I’m learning Brazilian jiu-jitsu with feminist activist Paola Diana and her coach, Charles Negromonte Santos. Diana is also an amateur boxer, Krav Maga enthusiast and early adopter of Muay Thai, the number one combat sport in Thailand. Like so many martial arts, this one starts with putting on an outfit that is antithetical to any real physical activity – heavy white outer jacket and loose, thick trousers, like putting on a straitjacket before you go for a run. At least it won’t be hard, I thought.

The emphasis is on self-defence, not fitness: we start with how to get away when someone grips you by the wrist. If they grip you with one hand, identify their weakest point – it’s the thumb, dummy – and twist your wrist so that its thinnest point is at their weakest, and simply pull your arm away. It’s effective and weirdly satisfying, though not as pleasing as getting away from a two-hand grip. For that, you make a fist of your trapped hand, grab it with your other hand, and simply break yourself out.

Next comes the floor work, which is when I break a real sweat. I’m on my back, legs in the air like a beetle; as Diana circles me, I spin round on my back, so I’m always facing her. The exertion is intense and unfamiliar, activating almost-never-used muscles in my core and lower back. Diana can’t really get to me without making contact with my feet – and she had better not do that, because once I connect with her hips, I have more strength in my hamstrings than she does in her flailing arms. (This is all theory, by the way; in real life, she has more strength in her fingers than I do in my entire body. Since she started Brazilian jiu-jitsu, her rings have got too tight.) I am also more stable, being on my back: I can kick her away and, if I’m fast enough, be up before she’s recovered.

I am told a purple belt in Brazilian jiu-jitsu could be 50kg (8st) and get any attacker, of any size, to submit; I don’t really believe this until I learn how to fend off a strangling attempt. It’s quite a complicated manoeuvre, which relies on the aggressor being in a very specific, straddling position; but let’s say he is. You wrap your legs around him so that your ankles meet behind his neck, and then – this is the devilish bit – you use your pincer leverage not on his neck but to break his arms. I watch Diana pretend-break Santos’s arms: you wouldn’t call it elegant, more scrappy and scrambly, but you would have bet your house on her getting away.

It’s an incredibly intelligent sport; much more focused on winning than on fitness. But if you have a passion for self-reliance, you’ll be hooked, and end up with a body like Hercules.

What I learned

The key is to take the aggression back to the aggressor, using their own strength against them