Bone Remodelling: One More Thing

Before I get into the crucial question of time and how long remodelling takes, I found an interesting article that finally provides a theory of support for much of what has been posted. I'll paraphrase the most interesting sentences of the article, and my comments:

ELECTRICAL PROPERTIES OF BONE, A REVIEW

"F and Y demonstrated that (dry) bone is piezoelectric, i.e. mechanical stress results in electric polarization, the indirect effect; and applied electric field cause strain, the converse effect. The piezoelectric properties of bone are of interest in view of their hyposthesized role in bone remodelling."

Hmmm. stress, which in our case would be concussion causes electrical activity in bone???

But, note, they're talking about dry bone, which means dead bone. There noting that dry bone has same electrical response to stress as certain minerals such a quartz, salt, zirconate and other non-living materials with ceramic properties.

"Wet collagen, however, does not exhibit a piezoelectric response. "

They fail to explain this and the relevance. They seem to contradict the statement when noting that rat limbs conduct weak electric signals, and that "Cartilage exhibits electrical response to applied force."

They note an electrical property called dielectric (as opposed to piezoelectric).

The article goes on:
"Bone Electricity: wet and dry:

Potentials observed in bent bone differ from predictions based on the results of experiments performed in compression. The piezoelectric polarization may consequently depend on the strain gradient as well as on the strain...the physical mechanism for such effects is hypothesized to lie in the fibrous architecture of bone."

They go on to note that apparently there is definitely "dielectric" behavior in citing the"fluid flow effects, possibly streaming potentials in wet bone".

And, here's a really big one: for you old codgers. wondering why your bones ache in low pressure and high humidity? "Dielectric permittivity of bone has been found to increase dramatically with increasing humidity and decreasing frequency." Again the "wetter" the bone, which also means the more alive the bone, the lesser the frequency conducted.

The study goes on to suggest that at 100% humidity the "pores" in bone are fully filled with fluid, whereas at 98% humidity they are not fully filled for the reason that they (the researchers)get almost no bone conduction at 100% humidity and 100 times more conduction when the humidity is at 98%.

By extrapolation, if the humidity is normal, the bone has significant conductivity and we may conclude, though the article says it's a controversial hypothesis, that the very act of exercise, or strain or compression, or bending causes electricity build up in bone which may contribute to remodel.

May we presume from this that the more the stress the more the electric build up and conductivity both in terms of speed and distance traveled for our horse.

This theory provides an added consideration to those remodelling effects in the prior posts. It notes the microscopic cavities in bone matrix filling up with fluid under some circumstances and that electricity goes through there in response to exercise presumably causing those remodelling effects in the prior posts. And so, just one more thing to consider that exercising our horse will or won't do depending on how far and fast we go.

Next post onto the question, post exercise how long do we wait before we start up again.

Training: Sunday was a raw day, much colder than they said with wind. Got to the farm intending to apply the lost shoe to Art, and woe, he's now lost both fronts, and so shoeing took some of the planned daylight. But we got a nice riderless workout in the mud of the normal running paddock, about 6 x 3f for both horses at decent speeds, very good energy. Skipped the tack work, as hopefully today, Monday, spring is sprung and things will start in earnest.