Of course, I had my expectations for the jiu-jitsu studio where Mark Zuckerberg trains and competes as a blue belt. In my imagination I imagined it to be very noble. High gloss white, with noble wooden floors and perfumed air. Cucumber water at the entrance. And preheated towels in the changing room.

The disappointment came as soon as we arrived. I signed up for a free trial lesson at Guerrilla Jiu-Jitsu in San Jose, California using an online form. Depending on traffic, it’s about 20 minutes from Mark Zuckerberg’s home in Palo Alto on wide, busy roads. Only to end up abruptly in a rather seedy neighborhood. It’s just before eleven in the morning. Two blocks from the studio, street prostitutes negotiate with their clients through car windows. That’s when I check for the first time whether I’ve entered the correct address in my sat nav.

The second time I do this is when I pass a huge homeless camp under a nearby bridge. And then again when I see two obviously very high men lying on the sidewalk. Can this be correct? Yes, that’s it. The gray building housing Guerrilla Jiu-Jitsu is wedged between construction sites and newly completed apartment blocks. From here, the Facebook founder proudly posted pictures of himself wearing a blue belt and his trainer Dave Camarillo. He competes for this studio. The large glass front with the blue inscription is dusty. Between the site fence and the house, the path leads to a parking lot in the backyard.

Behind an inconspicuous door are a tumble dryer and a washing machine. A narrow corridor leads to the training room. Pictures of fighters and fights hang on the walls. Also the rules of conduct. “When coaches explain something during the lesson, the students must listen either sitting or standing in a good posture,” it says, among other things.

On the mat, two men in white athletic uniforms wrestle. Contrary to what I expected, it does not smell like perfume. On the contrary, there is an acidic mixture of sweat, moisture and mold in the air. And it doesn’t look like preheated towels here either. A look into the open door to the women’s room reveals brutal simplicity. A toilet, a sink, a trash can – that’s about it. The supposedly luxurious changing room is a series of wooden cubicles with a simple curtain in the corner of the studio.

The greeting is friendly. The trainer looks me over briefly and then calls out to a helper which suit size is right for me. A white combat suit is quickly handed to me. Gradually, the other course participants arrive. The same ritual is repeated for all of them. Within ten minutes everyone is equipped with suits with “Guerrilla” written in black on the left shoulder. I signed up for the “Jiu-Jitsu Fundamentals” course.

I am surrounded by eleven men whose belts range from white (beginners like me) to brown (very advanced). After a short bow to Coach Chris, it all starts. Run laps, jump, run backwards and jumping jacks. Then somersaults – forward and then backward. Been a few years since I did this. But Chris won’t let me escape. I roll over the mat under his stern gaze.

Then things escalate quickly though. I’m assigned to Omid (name changed). He’s wearing a purple belt, so he’s been training jiu-jitsu for at least two years and is supposed to be teaching me grip techniques today. More precisely, this means that he sits on my upper body and head and tries to separate my interlocked hands. First by simply pulling on it, then later by pushing against it with his feet, legs and whatever else he has.

I’m not a real opponent for him, rather a victim. In the short breaks we talk a bit. He says he’s seen Zuckerberg here too. “He doesn’t do a show, he’s just here, nice guy,” he says quickly. He doesn’t want to reveal more, like everyone here who has obviously promised discretion. He is a programmer himself and uses an early lunch break in his home office for training. After 50 minutes I’m hoping to finally be released from my fighting position on my back.

But far from it. It was all foreplay. Now the real fighting. Two times five minutes. For me that means that after three seconds and a skillful wipe with my foot against my legs, I land on the mat for the first time with a crash. And actually from then on you can’t get back on your feet – instead you’re pushed down in a wide variety of very uncomfortable positions. In short: I don’t stand a chance. And my opponent no pity on me.

In the end I’m drenched in sweat, counting eight bruises on various parts of the body in the evening. As he releases me from the last hold, Omid says: “Well done, you didn’t give up.” A membership to Guerrilla Jiu-Jitsu costs $229 per month for six months of unlimited training. At the exit is a flyer announcing a Jiu-Jitsu tournament on September 2nd in San Jose. I ask the man at registration whether Mark Zuckerberg will compete again. He doesn’t answer me, just smiles.

Our author Alexandra Kraft also spoke to coach Steven Chao, who is part of Mark Zuckerberg’s inner circle. Read here how this “twitch” experiences: