Bone Cells and Impending Force

This post I'd like to analyze what's happening in that front lead leg as the horse breezes since I'm thinking the whole process which involves the entire structure of the bone and the various forces working on that structure will give us some significant clues as to what we need to be doing to avoid injury. Again, I'm focusing on the cannon bone, though the inquiry will be much the same for each bone in the lower leg.

In any particular workout the bone is, of course, in a particular state of development that we need to consider in planning the workout. In my barn, e.g., we've been taking it easier the last two weeks as it appears both of my youngsters are in mini-growth spurts, and I'm assuming recently laid down collagen that might be damaged or destroyed by too much work pressure at this point. My 13 year old, on the other hand, could withstand almost anything we'd want to throw out, but, according to his present training.

The point is that the development of bone in the the cannon is in a particular state of being, as we head to the track, which changes from workout to workout. For this workout we'll assume that we've planned well, that there is appropriate development for what we're going to do, and that our cannon is without existing microfracture or other injury. The forces then that we'll encounter in the breeze will be working on healthy bone tissue of sufficient strength for what we're planning.

I've identified the forces to be encountered in the prior posts, but, let's indeed get down to the nitty gritty and look at precisely what we're about here.

Please note the entire stride as it involves the lead leg. The stride begins with the lead leg elevating itself into the air in preparation for the downward arc into the track. The height of this depends a bit on the conformation and stride type of the horse as well as speed. Bounders e.g. will have their front leads higher than horses that chop along in the manner of Got Country Grip. Interestingly, I believe the higher the elevation of the lead leg probably the more force is generated as the hoof slams into the track, BUT, if you think about it, the maximum force during the weight bearing phase (where the entire weight of the horse momentarily places on the lead leg), might last slightly longer in the choppers as opposed to the bounders. Perhaps the bounder types are a little easier on themselves in this regard and can stand more work in terms of structure.

The lead leg elevates and slams into the ground. Then, of enormous significance, if you watch this closely in slo mo video you'll see the leg acting as a pendulum with a certain degree of force operating on ground contact which increases to a maximum point and then lightens again just before the leg completes the stride. Maximum force therefore applies only after a short period of prep for that force so that in the stride in terms of amount of force we have something that looks like this:

initial force--increasing force--maximum force--immediate release of maximum force.

There is thus a short momentary prep of bone cells for max force. Analyzing this "prep" phase brings about the question: do bone cells like muscle cells gird themselves for impending force?

Continue next post.

Training:
Sat. 8/2: Off
Sun. 8/3: Light 2 mile riderless gallop without tack work.
Mon. 8/4: riderless: 6f warm up + 1.25 miles steady at about 15 sec/f. Tack work: Rod trotted 5/8, Art trotted 6/8.