Hand Pattern Based on Second-to-Fourth Digit Ratio: Its Relationship to Sex, Body Mass Index, and Physical Activity.

Background: The second-to-fourth digit ratio is measured by dividing the length of the index finger by the length of the ring finger. A ratio <1 means that the ring finger is longer; this is known as the male pattern or "A" pattern. A ratio >1 means that the index finger is longer; this is known as the female pattern or "C" pattern.