I have two characters, a man and a woman, both serious MMA fighters. The woman is older and nearing the end of her career, the man is a young up-an-comer. I'm thinking she's probably UFC Bantamweight (135 lbs) and he'd be a light heavyweight, or maybe a class smaller. Anyway, I want them to train together. Not spar, probably, but whatever else two athletes of such different sizes could reasonably do. Would there be exercises that aren't really affected by size, and also are there exercises that totally wouldn't work with two people of different sizes? And, even more specifically - early on, he's being a real jerk and tries to physically intimidate her. She surprises him, flips him somehow, and he lands on his back on the mat. Then he mouths off a bit more and I want her to do something that is reasonably safe (like, not a throat punch or an eye gouge or anything!) but that would shut him up. Is there any sort of knuckle-to-the-solar-plexus trick or anything? Pain would be fine, silence would be great, but no serious injury. Thanks for any help with this - I know there are some martial artists around, and I'm eager to learn!
What is wrong with a foot/knee to the old family jewels? Not fancy, but highly effective. An elbow or fist to the kidneys a few times will remind him that he is not so big and bad. Mainly due to peeing blood for at least a day. No permanent damage, but painful none the less. If you really want to get more in depth with this, then you should probably look up a schematic of pressure points and nerves on the googles. Might even research a smidge on the effective ways of utilizing them in a 'combat' situation. Good luck.
She can use one of the many Judo throws to put him in his place, if you really want to go there. I'd suggest you check what YouTube has to offer as there are several videos of different kind of throws. He'll just smack on his back and feel like a tool, but it won't hurt him terribly because they'll be on a tatami anyway, I'd wager. Another option is basically to make them grapple and she e.g. armlocks or leglocks him in sparring and he has to tap out. Again, as there are many options, I'd suggest you peruse YouTube. I think there's also a video somewhere of Ronda Rousey putting some jerk in his place with a Judo throw, come to think of it. Might be exactly what you're looking for. I also remember a video of Cyborg Santos actually choking out some guy who was goofing around, but it might be a good idea to search her training videos in any case as she's a pretty badass lady. Holly Holm is another one. I've only met one guy who tried to sort of physically intimidate me, I guess. We were sparring in BJJ and he could've focused more on technique than strength to submit me like all the other guys did because a 250lbs guy vs. 110lbs girl isn't going to be a fair fight, and it's not going to be beneficial to either party if the guy just muscles through it. But there you go, we grappled despite the huge size difference. It's not ideal, but it's doable. Jerks are few and far between in gyms. Like I said, I've only met one. Anyway, your characters could practice e.g. striking together. She can hold up the pads and he'll try to impress her with his strikes. She'll keep up a relentless pace, however, and sooner or later his hands will start to weigh a ton while she's screaming for him to keep on going. She can show him grappling techniques and they can practice them together (depends on her level, but if she's serious about MMA and at the end of her career, she could have e.g. a purple or even black belt in BJJ). Men and women can do all kinds of training together from boxing to muay thai to BJJ to wrestling, it's just that the size and strength differences don't make it ideal, however it can still be úseful, especially for the woman. I'd also suggest you google "The Ultimate Fighter Ronda Rousey Miesha Tate" and watch at least some of the episodes of the season where they were coaches, so you'll see how the ladies trained the burly guys.
They can easily spar together in training (as long as there are some ground rules) because it's great to practice that way. Um, they could use training pads to practice roundhouses or punches or go through specific exercises to work on blocks or holds or things like that. Pretty much what @KaTrian said