To learn any martial art it is necessary to learn stances (well it is if you don't want to fall over!). Stances are a very fundament block of patterns as well. Some instructors spend a lot of time working on stances and insist that is done right, other are happy if you can put one foot in the other and not fall over.
If it hurts, you are either doing it wrong, or lack the necessary flexibility or strength at the moment -or you have run into the evil instructor. Contrarily to urban myth it is not nessary to have pain to make progress. Stretching should be done slowly, once warmed up, to the point of tension and held, over doing this hurts and pain usually equals damage (torn ligaments take forever to heal). Similarly joint pain (knees and back) either from stances or specific exercises is a sign that either you should not being doing this, or you need time to build up to them. Sadly in our sedimentary life styles, we are not use to exercise and often exercises like mantis pushups do as much harm as good. Be a wimp, tell the instructor you have a past back and knee injury and that you will treat some moves or exercise with caution (I always do press ups on my knees -I'm overweight and press ups have a habit of knacker my lower back in; use bench presses instead). Please note the following, in respect to warm ups and cool downs:
Increasing muscle length (stretching) can be achieved by one 30 second stretch, five days a week (Bandy & Irion 1994,1997).
A stance is to stop you falling over. That tends to be a bit embarrassing in a class. Take a stance and try and get someone to push you over, this is always a good test. The principal is to lower your centre of gravity; you may have come across those dolls with round heavy bottoms (no matter how you push, they always pop up again). Try this experiment, stand up get someone to push you over; sit down get someone to push you over. Theory says that it will more difficult to push someone over who is not standing (well know Quantum mechanics theory this is, but you need to hit someone using a cat).
Three meta rules for stances.
I'm sure that someone will correct me on this, but I am concentrating on simple practical stances (to stop you falling over), rather than crane stances on top of poles. Keep these rules in mind when you take the stance. Also some styles suggest a very rigid position, others suggest a light fluid stance. I would suggest most stances can be either, that depending on what you are trying to achieve; power - and heavy stance and punch; light sparring like jabbing a fluid unlocked stance.
1. Lower your centre of gravity -so it's more difficult to be pushed off balanced.
2. Brace yourself, concentrait on the support leg and "ground" yourself (like a washing line support pole)
3. Be a steady platform to deliver a technique (i.e. punch).
1. The Ready stance. This is the stance usually take when starting the class after bowing to the instructor; it is also the starting position for the patterns.
2. The Horse stance. Nearly always the first one taught; this is good for developing strength but is not a practical platform for delivering a technique. Take time to develop strength and not damage the knee joints.
3. Fighting stance. Not strickly an "official" stance, but it one that you will use for fighting and sparring.
4. Walking stance. Does what it says on the lable.
5. Foward stance. Like the walking stance but a little deeper. Good for improving static stretching on the hamstrings.
6. Back Stance. A slightly tricker stance to get to grips with, well I found it so. Quite a "cool" stance to show off with though. The weight is mainly on the back foot, with the feet making an L shape.