Remodeling: Humans/Horses II

The process is "bone remodeling". The end point, hopefully, race appropriate fracture resistance. We want to know how to get there absent any significant research. We speculate.

Human athletes activate bone osteoblasts and osteoclasts over time that gradually build up stressed bone per the diagram. Does the same process occur with the geometrically greater loads on our horses?

The June-Sept. 2008 blog posts estimated effects of one single breeze on the cannon bone. And now the plan is to view the process through multiple breezes to note both insufficiencies and optimization!

Start this with a brief review of the single breeze/race.

Whenever our horse heads to the track--I'm sort of considering Zenyatta in all those John Shirrefs You Tube videos-- cannon bone characteristics involve a specific state of being in a moment in time that will respond particularly to the coming breeze. Conclude: differing states of bone development react differently We may view the coming exercise with trepidation for the softly trained horse. For a "hard body" trained horse as TC winner Assault we may have limited worries.

Bone materials will sense forces and undergo protective changes as the horse runs down the track. Sensing occurs both mechanically to include signaling by fluid flow, and by electrical signaling at the atomic level and through nerves.

In response there are macro and local cellular reactions involving tightening and girding within the cells, cell to cell and within the whole structure including compaction and rebounding as well as twisting and bending in response to concussive, compressive and torsional forces coming at bone tissue from all directions.

Reactions to all this within the tissue vary with the type tissue. The hardened mineral lattice, limited by its nature and structure, will gird, compress, and push back to some extent, and we've noted this mattress spring effect decreases incrementally with each impact producing a little less bounce back than the one before. Within the lattice there is vibration, oscillation, and heat build up and release and all the mechanical-physical-electrical consequences resulting therefrom.

The softer materials, specifically the ductile rubbery bone collagen with each cell in various states of mineralization, and also the bone glue proteins that help hold everything together, have by their nature and greater fluidity differing reactions. Movement, gliding cell to cell, and significant rearrangement during the 240 strides of the breeze/race are in play with these softer tissues. Heat build up initially provides malleability and absorption but at some critical point heat causes these materials to become less sticky and supportive.

Regards these materials the breeze generates mechanical engineering factors-- stress intensity, shear modes, tear mode, the brittle-ductile transition phase as the number of thermal cycles increase and the structure approaches"critical strain" where there may be rupture peaks or peaking and the consequences that one cell may give way then another and another with less and less force necessary to rupture each succeeding cell as the rupture process proceeds. Yet, particular cracks are harmless as long as the entire structure maintains enough integrity to contain them--a crack, e.g. hits an osteon which stops crack propagation at that point.

You may gather in conclusion that the above processes for our horse differ significantly from what happens with the human runner. I'll be bold and speculate that in humans even at top 100 meter sprinting loads almost none of the processes exist that work during the breeze/race in our horse cannons.

Moreover, as my September posts noted, possibly the most significant difference between human and racing horse athletes is that in the particular event for the horse there is actually a percentage of cellular damage that occurs that I've guessed as being 1% destruction of bone cells spread diffusely through the cannon for any one event(in the "trained" bone).

The breeze/race for our horse thus differs substantially in effect as does our sprint race on our human tibia. So much so that I believe the remodel process between these species differs significantly. How, next post.

Training:
Wed. 2/18: the planned first tack accelerations postponed due to ground conditions. Riderless 1-2f full speed bursts: 3 x2. Will be able to get trailer out of mud today!