muscular sYstem 61
12 to 15 joints. The diaphragm has an effect on over 100 joints. It crosses some of those
directly and affects others by way of fascial and skeletal connections.
With a few exceptions, the deeper the layer of muscle or muscle tissue, the shorter it
is.^3 The shortest, deepest layers of muscle that cross one joint are called monoarticular, or
one-joint muscles. These one-joint muscles have very specific actions and support articula-
tion and discrimination at each joint. They are essential for the integrity and alignment of
individual joints.
As the muscle layers get more and more superficial, they become longer and broader,
and they cross more joints. If a muscle crosses more than one joint, every time it acts it has
a direct effect on all of the joints it crosses as well as an indirect effect on all of the joints
in the body. These longer muscles are called multi-joint muscles if they cross two or more
joints. The multi-joint muscles connect all the parts of the limbs together, and they integrate
the limbs into the torso. They give us the ability to negotiate large shifts of weight and
movement of the whole body through space, or, in the diaphragm, to coordinate sophis-
ticated shape changes in the torso.
Every joint has both one-joint and multi-joint muscles that surround it. Every joint has
the possibility of discrete and specific movement, and the potential for being integrated
into a flow of movement that travels through the whole body.
When we forget that we have the potential to move with specificity and articulation in
every joint, we might never find some of the movement possibilities that are available to us.
When we only use bigger and more superficial muscles, we work too hard. On the other
hand, when we focus only on the deep one-joint muscles, we can forget to look at the whole
picture of movement. All the layers are essential for healthy and efficient joint movement.
Kinetic chains of Muscles
In addition to examining specific muscles around a single joint or the layers of muscles from
deep to superficial, we can also consider how the muscles work together in kinetic chains.^4
In this case we no longer consider individual muscles but the ways that they are linked
together by connective tissue into long chains of dynamic action.
Whenever we engage a single muscle, it has an effect on the rest of the body by way of
the connective tissue. From anywhere in the body, movement follows a kinetic chain from
one muscle to another through the direct relationships of the connective tissues that link
the individual muscles and through the sensory-motor pathways of the nervous system
that sequence the firing of the muscles.
Never in life do we use a single muscle to do a task. In an efficient, integrated move-
ment, we engage enough muscles to get sufficient power for the task without expending
too much energy or recruiting so many muscles that we get in our own way.
FundaMental principles oF sKeletal Muscles
The following are basic ideas on how muscles work in relationship to the bones and nerves.
Understanding these principles can help to cultivate an awareness of the complexity and
sophistication of the muscular system. Also, this awareness might prevent the oversimplify-
ing that is so limiting to our movement choices.
(^3) Exceptions are as follows: the extensor digitorum brevis in both the hands and feet, which lies on top of the extensor
digitorum longus, and the psoas minor in the torso, which runs along the surface of the psoas major. Also, the psoas major
and the diaphragm are some of the deepest muscles in the body, and both cross many joints.
(^4) I first encountered the term kinetic chains in my study of Laban Movement Analysis and the Bartenieff Fundamentals,
though it is used by a variety of therapeutic modalities.