You can really hurt someone else, or, in this case, yourself.

In most combat sports, fighters are matched by their weight. Professional fighters with even weights are, in general, working from comparable amounts of muscle mass, which reduces the chances of one person getting a massive one-swing K.O. or another person fluttering around their massive opponent like a housefly on an elephant’s rear.

If you don’t do that, you get something like this. The woman below’s name is Lucie “Droběnka” Kotlárová (the nickname effectively just translates to “the petite one” — they’ve got sarcasm over there in Poland!). Rather than be paired with fighters her own size, she inevitably goes up against smaller opponents, leading to situations like these: