Larger Structures: What We Need To Know

Does the exercise program affect the macro or larger structures within the leg bones? The blog previously considered what happens at the atomic, cellular, micro level, and you may read those posts if interested.

Regards the structure of the bone at larger than the cellular level and how it reacts and builds itself in response to stress and exercise, we'd like to be specific--replace conjecture, superstition, old wives tales and even informed intuition with basic facts to the extent possible in the present state of the science.

The diagram above left illustrates these larger structures of cortical (hard) bone. Note specifically the:

Lamellae
Osteon
Periosteum

Note use of the term "compact" bone as bone is denser on the outside, more porous (spongy) inside.

Recall from the prior posts that the osteoblasts which construct new bone wind up as microscopic osteocytes--the new bone material which is collagen that will thereafter calcify, and that the osteocytes then arrange themselves into the round, tubular osteons. My understanding is that osteons are short instead of long--I've read a distance of a few millimeters to an inch or two. I'm uncertain which. At any rate the tubular osteons seem to end instead of running the length and breadth of the bone.

I'd presume that it is the osteons, their calcification and connection that give the bone its most basic strength. Again, my understanding is that the spaces between the osteons are filled in with calcified material that is weaker but which sort of "sticks" or glues the tubules together.

In the end, I'm thinking, the bones wind up as the equivalent of numerous very thick but short wires. If one wire fractures, the nature of the material makes it less likely that the fracture would extend to the next. This fracture blocking permits swift healing of any single fractured strand.

More, next post.

Training:
Wed. 7/29: The next 3 day cycle starts in terrible ground conditions:
Art: Early in the day Art escapes the farm and spends a few miles pacing after the neighbor's mares. But still has enough left for an energetic 2 miles walk-trot, mostly trot with a few strides of gallop where we can.
Rod: 1.4 miles walk-trot. Getting back into tack work. The knee issue is behind us.