Muscles, tendons and will

MUSCLES, TENDONS AND WILL Our Anatomy

MUSCLES, TENDONS AND WILL

Movement

1. Talking about muscles in general (p. 14)

Movements of the human body result from contraction of muscles (here voluntary or
striated muscles) which attach to the bones

Typically a muscle is attached to two different bones (except facial muscles and
sphincters). For a given body movement, the proximal bone, ORIGIN, is fixed and the
distal bone, INSERTION, moves as a result of muscle contraction. The distal bones
supposed to move freely in the space

Muscle is composed of BUNDLES of FIBERS (primary, secondary, tertiary), held
together and compartmentalized by FIBROUS partitions, APONEUROSIS, called (on a
progressively smaller scale) deep fascia, epimysium, perimysium and endomysium.
These connective tissue partitions (which are continuous with each other) allow easy
movement of one muscle or muscle group relative to another.
They can be extended beyond the muscle to form a strong fibrous CORD
called TENDON which is continuous with the periostium of a nearby bone

Looking Inward 1


Individual muscle cells (MYOFIBERS) are extremely long and contain many nuclei.
Each cell contains many functional units called SARCOMERES, divided by boundaries
called Z lines. Each sarcomere contains thick filaments (made of the protein MYOSIN)
and thin filaments (protein ACTINE); the thin filaments are anchored to the Z lines

In repose, the myosin and actin filaments are separated. When the muscle is
stimulated by a nerve, a series of chemical reactions involving calcium, ATP and
magnesium takes place, causing the thin filaments to "slide" along the thick filaments.
As a result, the Z lines move closer together, and each individual sarcomere (and
therefore the entire muscle) becomes shorter. This is the basis of muscle
CONTRACTION, the muscle PULLS from the attached bones

Muscle elasticity (p. 15)

Besides their (active) ability to CONTRACT, muscles have a (passive) property of
ELASTICITY

So, a muscle can be stretched to certain point, moving its insertion points further
apart, doing the reversed movement of its action. Example: the anterior neck
muscles, when they contract, are FLEXORS of the neck. During EXTENSION of the
neck, they become stretched. When this happens, because of their elasticity, they
tend to return to their initial length, returning the head to its anatomical position

2. Muscle shapes (p. 16)

Looking Inward 2


Muscles attach to bones in several manners:

Directly via muscle fibers (usually in broad insertion). Ex.: subscapularis

Via an aponeurosis (broad tendon). Ex.: quadratus lumborum

Via a regular tendon. Ex.: brachioradialis

Sometimes the tendon passes under a fibrous band. Ex.: tibialis anterior

A muscle can have several bellies or heads. Ex.: biceps (2 heads), triceps (3 heads),
quadriceps (4 heads)

Looking Inward 3


Some muscles can have several origins, which may be in more than one bone (i.e.:
the flexor digitorum superficialis originates from both the radius and ulna). Multiple
insertions are less common than multiple origins and usually involved finger and toe
bones (i.e.: interosseous muscles end, in a complex way, at the 1st phalanx and the
extensor tendon of the toe)

Muscles have different sizes and shapes: the fiber bundles of muscles are arranged in
many shapes

Depending on the orientation and attachment of their fibers, muscles may act in one
or several directions. Ex.: fibers of rectus abdominis run essentially parallel to each
other flexes the trunk; fibers of external oblique arranged like a fan anterior
flexion, side-bending or rotation of the trunk

LONG muscles are usually kinetic (able to produce visible external motion). SHORT,
deep muscles (those inserting on the vertebrae or foot bones) tend to be responsible
for precise, small-scale adjustments

MONOARTICULAR a muscle that crosses a single joint

POLIARTICULAR a muscle that crosses more than one joint. Ex.: rectus femoris (hip
and knee) flexor of the hip, extensor of the knee; it will be stretched in situations
involving simultaneous extension of the hip + flexion of the knee
3. Muscle contraction (p. 20)

Looking Inward 4


Speaking of a particular movement, the muscle which produces it is called AGONIST,
and the muscle which produces the opposite movement is called an ANTAGONIST.
Ex.: flexion of the hip, psoas is agonist and gluteus maximus is antagonist

SYNERGETIC: different muscles which cooperate to produce the same action.
Ex: dorsiflexion of the ankle = tibialis anterior + extensor hallucis longus + extensor
digitorum longus.
Mutually opposing muscles often function together to fix or stabilize a bone. Ex.:
serratus anterior + rhomboids and middle trapezious. By contracting at the same
time, they work together to fix the scapula

When a muscle contracts, it tends to draw its origin and insertion points closer
together. Anything opposing this RESISTANCE. Ex.: brachialis + biceps b., major
flexors of elbow. Their action can be opposed by several types of resistance:

The weight of the forearm (gravity)
The weight of some external object attached to forearm
The force of another person pulling on your arm
The tension in the muscles that oppose flexion (triceps, elbow extensor),
contraction of antagonist muscles

Looking Inward 5


Looking Inward 6


Looking Inward 7


Looking Inward 8


Few extra things

Contractions are controlled by the Central Nerve System (CNS), the brain controls
the voluntary contractions, while the spinal cord controls the involuntary reflexes

Muscle cells (muscular fibers), produce the contractions that move the body parts,
including inner organs. The associated connective tissue transports nerve and
capillary fibers to the muscle at the same time it wraps it up in bundles or sheaves.
Muscles also give shape to the body and generate heat

Three types of muscles:

Looking Inward 9


TYPE OF
LOCATION ASPECT TYPE OF ACTIVITY STIMULATION
MUSCLE

Powerful
Cylinder-shaped fibers, contraction, Fast
It attaches to the
Skeletal large, very long, no and intermittent on
bone and to the Voluntary by
branched, transversely the basal tone;
or fascia of the limbs,
striated, disposed in serves, above all,
the somatic
striated body walls and nervous system
parallel bundles; many to produce
head/neck
nuclei in the periphery movement or to
resist gravity

Involuntary;
Branching network intrinsic
fibers, many cells linked Powerful stimulation and
Muscles of the together, striated contraction, fast, propagation;
heart and nearby appearance from its constant and speed and
Cardiac portions of the orderly arrangement of rhythmical; pumps strength of the
great vessels myofilaments; a single, up the blood from contraction
centrally located the heart controlled by
nucleus the autonomic
nervous system

Viscera walls,
urinary system, Elongated, spindle-
Weak contraction,
some respiratory shaped appearance, in
slow, rhythmical or
passageways, thin sheets or small Involuntary by
sustained; serves
Smooth certain individual bundles,
above all to impel
the autonomic
reproductive smaller than the other nervous system
substances and to
organs and blood types, nonstriated;
restrain the flow
vessels, iris, glands, single central nucleus
etc

The structural unit of the muscle is the muscle fiber. The motor unit is the functional
unit composed by the motoneuron and the muscle fibers enervated by it. When
the nerve impulse reaches the motoneuron in the spinal cord, another impulse is
generated which determines the simultaneous contraction of all the muscle fibers
innerved by that motor unit. The number of muscle fibers in each motor unit goes
from one to few hundreds. The number of fibers changes depending on the size
and function of the muscle. Movements obey the activation of a progressive
number of motor units. Revising:

agonists work doing the movement

antagonists oppose the action of the agonists; when the agonist contracts, the
antagonist relaxes progressively inducing a smooth movement

synergists restrain the movement of the articulation inserted between when an
agonist crosses more than one joint; these muscles complete the action of the
agonist

Looking Inward 10


Looking Inward 11


Looking Inward 12


Looking Inward 13


ATP: adenosine triphosphate is a fundamental nucleotide to obtain cellular energy.

