If you are properly relaxed though it's not locked. Ultimately it's no different than just keeping you back straight or any other portion of any stance. I think "don't stick your but out" vs "tuck in the tail bone" may just be a matter of semantics. If you tuck the tailbone in correctly you can't even really see it's been done unless you are really looking for it.
And that is obviously not exclusive to kung fu. I catch myself in a "gamer's slouch" doing NGA. I have pictures of me doing it. I have a wife who occasionally tells me I'm doing it. I should probably stop doing it.
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DB is spot on with this. Pick a variety that suits your needs. I can't hold poses well - I'm too inflexible to relax into many of them - so I do a Vinyasa flow, which is more dynamic. I might improve if I did a style that held poses, but I'd be really sore for a while and unable to keep up with my MA.
In my class, I stand right next to a woman who is probably 10 years older than me. She is more flexible than the instructor, so Jennifer and I (both up front and center, usually) are the opposite ends of most poses.
If you can hold this posture daily, when you get old, you won't have hunched back. IMO, this is the most important static posture in all MA training.
I guess just make sure that doesn't promote some more of that good old anterior pelvic tilt c:
That's something I do on my own, but not a pose we use in yoga.
That looks like a pose I need to add to my practice. The low lunge is one I already use (very tight hip flexors), and the added bit of a back bend seems a good idea.
