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Functional Anatomy
Section One: The Skeleton
Functions of a Skeleton
The skeleton performs 5 basic functions:
FUNCTION
EXPLANATION
EXAMPLES
MOVEMENT
Where bones meet we
form joints. In
combination with
muscles, we create
movement.
Bones move because of
joints and muscles, e.g.
elbow moved by biceps
PROTECTION
Provide protection to
vital organs
Scapula – lungs
Skull – brain
SUPPORT
Give support for organs
and tissue so they do
not collapse.
Spine supports the head
and trunk
STORAGE
Minerals are stored in
bones
Storage of calcium and
potassium
SUPPLY
Red and white blood
cells are produced in
bone marrow
Femur produces red
blood cells
1.3 Axial and Appendicular Skeleton
All the bones of the skeleton are divided into
two main groups. These are known as:
1. Axial Skeleton
2. Appendicular Skeleton
AXIAL SKELETON
Consists of those bones forming the central
column of the body,
i.e. spine, skull and ribcage.
APPENDICULAR SKELETON
Those bones that attach to the axial skeleton,
i.e. shoulders, hips and the limbs.
1.4 Classification of Bones
Bones are classified
according to
their shape.
They fall into four basic
categories:
1. Long bones
2. Short bones
3. Irregular bones
4. Flat bones
Using the table, fill in the
basic
function of each type of
bone and
provide some examples of
these.
BONE
CLASSIFICATION
BASIC
FUNCTION
EXAMPLES
Long*
Production of
red blood cells
and white
blood cells.
Movement.
Humerus,
femur,
radius and
ulna
Short
Small of fine
movements
Carpals
(wrist)
Tarsals
(ankle)
Irregular
Movement
support and
muscle
attachment
Face and
vertebrae
Flat
Protection and
attachment
Shoulder
blade and
breastbone
*The length is
greater than
width
On the skeleton, colour the
short, flat, long and
irregular bones you can
identify.
What do you notice about the location of most
of the flat bones? Why might this be?
Located around the main organs, e.g. brain,
heart. To give
protection.
What do you notice about the location of most
of the long bones? Why might this be?
Located in legs and arms. These are the
regions of most joints and therefore
movement.
1.5 Identifying Bones of the Skeleton
As a pre-test, try naming as many bones as possible on the skeleton
below. Use common or anatomical terms.
Cranium (skull)
Vertebrae – cervical (neck)
Sternum (breastbone)
Ribs (ribcage)
Vertebrae – lumbar (lower back)
Pelvis (hip) = Ilium,
Ischium & Pubis
Metacarpals (palm)
Phalanges (fingers)
Tibia (shin)
Maxilla (face)
Mandible (jaw)
Clavicle (collarbone)
Ulna (forearm)
Scapula (shoulder blade)
Humerus (upper arm)
Radius (forearm)
Femur (thigh)
Fibula (shin)
Patella (knee cap)
Metatarsals (foot)
Tarsal (heel)
Phalanges (toes)
Identify and explain the function of the following skeletal structures.
A. Cranium
1. THE HEAD
(common name = skull)
Designed to protect the brain. Made up
A
B
C
of a number of inter-connecting bones.
B. Maxilla
(common name = face)
Houses the eyes and sinuses. Protects
these features against damage.
C. Mandible
(common name = jaw)
Responsible for talking, chewing etc.
2. THE RIBCAGE
Rib
3. THE CHEST
Ribs (common name = ribs)
12 pairs in all. Designed to protect the
heart and lungs
A. Sternum
(common name = breast bone
Protects the heart and lungs. It is the bone
pressed on in C.P.R.
)
4. THE SPINE
Cervical vertebrae. These are
small delicate bones responsible for
neck movement. There are seven
bones in all.
Thoracic vertebrae. Allow ribs to
attach to the spine hence there
are 12 of them (one for each rib
pair).
Lumbar vertebrae. These are the
largest of the vertebrae and are
responsible for weight-bearing.
There are five in all.
The sacrum (upper) and coccyx
(lower) are a series of fused
(joined) bones that help form the
pelvis.
What do the shapes of the bones tell you about their function?
Those that are larger have a roll in weight or load bearing
e.g. lumbar and thoracic. Smaller ones are important for
movement e.g. cervical.
