I came to my girlfriend's Pure Barre class with the best intentions. But I fell short, and then I almost fell down.

For the unfamiliar, Pure Barre is a class featuring a lot of intense isometric exercises packed into 55 minutes. They market the program as designed for women, but can't exclude men, I guess. Unsurprisingly, I was the only dude at my session.

I knew the class would be difficult. I intended to come mentally prepared and focused solely on determining whether or not guys should consider this program. I also figured, based on my vague understanding of what the class entailed, that it would be a good exercise for a skinny guy with a typical skinny-guy problem: my posture.

On the way over, I felt anxious. I had never taken an exercise class before, and I had visions of being the biggest embarrassment to my gender since Bobby Riggs. My girlfriend assured me that the instructor would define all the special terms used. Suddenly the whole thing felt like going to see David Lynch's Dune on opening night, with a sheet explaining all the alien words and characters . The only difference was my flop would be literal.

Once we arrived, I made a point of going to the bathroom. Paranoid about my presence annoying my all-female classmates, I walked to the far corner of the main room, then very conspicuously all the way back to the bathroom to make sure I had put the seat down on the toilet.

The class began with the instructor saying there were a lot of new people (comforting) and explaining Pure Barre as a combination of Yoga and ballet. When it comes to things I know anything about, she may as well have said Pure Barre is a combination of theoretical physics and motorcycle repair.

My girlfriend told me basketball shorts would be more comfortable than sweatpants. And if I can impart any wisdom on guys considering this class, let it be this: wear pants. A lot of the class involves binding your thighs together with a resistance band, which can be incredibly painful if you have hairy legs.

Along with the band, everyone was given a little dodgeball and pairs of two- and three-pound hand weights. Looking at these tools, the fatal hubris set in. How hard could something involving two-pound weights really be?

Really hard.

The class involves six stages. In hindsight this seems impossible, as six stages over 55 minutes is only about nine minutes per stage. But our instructor warned that "Pure Barre time" is longer than regular time.

The first and fourth parts—"warm up" and "flatten abs"—were the hardest for me as they involved many different kinds of sit-ups and crunches (bad posture, weak back).

The second stage, "sculpt arms," was the easiest and maybe the least appealing to a male audience. Guys are typically concerned with bigger arms, not more-sculpted arms. I remember holding the weights behind my back and making small circular movements with my arms. The whole class is like this—small movements until the muscles being worked start to quiver.

Third was "tone thighs," which happened mostly on the ballet barre. Having toned thighs is not super high on my fitness goals, but ballerinas are jacked, so I was game.

Then came "lift seat," which featured the instructor often calling on us to "tuck." Contrary to my girlfriend's warnings, there weren't a ton of terms of art. Really, the only thing I had to learn was "tuck," though I'm still not entirely sure what it entails. Supposedly you "pull your abs in and tuck your hips under." I think I was doing that, but a tape of my workout would probably show otherwise.

Finally, before the cooldown period, came the aforementioned ab-flattening. Toward the end, we did a kind of lying leg raise, in which you stick your legs straight up until your abs contract. Here is where I tapped out and tipped over. Around this time the instructor, sensing the newbie's desperation, said, "You're all in this together. Feed off each other's energy." An oddly reassuring combination of something you might hear in a foxhole followed by something you might hear at an Earth, Wind & Fire concert.

In the end, I was beat. I could definitely see a Pure Barre membership helping with my back, though a more traditional workout like this one would too, and with less self-consciousness about how I left the bathroom.

For all the guys considering tagging along with a girl, I'd say go at least once. If nothing else, It could help her. My girlfriend said that laughing at my bad form really took her mind off the pain and helped her achieve personal-best reps. Who says I'm not supportive!