(a) Sinusoidal loading was applied non-invasively to the rat lower hindlimb, which was constrained between a custom-made knee cup and foot holder. The lower limb was compressed in the direction indicated by the arrows. (b) Strain-gage calibration of the loading device using control rats (n=3; each rat represented by a symbol, ● ▲ ◆) illustrates the relationship between applied load (N) and measured deformation (microstrain) of the proximal tibia. After tracer injection, an applied load of 14 N, which engenders ~500 microstrain at the medial proximal diaphysis, was applied at 1 Hz to mimic slow walking.