Conclude: Speed and Fracture Resistance

Forces acting on the equine skeleton produce the bone remodeling on right. How much speed, which also means how much force, do we need to produce race surviving fracture resistance?

I've outlined in the previous posts what is available:

1. There are few studies. Human fracture resistance, much less equine, still in its infancy.

2. My personal observations of slow breezing trainers over the years whose horses tend to quickly disappear. My guess that statistical analysis would confirm that slow breezing trainers are unable to avoid fractures and chips.

3. On board detection of the concussive forces at various speeds. The rider can sense the transition from ground flicking to bounding as speed increases and also the concussive feel of each stride as the horse goes through decreasing fractions. And so, the rider's sense that the transition from flicking to bounding completes at about :12.5/f.

4. Visual observation at various speeds of foot fall, reach and length of stride, confirming rider feel that the horse is in full bounding action and thus increased concussive load at about :12.5/f.

5. Consequently we presume bone reacts in response to increasing loading factors so that in :13s we have maybe 20% less load than in :12s, e.g. 9600 lbs./sq. inch as opposed to 12,000 lbs./sq. inch.

6. That there is some point as the fractions decline of maximum load, and that the percentage increase in load as we go faster than :12s may actually decline due to decreasing hoof to ground contact as bounding speed increases. I've estimated max load at 13,200 lbs./sq. inch regardless of speed.

7. And finally, the assumption that bone remodels in response to the load factor, i.e. we get less remodeling in terms of size, quality and density at 9600 lbs/sq. inch than we do at 12,000 lbs/sq.inch.

So, for this skeleton of our venerable racer:I've concluded that bare minimum galloping speed to get fracture resistance at racing speeds is :12.5/f. Slower, and you get insufficient remodelling. Thus, what should our trainer do in terms of speed, next post.

Training: Sat. morning at 9:00 a.m. and it's 19 degrees in KC. But, we're happy. Temps are going straight up. Horses had several quick riderless bursts Friday over the new snow in the Astride paddock. They got over the snow much better than myself. We'll repeat today as we brace ourselves for the coming mud.