Looking Inward 14


4. Types of contraction (p. 22)

Concentric shortening and eccentric lengthening

Concentric contraction

When the muscle is stimulated by a nerve and the muscle responds by shortening.
Ex.: biceps brachii in the forearm shortens concentrically when lifting up a book,
because the origin and insertion points of the muscles are drawn together so the
muscle is shorter in length or contracted

Eccentric lengthening

When we put the book down, we do not ordinarily drop an object we have just
lifted, we set it down carefully by slowly extending the elbow, and we accomplish
that by allowing the muscle as a whole to become longer while keeping some of
its muscles fibers in a state of contraction; in fact can be a bit delicate for the extra
work concentrated on those few fibers. Whenever a muscle increases in length
under tension while resisting gravity, that movement is eccentric lengthening,
typically in actions where we try to slow down a load. It’s usually called
lengthening under tension. This “lengthening” can give way to confusion since,
although the muscle is lengthening and extending, it’s doing it under pressure and
doing no more than going back to its natural resting position

We see both actions in most natural daily activities: when walking up a flight of
stairs, the muscles lifting us up are shortening concentrically; when walking back
down the stairs the same muscles are lengthening eccentrically Ito control our
descent.

Looking Inward 15


In Hatha yoga we see both constantly, as when the back muscles shorten
concentrically to lift the torso up from a standing forward bend. Then as we slowly
lower back down into the bend, the back muscles resist the force of gravity that is
pulling us forward, lengthening eccentrically to smooth our descent

Isotonic and isometric activity

Isotonic

Meaning (iso: equal, same - tonic: tone, tension) constant tension. Muscle fibers
shorten under a constant load, but this rarely happens in reality. Over time the term
has become corrupted to apply generally to exercise that involve movement,
usually under conditions of minimal or moderate resistance. Ex.: raising and
lowering a book repetitively is an isotonic exercise for the biceps brachii and its
synergists. Most athletic activities involve isotonic exercise because they involve
movement

Isometric

Meaning (iso: equal, same - metric: measure/length) constant measure or length.
It’s holding still, often under conditions of substantial or maximum resistance. Ex.:
holding the book still, neither allowing it to fall nor raising it is an isometric exercise
for the same muscles mentioned above. Any and every Hatha yoga posture that
we are holding steadily with muscular effort

Looking Inward 16


Relaxation, stretching and mobility

The relaxation is the moment when the contraction is over. The different myofibers
(actin and myosin) move back into their place and the H zone widens back again.
Relaxation is the result of the end of the nerve impulse in the neuromuscular plaque.
With certain training we can learn to relax most of our skeletal muscles completely.

If a relaxed muscle is gently stretched we can easily go with the stretch provided we
have enough flexibility. But if we pull too suddenly or there is any appreciable pain,
the nerve system will resist relaxation and keep the muscle tense.

Finally, if you allow yourself to remain near your limit of passive but comfortable
stretch for a while longer, you may feel the muscles relax again, allowing you to
stretch a bit more. This is easier working with partners because stretching on your own
is more demanding because you are concentrating on two tasks at the same time:
creating the necessary conditions for the stretch, and relaxing into that effort. But the
same rules apply, if you go too far and too quickly, pain inhibits lengthening, prevents
relaxation and spoils the work

Looking Inward 17


Factors related to SSC (Stretching Shortening Cycle))

The combination of eccentric contractions (when the muscle is active while
stretching) and the concentric phase that follows forms a type of natural muscular
function called Stretching-Shortening Cycle (SSC).

T
h
e

c
h
a
r
a
c
t
e
r
i
s
t
i
c

o
f

t
h
e SSC is that the last contraction of the cycle (concentric phase) is more powerful
when immediately preceded by an eccentric contraction than when doing it
isolated.

Looking Inward 18


Golgi tendon organ

It is a sensory propioceptive receptor placed in the tendons of the skeletal muscles
(near musculotendinous junctions).

Looking Inward 19


The body of the Golgi tendon organ is made up of strands of collagen, connected
at one end to the muscle fibers, and at the other merge into the tendon proper.

When muscles shorten (probably due to the stretch reflex), tension is felt in the
point where the muscle is connected to the tendon, place of the Golgi tendon
organ. This registers the change in the tension and the proportion of such change
and sends signals to the dorsal spine to save this information. When this tension
exceeds certain threshold, activates the myotatic reflex than inhibits the shortened
muscles and forces them to relax

One of the reasons to keep a stretch for a prolonged period of time is that in this
way the spindle of the muscle gets used to the new length and reduces its signals.
Gradually, its stretching receptors can be trained to allow to increase the length of
the muscles

Looking Inward 20


This basic function of the Golgi tendon organ helps to protect the muscles, tendons
and ligaments from injures. The reaction of the myotatic reflex is only possible
because the signal from the Golgi tendon organ to the spinal cord is powerful
enough as to overcome the signal from the skeletal muscles that leads to muscle
shortening

Looking Inward 21


When an agonist shortens to cause the desired movement, it usually forces the
antagonist to relax.

To lengthen, it is easier to stretch a muscle that is relaxed than a muscle that is
shortening. Using these situations, when the reciprocal inhibition occurs, we can
achieve a more efficient stretch inducing the antagonist to relax during the
stretching due to the reduction of the agonists

We can also relax any muscle used as synergist by the muscle we are trying to
stretch

The elongation helps to strengthen the muscle because the capacity of muscle
shortening (that is, of generating strength) depends on the initial length. The more
the initial muscle length, the better will be the muscle contraction generating more
strength

(*No olvides estirarte primero)

When we have problems to relax, isometric tension-relaxation exercises with reference to
the Golgi tendon organ 14-5-10/Ángel

Looking Inward 22


5. Phasic muscles and postural muscles

Restorative alignment

Deficient alignment is practically always associated with an imbalance in the
surrounding musculature; the maintained bad alignment results in the shortening of
some muscles and the constant overstretching of others.

When certain muscles are used more frequently than others (at work, doing sports
and other activities from daily life), they become more rigid and strong, while the
opposite muscles, less used in comparison, become weaker. The consequence is a
bad position in the articulation or articulations involved.

Most of the therapeutic concepts focus mainly on strengthening the muscles
without taking into account the importance of stretching the shortened muscles as
well.

