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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5521_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter 4 / Kinesiology and Biomechanics
Scapular
(shoulder blade)
151
Occipital (base of skull)
Cervical (neck)
Deltoid
Brachial (arm)
Lumbar
(small of back)
Iliac
(hip)
Sacral (sacrum)
Gluteal (buttock)
Popliteal
(back of knee)
Tarsal (ankle)
B
Figure 4-4. (continued ) (B) Posterior body regions.
Plantar
(sole of foot)
152 INTRODUCTION TO MASSAGE THERAPY
The anterior body regions (Fig. 4-4A) include:
• Cranial (KRAY-nee-uhl)
• Facial (FAY-shuhl)
• Thoracic (thoh-RASS-ik)
• Axillary (AK-sih-lair-ee)
• Brachial (BRAY-kee-uhl)
• Antebrachial (AN-tee-BRAY-kee-uhl)
• Carpal (CAR-puhl)
• Phalangeal (fuh-LAN-jee-uhl)
• Abdominal (ab-DOM-ih-nuhl)
• Pelvic (PEL-vik)
• Inguinal (IN-gwih-nuhl)
• Femoral (FEM-or-uhl)
• Patellar (pah-TEL-er)
• Tarsal (TAR-suhl)
The posterior body regions (Fig. 4-4B) include:
• Occipital (ok-SIP-ih-tuhl)
• Cervical (SER-vik-uhl)
• Deltoid (DEL-toyd)
• Scapular (SKAP-yoo-lahr)
• Brachial (BRAY-kee-uhl)
• Lumbar (LUM-bahr)
• Iliac (IL-ee-ak)
• Sacral (SAY-kruhl)
• Gluteal (GLOO-tee-uhl)
• Popliteal (pop-lih-TEE-uhl)
• Tarsal (TAR-suhl)
• Plantar (PLAN-tahr)
Incorporating Terminology into
a Massage Session
If a client came to your office complaining that the inside
of her right wrist was hurting, it could mean any number
of things. The “inside” of the wrist could refer to the anterior side of the wrist or the medial side of the wrist, and the
pain could be on the proximal or distal side of the carpals.
If you were to note the client’s complaint of pain in your
massage session notes, you could use one of the following
descriptions:
• Client complained of pain on the medial side of the
right wrist, proximal to the carpals.
• Client complained of pain on the medial side of
theright wrist, distal to the carpals.
• Client complained of pain on the anterior side of the
right wrist, proximal to the carpals.
• Client complained of pain on the anterior side of
theright wrist, distal to the carpals.
Proper terminology clarifies the situation and reduces the
confusion. For the subsequent visit, any therapist could pick
up the session notes and know which area was problematic.
This section focuses on kinesiology, which is the study of
human movement. You will explore arthrology (the study of
the joints) as well as myology (the study of the muscles). The
cooperation of the joints and muscles creates simple and complex body movements that are also described in this section.
Arthrology
A joint is the mechanical structure where neighboring bones
are connected with connective tissue and cartilage. Joints are
passive structures that primarily allow movement to occur
between bones, but they also provide stability and shock
absorption.
The attached ligaments and the soft tissue joint capsules
limit movement at the joint, providing stabilization to the joint
and the entire skeleton. By limiting movement, the ligaments
keep the joint from moving into positions that can injure the
bones, the muscles, or surrounding soft tissues. Joints also
function as shock absorbers in the body. The articular cartilage
and subchondral bone provide some shock absorption, and
within synovial joints there is synovial fluid that absorbs shock.
Types of Joints
There are three main types of joints that can be classified
according to the amount of movement that can occur at
the joint or by the material found between the bones of
the joint. The joints that are nearly immovable are called
fibrous or synarthrotic (SIHN-ahr-THRAH-tik) joints. The
joints that are slightly movable are cartilaginous or amphiarthrotic (AM-fee-ahr-THRAH-tik) joints. The joints that are
freely movable are called synovial or diarthrotic (DAHY-ahrTHRAH-tik) joints (Table 4-2).
