The capacity for functional adaptation within the skeleton was studied using the functionally isolated turkey ulna preparation. The results of this study would suggest that adaptive bone remodeling is extremely sensitive to alterations in both the magnitude and distribution of the strain generated within the bone tissue. At present, it appears that a loading regime can only influence bone remodeling when it is dynamic in nature. The full osteogenic potential of its influence is then achieved after only an extremely short exposure to this stimulus. The potency of the stimulus appears to be proportional to the magnitude of the strain engendered. As strain levels that are acceptable in one location induce adaptive remodeling in others, it would appear that each region of each bone is “genetically programmed” to accept a particular amount and pattern of intermittent strain as “normal.” Deviation from this “optimal strain enviroment” will stimulate changes in the bone's remodeling balance, resulting in adaptive increases or decreases in its mass.