Looking Inward 23


Two groups: phasic and postural

Phasic muscles, for movement, are the most superficial and tend to be
polyarticular. They are basically formed by fast fibers that produce strength but
have little resistance. With time and use tend to become shorter and tight

Postural muscles, for stability, on the contrary, they are deeper, cross only one joint
and are made by slow fibers, good for endurance. They tend to become weaker
and to lengthen with time. Their function is to take part in the maintenance of the
posture and work against gravity

Initially both groups complement each other to stabilize and move; in time the
phasic muscles can inhibit the action of the tonic muscles and try to accomplish
that function themselves. This inhibition of the stabilizing muscles and the
preferential recruitment of the moving muscles is fundamental in the development
of imbalance and it is the essence of what wants to be detected and if possible,
reverted

TONIC MUSCLES PHASIC MUSCLE

Neck, shoulder girdle & arm
Sternocleidomastoid Rhomboids
Pectoralis major Trapezium (ascending)
Levator scapularis Trapezium (horizontal)
Trapezium (descending) Triceps brachii
Biceps brachii
Scalenus

Trunk
Erector spinae, lumbar and cervical region Erector spinae, central thoracic region
Quadratus lumborum Abdominal

Pelvis- thighs
Biceps femoris Vastus medialis
Semitendinous Vastus lateralis
Semimembranosus Gluteus medius
Iliopsoas Gluteus maximus
Rectus femoris Gluteus minimus
Adductors
Gracilis
Piriformis
Fascia lata tensor

Calf & foot
Gastrocnemius Tibialis anterior
Soleus Peroneus

Looking Inward 24


Common muscle imbalances

Many people develop a similar muscular imbalance configuration, almost
standardized. While there are many individual variations due to the different
activities of the subjects, there is a consistent pattern that results basically from the
way we are used to use our postural muscles. There seems to exist a neurological
component since these patterns are common and widespread (note from Paola)

Upper body patterns

neck, middle and upper back, and shoulder girdle show this type of
configuration: tension in the extensors of the neck, the upper trapezium and the
levator scapularis

opposite muscles group: longus capiti and colli (anterior head and neck) and
lower trapezium are usually loose and it is necessary to strengthen them

in the shoulder the anterior muscles, pectoralis major and minor are usually
hypertonic (tense), while the infraspinatus, teres minor, rhomboids and thoracic
portion of the spinal erector are inhibited (loose and overstretched)

these muscular imbalances end up in very common postural patterns where
shoulders move forward and the kyphosis is increased, the head tilts forward and
cervical lordosis is lost

Lower body patterns

there are frequently similar imbalances in the lumbar and pelvic areas. The
erector spinae muscles are usually tense and hypertonic, while the abdominal
muscles are loose. The flexors of the hip are tight while the inner side of the thigh
is not working well with the gluteus maximus, interfering with the complete
extension of the hip. It seems that this combination is a factor contributing to the
tension of the muscles of the back of the thigh

the tight hip flexor muscles will inhibit the posterior ones, which suffer stress during
extension. As a result those muscles are overloaded

it is impossible to separate the muscles which connect nearby body segments to
analyze the possible imbalances correctly, since the alterations in some provoke
changes in the position of the bones where the others are inserted

Looking Inward 25


See more about muscular chains

Looking Inward 26


Looking Inward 27


6. Deep back muscles (p.64)

Long- splenius capitis and cevicis, erector of the trunk and transversospinalis- and
short muscles -interspinalis and intertransverse
The long muscle are subdivided in parts depending on its location in the different
regions of the vertebral spine

Looking Inward 28


They usually act having the pelvic girdle, the vertebrae and the ribs as a fixed point;
the contraction of the muscles pulls from the superior insertions and provokes a
movement of the portions of the trunk situated above.
In this way, in a standing position with the trunk flexed, the bilateral contraction
provokes the extension of the body segment. The hip stays fixed and pulls from the
vertebral spine backward, producing extension.
If there is unilateral contraction there is flexion to the same side

Looking Inward 29


However, there is no reason for the contrary not to happen, if the upper portions are
fixed, these muscles pull the pelvis from the ribs or from the vertebrae. Like a gymnast
in the rings, stabilizing the scapula, the shoulder girdle plays the role of an
intermediate base and also it is necessary that the deep dorsal muscles, taking as a
fixed point the superior vertebrae, pull those below and the pelvic girdle

Since the short muscles have a segmental structure and the long muscles are divided
depending on their location in relation to the vertebral spine, some weak point can
be found in some portion

Looking Inward 30


Looking Inward 31


To strengthen these muscles, we need to remember their actions: extension, flexion
and rotation of the trunk. It is also important to use the gravitational action with the
double purpose of giving variety to the resists and increasing or decreasing their
difficulty when necessary. Ex.: when we perform strengthening exercises in decubitus
prone (laying facedown) it demands more effort from the extensor musculature of
the trunk, since they are working against the gravity force during the whole range of
the movement

Looking Inward 32


To lengthen the extensors of the trunk, we need to do the opposite movement,
flexion of the trunk, which can be associated with rotations, acting in this way on the
oblique fibers.
It is important to carry out flexion in the different regions of the vertebral spine:
cervical, thoracic and lumbar; if it is performed keeping the trunk extended rotating it
around the hip joints, the vertebrae keep their position and the posterior muscles of
the trunk stay with same length and those posterior of the hip (joint where the
movement takes place) lengthen

Looking Inward 33


7. Lateral muscle of the lumbar spine: Quadratus lumborum (p. 63)

Looking Inward 34


Posterior and lateral to the vertebral column, helps to hold the weight of the pelvis
when we stand on one foot only. A group of fibers of this muscle, which have an
oblique direction and insert in the transverse processes of the lumbar vertebrae,
provoke a lateral concave curve towards the opposite side. The main function of this
muscle is the stability of the lumbar spine, that is why is important the balance in the
activity of the quadratus lumborum on both sides of the vertebral spine

Its role in extension, hyperextension and in the lateral flexion of the trunk, is affected
by the position, or better said, by the changes in the position of the trunk

Its action in Trikonasana

It pulls from the ribs from the left side towards the hip of the same side (isometric
activity) preventing that side from overarching, from rounding, with the consequent
loss of space on the right side. Through its action keeps the left side plane and in this
way the right side will have room for elongation

Looking Inward 35


8. Abs and the rest. Anterolateral muscles of the abdomen

Looking Inward 36


They are part of the muscular corset (core) to hold the adequate posture.
They are not only in the anterior part of the abdomen, but also reach the ribs and the
vertebrae in the back.
The transversus, the internal and external obliques and the rectus abdominis form a
strong frontal support cushioning the viscera and keeping them in place; at the same
time, they are subjected to considerable stress because of the pressure of the viscera
against them. If the abdominal wall is weak, the viscera will press more and the
muscles will become longer and weaker.

Transversus abdominis (p. 92)

Looking Inward 37


It is the deepest one. The only one that due to its biomechanics has repercussions
in the vertebral spine. It prevents the collapse of the pelvic base. The structural
integrity and balance depend on it. It is much more important than the rectus
abdominis because it provides the true essential strength and corrects the pelvic
alignment.
It attaches below to the inguinal ligament and iliac crest; posteriorly to the
thoracolumbar fascia; above to the inner surfaces of the ribs 7-12 (where it
interdigitates with fibers of the diaphragm); and anteriorly to the linea alba (a
tough fibrous band stretching from the xiphoid process to the symphysis pubis).