Chapter 4 / Kinesiology and Biomechanics
Type of Joint Characteristics Location
153
Synarthrotic Nearly immovable,
fibrous
Amphiarthrotic Slightly movable
cartilaginous,
Diarthrotic
(synovial)
Freely movable, joint
capsule with synovial
fluid
Skull sutures
Pubis symphysis,
between vertebrae
Shoulder, hip, knee,
elbow
Coronal suture
Lambdoidal
suture
Pubic symphysis
Ball-and-socket Provides the greatest
range of motion and
allows movement
in many directions
(circumduction)
Condyloid Allows movement in
two planes (flexion,
extension, lateral
movement)
Glenohumeral joint
(shoulder), acetabulum
(hip joint)
Metacarpophalangeal
joints, between occiput
and C1 (atlas)
Clavicle
Scapula
Phalanx
Head of humerus
Metacarpal
continues on following page
154 INTRODUCTION TO MASSAGE THERAPY
Type of Joint Characteristics Location
Gliding Bones slide past each
other (side to side
movement)
Hinge Allows movement in
one plane (flexion,
extension)
Pivot Allows rotational
movement
Between carpals, between
tarsals acromioclavicular
joint
Elbow joint, knee joint,
between phalanges
Between C1 (atlas) and
C2 (axis), between radius
and ulna
Carpals
Humerus
UlnaRadius
Humerus
Saddle Allows movement in
many directions
Carpometacarpal joint of
the thumb
Fibrous (Synarthrotic) Joints
Fibrous joints are made up of bones held together with
fibrous connective tissue. These fibrous joints are functionally classified as synarthrotic, meaning very little, if any,
movement occurs. The sutures of the skull (the cranium
UlnaRadius
Carpal
Metacarpal of thumb
and the face) are examples of fibrous joints. While soft
during infancy, these joints ossify as the child grows into
adulthood, at which time there is very little movement that
occurs at the sutures. Craniosacral therapy facilitates the
movement of these joints, helping to restore homeostasis.
Chapter 4 / Kinesiology and Biomechanics 155
Understanding that bones are living tissue and remodel
according to the stresses placed on them, it is simple to see
how fibrous sutures are movable, even if only slightly.
Cartilaginous (Amphiarthrotic) Joints
Cartilaginous joints, true to their name, have cartilage
between the bones. They are functionally classified as
amphiarthrotic joints, indicating their ability to move
slightly. Thepubis symphysis and the joints between the
vertebral bodies are examples of cartilaginous joints.
Synovial (Diarthrotic) Joints
The most prolific joints in the body are the synovial joints.
The easy movement that occurs at these joints leads to their
functional classification as diarthrotic joints. Synovial joints
have several components:
• Articular cartilage—hyaline cartilage that covers the
articular surfaces of the bones to reduce friction
• Bursae—synovial membrane–lined sacs full of synovial fluid that cushion the movement of tendons
over bones (not present in all synovial joints)
• Joint capsule—a fibrous connective tissue sac that
encloses the joint cavity
• Joint cavity—a space between the bones of the synovial joint that contains a lubricating, cushioning fluid
• Ligaments—fibrous connective tissue bands that
hold the bones of the joint together and stabilize the
joint
• Synovial membrane—the lining of the joint capsule
that secretes synovial fluid, a thick, colorless, lubricating fluid similar in consistency to egg white
These freely movable joints are called synovial joints
because the joint cavity is filled with synovial fluid. Produced
in response to movement of the joint, synovial fluid provides lubrication for the joint, allowing free movement, and
it also helps prevent injury to the hard structures involved
in the movement. Examples of synovial joints include the
knee, the shoulder, and the elbow.
There are six different types of synovial joints, grouped
by their mechanical structure: gliding, hinge, pivot, condyloid (KAHN-dih-loyd), saddle, and ball-and-socket. Table 4-2
includes illustrations of these joints. The mechanical structure determines the kind of movement possible at a joint
and the degree to which a joint can safely move, also known
as its range of motion.
Gliding Joints
The bones of gliding joints have flattened sides that allow
small amounts of sliding movement in a single plane
between the bones. To demonstrate, put your hands flat on
the table, thumbs touching, and slide your hands along each
other while keeping your thumbs touching and your hands
flat on the table. Gliding joints are found at the acromioclavicular joint; the interphalangeal, intercarpal, and intertarsal
joints; and at the joints between superior and inferior vertebral facets. The joint is involved in body movements such as
inversion and eversion of the ankle.
Hinge Joints
Hinge joints have a concave surface (a depression) on one
bone, a convex surface (a rounded shape) on the other, and
are held together with strong, collateral ligaments. The
structure allows hinge joints to move in only one plane,
very similar to the swing of a door. To visualize, think
of a door hinge and how it can only open or close. The
elbow, knee, fingers, and toes are examples of hinge joints
that allow the body movements called flexion, commonly
referred to as “bending,” and extension, commonly called
“straightening.” The temporomandibular joint (TMJ) is a
specialized hinge joint (see Box 4-1).