5. THE SHOULDER
A. Scapula
blade )
B
A
(common name = shoulder
Protects the lungs. Forms shoulder joint.
B. Clavicle (common name = collarbone)
Holds the shoulder in place. Easily broken.
A. Humerus (common name = upper arm )
6. THE ARM
Prime function is movement.
B. Radius (common name = Forearm )
Prime function is movement, always located
A
on thumb-side of forearm.
C. Ulna (common name = forearm )
Prime function is movement.
B
D. Carpels (common name = wrist )
C
Prime function is movement.
D
E
F
E. Metacarpels (common name = palms )
Prime function is movement.
F. Phalanges (common name = Fingers )
Prime function is movement.
7. THE PELVIS
A. Ilium (common name = pelvis)
Protects intestines
A
B. Pubis ( common name = pelvis)
Forms front of pelvis. Has to
separate
in childbirth.
B
C
C. Ischium (common name = pelvis)
Forms the ‘boney bum’.
A. Femur (common name = thigh )
8. THE LEG
Largest bone in the body, responsible for support
and movement.
B. Patella (common name = knee cap )
Protects the knee joint.
C. Tibia (common name = shin )
Support and movement.
A
‘Thinner’ bone of leg. Support and movement.
B
E. Tarsels (common name = ankle)
C
Bones of the ankle and heel. Support and balance.
D
E
D. Fibula (common name = shin)
F. Metatarsels (common name = foot)
Form the sole of the foot. Support and balance.
F
G
G. Phalanges (common name = toes)
Support, movement and balance.
Functional Anatomy
Section Two: Terms of Direction
2.2 The Anatomical Position
In order to explain the positioning of bones, organs, muscles and the
like on the human body, anatomists have agreed on a
standardised position for the human body in all cases. This is
known as the anatomical position.
THE ANATOMICAL POSITION
There are four key features to note:
1.
Palms face forward
2.
Body is upright
3.
Thumbs point outward – so radius and ulna and uncrossed
4.
Face is forward
The terms of direction in the next section are
all with respect to this position.
Why is it important to always talk about the
position of organs, bones and muscles in or
on the human body with respect to the
anatomical position?
This enables everyone to talk from the
same point of view regardless of their
profession or level of expertise.
2.3 Anatomical Terms of Direction
These refer to the position of parts of the body, or of one part with respect to
another.
Term
Definition
Examples
Anterior
On the FRONT of the
body or limb
1. The chest is on
the anterior of the body
2. The face is an anterior
aspect of the head.
Posterior
On the BACK of the
body or limb
1. The buttocks are on
the posterior of the body
2. The calf muscles are
on the posterior of the leg
Superior
Above or on top of
1. The cervical vertebrae
are superior to the thoracic
vertebrae
2. The thoracic vertebrae
are superior to the lumbar
vertebrae
Term
Definition
Inferior
Below or beneath
Medial
Examples
1. Thoracic vertebrae are
inferior to the cervical
vertebrae
2. The lumbar vertebrae are
inferior to the thoracic
vertebrae
1.
Nearer the midline of
the body
Lateral
Further away from the
midline of the body
The big toe is on
the medial aspect
of the foot
2. The little finger is on
the medial aspect of the
hand
1. Little toe is on the
lateral aspect of
the foot.
2. The thumb is on
the lateral aspect
of the hand
Term
Definition
Distal
Further away from the
body. Usually refers to
the limbs.
Proximal
Examples
1. Wrist is distal to the
elbow
2. Elbow joint is distal to
the shoulder joint
1.
Nearer the body.
Usually refers to the
limbs.
Elbow is proximal to
the wrist joint
2. Shoulder joint is
proximal to the elbow
Face down
A press-up is on the
PRONE position
Prone
Supine
Face up
A sit-up is on the SUPINE
position
Term
Definition
Deep
When a muscle is
BENEATH another
with respect to the
skin surface
Superficial
On the surface of
the body or limb
Examples
The ilio psoas is a
deep muscle
of the hip
Iliopsoas
Pectoralis major is
a superficial
muscle of the
chest
Pectoralis Major
This exercise has shown that the terms of direction compliment each other. Complete the
list below by placing the opposite term next to the one provided.
Superior -
Inferior
Anterior -
Posterior
Proximal -
Distal
Medial -
Lateral
Deep
Superficial
Supine -
Prone
-
Functional Anatomy
Section Three: The Joints
3.2. Overview of Joint Types
There are three broad categories of joint type in
the body. They are classed according to the
degree of movement possible.