(The one in red)

Action:
The contraction of its circular fibers reduces the diameter of the abdominal region.

if the vertebrae are fixed collects the abdomen inward

if the aponeurosis is the fixed point lumbar lordosis

Hands on waist, cough and sneeze and you will find it
Internal oblique (p. 93)

Looking Inward 38


Lies between the transversus and external oblique. It is smaller and the average
direction of its fibers has the opposite direction of those of the external oblique of
the same side.
It is attached below to the inguinal ligament and iliac crest; posteriorly to the
thoracolumbar fascia; above to the ribs 9-11; and anteriorly to a very broad
aponeurosis

The average direction of its fibers is anterosuperior, progressively changing until the
most anteroinferior fibers are transversal or horizontal.

unilateral contraction sidebending or ipsilateral rotation of the spine and
ribcage to the same side

bilateral contraction compression of the abdomen and assists in flexion of the
trunk

if both the vertebrae and pelvis are fixed pulls from the ribs down and
backward: assists in expiration (Moves the thoracic block in line with the pelvic
bock)

External oblique (p. 94)

Looking Inward 39


It is external to the other two muscles mentioned above. It is the biggest. It is
attached above to the outer surface of ribs 5-12 (where its fibers intertwine with
those of the serratus anterior and latissimus dorsi). In front and below it forms a
broad aponeurosis ending at (and contributing to) the linea alba and inguinal
ligament. The average direction of the fibers is anteroinferior, i.e., perpendicular to
those of the internal oblique

Action:

unilateral contraction side-bending to the same side and contralateral
rotation of the spine and ribcage. If the pelvis is the fixed point, pulls from the ribs
and vice versa

bilateral contraction compresses the abdomen and assists in flexion of the
trunk. With the pelvis fixed pulls from the ribs (assists in expiration)

The synergic action of the obliques and quadratus lumborum in Trikonasana (tri-angle
pose) and other little details

The vertical fibers of both obliques assist the quadratus lumborum in pulling from
the ribs and pelvis toward each other and in keeping in Trikonasana the up facing
side plane instead of arching

The obliques act synergetically in the movements of spiral rotation of the trunk:
external oblique + the opposite internal oblique (referred to as “same side
rotator”). Ex.:
Rotation of the trunk to the R with flexion R internal oblique + L external oblique

The obliques, with its intertwined diagonal cross-shaped tissues, act as a good
fulcrum to rotate the trunk against gravity

Many fibers from the external oblique continue into the fibers of the internal
oblique of the opposite side. The external oblique acts together with the internal
oblique, so contracting the most lateral fibers of the obliques creates inner
abdominal pressure which contributes to the expulsion of abdominal contents in
defecation or urination. If the diaphragm is relaxed they produce an active
expiratory effort

If you tend to hyperextend the inferior part of your back the obliques will assist in
holding the internal organs and moving them towards the lumbar area with the
help of the transversus. Their action helps to lengthen the inferior part of the back,
so it is not hyperextended neither overarched
Rectus abdominis, 6-pack (p. 95)

Looking Inward 40


It is the most superficial and is located anteriorly, inside a rectus sheath form by the
aponeuroses of the three preceding muscles. It runs from the crest and symphysis
of the pubis to the xiphoid process and cartilages of ribs 5-7

It takes the pubis closer to the sternum; it is the most direct of the flexors of the
trunk and also assists the other three in compressing the abdomen. Active
expiration

Exercise are usually performed from decubitus supine position (lying on back, facing
up), making the most of the gravity force during the whole flexion and extension of

Looking Inward 41


the trunk. Same as in the case of the extensor musculature of the trunk, to strengthen
it we need to observe that this muscle extends between the ribs and the pelvic
girdle, so we need preferably movements that take the thorax closer to the pelvis or
vive versa

Wide flexions in the trunk involve the articulation of the hip and the anterior muscles
to the hip, NO the intervertebral joints, so it is preferable to make “short” movements,
at the level of the cervical, thoracic and lumbar regions of the vertebral spine

It is not recommended to do leg-abdominal work because the “psoas paradox” may
show up, the inversion of its function, acting as hyperextensor of the lumbar spine. If
the abdominal muscles contract at the same time the legs are coming up, there is no
forward tilt of the pelvis as a result of the action of the psoas, but if the abdominal
muscles are weak, the pelvis tilts forward and the lumbar vertebrae with move away
from the floor, increasing the lumbar lordosis, a effect we do not desire. We can
perform it not lowering the legs more than 30°

Looking Inward 42


Looking Inward 43


Looking Inward 44


9. Deep hip muscles I (p. 208)

Group of six muscles: Piriformis, obturator internus and externus, gemellus superior and
inferior and quadratus femoris. They go from the pelvis to the greater trochanter. They
are covered by the inferior half of the gluteus maximus
They are external rotators. They stabilize the hip by straightening and holding the
femoral head in the acetabulum

Piriformis (p. 209)

Originates in the anterior sacrum and goes poster inferiorly (outward and
downward), passes under the greater sciatic notch, which forms like a bridge
above the muscle, and inserts on the superior surface of the greater trochanter.
Connects the sacrum with the femur

Action:

if the sacrum is fixed laterally rotates the femur and abduction and flexion

if the femur is fixed:

bilateral contraction contributes to retroversion of the pelvis
unilateral contraction medial rotation of the pelvis around the femur

The following structures come out of the pelvis through the greater sciatic notch:

Location Name Vessels Nerves
2 1 3
Above the piriformis muscle suprapiriformis notch superior gluteal vessels gluteus superior
3
gluteus inferior
pudendal
inferior gluteal vessels sciatic
2
Below the piriformis muscle infrapiriformis notch medial pudendal artery posterior femoral
and vein cutaneous
obturator internus
quadratus femoris

Looking Inward 45


If it is very voluminous, in its passage through the greater sciatic notch may
compress the many vessels and nerves that pass this way.

Looking Inward 46


Sciatic nerve innervates the skin of the leg, the muscles of the back of the thigh
and those of the leg and foot. It is the longest and widest single nerve in the
human body, the main nerve in the sacral plexus. It originates from the roots L4-S3,
although the principal roots come from L5-S1.
Occasionally (1-10% of the cases) it goes through the piriformis muscle

The piriformis muscle is the main external rotator when the hip is neutral or
extended.
It is also abductor when the hip is flexed in 90°. If it is a complete flexion it seems to
act as internal rotator.
Its function is often to restrain a vigorous or fast internal rotation of the hip. The
inferior fibers of the piriformis are able to produce a strong force which tends to
move the base of the sacrum forward and the vertix of the sacrum backward
(nutation)

Looking Inward 47


Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve
is compressed or otherwise irritated by the piriformis muscle causing pain, tingling
and numbness in the lumbar region, groins, perineum, buttock, hip, back of the
thigh, leg and foot.
The pain can be chronic and worsens when the piriformis is firmly pressed against
the sciatic nerve, as in seating for long periods, the muscle thickens in repose (from
having been contracted and shortened actively). This pseudo sciatic of the
piriformis is less painful than the true sciatic that originates with a herniated disk at a
lumbar level

Symptoms are usually associated with spasm of the piriformis or with the
compression of the sciatic nerve. Referred pain can be felt in the posterior thigh,
most of the lower leg, the entire foot, and part of the pelvis. Decrease of ROM in
inner rotation of the same side of the hip

In many of the piriformis syndrome cases, there is a rotation of the sacrum towards
the same side or towards the contralateral oblique axis, as a result of a
compensatory rotation in the lumbar vertebrae in the opposite direction. The
rotation of the sacrum often creates the sensation of having a shorter leg on that
side

Looking Inward 48


Compensatory and facilitator somatic dysfunctions create advantages in the
cervical and thoracic area and pain in the lower back and also stomach disorders
and headaches. The ROM of vertebrae T10 and T11decreases, the texture of the
tissues from T3 and T4 changes, pain and decrease of ROM on the contralateral
side of vertebra C2 and injure on the same side of the occipital-atlas joint

