Science of exercise
To date I have proposed the following
a) A ring of contractile tissue runs from our nose, over the head and down
either side of the spine to the sacrum and then continues around your crutch
to the lower abdomen. In a continuous manner the muscles complete a ring by
coursing up the abdomen to the chest and onto the head via the
sternocleidomastoid muscle.
b) Another ring of contractile tissue encircles us from the crown of the
head to the ears, down the lateral sides of your chest/abdominal wall to the
space between the genitals and anus. The body wall is 3 muscle layers thick;
this Ocontractile fieldą uses only the outer 2 of the 3 layers.
c) Biomechanically when the spine is bent to the side and at the same time
bent either forwards or backwards a helical or torqueing takes place in the
spine. The last couple of weeks have outlined how your spine uses muscles
that project their power across the mid-line to do this. Helical movement
patterns have been very important in the acquisition of bipedal gait. In
turn bipedal gait has been very important in the development of a big brain
and manipulative hands.
So how do the limbs fit into this picture? Obviously they are an essential
element to human movement. To understand limb function once again we need
recourse to embryology and evolutionary biology.
By the end of the 4th week post-conception limb buds are visible with a
microscope. They emerge from an intermediate zone on the body wall of the
embryo. Intermediate because they emerge between the spinal area at the back
(the somites) and the large visceral swelling at the front of the embryo. At
this stage of embryonic development the heart/liver and the stalk to mum are
large organs. Because of the intermediate nature of early limb development
both the back body and the front body contribute the massive cellular
migration that is needed to create a limb.
Millions of cells stream into the limb bud. These cell need to know
where to go and they need to differentiate into the various tissues that
form a limb, e.g. muscle, bone, nerve, blood vessels etc. Each of these
tissues needs to be considered if we are to understand limb development.
The muscle cells appear to migrate into the limb from the back of the
body, the spinal region. Muscle cells flow into the limb and then coalesce
into a ventral and dorsal condensations. The ventral muscles form the
flexors of the arm and leg; the dorsal muscle condensation forms the
extensors of the limbs. So all the muscles of the limbs come from the back
and form flexors/extension groups.
From the front, visceral part of the embryo another group of cells are
migrating into the limb buds. These cells form the bone and tendon part of
the limbs. Limbs are therefore a form of fusion of both the back and front
body of the embryo.
And the limbs then twist. More on this next time.
Phillip Beach D.O. D.Ac
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