This paper shows that axial loading can induce an almost complete fracture line through the bone through one side to the other.  But the break is on the wrong axis.  If fatigue loading was induced via transverse loading (lsjl or lateral impact loading) it is very likely that the micorodamage would be along the right axis.  But to induce bone fatigue in this way would likely require heavier loads than inducing sufficient hydrostatic pressure to induce chondrogenesis as the goal of increasing fluid forces in the bone is to encourage bone decay and induce differentiation of tissues that are capable of interstitial growth.

Role of Calcitonin Gene-Related Peptide in Bone Repair after Cyclic Fatigue Loading

“We used the rat ulna end-loading model to induce fatigue damage in the ulna unilaterally during cyclic loading. We postulated that CGRP would influence skeletal responses to cyclic fatigue loading. Rats were fatigue loaded and groups of rats were infused systemically with 0.9% saline, CGRP, or the receptor antagonist, CGRP8–37, for a 10 day study period. Ten days after fatigue loading, bone and serum CGRP concentrations, serum tartrate-resistant acid phosphatase 5b (TRAP5b) concentrations, and fatigue-induced skeletal responses were quantified. cyclic fatigue loading led to increased CGRP concentrations in both loaded and contralateral ulnae. Administration of CGRP8–37 was associated with increased targeted remodeling in the fatigue-loaded ulna. Administration of CGRP or CGRP8–37 both increased reparative bone formation over the study period. Plasma concentration of TRAP5b was not significantly influenced by either CGRP or CGRP8–37 administration.”

“sensory innervation of bone may have regulatory effects on skeletal responses to bone loading”

“Periosteum, endosteum, and bone tissue are all innervated by nerve fibers. This innervation exhibits plasticity in response to mechanical loading, in that a single loading event results in persistent changes in neuropeptide concentrations in both loaded and distant long bones, as well as changes in the neural circuits between limbs”

“Individual bone cells are directly connected to the nervous system via unmyelinated sensory neurons. Bone cells express a range of functional neurotransmitter receptors and transporters, including those for calcitonin gene related peptide (CGRP)”

“12 rats were fatigue loaded until 40% loss of stiffness was attained, using an initial peak strain of −3,000 µε (Fatigue group). ”

“To induce fatigue, the load applied to the ulna was incrementally increased until fatigue was initiated, as indicated by increasing displacement amplitude from a stable baseline. ”