Every tension at the end of the spine is transmitted to the legs through the pelvis
and hip, and it is precisely there where the piriformis has a protagonist role. In a
standing position, it rotates the hip laterally (outward) and moves the thigh away
from the center of the body (abduction), creating an excessive tension in the spine
that can overload its base, the sacrum bone which is like the foundations of the
vertebral spine.
If the sacral bone is not in alignment with the iliac bones from both sides, in each
stride the sacroiliac joint is jammed, blocked. This joint has a very short articular
trajectory, but it is enough to produce a clamp effect in the sacrum, and that
tenses excessively the muscle that originates in each of its sides and heads to the
hip, and that is no other than the piriformis

Looking Inward 49


In some cases, the muscle can be damaged due to a fall on the buttock. The
hemorrhage in and around the piriformis muscle damages the muscle. The
piriformis swells up and compresses the sciatic nerve. The injure heals quickly, but
the muscle is in spam. The sciatic nerve stays irritated and keeps on being a
problem. Finally, the muscle heals, but some of its fibers are substituted by scar
tissue. The scar tissue is not as flexible and elastic as the tissue in the normal muscle.
The piriformis can be tense and apply a constant pressure on the sciatic nerve

Sitting can result difficult. Generally, people with piriformis syndrome do not want
to sit down. When they sit they tend to do it on the contralateral buttock and the
affected buttock tilting upward. The pain is also aggravated by squatting

Weakness, rigidity and general restriction of movement are also frequent in this
syndrome. Before stretching the piriformis, the articular capsule of the hip has to be
mobilized anterior and posteriorly, to allow a more efficient stretch.
The affected leg often rotates laterally (the toes move outward) when the person is
relaxed. You can observe it easily when they are lying on the mat

The right leg is usually affected alter driving some distance if the foot was in lateral
(external) rotation while pressing the gas pedal

Looking Inward 50


Looking Inward 51


Looking Inward 52


Quadratus femoris (p. 210)

It inserts in the lateral ischium, behind the obturator foramen, and runs in a
horizontal line laterally (outward), ending up in the posterior aspect of the greater
trochanter

Action:

if Iliac bone fixed lateral rotation of the thigh


bilateral contraction contributes to retroversion of the pelvis
unilateral contraction medial rotation of the iliac around the femur

Obturator internus (p. 210)

It arises from the internal surface of the iliac, from the obturator membrane and
adjacent portions of the ischium and ilium, its fibers pass posteriorly through the
lesser sciatic notch, make a sharp bend around the body of the ischium, where
there is a bursa to reduce friction and inserts on the medial aspect of the greater
trochanter. It helps to stabilize the hip joints because of its broad origin.

Action:

if the iliac is fixed it laterally rotates the femur, in flexion and abduction


bilateral contraction retroversion of the hip
unilateral contraction medial rotation or medial flexion of the iliac.

Looking Inward 53


Gemellus superior and inferior (p. 211)

They are like satellites of the obturator internus, inserted above and below its distal
borders, end up in the greater trochanter.

They reinforce the actions of the obturator internus.

Obturator externus (p. 211)

It arises from the external surface of the obturator
membrane, passes posterior to the femoral neck,
and inserts on a fossa on the medial surface of the
greater trochanter.

Action:

if the iliac is fixed is the ideal lateral rotator of
the thigh, and assists in flexion and abduction

bilateral contraction anteversion of
the pelvis
unilateral contraction medial rotation
or medial flexion of the iliac

Obturators and gemelli: the hammock (p. 212)

Because of their combined action, they have been compared to a hammock
supporting the pelvis from the femur.

Observing from the side, the obturator internus and the gemelli run from the
greater trochanter in a posteroinferior direction while obturator externus runs
anteroinferiorly:

if the pelvis is fixed they will pull the femur down relative to the pelvis

if the femur is fixed they will lift the pelvis relative to the femur

Either way, they tend to pull apart the hip joint on a very small scale. This is a
decompressive effect which is quite beneficial for certain painful conditions (e.g.,
worn-down cartilage).

Looking Inward 54


10. Deep hip muscles II

Iliopsoas (p. 62-213)

It is located in the abdominal cavity, running anterior to the pelvis, posterior to the
inguinal ligament and inserts on the lesser trochanter (the anterior part of the
thigh). There is a bursa to reduce friction where it bends at the anterior pelvis. It is
constituted by two portions: psoas major and iliacus. They are often described as a
single muscle because they share the same tendon and have the same action on
the thigh. But their superior attachments are different: when the femur is fixed,
iliacus acts on the pelvis, the psoas on the lumbar spine

Looking Inward 55


Psoas or psoas major

arises from the bodies of T12 through L5, and from the arches of fascia which
connect the boney parts of the vertebral bodies but do not attach to the
intervertebral disks. It goes inferiorly and a little anteriorly towards the internal
iliac fossa where is going to meet the iliac portion of the muscle. It inserts on the
lesser trochanter

action:

if the vertebrae are fixed: flexes the hip and works as a weak adductor and
lateral rotator


bilateral contraction it has been described as a lumbar muscle
involved in increasing lordosis, but this polyarticular muscle can have a more
complex action on the level of the lumbar spine. Because of its placement on
several levels in the convex area of the lumbar spine, this muscle participates in
straightening the spine, in combination with the posterior transversospinalis
muscles
unilateral contraction pulls the lumbar spine into sidebending, flexion
and rotation of the side opposite the contraction

Looking Inward 56


Iliacus

arises from the entire internal iliac fossa and inserts on the lesser trochanter via a
tendon

action:

if the iliac is fixed action is identical to that of the psoas in flexing the hip
with a little adduction and lateral rotation

bilateral contraction flexion of the pelvis (the ASIS move forward and
downwardly)
unilateral contraction flexion of the pelvis and rotation towards the
contracted muscle
Me gustaría, al menos en los más importantes, ofrecer ejercicios de yoga, posiciones, para estirar o fortalecer el músculo en concreto.
Dejo esta nota acá ahora vale? Es para acordarnos jijiji

In its path, the iliopsoas is related with important organs: diaphragm, kidneys,
ureter, kidney vessels, colon, primitive iliac arteries and external iliac arteries and
veins. It has an especially close relationship with the lumbar plexus, which is crossed
by the muscle.
The iliopsoas is innervated by the lumbar Plexus and femoral nerve

Looking Inward 57


Action:

if the vertebrae are fixed flexes the hip, and works as a weak adductor and
lateral rotator


bilateral contraction participates is straightening the lumbar spine
unilateral contraction pulls the lumbar spine into sidebendig, flexion,
and rotation of the side opposite the contraction.

