Many people assume that grip strength is primarily determined by the size of a person's forearm, particularly the wrists. But many other factors inside the hand really make a difference. The size, strength and structure of the hand -- including the palm and fingers -- all contribute to grip strength, and can vary widely.
Reflexes can also vary. For instance, how someone squeezes something can produce a unique pattern. The pattern can be detected by sensors, which read and record the size and force of a user's hand during the first second of squeezing.
There are several kinds of grip strength. A firm handshake, for example, is a form of crushing strength, while the ability to exert crushing strength on something and sustain it over time is an example of supporting grip strength. Pinch grip strength is the ability to grasp and lift an object between your thumb and fingers, and relies very heavily on the strength of the thumb.
Scientific studies disagree about what grip strength shows about a person's health. One study conducted by the Boston University Arthritis Center found that men with a strong grip were more likely to develop arthritis in certain joints of their hands and fingers. Another study conducted by the Honolulu Heart Program found that low grip strength could be an indicator for disability later in life.