Anatomy, Physiology Smoking Gun

The above illustration is the most clear I've found, and refreshes my own memory of what was discussed here way back in July.

While it has always been clear that bone remodels when exposed to the stress of exercise, the manner and mode of this remodeling in horses at the molecular/microscopic level has hardly been looked at, except on this blog. There is human research mostly involving osteoporosis but much of that is "for sale". I have, however, bumped into one paragraph of research that, voila, does support much of what was surmised on this blog way back in July and before. It's technical, but an encapsulation of basic info, if you care to read. The highlights and info in parentheses has been added:

(Excerpt appearing in the Journal of Orthopaedic Research based on work done in the Department of Kinesiology, Penn State University in January 2006. Unknown, of course, why it takes till the year 2006 to ask the questions. Nevertheless, significant info.)

"The objective of this study was to determine if the material properties of bone at the lamellar level are related to the predominant mode and magnitude of mechanical strain experienced in situ. The tibia and first metatarsal bones of five unpaired cadaveric lower extremities were instrumented with strain gauge rosettes and subjected to repeated loading trials in an apparatus that replicates the muscle forces and external loads experienced by the foot while walking. The spatial distributions of axial strain within diaphyseal cross sections taken from each bone were subsequently determined. Nanoindentation measurements were then performed on the same cross sections to determine the compressive elastic moduli of individual lamellae located with osteonal, interstitial and outer circumferential microstructures. 20% of the variance in interstitial elastic modulus within cross-sections of diaphyseal bone was explained by local strain magnitude. Lamellae residing in regions of compressive strain displayed significantly higher compressive elastic modulus values than those located in predominantly tensile regions. Elastic moduli of interstitial lamellae were 11% greater than those of osteonal or outer circumferential lamellae, irrespective of strain or anatomical location. (i.e. greater strain on the inner than the outer bone.) in the material properties of individual bone lamellae located within different anatomical location. Differences exist in the material properties of individual bone lamellae located within different anatomical regions and different micro structures, AND THESE DIFFERENCES ARE RELATED TO THE DISTRIBUTION OF AXIAL STRAIN. THESE FINDINGS SUGGEST THAT MECHANICAL STRAIN, OR ANOTHER CLOSELY RELATED VARIABLE, MAY INFLUENCE THE DESIGN AND ULTIMATE MECHANICAL BEHAVIOR OF THE EXTRA-CELLULAR MATRIX FOUND IN LAMELLAR BONE."

There you have it. Exercise--the exercise program--influences the "design and ultimate mechanical behavior of the extra-cellular matrix"!!! We can avoid further speculation, intuition be dammed, the schematic, formula and design of our program--i.e. speed, distance and frequency does significantly impact both design and strength of the larger bone structures. In this sense, what the horse does on track, i.e. the precise exercise schematic, matters.

Training:
Fri. 10/23: Off a 3rd straight day due to wet conditions.