Looking Inward 58


Looking Inward 59


Looking Inward 60


Looking Inward 61


LUMBAR PLEXUS

Looking Inward 62


Gluteus minimus (p. 216)

A small muscle originating just anterior to gluteus medius and inserting on the
anterior aspect of the greater trochanter

Its action is similar to that of the anterior fibers of the gluteus medius, but weaker

if the iliac is fixed: flexion, abduction and medial rotation of the thigh

bilateral contraction anteversion of the pelvis
unilateral contraction lateral flexion or lateral rotation of the pelvis

Gluteus medius (p. 215)

It has a broad origin on the external iliac fossa. Its fibers converge and insert on the
lateral aspects of the greater trochanter

Action:

if the iliac is fixed: its major action is abduction of the hip, but it can also assist in
flexion with its anterior fibers and extension with its posterior fibers

bilateral contraction it is involved in both anteversion and retroversion of the
pelvis, depending on whether the anterior or posterior fibers contract
unilateral contraction it acts in lateral flexion of the pelvis, and also, very
important, it stabilizes the pelvis during walking or standing on one foot, to
prevent it from collapsing to the opposite side

Looking Inward 63


11. Deep hip muscles III (+ 1 of the hip and knee): The adductors (p. 224)

They are a group of five muscles having their bodies on the medial thigh

They originate gradually on the pubis and insert on the linea aspera of the femur

Action of the group as a whole:
If the pelvis is fixed their primary action is adduction of the femur. To a lesser
degree they can act from anatomical position as hip flexors or lateral or medial
rotators.
If the hip is in flexed position they act as extensors. Gracilis (polyarticular) can
also flex and medially rotate the knee.
If the femur is fixed they are involved in anteversion, medial flexion
(sidebending), lateral rotation, or (in the case of gracilis and the posterior portion
of adductor magnus) medial rotation of the pelvis

These muscles, especially the gracilis, are frequently strained or torn (“pulled
groin”) during movements involving sudden or extreme abduction of the thigh

Looking Inward 64


Pectineus Runs from the lateral pubis

Adductor brevis Runs from the medial pubis

Looking Inward 65


Adductor longus Originates even more medially on the pubis. It runs anterior to
adductor brevis (almost completely covering it

Adductor magnus (p. 225)

The largest and strongest of the group is really a compound muscle innervated by two
different spinal nerves (obturator nerve and sciatic nerve). Two portions:
The anterior portion originates from the ischiopubic ramus, runs inferomedially, and
has a very broad insertion on the linea aspera
The posterior portion originates from the ischial tuberosity, runs straight down, and
inserts just above the medial femoral condyle

Looking Inward 66


Gracilis It is a long, thin, superficial, comparatively weak muscles running from the
inferomedial pubis vertically down the thigh (medial surface) and inserts on the tibial
shaft just below the medial condyle, it’s biarticular, crossing the hip and femur

Action of the group as a whole:
If the iliac is fixed adduction of the femur, also flexion and lateral rotation
If the femur is fixed medial side bending, anteversion and lateral rotation of the
iliac (except for the recto interno and the haz vertical from adductor mayor which
produce medial rotation)
It acts as a flexor when in anatomical position or with the hip extended. If the hip is
flexed they become extensors.

Looking Inward 67


Looking Inward 68


Looking Inward 69


12. Hip and knee muscles I: The superficial

Tensor fasciae latae (p. 229)

Gluteus maximus (p. 228)

Deltoid gluteus (superficial portion of gluteus maximus and tensor fasciae latae) (p. 229)

Looking Inward 70


13. Hip and knee muscles II

Quadriceps femoris (p. 217)

The muscle as a whole is one of the strongest of the body. It has four bodies which
converge into a single tendon that inserts on and surrounds the patella and forms
the patellar tendon that inserts in the tibia. Their action is extension of the knee

Looking Inward 71


Vastos intermedius it is the deepest, it originates in the upper femoral shaft and
its fibers follow the axis of the femur.
It is wrapped up in the vastus lateralis and medialis

Vasti they arise from either side of the posterior femoral Shaft, wrap around the
sides to meet anteriorly: Vastus medialis (internal) and vastus lateralis (external).
They give lateral stability to the knee. They are the active complement of the
ligaments.
They assist in rotation of the tibia and literally pull from the patella.

The three vasti can be stretch by full flexion of the knee and hip.

Rectus femoris Arises from the anterosuperior iliac spine, and passes superficial
to the three vasti to insert on the common tendon.
Thus, unlike the vasti, it crosses the hip as well as the knee, acting on both joints
If the pelvis is fixed it flexes the hip and extends the knee (e.g., in walking)
If the femur is fixed it can act in anteversion of the pelvis

Looking Inward 72


For stretching rectus femoris, the hip must be in extension and the knee in flexion,
moving the insertion points away from each other on the pelvic girdle and on the
femur or on the leg bones.

Looking Inward 73


Looking Inward 74


Sartorius (p. 220)

It is a thin muscle, the longest in the body, superficial. It originates from the ASIS,
runs medially down the thigh, superficial to the quadriceps and inserts on the
superomedial shaft of the tibia

It takes part in flexion and abduction
Polyarticular muscle: crosses and acts in the hip and knee joint.

if the iliac is the fixed point it flexes, laterally rotates and abducts the hip
(femur) and flees the knee with the tibia in medial rotation

bilaterally anteversion of the pelvis
unilaterally anteversion of the iliac, medial rotation and lateral side
bending of the pelvis

Looking Inward 75


14. Hip and knee muscles III: The hamstrings (p. 221)

Semitendinosus, semimembranosus and biceps femoris have their origin in the ischial
tuberosity and they insert in the tibia and in the head of the fibula

They are in the back of the thigh, from the hip to the knee, producing extension of
the thigh and flexion of the leg. They are muscles for movement and with time and
use they tend to get shorter and harder, especially when we stay daily seated for
hour with the legs flexed. And then, when we want to stretch the knees, we curve the
lower back. Working to stretch them, with patience and consistency will relieve the
inferior part of the back

To stretch them, flex the thigh with the leg extended. Here the insertion points move
away from each other and the muscles stretch. Equally, wide flexions of the trunk, as

Looking Inward 76


when trying to touch your toes from standing or seated positions, with knees
extended, pelvic girdle moving around the femoral head (the hinge), increasing the
inclination of the pelvis so the ischial tuberosity move away from the insertion points in
the tibia and fibula, provoking the stretch of the muscles. Combine it with the pushing
from the centre of your heel in the opposite direction

Combined stretching exercises, 30-1-2009/Ruby y amiga

When performing poses to stretch them, give yourself a little massage in the back of the
knees in the tendons that delimit the popliteal fossa (p.222)

Remember, medial rotation of the thigh, sitting bones move away from the heels and
muscles in the pelvic floor active pulling, recoiling the coccyx

Looking Inward 77


Semimembranosus and semitendinosus Extension of the femur, flexion and medial
rotation of the knee
Biceps femoris Extension and flexion and lateral rotation of the knee

They are polyarticular muscles, crossing and acting in the hip and knee joints,
combining the actions of both joints:

if the iliac bone is the fixed point take the femur in extension (specially if the hip
is at the beginning of the flexion)

if the femur is fixed takes pelvis in retroversion

The lack of flexibility in the hamstrings can be responsible of flexions in the lumbar
region, and indirectly, of discs ailments in this zone

Looking Inward 78


SHOULDER GIRDLE MUSCLES

Includes a big group of muscles divided into two categories:
scapulo-thoracic shoulder, which consists of the muscles that mobilize and fix the
scapula and clavicle with respect to the thorax
scapulo-humeral shoulder, which consists of the muscles that mobilize the humerus and
stabilize it with respect with the glenoid cavity of the scapula

It is important to highlight that the mobility of the sternoclavicular and acromioclavicular
joints allows the scapula to move in various directions, so the glenoid cavity can point in many
directions, greatly increasing the ROM of the glenohumeral joint (humerus)); there is a close
relation between the movements of the humerus, scapula and clavicle. The position of the
scapula, independently of its clavicular relation, obeys the muscular dispositions between this
bone and the vertebral spine … So, if from the skeletal-articular point of view there is not a
direct relation between the scapula and the vertebral axis, from the functional point of view
we have several elements that establish this relation