Pivot Joints
The pivot joints also fit together with matching surfaces,
but one bone pivots within the annular (ring-shaped) ligament of the other bone. The resulting rotational movement
occurs in a single plane in which one bone can pivot against
the other. The proximal radioulnar pivot joint creates pronation and supination of the forearm. There is also a pivot
joint between the atlas (C1) and axis (C2).
Condyloid Joints
The condyloid joint (also called the ellipsoid joint) is created
from a convex, rounded, or oval projection at the end of one
bone that fits into a concave surface on the other bone. The
structure can rotate in two separate planes, allowing for body
movements such as flexion, extension, adduction (movement
of the bone toward the midline of the body), and abduction (movement away from the midline). Theradiocarpal
joint, metacarpophalangeal joints, and the joint between the
occiput and the atlas are examples of condyloid joints.
Saddle Joints
Saddle joints have matching concave and convex surfaces,
each shaped like a saddle. The structure allows for rotational
movement in two planes. The carpometacarpal joint of the
thumb and the calcaneocuboidal joint of the ankle are the
only saddle joints, allowing flexion, extension, adduction,
and abduction.
Ball-and-socket Joints
The ball-and-socket joint is made up of a large, spherical
protrusion on one bone that fits into a cuplike cavity on
the other. The ball-and-socket joints are multiaxial, meaning that rotational movement can occur in several different
planes, and are therefore involved in many different body
movements. Ball-and-socket joints include the shoulder and
156 INTRODUCTION TO MASSAGE THERAPY
the hip, and are involved in flexion, extension, adduction,
abduction, rotation (where a body part turns or pivots about
The Temporomandibular Joint
(TMJ)
its long axis), and circumduction (a combination of abduction, adduction, extension, and flexion that occurs in one
continuous movement).
Mandibular fossa
Synovial membrane
and cavities
External acoustic meatus
A Articular structures
Temporomandibular
Articular
capsule
Stylomandibular
ligament
ligament
B Ligaments
Articular disk
of meniscus
Fibrocartilage
Mandibular
condyle
Temporal bone
External
pterygoid
muscle
Range of Motion
Range of motion (ROM) is defined as the amount of movement that occurs at a joint. A normal ROM is the distance
and direction that a joint can sustain without damage to
surrounding tissues. The amount of movement is scientifically measured in degrees, and normal ranges are specific
to each joint. Massage therapists tend to evaluate the movement more for quality and general quantity, without measuring degrees, to get information regarding the structures
involved in a client’s pain pattern.
Active ROM (AROM) requires a client to actively move
her own joint, usually to demonstrate the quality and/or
quantity of movement. AROM can provide information
regarding condition of the muscles and tendons.
Passive ROM (PROM) requires the client to remain
relaxed while the therapist moves the client’s joint to
determine quality and/or quantity of movement. PROM
evaluations can provide information regarding the passive
structures involved in the movement, such as ligaments
andjoints.
Resisted ROM, also called manual resistance, requires
the client to actively attempt to move a joint while the therapist applies a small amount of resistance. These two counteracting forces result in an isometric contraction of the
client’s muscles that provides information about the condition of the client’s soft tissue. More detailed information
about ROM is covered in Chapter 7, Assessment.
The temporomandibular joint. (A) Articular structures.
(B)Ligaments. (Reprinted with permission from Premkumar
K. Anatomy & Physiology: The Massage Connection. 3rd ed.
Philadelphia: Lippincott Williams & Wilkins, 2012.)
The TMJ comprises the joint and joint capsule between the
temporal bone and the mandible of the jaw. It is a modified
hinge joint that allows for elevation, depression, protraction,
retraction, and lateral deviation of the mandible. Muscles
of the TMJ are the major muscles involved in chewing:
lateral pterygoid, temporalis, and masseter. Tightness in
the TMJ muscles and forward head posture can create TMJ
dysfunction. Massage techniques that relax these muscles
may alleviate pain at this joint.
