ExRx.net

Shouting, fiercely and with meaning, will improve performance whether you're squatting, benching, running a 40, 200, etc.
How? Well if you do it right (you'll know when you do it right), it causes inhibitory areas of your CNS that would normally be active to actually be temporarily inhibited themselves thereby allowing in a greater performance output.

Really thats interesting.

martial artists have been doing this for centuries, the yell they elicit when punching/kicking/etc. isnt to scare the $h!7 out of their opponent, though it could help, its because you produce more force.

There is a downside for fighters though. Take a good hit to the jaw with your mouth open and the results aren't going to be pretty.

well, if youre uhh... good, that wont happen that often. :) besides I'm advertising it for non-martial art use

If you know what you are doing then your guard should be up and then that won't happen. Also if your shouting your mouth will be open for maybe up to a second so chances are they won't hit your teeth. Also you should be wearing a mouth guard.

Guard up or not, shouting with a mouth guard in is a bad idea. In one set of MMA rules I've seen, shouting or kiai-ing is disallowed. I asked why, and it's for safety, to ensure the practitioners don't spit out (or partly swallow!) their mouthguards. We make all sorts of noises in practice, though.

On the other hand, full-mask karate variations I've seen require a proper kiai to score (in scored matches) and don't penalize it...but those folks don't use mouthguards generally because their mask is all-covering so it's not required.

I can't comment on MMA, but I went to a boxing gym over one summer, really just to learn how to box properly and it's just one of those things I like...

Anyway, first few sessions I got told to say "bah" on every punch. This was to teach me how to breath properly when fighting - if your inexperienced, you naturally just hold your breath and let your arms go, which makes you fatigued in a very short amount of time. It also teaches you to slow down and think about what your doing...

Kind of like enforcing a lifting tempo on beginners who can't lift under control and just jerk the weights about. Making them lift slower makes it easier for them to concentrate on using the correct muscles...And breathe properly when lifting...

KPj

Sometimes after a really good set where I lifted my a$$ off I feel like yelling and hitting something. Is that similiar?

Nope, you wanna do the yelling during/right before the set. Afterwards it won't really help because you're done with the performance, in that case a set.

maybe i should wrap a towel around my head right before i lift so i can scream into it and then lift haha. Why do I feel all aggressive after a great set its almost like YEAH!!!! BABY YEA I LIFTED THAT!!!! Maybe its left over adrenaline?

something like that, ideally you'd be getting that during the exercise though I imagine

The yell connects you to deeper things inside, as if you were pulling them up, the strenght, I mean. But it roots deep inside. Some weightlifters shout (to stimulate themselves), it matters a lot more the effect in oneself than that threatening supposition.

isnt holding the breath good too?

very true - hence all the grunts and yells from tennis players.