The scapular adductor muscles, i.e., the ones that pull the scapula towards the vertebral
spine (mainly the rhomboids and middle fibers from the trapezius) tend to get weak and long
due to the posture usually adopted in our daily life where the scapula moves away form the
vertebral axis and becomes prominent in the back (winged scapulae). This pattern is
reinforced by the shortening of pectoral major

Looking Inward 79


We need to pay especial attention to the adductor muscles, for this, working in pairs can
be very useful, where one person is opposing resistance to the movement of adduction of the
scapula. To achieve the action of these muscles we can perform movements of the arm that
involved the adduction of the scapula, against the resistance of the other person; from
horizontal position, with the forearm extended or flexed, extend the arm (moving it backwards)
while another person offers resistance to the movement.
These exercises have the advantage that, apart from strengthening the scapular adductor
muscles they also achieve the elongation of the pectoral major

Looking Inward 80


15. Shoulder muscles (p. 114)

Each scapula, extremely mobile bone floating in the superior part of the back, is a
stable connection for the humeral head, stable almost entirely thanks to 5 muscles on
each side that keep it in place. Apart from stabilizing the scapula they move it
around the surface of the upper back.

From 1 to 5, from the deepest to the most superficial:

2 towards the front of the chest:

1. serratus anterior
2. pectoralis minor

3 in the back:

3. rhomboids
4. levator scapulae
5. trapezius

All the movements provided by these muscles are crucial for the inversion poses
where the superior extremities have to hold the position, and we depend more on
strength and flexibility than on strong bones and joints designed to bear the weight
of the body
The pelvis is connected to the spine by the sacroiliac joints and forms a relatively
stable origin from which the muscles can move the thighs while the scapulae
themselves take part in the movement of the arms. Therefore, the movements of
the scapulae are very important in all inversion and semi-inversion positions

Looking Inward 81


Serratus anterior

It is a broad, thin muscle covering the lateral ribcage (lateral superior face of the
thorax). Its name is due to its saw-shape. It is formed by 10 muscular bellies. From
the surface only the last three inferior bellies are noticeable

It originates from the upper ten ribs, we consider 3 levels:

upper portion: ribs I and II (converging moderately)

middle portion: ribs III to V (diverging)

lower portion: ribs VI to X (converging). This portion interweaves with the fibers of
the external oblique of the abdomen

It inserts along the entire medial border of the scapula. Three levels:

upper fibers: superior angle of the scapula, they are ascending and insert on the
anterolateral surface of the ribs I and II

middle fibers: medial border of the scapula, they are more or less horizontal and
insert on the anterolateral surface of the ribs III, IV and V

lower fibers: inferior angle of the scapula, they are descending and insert on the
anterolateral surface of the ribs VI, VII, VIII, IX and X

Looking Inward 82


Function:

If the ribs are fixed it flattens the medial border of the scapula against the
ribcage and fixes it against the thorax assisted by the rhomboids

Upper fibers: pull the scapula laterally (abduction) and into upward
rotation
Middle fibers: in actions such as push-ups, the middle fibers of trapezius
(adductor) and serratus (abductor) contract simultaneously to stabilize
the scapula
Lower fibers: together with the lower trapezius depress the scapula
moving its inferior angle laterally to allow the elevation of the arms
beyond the horizontal

There are some fatty layers (gliding planes) separating serratus from the ribcage and
from the subscapularis muscle. These increases the mobility of the scapula and are
important in many complex movements of the shoulders.

If the scapula is fixed the lower fibers lift the middle ribs, acting as inspiratory
muscles

Looking Inward 83


Pectoralis minor (p. 116)

Deep muscle covered by the pectoralis major
It originates from ribs 3-5 and inserts on the coracoid process

Actions:

if the ribs are fixed pulls the scapula downward and forward, tilting the
scapula above the ribcage by lifting the inferior angle upward

if the scapula is fixed elevates the ribs acting as an accessory inspiratory
muscle

Rhomboids (major and minor) (p. 117)

Flattened muscles between the spine and the scapula
They originate from the spinous process of C7 and T1-T4 and insert on the media
border of the scapula

Actions:

if the spine is fixed adduct the scapula and rotate it downward
if the scapula is fixed pull the thoracic vertebrae laterally

Looking Inward 84


Looking Inward 85


Levator scapulae (p. 117)

It originates from the transverse processes of C1-C4 and inserts on the superior
angle of the scapula. Its oblique fibers go from the base of the head in a
downward and outward direction

Actions:

if the spine is fixed elevation and downward rotation of the scapula (glenoid
cavity pointing downward)
if the scapula is fixed can reinforce the actions of the splenius cervices:

bilateral contraction extend the head and cervical spine
unilateral contraction sidebending and rotation toward the
contracting side.
The ROM of the elevation of the scapula is about 10 cm of which this muscle is
responsible for 5 of them

Looking Inward 86


Looking Inward 87


Trapezius (p. 74-118)

Superficial, large, important diamond-shaped muscle which practically covers half
of the spine on both sides, running from the base of the cranium (skull) to the very
last thoracic vertebra.

Origins:

upper fibers: on the occiput, nuchal ligament and spinous processes of the
cervical vertebrae down to C7. They are overworked in excess in positions such
as sitting in front of a computer or driving which involve a prolonged static load
from the suspension of the arms neck pain, muscular rigidity, headache

middle fibers: on the spinous processes from C7 down to T3

lower fibers: on the spinous processes from T4 down to T12

Insertions:

upper fibers: the lateral superior 1/3 border of the clavicle (collarbone) and
acromion

middle fibers: scapular spine

lower fibers: a tubercle at the medial end of the scapular spine

Functions:

If the spine is fixed:

simultaneous contraction of all the fibers adducts the scapula

upper fibers elevation and upward
rotation of the scapula, traction of the
clavicle

middle fibers adduction of the
scapula. When force needs to be
exerted or absorbed by the arm, the
middle fibers (adductor) act together
with the serratus anterior (abductor) to
stabilize the scapula

lower fibers depression and upward
rotation of the scapula (glenoid cavity
pointing upward)

If…what does it happen when you move both shoulders forward? And only one?

Looking Inward 88


Between T7 and T12conects with the latissimus dorsi, forming a “diamond” which is
an important point in the structure of the vertebral spine, strong and sensitive at
the same time. If there is too much rigidity in this point or wrong strength, the
access to the deepest muscles becomes difficult and all the work is done by these
superficial muscles. On the other hand, if there is mobility and good coordination, it
will be a key point for the practice

It is the main responsible for keeping the position of the shoulders when we carry
weight, that is why the trapezius works quite enough when bearing weight in the
arms, below the head as well as above the head.
It becomes a very important muscle for maintaining the posture and most of the
problems related with having loaded shoulders are due to a bad contraction of
this muscle

When force has to be exerted or absorbed by the arm, the middle fibers
(adductors) work in synergy with the serratus anterior mobilization of the
vertebrae of the superior part of the back + relaxation of the upper fibers of the
trapezius = PECTORAL STRETCH improves the position of the shoulders, away from
the ears, downwardly and laterally (Work it out on the MITRA)

Looking Inward 89


Articular trauma: the general stability of the synovial joints is established by the
action of the muscles surrounding them. Excessive stress in the articulations results in
strained muscles and tendons or rupture of ligaments and capsules. When the
stress is chronic there are degenerative changes. The incorrect patterns of
movement are one of the causes of articular dysfunction

