Healthcare and Medicine Reference
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Thus we can see the bones as the primary compres-
sion members (though the bones can carry tension as
well) and the myofascia as the surrounding tension
members (though big balloons, such as the abdomino-
pelvic cavity and smaller balloons such as cells and
vacuoles (see last section of this chapter) can also carry
compression forces). The skeleton is only apparently a
continuous compression structure: eliminate the soft
tissues and watch the bones clatter to the floor, as they
are not locked together but perched on slippery carti-
lage surfaces. It is evident that soft-tissue balance is the
essential element that holds our skeleton upright - espe-
cially those of us who walk precariously on two small
bases of support while lifting the center of gravity high
above them.
Tensegrity structures are strain
distributors
A tensegrity model of the body paints an altogether dif-
ferent picture - forces are distributed, rather than local-
ized (see Fig. 1.51). An actual tensegrity structure is
difficult to describe - we offer several pictures here,
though building and handling one gives an immediate
felt sense of the properties and differences from tradi-
tional views of structure (see p. 49) - but the principles
are simple. A tensegrity structure, like any other, com-
bines tension and compression members, but here the
compression members are islands, floating in a sea of
continuous tension. The compression members push
outwards against the tension members that pull inwards.
As long as the two sets of forces are balanced, the struc-
ture is stable. Of course, in a body, these tensile members
often express themselves as fascial membranes, not just
as tendinous or ligamentous strings (Fig. 1.57).
The stability of a tensegrity structure is, however,
generally less stiff but more resilient than the continu-
ous compression structure. Load one 'corner' of a
tensegrity structure and the whole structure - the strings
and the dowels both - will give a little to accommodate
(Fig, 1.58). Load it too much and the structure will ulti-
mately break - but not necessarily anywhere near where
the load was placed. Because the structure distributes
strain throughout the structure along the lines of tension,
the tensegrity structure may 'give' at some weak point
at some remove from the area of applied strain, or it may
simply break down or collapse.
In a similar analysis, a bodily injury at any given site
can be set in motion by such (often) long-term strains in
other parts of the body. The injury happens where it
does because of inherent weakness or previous injury,
not purely and always because of local strain. Discover-
ing these pathways and easing chronic strain at some
remove from the painful portion then becomes a natural
part of restoring systemic ease and order, as well as
preventing future injuries.
Fig. 1.58 The spine is modeled in wooden vertebrae with
processes supported by elastic 'ligaments' in such a way that the
wooden compression segments to do not touch each other. Such
a structure responds to even small changes in tension through the
elastics with a deformation through the entire structure. It is
arguable whether this simple model really reproduces the
mechanics of the spine, but can the spine be said to operate in a
tensegrity-like manner? (Photo and concept courtesy of Tom
Flemons,
Fig. 1.57 While most tensegrity sculptures are made with cable-
like tension members, in this model (and in the body) the tension
members are more membranous, as in the skin of a balloon.
(Photo and concept courtesy of Tom Flemons, www.
intensiondesigns.com.)
www.intensiondesigns.com. )
50
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