In our class, the benefits of yelling/shouting, i.e. Kihap, in sparring are sometimes pointed out. If yelling is so beneficial, why MMA fighters don't yell often? Or do they?
As per the provided link, there's a number of factors going on.
- First of all, a kiai is as much about a forceful exhalation and a focus of purpose as it is actually yelling. Many of the fighters do just that, grunting or exhaling on a heavy strike without actually yelling.
- One of the other purposes of a kiai is to startle the opponent. In the Octagon, most fighters are prepared for battle, so to speak, so there are less likely to startle if someone yells.
- There is also the cultural difference that many people get into MMA from boxing, which doesn't tend to do the yelling thing.
- The kiai is often done on a single decisive strike, something that a TMA like Karate tends to emphasize whereas MMA tends to focus on multiple successive blows.
- Lastly, the traditional kiai in martial arts, especially during forms, is often used as much to synchronize movements (or to indicate such precision) as to actually generate power to attack.