Chi Sau literally: “sticking hands”) is a term for the principle and drills used for the development of automatic reflexes upon contact and the idea of “sticking” to the opponent (also known as “sensitivity training”). In reality, the intention is not to “stick” to your opponent at all costs, but rather to protect your centerline while simultaneously attacking your opponent’s centerline.
In Wing Chun, this is practiced by two practitioners maintaining contact with each other’s forearms while executing techniques, thereby training each other to sense changes in body mechanics, pressure, momentum and “feel”. The increased sensitivity gained from this drill helps a practitioner attack and counter an opponent’s movements precisely, quickly, and with appropriate techniques.
Chi Sau additionally refers to methods of rolling hands drills (Chinese; Lūk Sáu; literally: “rolling hands”). Luk Sau participants push and “roll” their forearms against each other in a single circle while trying to remain in relaxed form. The aim is to feel force, test resistance, and find defensive gaps. Other branches have a version of this practice where each arm rolls in small, separate circles. Luk Sau is most notably taught within the Pan Nam branch of Wing Chun where both the larger rolling drills as well as the smaller, separate-hand circle drills are taught.
In some lineages (such as the Yip Man and Jiu Wan branches), Chi Sau drills begin with one-armed sets called Daan Chi Sau (Chinese Dāan Chī Sáu; literally: “Single Sticking Hand”), which help the novice student to get the feel of the exercise; each practitioner uses one hand from the same side as they face each other. Chi Sau is a sensitivity drill to train and obtain specific responses and should not be confused with actual sparring or fighting though it can be practiced or expressed in a combat form.