Martial Arts training affects posture

[chi sao]

I've been doing martial arts since july and I've noticed one thing thats common with almost everyone in the class: their posture!

Nobody can seem to stand up straight. It is common to keep your chin down during combat and keep your fists near your chin (depending on which martial art and your stance) and i've been thinking that we're overtraining our muscles in that area. (Especially when we practice 'trapping', it requires a great deal of shoulder endurance.)

Is the reasoning behind the poor posture due to muscle imbalances? If so, would it be the trapezius that we're overusing and should we be doing exercises on the opposite side (i think the pecs?) to balance this?

[quaribc]

it good be because none of you guys work the middle of your back properly. which can achieve through deadlift and rows. this is very common with martial artists.

if you guys do mostly pullups, then you need to do some something for your middle back as well. if that doesn't help, then it could be something more specific with your shoulders.
do some search on t-nation on shoulder movements and try them out.

good luck.