Sanchin Dachi (stance) is a very importance stance in Karate. It provides a sense of stability and rootedness to the earth, which is important to have when defending yourself from a larger opponent.
I have found this stance to be very effective in close quarters combat situations. I work in an office setting in a small office with chairs and desks. Our waiting room is also full of chairs and tables. There is very little room to move into a fighting stance you would use in kumite or as you see in full contact mixed martial arts. It is not for the ring, but for the street. I have used this stance (and the kata's bunkai/street applicaton) in an office self-defense setting. It works!
When practicing Sanchin Dachi it is traditional to carry heavy weights in your hands hanging down from the sides. This helps with a sense of stability and being close to the ground. It also help your muscles, tendons and nerves get used to pressure upon the legs so it becomes natural to stay this way when when someone is pressing you in an attack.
Many Karate-ka will tell you that when first practicing this stance it feels very awkward...but after years of training it becomes very natural and easy. In fact, you might just find yourself standing like this when waiting in line for a movie or at the grocery store. The stance itself can provide a sense of alert calmness as well.
Even though Sanchin Dachi might feel and look like an immobile stance, it is in fact very mobile when you learn how to use the feet and hips to manipulate your opponent. Notice the inward 'hook' position of the front foot in the photo. This can be used to hook your foot behind your opponent's leg to uproot him...or this leg position can protect you from a front kick to the groin by simply lifting your knee.
A front scrotal kick can also be 'caught' by both your legs as you squeeze them together...this one takes some practice....but all it takes is missing a few times and you get the hang of it. I could go on and on about Sanchin Dachi, however, I want to hear what you know.
I invite any readers out there to respond with how Sanchin Dachi helps them or how they use it in self-defense...or in any way for that matter. Or any training tips on making the legs stronger, etc. We love to learn at the Broken Bokken Dojo.