The three categories are:
1. Immovable
Also known as fibrous joints
2. Slightly movable Also known as cartilaginous
joints
3. Freely movable Also known as synovial joints
We shall look at all these categories in turn.
3.3 Fibrous Joints
These are non-movable joints. They are the result of tough
fibrous tissue forming where the two bone ends meet.
What is the function of a fibrous joint?
To provide protection.
Examples include:
1. Skull
2. Pelvis
Fibrous joint
3.4 Cartilaginous Joint
These are slightly-movable joints. They are the result
of cartilage forming where the two bone meet. This
gives a fair degree of resilience.
What is the function of a cartilaginous joint?
To act as shock absorbers.
Examples include:
1. Invertebral discs Cartilaginous
Joints
2. Ribs to sternum
3.Where pubic bones meet
3.5 Synovial Joint
These are freely movable joints. The only limitation in range of
movement is as a result of bone shape at the joint, and
ligaments.
What is the primary function of a synovial joint?
To provide movement.
All synovial joints follow the same basic structure as shown
The key components of your illustration have important roles to play in
maintaining the structure of the joint.
1.
Join bone to bone for stability
Ligaments
2. Capsule
Provides stability and protection from infection
3. Cartilage
Reduce wear and tear on bones
4. Synovial Fluid
Lubricates the joint and provides shock
absorption
5. Synovial Membrane
Produces synovial fluid
In some joints, for example the knee, there are pads of fat and/or discs of
cartilage to further help absorb shock and reduce general ‘wear and tear’.
3.6 Types of Synovial Joints
Synovial joints can be divided into six basic types. The types are
governed by the type of movement or movements they allow.
The six basic types are:
1.Gliding
2.Hinge
3.Pivot
4.Condyloid
5.Saddle
6.Ball and Socket
1. Gliding
Definition: The bone surfaces are small and flat, or slightly
concave and one bones slides over the other.
Examples:
1. Carpals and tarsals
2. Ribs and vertebrae
3. Scapula and ribs
Movements: Only slight movement is possible due to the
restrictions of attached ligaments.
Movements possible are:
1. side to side
(abduction / adduction)
2. Back and forth
(extension/flexion)
2. Hinge
Definition: Two bones join in such a way that movement is
possible only in one direction, usually at right angles to the
bones.
Examples:
1. Elbow
2. Knee
3. Ankle
Movements: A uniaxial joint allowing movement in only one
direction
The only movement possible is:
Back and forth
(extension/flexion)
3. Pivot
Definition: A joint constructed in such a way that rotation only
is possible (usually about the long axis of the bone)
Examples:
1. Atlas and axis of neck
2. Radius and humerous
Movements: A uniaxial joint allowing movement in only one
direction
The only movement possible is:
Rotation
4. Condyloid
Definition: Also known as an ellipsoid joint. The bone ends make
the shape of an ellipse.
Examples:
1. Carpals and radius
2. Metacarpals and phalange
Movements: A biaxial joint allowing movement in two main
directions.
The movements possible are:
1.
Back and forth
(extension/flexion)
2.
Side to side
(abduction/adduction)
3.
Some Circumduction
5. Saddle
Definition: The bone ends are shaped like a rider on a saddle
Example:
1. Carpal/metacarpal of thumb
Movements: A biaxial joint allowing movement in two main
directions.
Movements possible are:
1. side to side
(abduction / adduction)
2. Back and forth
(extension/flexion)
6. Ball and Socket
Definition: A ball-shaped bone end fits into a socket or cupshaped bone.
Examples:
1. Hip
2. Shoulder
Movements: A multiaxial joint allowing
movement in many directions around the joint.
The movements possible are:
1.
Back and forth
(extension/flexion)
2.
Side to side
(abduction/adduction)
3.
Rotation
4.
Circumduction
The shoulder joint is the most freely moving ball and socket joint
we have. The illustration may help you with your answer.
Why is the shoulder joint so freely moving?
Because the socket is shallow.
What do you suppose is the risk of such a freely moving joint?
It is easy to dislocate.
3.7. Movements at Synovial Joints
Just as we learnt a set of terms to describe the positioning of bones, muscles
and organs in the body, so we have a set of terms to describe how joints
move.