Myology: The Study of Muscles
Skeletal muscles, introduced in Chapter 3, are the focus of
massage therapy. To summarize, an entire skeletal muscle
is made up of thousands of muscle cells bundled together
in an organized fashion with connective tissue sheaths, and
intertwined with blood vessels, nerves, and proprioceptors. The neuromuscular junctions are the points of communication between the nervous system and muscular
system, but the muscles cannot contract without energy
in the form of adenosine triphosphate. Muscular contraction, a form of mechanical work, can be classified according to muscular work and the resulting movement. Joint
movements, or movements of the joints of the skeleton,
Chapter 4 / Kinesiology and Biomechanics
157
are accomplished with muscular work. The different kinds
of joints are discussed in the arthrology section above, and
the muscles responsible for those movements are discussed
in this section. Muscles have many functions: they contract
and work together to move the skeleton, they can stabilize
parts of the body to help other muscles create the appropriate
movement, and they can work against each other to balance
movements.
Skeletal Muscle Contraction
Skeletal muscles require nerve impulses and energy in order to
contract. In Chapter 3, we discussed the way a nerve impulse is
transmitted from the nervous system to the muscular system
at the neuromuscular junction. Once the nerve signal arrives
at the muscle, there must be sufficient energy to activate muscle contraction. The body can generate the necessary energy
in different ways, and the mechanism utilized at the time is the
one that best fits the body’s resources and immediate needs.
Nerve Supply to Muscles
A nerve impulse starts out at the central nervous system
(CNS) and is quickly transmitted out to the muscles to activate a contraction. The first major detour from the brain
and spinal cord is through one of the intertwined, complex
nerve plexuses (see Fig. 3-46):
• Cervical plexus—includes C1–C4 nerves, and innervates muscles of the head, neck, and diaphragm
• Brachial plexus—includes C5–C8 and T1 nerves, and
innervates the muscles of the upper extremities
• Lumbar plexus—includes L1–L4 nerves, and innervates the abdominals, thigh flexors, knee extensors,
and hip adductors
• Sacral plexus—includes L4, L5, and S1–4 nerves, and
innervates the gluteal muscles, hamstrings, and several leg and foot muscles
The individual nerves that carry impulses to particular muscles can be located in the special muscle section and
plates at the end of this chapter.
Once the impulse has been diverted along the appropriate nerve plexus, it travels down the appropriate nerve,
eventually arriving at the neuromuscular junction.
Neuromuscular Junction
The very end of the motor neuron is called the axonal
terminal. The microscopic gap between the axonal terminal
and the muscle cell is called the synaptic cleft. This collection
of structures where the nervous system and the muscular
system communicate is called the neuromuscular junction.
When the nerve impulse reaches the axonal terminal, a
chemical is released into the synaptic cleft and received by
the muscle cell. The chemicals trigger the muscle to contract.
Energy Requirements for Muscle
Contraction
Muscle contraction requires energy. This energy can only be
provided by a chemical called adenosine triphosphate (ATP),
which is created in our bodies naturally. Muscles store their
own ATP, but only enough for about 1 to 2seconds of contraction, so it must be regenerated constantly. ATP is created in three ways: direct phosphorylation, the anaerobic
mechanism (without oxygen), and the aerobic mechanism
(with oxygen). Figure 4-5 illustrates the three mechanisms
for regenerating ATP for muscle contraction.
Direct Phosphorylation
During strenuous exercise, our bodies use the ATP stored in
muscles in addition to all three mechanisms of creating ATP.
Glucose
ATP
Pyruvic acid
O
2
CO
2
H2O
Aerobic respiration produces
carbon dioxide (CO2) and
water (H2O)
Figure 4-5. Mechanisms for generating adenosine triphosphate (ATP) in muscles. (A) Aerobic
respiration produces carbon dioxide and water. (B) Anaerobic mechanism (glycolysis and the
formation of lactic acid in the absence of oxygen). (C) Direct phosphorylation of adenosine
diphosphate (ADP) by reaction with CP.
Fatty
acids
ATP
Glycogen
Glucose
ATP
Pyruvic acid
Lactic acid
Anaerobic mechanism
(glycolysis and the
formation of lactic acid
in the absence of oxygen)
ADP
ATP
CBA
Direct phosphorylation
of ADP by reaction with
creatine phosphate (CP)
CP
158 INTRODUCTION TO MASSAGE THERAPY
At first, the cell can use the stored ATP to contract. Asstored
ATP is being used up, additional ATP molecules can be generated via direct phosphorylation, the quickest mechanism
for creating ATP. In this process, creatine phosphate (CP)
stored only in muscle cells transfers a phosphate group to
nearby adenosine diphosphate (ADP) molecules to create
ATP. See Figure 4-5A. The disadvantage of this mechanism is
that CP is depleted just as fast as ATP is created, and when it
is gone, the muscle must generate ATP another way.
