Activity Details
MMA (or Mixed Martial Arts) is a combat activity that players can discover in GTA 6.
The activity was first teased in Trailer 2, which showed 
The two fighters appear to be in an octagonal arena, similar to the UFC's fighting grounds, though with walls made up of chain-link fences. A small audience is shown to be watching the fight and celebrating as Lucia strikes her opponent.
The event looks to be a small event, with mixed gender competitors, suggesting that it may be an underground activity that's not strictly regulated.
A screenshot released by Rockstar Games also shows Lucia training with a punching bag, possibly readying herself for an upcoming fight.
Although not currently confirmed by the developer, fans speculate that MMA might be a side activity in GTA 6, that allows characters to learn new moves to enhance their hand-to-hand combat.