Term
Definition
Flexion
Bending or
decreasing the
angle between
two bones
Examples
1.
Trunk
Bending forwards
(sideways – lateral
flexion)
2.
Shoulder
Moving the arm forward
3.
Arm
Bending at the elbow
4.
Wrist
Bringing the palm
towards the forearm
5.
Hip
Raising the thigh
towards the trunk
6.
Knee
Bending at the knee
Term
Definition
Extension
Straightening or
increasing the
angle between
two bones
Examples
1.
Trunk
Straightening up
2.
Shoulder
Moving the arm backward
3.
Arm
Straightening the elbow
4.
Wrist
Straightening the wrist
5.
Hip
Moving the leg backward
6.
Knee
Straightening the knee
Term
Definition
Abduction
Moving a limb or
part of a limb away
from the midline of
the body
Adduction
Moving a limb or
part of a limb
towards the midline
of the body
Circumduction
A combination of
flexion, extension,
abduction and
adduction.
The movement of
the limb resembles
the shape of a cone
Examples
Moving outwards on a
star jump
Bringing the limbs back
together in a star
jump
The arm stroke in
Butterfly
Term
Definition
Rotation
Twisting of a limb
about its long axis
Supination
Movement of the
hand into a palm-up
position
Holding a bowl of
soup
Pronation
Movement of the
hand into a palmdown position tipping
the soup out
Examples
Turning the head
Twisting
the trunk
Turning a card over
Turning a page in a book
Turning a card face
down
Closing a book
Term
Definition
Inversion
Movement of the
sole of the foot
inward
Eversion
Movement of the
sole of the foot
outward
Dorsi flexion
Movement of the
top of the foot
upward, closer to
the shin
Plantar flexion
Movement of the
sole of the foot
downward
Examples
Underarm Volley ball serve
Frame
Joint
Bones at the joint
Movement or
Position
A
Knee
Femur (thigh) & Tibia
(shin)
Flexion
A
Trunk (at hip)
Pelvis (hip) & Femur
Flexion
A→D
Right Shoulder
Scapula (shoulder blade) &
Humerus (upper arm)
Flexion
A→C
Right Hip
Pelvis (hip) & Femur
Extension
A→D
Right Foot (at ankle)
Tibia, Fibula (shin) &
Tarsals (ankle)
Plantarflexion
A→D
Right Knee
Femur & Tibia
Extension
A→D
Right Hand (at wrist)
D
Right Elbow
Radius & Ulna (forearm) & Slight (flexion)
Carpals (wrist)
Radius, Ulna & Humerus
Extension
Functional Anatomy
Section Four: The Muscles
4.2 Identifying Muscles
Trapezius
Deltoid
Biceps
Triceps
Pectoralis Major
Latissimus Dorsi
Rectus Abdominus
Gluteus Maximus
Hamstrings
Quadriceps
Gastrocnemius
4.3 Guide to Individual Muscles
[A] PRIME MOVERS OF THE TRUNK
1. Rectus adbominus:
Location : A group of two muscles running lengthwise along the medial
aspect of the abdomen. They are rather like two columns of
muscle running up either side of the belly button.
They run from the pubis (pelvis) to the cartilage of the 5th, 6th
and 7th ribs.
Movements:
Rectus abdominus allows two basic
movements.
1. Flexion of the trunk
2. Lateral flexion of the trunk
Application: Typical sporting actions include:
1. Sit ups
2. Cartwheels
3. Pike in diving
Rectus Abdominus
[A] PRIME MOVERS OF THE TRUNK
2. Erector Spinae Group:
Location : One of the main muscles located in the lower back and one of
the few visible. It runs from the pelvis to the lumbar vertebrae.
Movements: Erector spinae group allows two basic movements.
They are:
1. Extension of the spine
2. Lateral flexion of the trunk
Application
Typical sporting actions include:
1. Straightening out from a pike
2. Rowing
3. Swimming (body position)
Erector
Spinae
[B] PRIME MOVERS OF THE SHOULDER
1. Trapezius:
Location : A large triangular muscle located on the posterior aspect of
the body.
It runs in a triangular shape from the base of the skull, the 7th
cervical vertebrae and all the thoracic vertebrae, to the scapula
and clavicle.
1.
2.
3.
4.
Movements: Trapezius allows four basic movements.
