Abstract: Mechanical forces that act on bone are generated from impact with the ground (ground-reaction forces) and from skeletal muscle contractions (muscle forces or muscle-joint forces), but the relative importance of these two sources has not been elucidated yet. Both muscle-joint forces and gravitational forces seem to be able to induce bone adaptation independently. Bone is sensitive to a variety of mechanical parameters including, but certainly not limited to, strain magnitude, strain rate, strain gradient, strain frequency, duration, acceleration, or rest intervals. Under the same strain magnitude, power training is more effective than strength training, and high impact/odd impact activity is more effective than low impact activity in augmenting BMD. A few loading cycles seem sufficient for bone accretion; while a long duration seems to make bone less sensitive. And a rest period after each loading cycle can increase the osteogenic response. Endurance activities seem to be beneficial to a less degree at increasing BMD due to sustained, long duration exercises which may be related to lower Testosterone/Cortisone ratio or female Estrogen levels. Combined protocols integrating odd- or high-impact exercise with resistance exercise are more effective in increasing BMD than single type exercises. The effect of vibration of certain frequency on BMD needs to be studied in the future.