Anaerobic Cellular Respiration
The anaerobic process takes over after direct phosphorylation. When the oxygen in the muscle cells has been used for
other cellular metabolic processes, the body enters a state of
oxygen debt. The muscles can still produce ATP even during oxygen debt by using the anaerobic respiration mechanism. In the absence of oxygen, a glucose molecule can be
broken down through the process of glycolysis to produce
ATP, allowing the muscle to contract. The process is faster
than aerobic respiration, but it is not very efficient—only
two ATP molecules are generated from each molecule of
glucose. See Figure 4-5B.
A side effect of anaerobic respiration is lactic acid production. Recent research strongly suggests that lactic acid is
not involved in muscle fatigue nor muscle soreness. Muscle
soreness is likely the result of microtears in the muscle.
Infact, lactic acid can be converted back into pyruvate to
be used in aerobic respiration in the muscle cells and used
as a source of energy. A small amount of the lactic acid in
the muscles is carried to the liver via the blood, where it is
converted back to glucose with energy from ATP.
Muscle fatigue in endurance activity occurs when all
available glycogen is consumed, the mental component of
exhaustion comes into play, blood supply may be insufficient, and muscles may not respond as quickly or strongly as
they had been. True muscle fatigue, however, occurs when
the muscle cannot contract at all because of a lack of calcium ions in the sarcoplasm. With prolonged muscle activity, calcium leaks out through the calcium channels in the
sarcolemma that are normally closed. Insufficient levels of
calcium result in the inability to sustain muscle contraction.
In this instance, true muscle fatigue is exhibited when athletes wobble and collapse toward the end of extreme endurance events.
Aerobic Cellular Respiration
Aerobic cellular respiration uses ATP to break down glucose
and generate more ATP. See Figure 4-5C. There are three
separate stages of aerobic respiration, including glycolysis,
the Krebs citric acid cycle, and the electron transport system.
Glycolysis, the process of breaking down glucose, is actually an anaerobic process that can occur in the presence of
oxygen but does not require oxygen. What makes the threestep process an aerobic one is the fact that mitochondria are
required to generate the ATP this way, and they require oxygen. Although it is the slowest method for generating ATP, it
is also the most efficient.
The term “aerobic exercise” reflects the aerobic respiration process of generating ATP in the muscles, where moderate movement can be done for an extended period of time
without needing to breathe heavily (acquire additional oxygen) following the activity.
Proprioceptors
Muscle contraction is controlled on a more refined level by
the proprioceptors of the nervous system. Proprioceptors
(PROH-pree-oh-SEP-torz) are sensory nerve cells that
respond to body position, muscle tone, and equilibrium.
Muscle spindles are complex proprioceptors found in
the muscles that are sensitive to the length of the muscle
fibers and respond to changes in that length. Golgi (GOHLjee) tendon organs are proprioceptors found between the
collagen fibers in tendons that respond to muscle tension at
the tendon (see Fig. 4-6). Together, the muscle spindles and
Golgi tendon organs provide information to the CNS regarding the length and tension of a muscle and its tendon(s).
Proprioceptors within a joint capsule are Ruffini end
organs and Pacinian corpuscles. Both respond to pressure
within a joint, essentially sensing the position of the joint
by sensing different amounts of pressure at different places.
The muscle spindles and Golgi tendon organs respond
as muscles move a joint through its ROM, but joint proprioceptors are active when a joint is at the ends of its range.
All of the proprioceptors act as a group to provide a sense
of joint position, body position, effort, heaviness, and
timing of movement; together, this is sometimes called a
kinesthetic sense.
Manipulating the muscle spindles and Golgi tendon
organs with advanced massage techniques can encourage
muscles to shorten or lengthen. One of these techniques,
appropriately called proprioceptive neuromuscular facilitation, is discussed in Chapter 10, Therapeutic Applications.
Types of Muscle Fibers
Each muscle has a combination of slow-twitch fibers and
fast-twitch fibers that determines the endurance and speed
of that muscle’s contractions. The ratio of the fibers varies
from muscle to muscle and person to person, depending on
the person’s physical activity and genetics.