They are:
Raise the head
Pull the shoulders back
Trapezius
Raise the scapula
Drop the scapula
Application: Typical sporting actions include:
1. Pulling shoulder when throwing
2. Rowing
3. Looking up in basketball
[B] PRIME MOVERS OF THE SHOULDER
2. Latissimus Dorsi:
Location :
Latissimus dorsi
The broadest muscle of the back. It forms the
back of the armpit.
This is a large triangular muscle which covers
the lumbar and lower thoracic region of the back.
It runs from the lower thoracic and lumber regions,
to the anterior aspect of the humerus
Movements:
Latissimus dorsi allows three basic movements.
They are:
1. Adduction of the upper arm
2. Extension of the shoulder
3. Internal rotation of the shoulder
How can latissimus dorsi allow internal rotation of the
shoulder to occur if it is a muscle located on the back?
Because it attaches to the humerus
Application: Typical sporting actions include:
1. Recovery in breaststroke
2. Ten-pin bowling
3. Drawing arm back to punch
[B] PRIME MOVERS OF THE SHOULDER
3. Deltoid:
Location : A triangular shaped muscle located on the superior aspect of
the shoulder i.e. above the shoulder joint
It runs from the scapular and clavicle to attach at the humerus
Deltoid
Movements: Deltoid allows four basic movements.
They are:
1. Flexion of the shoulder
2. Extension of the shoulder
3. Abduction of the arm
4. Rotation of the shoulder
Application: Typical sporting actions include:
1. Throwing
2. Punching
3. Swimming
[B] PRIME MOVERS OF THE SHOULDER
3. Pectoralis Major:
Location : A large triangular muscle located on the chest.
It runs from the clavicle, sternum and the 6th rib, to the
humerus.
Movements: Pectoralis major allows three basic movements.
These are:
1. Flexion of the shoulder
2. Abduction of the arm
Pectoralis major
3. Rotation (internal) of the shoulder
Application: Typical sporting actions include:
1. Throwing
2. Punching
3. Press-ups
[C] PRIME MOVERS OF THE ELBOW
1. Biceps Brachii:
Location : A two-headed muscle (biceps) located on the anterior aspect
of the humerus
It runs from the scapular to the upper aspect of the radius
Movements: Biceps allows two basic movements.
They are:
1. Flexion of the elbow
2. Flexion of the shoulder
Application: Typical sporting actions include:
1. Biceps curl
2. Rowing
3. Recovery in breaststroke
Biceps Brachii
[C] PRIME MOVERS OF THE ELBOW
1. Triceps Brachii:
Location : A large muscle located on the posterior aspect
of the humerus.
It runs from the scapular, over the posterior aspect of the
humerus, to the upper part of the ulna.
Triceps Brachii
Movements: Triceps allows two basic movements.
These are:
1. Extension of the elbow
2. Extension of the shoulder
Application: Typical sporting actions include:
1. Karate chop
2. Press-up
3. Punching
[D] PRIME MOVERS OF THE WRIST
1. Flexor digitorum:
Location : This is one of the main gripping muscles of the
anterior aspect of the forearm.
It runs mainly from the proximal aspect of the radius and
ulna, over the anterior of the forearm, to attach to the
fingers.
Flexor digitorum
Movements:
Flexor digitorum has two basic movements.
1. Flex the fingers (make a fist)
2. Flex the wrist
Application: Typical sporting actions include:
1. Punching
2. Hold a racquet
3. Wrist ‘dink; in a set shot (volleyball)
[D] PRIME MOVERS OF THE WRIST
2. Extensor digitorum:
Location : This is one of the muscles in direct opposition to
the flexor digitorum. It is located on the posterior aspect of
the forearm.
It runs over the posterior of the forearm, to attach to the
fingers.
Movements: Extensor digitorum allows two basic movements.
1. Extend the fingers
2. Extend the wrist
Application: Typical sporting actions :
1. Karate chop
2. Fending in tackling
3. Set shot in (volleyball)
Extensor
digitorum
[E] PRIME MOVERS OF THE HIP AND KNEE
1. Illiopsoas:
Location : This is a group of three muscles located deep inside the hip
region.
It runs from the lumbar vertebrae and pelvis to the upper
femur.
Movements: Illiopsoas allows one basic movement.