During activities which involve lifting up the arms the stabilization of the scapula is
the key. The superior part of the trapezius and the levator scapulae fix the scapula
from above, while the inferior part of the trapezius and the serratus anterior do it
from below. The superior muscles are inserted on the cervical spine while the
inferior muscles are inserted on the thoracic spine. As the superior fixing muscles
are normally excessively active and the inferior ones inhibited, the over-solicitation
of the cervical spine in activities with loads or lifting the arms to reach something is
common

Looking Inward 90


Tripod exercise from B4L, to stretch especially the upper fibers

Exercises to expand the armpits muscles thorax arms 21-8-08/Spid

Looking Inward 91


Within this section we have two more little muscles:

Subclavius (p. 116)

Small cylinder shaped muscle, it originates on rib I and its cartilage and inserts on
the underside of the clavicle

Action: Depresses the clavicle and shoulder. It can also stabilize the
sternoclavicular joint

We have been told that this little muscle could be very useful if humans still walked
on all fours. Some people have one, some none, and a few have two

What do you think?

Who is she/he laughing at?

Looking Inward 92


Sternocleidomastoid (SCM) (p. 116)

Long and robust, the largest and most important anterolateral muscle of the neck

Origin: on the mastoid process and the curved superior occipital line

Insertions: dual insertions on the sternum (cylindrical) and clavicle (flattened), near
their junction on the manubrium. In between them we found the Sedillot triangle,
which allows an access to the jugular vein

In the middle area of the muscle there is a zone where multitude of nerves
converge

Actions:

when the skull is fixed: elevates the sternum and clavicle, assisting in inspiration

when the thoracic cage is fixed:
Unilateral contraction ipsilateral sidebending and contralateral
rotation of the head, as well as extensión
Bilateral contraction extension of the head, stressing the cervical
lordosis (concave)

Looking Inward 93


Stretching the trapezius and the SCM
Sitting on a chair grab with one hand the side of the chair. Flex the neck, tilt the
head towards the opposite side to the one to stretch and turn the head towards
the side of the stretch, when feeling the tension we know we found the area to be
stretched and we hold the posture of the head supporting it with the other hand.

To increase the stretch
we sift our weight
towards the opposite side
to the one we are grabbing

Moving the scapula with a partner

Looking Inward 94


Looking Inward 95


16. Deep glenohumeral (scapulohumeral) muscles of shoulder joint (p. 120)

Subscapularis

Supraspinatus

Infraspinatus (p. 121)

Teres minor

Rotator cuff muscles (p. 122)

Coracobrachialis

Long muscle more suitable for movement than for strength is the smallest of the
three muscles that attach to the coracoid process of the scapula (the other two,
pectoralis minor and biceps brachii)

It arises from the apex of the coracoid process in common with the short head of
the biceps brachii and inserts by means of a flat tendon on the medial surface
of the humeral shaft, near the middle

Actions: flexes and adducts the arm at glenohumeral joint (shoulder)

Looking Inward 96


Biceps brachii (p. 123-139)

Close to the coracobrachialis. Topographically is connected to the elbow but
functionally is very important in the scapulohumeral joint

It is a two-headed muscle located on the upper arm. Both heads arise from the
scapula and join to form a single muscle belly which is attached to the upper
forearm. While the biceps crosses both the shoulder and elbow joints, its main
function is at the latter where it flexes the elbow and supinates the forearm. Both
these movements are used when opening a bottle with a corkscrew: first biceps
unscrews the cork (supination), then it pulls the cork out (flexion)

So, two origins and one insertion:

proximally (towards the body), the short
head of the biceps originates as a tendon from
the coracoid process, goes down vertically
and becomes a fleshy body

the long head originates on the supraglenoid
tubercle just above the shoulder joint from
where its tendon passes down along
the intertubercular groove of the humerus and
along the bicipital groove before merging with
the body. When the humerus is in motion, the
tendon of the long head is held firmly in place
in the intertubercular groove by
the greater and lesser tubercles and the
overlying transverse humeral ligament. During
the motion from external to internal rotation,
the tendon is forced medially against the lesser
tubercle and superiorly against the transverse
ligament

insertion: The two heads continue downward
and form one tendon, which passes anterior to
the elbow joint and inserts at the bicipital
tuberosity of the radius

Looking Inward 97


Functions:

The biceps is tri-articulate, meaning that it works across three joints. The most
important of these functions is to supinate the forearm and flex the elbow. These
joints and the associated actions are listed as follows in order of importance:

proximal radioulnar joint (upper forearm) contrary to popular belief, the
biceps brachii is not the most powerful flexor of the forearm, a role which
actually belongs to the deeper brachialis muscle. The biceps brachii functions
primarily as a powerful supinator of the forearm (turns the palm upwards). This
action, which is aided by the supinator muscle, requires the elbow to be at least
partially flexed. If the elbow, or humeroulnar joint, is fully extended, supination is
then primarily carried out by the supinator muscle

humeroulnar joint (elbow) the biceps brachii also functions as an important
flexor of the forearm, particularly when the forearm is supinated. Functionally,
this action is performed when lifting an object or when performing a biceps curl.
When the forearm is in pronation (the palm faces the ground), the
brachialis, brachioradialis, and supinator function to flex the forearm, with
minimal contribution from the biceps brachii

glenohumeral joint (shoulder) several weaker functions occur at the shoulder
joint. The biceps brachii weakly assists in forward flexion of the shoulder joint
(bringing the arm forward and upwards). It may also contribute to abduction
(bringing the arm out to the side) when the arm is laterally rotated. The short
head of the biceps brachii also assists with horizontal adduction (bringing the
arm across the body) when the arm is medially rotated. Finally, the long head of
the biceps brachii, due to its attachment to the scapula, assists with stabilization
of the shoulder joint when a heavy weight is carried in the arm

Flexed arm in
the pronated position (left);
with the biceps partially
contracted and in
a supinated position with
the biceps more fully
contracted, approaching
minimum length (right)

Looking Inward 98


Triceps brachii (p. 123-140)

Latin for "three-headed arm muscle" is the large muscle on the back of the upper
limb. It is the muscle principally responsible for extension of the elbow
joint (straightening of the arm)

Origins:
Each of the three heads has its own motoneuron subnucleus in the motor column
in the spinal cord. The medial head is formed predominantly by small type I fibers
and motor units, the lateral head of large type II b fibers and motor units and the
long head of a mixture of fiber types and motor units. It has been suggested that
each head "may be considered an independent muscle with specific functional
roles"

the long head, biarticular arises from the infraglenoid tubercle of the scapula

the lateral head arises from the lateral posterosuperior shaft of the humerus

the medial head (deep head) arises from the posteroinferior humerus. The
medial head is mostly covered by the lateral and long heads

Insertion:
The fibers converge to a single tendon to insert onto the olecranon process of the
ulna (though some research indicates that there may be more than one tendon)
and to the posterior wall of the capsule of the elbow joint where bursae (cushion
sacks) are often found. Parts of the common tendon radiate into the fascia of the
forearm and can almost cover the anconeus muscle

Looking Inward 99

Muscles, tendons and will

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Muscles, tendons and will

Semelhante a Muscles, tendons and will (20)

Mais de SonyJames

Mais de SonyJames (8)

Último

Último (20)

Muscles, tendons and will