BJJ requires a lot of the little muscles of the back to work. Basically it requires back and hip flexibility. That is most basic for ease of movement for the sport and therefore the enjoyment of it. Then it requires knee flexibility and foot flexibility if you wanted to trap someone, say your legs locking his head or just be ready to slide into any versatile position.
The low back and hips are required to move quickly and powerfully to get out of trapped positions or to sit on someone.
The upper trunk is required to do spins from a point. A pivot. The one where your legs are up in the air. I still don’t get this so I am basically stuck with friction to the floor.
Since I am not too flexible, totally working on it I find my joy in just attending class and looking for improvements that I mentioned above. I mean what’s the point of technique if I can’t get there fast and smoothly enough? I can’t even separate grabbing my own arm left from right.
It’s a real weird sport but because of that quite interesting to me. It is quite counter intuitive. What I see and understand may not necessarily be translated to actually being able to do it.
But it’s my daily sport now.