Figure 9.

Diagram illustrating the tensile forces acting on collagen fibers and cells acting in the skin. Collagen fibers are stretched in tension under normal physiological conditions. This causes the fibroblasts attached to the collagen fibers to generate a retractive force via attachment through integrin and decorin molecules. These attachments serve as a feed-back mechanism to skin cells reflecting the current level of loading. Increased external loading stretches the collagen fibers as well as the attached cells up-regulating mechanotransduction under normal physiological conditions. This explains why weightlifting increases muscle size and also generates more skin to cover the larger muscles due to fibroblast loading via increases in skin tension. Note the role of integrin–collagen–fibroblast attachments as well as collagen–decorin attachments at the d and e bands.