From Sensei Kurt Tezel, San-Dan
Cocoa Beach Ueshiro Shorin-Ryu Karate Dojo
One of the most common mistakes when first learning Jigotai Dachi is to bend the knees forward of the feet. This does a number of things: It unnecessarily exposes the groin, puts undo stress on the knees and will inevitably cause a lack of balance when executing techniques with the arms.
There are a couple of useful exercises to correct this. Line up against a wall with your toes touching the base of the wall and squat. You will immediately feel your weight shift from the toes to the heel and consequently become "rooted down". Have a partner hold a padded target while you squat punch. Periodically have your partner move the target out of the way. If your weight and knees are in the correct position you will maintain your balance without diminishing the power.