I knew I was in trouble when I heard that laugh. I was on the phone with my high school track buddy Brandon last fall, finalizing details of an upcoming trip to visit him in Boston, when he ended the call with a taunting cackle. "Bring some workout gear," he goaded. "I've got a little something for you."

The next Sunday, we were heading to Crossfit New England—a 5,000-square-foot warehouse in suburban Natick, Mass. "Dude," Brandon said, "I haven't been this excited about a workout program since I used to run in college." I understood. Being an editor at Men's Fitness, I'm constantly bombarded with "new" workout ideas and strategies. Still, I hadn't really found anything that gave me the rush I enjoyed playing a sport. In the gym I was never a "lifting guy" and had become bored with cardio workouts, often finding myself in the same fi tness rut we caution our readers against.

I had heard of Crossfit. Its goal is not to promote specialized fitness—like spinning, for example—but to enhance your overall athleticism: cardiovascular endurance, strength, flexibility, power, speed, agility, and balance. It was created by Southern California trainer Greg Glassman in the '80s and went national in 2001. Initially the program gained popularity among police, fi re, and military personnel because of its mix of functional strength and metabolic conditioning. "The biggest benefit is it's a very broad, inclusive type of fitness," says Court Wing, one of the founders of Crossfit New York. "If you never ask your body to work hard, it's not going to happen."

Our class began with a vigorous warm-up that included a rope climb, situps, and a series of stretches. Then, the 15 of us headed outdoors for an 800-meter run at full speed. After losing my lungs (and nearly my breakfast) in the fi nal 200, I was ready to call it a day—before being told that the real workout was about to start. Back inside, each person was told to do five pullups, plus as many clean and jerks as they could do in one minute. The goal was to do this each minute until you amassed 50 total clean and jerks. Since it was my first time, I was urged to sub pushups for the lifts. Like that really helped. By the time I finished, I felt awful. Then I looked at Brandon, who had not long before carried the extra pounds that come with new fatherhood and frequent business travel. Now he resembled the athlete I knew 15 years ago. The gauntlet had been laid down. I was in.

Before I could jump into crossfit in New York, I had to go through six beginner classes where instructors teach the proper form on basic lifts and movements, including squats, pushups, pullups, deadlifts, cleans, Turkish get-ups, and more. Because I had no heavy lifting experience, this was crucial for me to master. "The most frustrating thing I hear from people who criticize Crossfit is that they judge it prior to checking it out," Wing says. "They look at the workouts and never get beyond the basics. But to succeed, you've got to learn those basic mechanics."

Crossfit is available in roughly 1,700 gyms (known as affliates) in 48 states and 36 countries. Each day, a new workout (the WOD; most go by names like Angie or Helen) is entered into the main Crossfit webssite [crossfit.com]. Affliates can choose to follow the WOD exactly or adapt it to suit their own gym setup or clientele. It's rare to see the same WOD more than once every few months, although some universal workouts allow members to compare their times with others training in different locations. "Angie," for example, is simply 100 pullups, pushups, situps, and squats performed as fast as one can.

After a few classes with training wheels, I did my fi rst workout—the dreaded "Fight Gone Bad" (get the full WOD at mensfitness.com/crossfit). I scored 153 (over 200 is a decent mark). Not great, but I felt good. I also knew I had a hell of a long way to go, especially after tackling the Ensign a few days later. This gruesome WOD includes six three-minute rounds of power cleans, pushups, and alternating air squats/ ring dips. Even after I scaled down the weight on the clean and switched to box dips, I still struggled to fi nish. That's the point. "Even if you go through a WOD at a reduced volume," Wing says, "if you're pushing yourself, you should still get an ass-kicking."

People around me were finishing WODs with no problem. The long-dormant competitor in me was kicking in, but I quickly learned to stop comparing myself to others and focus on improving my own benchmarks. As I moved into four workouts every week, progress came quicker. I gradually upped the weight on some of the lifts and started seeing big improvements in pullups, double-unders (jump rope), and box jumps. Six weeks after my first full class, I scored a 190 on Fight Gone Bad. A step up—although watching the guy next to me hit 300 was a Georges St-Pierre kick in the teeth.

Any discouragement didn't last long. The challenge of continued improvement was exciting and the motivation I got from others in the group was unlike anything I'd experienced. Rather than the "how much can you bench" bravado that permeates much of the traditional gym culture, the Crossfi t dynamic feels much more teamlike. Several times, the firebreathers in the group came over to root me on as I struggled to finish a workout they'd just completed. "Crossfitters are willing to push you in a way that's going to make you work harder than you ever have before," Wing says.

Some hardcore lifters aren't convinced. Critics say the classes often seem random or haphazard and that you don't know what you'll be doing in the gym until the workouts show up online the night before, making it diffucult to form a long-term strategy for your gains. Wing's retort: "If you look at the workout template, you will see there are cycles," he says. "Our biggest interest is in your body's work capacity. We're trying to improve all aspects of your overall fitness."

It has worked for me. In the 12 weeks, I put on significant (at least for me) muscle in my chest and arms and carved out some definition in my midsection. My diet also improved, mostly out of necessity. If I knew I had a brutal workout in the morning, pizza was not an option. Most importantly, I'm excited to have found something that reawakened my inner competitor. Speaking of which, I'm heading back to Boston next week. This time, I've got something for Brandon.