Fig. 7. (A) Bone cell mechanosensitivity declines soon after a loading bout (black line) is initiated, until a mechanosensory saturated state is reached where further mechanical stimulation produces no further osteogenic response. A recovery period, during which mechanical stimulation is drastically reduced or withheld, is required to return sensitivity to its preload value (100 % mechanosensitivity is represented by the broken line at the top). (B) When bone cells are stimulated, then allowed to recover (grey line) for a period sufficient to restore full sensitivity (approximately 8 h on the basis of the data presented) before the next bout is applied, the succeeding loading bout will stimulate fully sensitive cells. Consequently, a robust anabolic response can be generated from each bout. (C) The same initial loading bout as applied in B will stimulate the cells, but if subsequent bouts are initiated before full recovery has been achieved, the loading bouts will be applied to cells experiencing (temporary) mechanosensory impairment. Consequently, a compromised osteogenic response will result. Note that bouts 2–4 begin when the cells are at approximately 50–60 % of maximal sensitivity. B is representative of the 8 h recovery group; C is representative of the 0.5 h group.
