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Fig. 1.10 'Virtually all the tissues of the body generate electrical fields when they are compressed or stretched [which are] representative
of the forces acting on the tissues involved .. . containing information on the precise nature of the movements taking place. . .. One of
the roles of this information is in the control of form' (Oschman 2000, p. 52). (A) Stress lines in a loaded plastic model of the femur.
(Reproduced with kind permission from Williams 1995.) (B) Any mechanical force which creates structural deformation creates such a piezo-
electric effect, which then distributes itself around the connective tissue system. (Reproduced with kind permission from Oschman 2000.)
(C) The trabeculae of bone which form in response to individualized stresses. (Reproduced with kind permission from Williams 1995.)
intervene in human structure and movement. To con-
tinue the metaphor for a moment, the human body is a
talented 'building' that is readily moveable, self-repairs
if it is damaged, and actually reconstructs itself over
both the short and medium term to respond to different
'weather conditions' such as a prevailing wind, a
typhoon, or an extended drought.
Stress passing through a material deforms the mat-
erial, even if only slightly, thereby 'stretching' the bonds
between the molecules. In biological materials, among
others, this creates a slight electric flow through the
material known as a piezo- (pressure) electric charge
(Fig. 1.10A and B). 1 9 This charge can be 'read' by the cells
in the vicinity of the charge, and the connective tissue
cells are capable of responding by augmenting, reduc-
ing, or changing the intercellular elements in the area.
As an example, the head of most everyone's femur is
made of cancellous, spongy bone. An analysis of the
trabeculae within the bone shows that they are bril-
liantly constructed, to an engineer's eye, to resist the
forces being transmitted from the pelvis to the shaft of
the femur. Such an arrangement provides the lightest
bones within the parameters of safety, and could easily
be explained by the action of natural selection. But the
situation is more complex than that; the internal bone is
shaped to reflect not only species' needs but also indi-
vidual form and activity. If we were to section the femur
of someone with one posture and someone else with a
quite different posture and usage, we would see that
each femoral head has slightly different trabeculae, pre-
cisely designed to best resist the forces which that par-
ticular person characteristically creates (Fig. 1.10C). In
this way, the connective tissue responds to demand.
Whatever demand you put on the body - continuous
exertion or dedicated couch potato, running 50 miles a
week or squatting 50 hours a week in the rice paddies
- the extracellular elements are altered along the path
of the stress to meet the demand within the limits
imposed by nutrition, age, and protein synthesis.
With the concept of piezo-electric currents, this
seeming miracle of preferential remodeling within the
intercellular elements becomes easier to understand.
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