Directional variations in the extensibility of human skin.

When an extending load is applied to human skin in vivo or in vitro the skin stretches with small increases in load until a limit is reached (limit strain) after which much greater increases in load are required to extend it further (terminal stiffness). At many sites there are marked directional variations, the direction of maximum limit strain being the same as that of minimum terminal stiffness and vice versa. The directional variations of extensibility at constant load on a young male body have been measured and recorded.