Influence of External Forces on Bone

The role of cells residing within skeletal tissues is to maintain a balance between the processes of resorption and formation. When these two processes are essentially equal, a conservation-mode of remodeling exists 

Studies involving fluid shear, hydrostatic compression, biaxial and uniaxial stretch, or a combination of two or more of these factors indicate that fluid shear is a major factor affecting bone cell metabolism and cells subjected to mechanical stress reshape and align themselves with their long axis perpendicular to the axis of force. Cells also exhibited remodeling of the actin cytoskeleton and increases in PKC levels, processes thought to be involved in the early phase of mechanochemical transduction. 

At the physiological level, gravitational loading on skeletal tissues is known to be important. After space missions of varying periods, histomor-phometric studies of bones from rats provided insight into the time course of cancellous bone cellular events these events include a transient increase in resorption and sustained decrease in bone formation (Vico et al., 1998). Bone loss in rats occurred first in weight-bearing bones, and the time 

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