Iāve watched a bunch of it in videos (yeah, Iām that guy right now ). It doesnāt look much different in that regard than wrestling, which I did quite a bit of.
No idea how that would be low cardio, except for an instance where youāve got a guy whoās got a ton of experience paired up with a low rank, and heās taking it really easy on him. But that high rank most likely has a really good cardio base from working with higher ranks regularly and knows how to pace himself, especially against newbies without that base.
That's exactly how it could be low cardio......there are fat guys who were once in phenomenal shape 15 years ago when they were blue belts competing, but now let it go .....and their game is mostly the stalling grip game with a strong grip and with the gi only. And they also come in late, to skip the warmup...and I'm talking every single time almost.
And Jitsu's 90 minute classes are low in cardio compared to Mai Thai's 90 min, usually. Because you do a 20-30 min. warmup, which is good in cardio....but then the next 30-40 min is low cardio, learning 1 or 2 techniques.....sitting there getting cold, then figuring it out by doing it slowly, lots of stop & go, then the Instructor stops the class to re-explain, etc......then the last 30-40 minutes is sparring, which is good cardio but again, you can lay and pray.
It also depends on the school and sometimes who's running the class, but this is average. Unless it's training for an upcoming competition, then it's warmup 30 mins then spar 60 mins, then another 20-30 minutes of mock competition. Our competition kid's class goes through this for 3 hours straight each day almost and we still only win the school trophy like 1 out 5.