Slow-twitch Fibers
Slow-twitch fibers (also called Type I fibers) are smaller in
size than the fast-twitch fibers. They are red due to their rich
blood supply and higher iron content, and rely on aerobic
cellular respiration for energy. See Figure 4-7. They are slow
to contract and are not very powerful, but they can remain
Chapter 4 / Kinesiology and Biomechanics
159
Spinal cord
Figure 4-6. Muscle spindles and Golgi tendon organs.
Sensory nerve
Motor nerve
Muscle
spindle
Sensory nerve
Golgi tendon organ
Tendon organ capsule
(connective tissue)
contracted for long periods of time. Slow-twitch fibers are
more prevalent in muscles that need to sustain contraction
over long periods of time, such as the erector spinae, the
postural muscles of the back.
Fast-twitch Fibers
There are two kinds of fast-twitch fibers (Fig. 4-7). Type IIa
are pink and are slightly larger than the slow-twitch fibers.
Type IIx are the largest fibers, and since they do not have a
blood supply, they appear white. Fast-twitch fibers contract
I Slow-twitch fibers
Note smaller diameter
and darker color
from myoglobin
IIa Fast-twitch fibers
Note larger diameter
and paler color
quickly and powerfully in short bursts, utilizing the anaerobic respiration mechanism. The powerful muscles in the
arms and legs tend to have a higher proportion of fasttwitch fibers.
Skeletal Muscle Activity
In Chapter 3, we discussed the two kinds of attachments
of skeletal muscles: the origin is where a muscle attaches
to a bone or connective tissue structure that is generally
Lateral view Cross-sectional view
Figure 4-7. Muscle fiber types. (Reprinted with permission from Cael C. Functional Anatomy, Musculoskeletal
Anatomy, Kinesiology, and Palpation for Manual Therapists. Philadelphia: Lippincott Williams & Wilkins, 2010.)
160 INTRODUCTION TO MASSAGE THERAPY
Tendons
Biceps brachii
Insertion
Radius
Ulna
Figure 4-8. Muscle attachments: origin and insertion.
Humerus
Tendon
Origins
Scapula
stationary, and the insertion is the attachment that moves
most during normal contraction, often at the distal end
(Fig.4-8).This simple description for origin and insertion
becomes a little more complicated when learning about
muscle activity because contraction of a skeletal muscle
may or may not result in movement. If no movement is produced when the muscle contracts, it is considered a static
contraction. If some kind of movement results from the
muscle contraction, it is called a dynamic contraction.
Significant increases or decreases in muscle activity
impact the condition of the muscles, sometimes to the point
that the health of the muscle is affected. Restrictions and
dysfunctions in the ability of a muscle to perform normal
contractions are the main focus of therapeutic massage,
with the goal being restoration of the client’s maximum
functional muscle contraction.
Static Contractions
Static contractions, also called isometric contractions, do not
produce movement of bones or body parts. In this situation,
a muscle contracts, exerting force on its attachments, but the
attachments do not move. See Figure 4-9A. Microscopically,
the cross bridges attach, but the myofilaments do not slide
closer together. Instead of producing movement and heat,
isometric contractions only create heat. Squeezing your
knees together and clenching your jaw are examples of isometric contractions.
Muscle tone is another example of static contraction.
Ina healthy, awake person, every skeletal muscle is in a state
of partial contraction called muscle tone. The nervous system is constantly sending signals to approximately 10% of
the muscle’s cells to remain contracted, so the muscle cells
within a whole muscle take turns being contracted to avoid
fatigue. Muscle tone is especially important for maintaining
posture or joint position. When people speak of “good muscle tone,” they are referring to muscles that appear healthy
and firm, not necessarily the partial contractions that hold
our bodies upright.
Dynamic Contractions
Dynamic contractions, also called isotonic contractions,
result in some kind of body movement as the muscle attachments get closer together or farther apart. Dynamic contractions can be either concentric or eccentric.
In concentric contractions , the myofilaments slide
together, the muscle shortens, and the attachment sites of the
muscle move closer together (Fig. 4-9B). Examples of concentric contractions include finger flexion and knee flexion.
Muscle contracts
but does not shorten
Muscle contracts
and shortens
Muscle contracts and
lengthens
AB C
No movement
Figure 4-9. Types of contractions. (A) Static, isometric—the muscle contracts but does not shorten. (B) Dynamic, concentric—the muscle
shortens as it contracts. (C) Dynamic, eccentric—the muscle lengthens as it contracts. (Reprinted with permission from Cael C. Functional
Anatomy, Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists. Philadelphia: Lippincott Williams & Wilkins, 2010.)