This is:
1. Flexion of the hip
Application: Typical sporting actions include:
1. Kicking
2. Running
3. Cycling
[E] PRIME MOVERS OF THE HIP AND KNEE
2. Gluteus Maximus:
Location : This is a the large fleshy muscle that makes up your backside.
You are probably sitting on it right now! It is an extremely
powerful muscle.
It is located on the posterior aspect of the hip running from
the ilium (pelvis), sacrum and coccyx to the upper third of the
femur.
Movements: Gluteus maximus
allows three basic movements.
1. Extension of the leg
2. Abduction of the leg
3. External rotation of the leg
(rotating outwards)
Application: Typical sporting actions include:
1. Kicking
2. Running
3. Jumping
[E] PRIME MOVERS OF THE HIP AND KNEE
3. Quadriceps:
Location : This is a group of four (quad) muscles located on the anterior
aspect of the thigh.
The four muscles making up the quadriceps group
are:
1. Rectus femoris
2. Vastus medialis
3. Vastus lateralis
4. Vastus intermedius (not shown)
Movements:
Quadriceps allows
two basic movements.
1. Extension of the knee
2. Flexion of the hip
Application: Typical sporting actions include:
1. Kicking
The Vastus intermedius is not shown
2. Running
because it lies under the Rectus femoris, so
3.
Jumping
is not visible.
Consider the illustration. Label the muscles of
the quadriceps group you can identify.
Rectus femoris
Vastus lateralis
Vastus Medialis
[E] PRIME MOVERS OF THE HIP AND KNEE
3. Hamstrings:
Location : This is a group of three muscles located on the posterior
aspect of the thigh.
Since they are in direct opposition to the quadriceps and are
generally weaker they are prone to injury.
The three muscles making up the hamstrings group are:
1. Semitendinosus
2. Biceps femoris
3. Semimembranosis
Movements: Hamstrings allows two basic movements.
These are:
1. Extension of the hip
2. Flexion of the knee
Application: Typical sporting actions include:
1. Kicking
2. Running
3. Jumping
[F] PRIME MOVERS OF THE ANLKE
1. Gastroncnemius:
Location : This is a the large fleshy muscle located on the posterior
aspect of the lower leg.
It runs from the distal aspect of the femur to the tarsal's
(heel)
via the Achilles tendon.
Movements:
Gastrocnemius allows two basic movements.
These are:
1. Knee flexion
2. Plantar flexion
Application: Typical sporting actions include:
1. Kicking
2. Pointing toes
3. Jumping
[F] PRIME MOVERS OF THE ANLKE
2. Soleus:
Location : This muscle lies beneath gastrocnemius and serves largely the
same function. It shares the Achilles tendon with
gastrocnemius.
It runs from the proximal aspect of both tibia and fibula to
the
same position as gastrocnemius on the heel
Movements: Soleus allows one basic movements.
1. Plantar flexion
Application: Typical sporting actions
include:
1. Kicking
2. Pointing toes
3. Jumping
[F] PRIME MOVERS OF THE ANLKE
3. Tibialis anterior:
Location : This muscle is located on the anterior aspect of the lower leg.
It lies mainly over the tibia and can be felt running along its sharp
edge.
It runs from the proximal aspect of the tibia to the toes.
Movements:
Tibialis anterior allows two basic movements.
1. Dorsi flexion
2. Inversion
Application: Typical sporting actions include:
1. Passing with the outside
of the foot (soccer)
2. Kicking (recovery)
3.
Rowing
4.4 Agonists and Antagonists
When muscles create movement, they tend to work in pairs.
When one muscle (or group), contracts to generate the
movement, the opposing muscle (or group) relaxes.
This is known as Reciprocal Inhibition.
Each muscle in the pair is labelled as either the agonist or
antagonist.
Agonist:
The muscle that produces the movement.
Agonists are also referred to as prime movers. Why?
Because they are the main muscle
producing movement (prime = main).
Antagonist:
This muscle that opposes motion
Consider the example of a bicep curl.
The movement occurring at the elbow is flexion
The agonist muscle would be
biceps
The antagonist muscle would be
triceps
The prime mover would be biceps
When the person extends the arm i.e. to lower the
weight:
The agonist muscle would be
triceps
The antagonist muscle would be
biceps
What other role does the antagonist muscle play in the
lowering of the weight?
Controls the speed at which weight is lowered in
order to help prevent injury.