Chon-ji: Back Stance
Another picture I ripped off from Google images.
What was interesting was a more subtle problem discovered when I was teaching her the back stance or Hugul Ja Sae (though I never ever learned the Korean terminology until now), required for Chon-ji. Taekwondo's back stance, even in our 'traditional' style, is shorter than that of karate's Kokutsu-dachi.
What happened in our lesson was that Jacqui would be in back stance but have a posture that resembled a cat stance or neko ashi dachi. Her hips were tilted backwards and CoG was closer to the back foot, rather than 70% - as is required. I think that the shortening of the TKD back stance creates a larger opportunity to mess up the back stance. The analogy I used to try to resolve this problem was to show her that the back stance was like lowering your backside onto a stool or chair placed close to your back leg, but between your legs. The neko ashi dachi or cat stance would be having a stool behind your back leg, outside the base of both of your feet.
The link I had above on how to assume a back stance in tae kwon do states that from a back stance, you can easily throw a front kick without telegraphing your movements. I think that is utter crap. You should be able to throw most kicks from most basic stances without telegraphing your movements. The back stance is not a better 'defensive' stance. In fact, the forebalance or truncated forebalance (which we call a 'combat' stance) is a better self defence stance. The back balance is just that - a stance where you have had to shift your COG backwards or had to snake your foot forwards. It is a not to be dismissed - the reverse snap punch, one of the most powerful weapons in the karate-ka's arsenal is launched typically in the back stance. It is a weapon of subversion - it'll hit you without you knowing it was launched and you'd underestimate it because of it's subtlety.