Chin (boxing)

In combat sports such as boxing, kickboxing and mixed martial arts, a fighter's chin is a figurative term that refers to an ability to tolerate physical trauma to the chin or jaw without being knocked unconscious. The fictional Rocky Balboa character of the Rocky franchise epitomizes the concept of a boxer with a granite chin.

A fighter with a "good chin" refers to a fighter with the ability to absorb blows to the chin or jaw without being struck unconscious, which can also be called a "granite chin", an "iron chin" or the like. Generally, the jaw portion of the skull, and specifically the point of the chin, is the area most vulnerable to a knock-out blow and therefore having an exceptional tolerance to punishment in this area is a great advantage to a fighter.

Although such fighters have been knocked out, it is rare. There is a dispute as to the physiology of having a "good chin". Some believe that a strong neck that resists a sudden angular acceleration of the head is what makes a "good chin". Supporters of this belief point to Evander Holyfield and Marvin Hagler, both of whom were strong and had large trapezius muscles around the neck. Others believe that it is genetics that decides whether a fighter will have a good chin or not.

A fighter with a "bad chin", "china chin", "suspect chin", or "glass jaw" refers to fighters with limited ability to absorb punishment to the chin or jaw. Many clubfighters and journeymen may have glass chins, although it may depend on weight class or sometimes legs. Some boxing experts, such as Teddy Atlas, believe it to be a mindframe. Additionally, some fighters have been known to have better chins as a result of moving up to a higher weight class. One example of this is Miguel Cotto, who was seen as having a relatively weak chin at light welterweight but was harder to hurt once he moved up to welterweight.

...
Wikipedia