Exercise? Since lots of us are into guns and many use for self defense, 1 should also be in some shape. Not bodybuilder, but able to last in a tussle with another person. At 1 skill builder, the shooters had to run/jog and many where out of gas after. Like heart attack breathing kind. Had 1 guy who's older (50s) and does crossfit and he was fine. He wasn't even breathing hard.
Force on Force classes pretty much don't exist in HI, but being in some shape is what everyone can do. Plus it's good for the health. I'm not a fan of BJJ cause going on your back is a huge mistake, especially with multiple attackers. There is a Krav Maga class across Beretania Safeway, but IDK if open due to CV. And they don't do much strenght/endurance training, more skills training. So strength and endurance is something you would have to do on your own.