Bone mineral content and density (BMC, BMD) losses appear in various disuse conditions. To abate BMC and BMD losses, exercise may provide greater mechanical loads and impact forces to the human skeleton from muscle contractions that attach to various bones of interest. Specifically, stimuli imparted to bones refers to magnitudes, rates and frequencies of strains engendered by exerciseinduced mechanical loads and impact forces. Yet exercise’s impact on BMC and BMD has yielded mixed results due to limited delivery of one or more strain component. To perhaps best prevent BMC and BMD losses, exercise must routinely elicit high strain magnitudes, rates and frequencies to specific bones of interest. A paradigm that may best yield high strain magnitudes, rates and frequencies must entail dynamic high-speed activity; whereby successive repetitions see a light load abruptly and rapidly change its direction of movement and, when occurs, imparts large impact forces. A recent 30-workout intervention on an inertial exercise trainer (IET; Impulse Technologies, Newnan GA) produced large calcaneal BMC (+29%) and BMD (+33%) gains in ambulatory subjects. Throughout the intervention, Δ force/Δ time values achieved on the IET exceeded 2250 N.s^-1 at a rate of 2.0-2.5 repetitions per second. Despite the promising results from healthy ambulatory subjects, similar research is needed with disuse conditions if the IET gain acceptance as an exercise modality used to treat bone loss.

Magnitude, Rate, Frequency, Impact force, Osteogenic, Physical activity, Mechanotransduction