Cant help you specific to the Jujitsu, Brazillian or otherwise. My practice has an Okinawan heritage. That said, having been a martial artist, (one art) for more than a day or two I have a couple ideas…
Most likely spikes are likely caused by massive adrenaline whether specific to sparring or caused by the activities leading up to it. One likely factor.
Another could certainly be whatever you ate before class, but unless its carb heavy I cant imagine anyone doing that before any martial arts class, it be a baaaaad idea more than once or twice. Can’t imagine that being a serious factor, but whatever you eat/ate before class could be a piece certainly.
Where do/did you inject when you get the spikes? Does it always happen, or just certain days, certain practices/activities (e.g. king of the hill). Could be a connection between where you put the injection and the activity you are focusing on that class(es). Not likely a huge factor but might be a piece. IF you’re doing a lot of bag work and you injected into your arm recently… it can get absorbed faster and could easily produce a spike by doing so.
How about your short acting insulin (or long acting), any chance its dropped off, you have little/none on board when the middle of class occurs? Thats a likely suspect I would think.
How bout, because your practice IS so much heavy physical activity, pinning, submissions, body to body could the highs your experiencing be a bounce, a rebound caused by a real “low level” low, and the high was your body’s adrenaline response caused by that?
What kind of spike are we talking about? Fifty, a hundred, several hundred points… does it come back down after class, presumedly once you use a couple units to get there?
Glad to help, if I can…