While much emphasis is given to the resident bone cells(primarily osteocytes) and their response to the local loadimposed on bone, new research implies that response to themechanical load (exercise) may also be neuronally regulatedand therefore systemic, with a resultant effect on multiplebones [54]. Sample et al. [54] showed that in young rats,intense mechanical stimulation of one limb can illicit aresponse in other limbs and even in the entire skeleton.This newest discovery may explain why increased BMDafter localized mechanical stimulation could be recorded inskeletal sites that were not directly stimulated (e.g., increasedforearm BMD with walking) [23]

an either one alone [45]. One year of briskwalking combined with gymnastic training either increasedor maintained the spine BMD in postmenopausal women[25]. Results from an earlier meta-analysis showed thatwalking with other AEXs significantly affected the BMD atspine, but not hip [46]. Bone mass increases or decreasesin response to mechanical loading depending on whetherthe thresholds controlling bone formation and resorptionhave been reached [47]. A few studies have demonstratedthe importance of walking intensity on