior lighting, which gives everyone a strange, colorful glow that you don't even notice after the first few minutes of sweating. (The founders of Orangetheory Fitness are fans of the University of Florida Gators, hence the color.)

On one side of the studio is a row of treadmills, on the other are water rowing machines. In the back, there are the suspension straps, moveable weight-lifting benches, Bosu balls and mats. Newbies watch a quick video about Orangetheory's concept, then are given a heart-rate monitor to wear during exercise. Once you purchase classes, you also can buy an inexpensive monitor at the studio or elsewhere. Heart-rate monitors connect to the studio's digital screens to display exertion levels and how many calories each person is burning. That alone makes the experience a little competitive.

The workouts - 26 minutes of cardio and 26 minutes of core strength training - are done in intervals designed to get you 12-20 minutes of exercise at 84 percent or higher of your maximum heart rate. The idea behind interval training is that if your heart rate is pushed to maximum then lowered and repeated multiple times, it increases your caloric burn long after your workout is over. All of that sounds much more complex than the experience really is. Our trainer, Robert, explained that no two workouts are the same, and the order of exercises and time spent at each varies as well.

We started on the treadmill at "base pace," which is equivalent to a warm-up. Then you move to "push pace" and finally "sprint," meaning run or walk like your life depends on it. It's your choice whether to exercise like a power walker, jogger or runner; each category has a specific range for miles per hour on the treadmill and the incline. I opted for the jogger pace. After a few minutes of warm-up, Robert yelled "Push Pace for three minutes," and that is when it started getting tough. We increased the treadmill's incline while running for few minutes, then reduced it for a one-minute rest. Then we did it all over again. When he called out "sprint pace," I felt like I was trying to race Olympian Carl Lewis. But in a few minutes we got to rest - only to start it all over again.

By the 15-minute mark, I felt like my heart was screaming, but I'd only reached 75 percent of my maximum heart-rate goal. That's the great thing about seeing your heart rate on a giant screen. You know when you need to push yourself harder.

We switched to free-weight exercises for arm work, interchanged with suspension bands for hamstrings and core strengthening. Then we rounded out the workout on the water rower in the same interval manner as the treadmill. And, finally, we finished with a series of deep stretches.

I was exhausted - in a good way. But I was even more surprised by the euphoric feeling that continued: the warm glow you have after a hard workout.

Fitness Level: All levels and ages. Also attracts those looking for an interval workout.

Intensity: Medium to high. Since the goal is to get the heart rate up to burn calories, the harder you work, the better the burn.

Results: Results vary, based on intensity, but women can burn 500 calories in a 60-minute class, men 700-800 calories.

Gear: Standard sweat-wicking workout wear, but women should definitely wear a supportive sports bra. Bring a water bottle and towel.

Price: Month-to-month memberships are $59-$159; packages are $180 for 10 weeks or $450 for 30 weeks. Many Orangetheory clients have gym memberships elsewhere, such as the 24 Hour Fitness that's right next door.