Figure 1.9 Stress Distribution Within a Body (Compression, Tension, and Shear) Animation Video

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Stress Distribution Within a Body (Compression, Tension, and Shear)

Directional force distributes stress within the human body that may cause injury. The effect of a given force depends on its size, direction, application point, and how long it is applied. These examples exaggerate the effects of the different directional forces for purposes of illustration.

Compressive force, or compression, is a squeezing force. Compressive forces acting on an object result in squeezing or compressing it into a shorter, wider shape.

Another force called tensile force, or tension, has the opposite effect. Tension is a pulling force. Application of tensile force lengthens and narrows the object.

While tension and compression act along the length of the object, shear force acts perpendicular to the length of an object. When a shear force is applied, a portion of the object slides, or shears, along another portion.

Each of these directional forces can cause injury to the body. However, different types of tissues respond differently to directional forces. Bone, for example, is best at resisting compressive forces, but is easily injured by shear force. The skin is particularly good at resisting tension, or stretching, but can be injured by compression and shear.