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Basic Anatomy and Movement

Origins of Anatomy

The study of the human body has its origins in prehistoric times, making it one of the oldest known sciences. The term anatomy comes from the Greek word anatome- , which means “dissection” or “to cut apart.” Originally, ana-

tomical understanding came largely from observations of dissected plants and animals. For the purposes of this chapter, basic skeletal muscle anatomy is pre-sented. Primary muscle groups commonly used in fitness programs are described, as well as suggested exercises for working those muscles in an exercise setting.

Anatomical TerminologyLearning new anatomical terms may seem like learning a foreign language

since the structures were originally named in the languages of Greek, Latin, and Arabic. Once you understand the important anatomical, directional, and regional terms associated with the structures of the body (Table 2-1), you will find that most tissues are named quite descriptively. A good example is the comparison between the biceps brachii and biceps femoris muscles. Biceps refers to a “two-headed muscle.” Therefore, both muscles are composed of two heads. The location of each muscle, however, is quite different. The word brachii comes from the root term “brachium,” which means muscle of the arm, whereas the word femoris comes from “femur,” which is the large bone of the thigh. The biceps brachii is a muscle of the front, upper arm and the biceps femoris is a muscle found in the back of the thigh. Table 2-2 provides a brief list of common anatomical terminology that will help you decipher the root words, and thus the meanings, of many bodily structures.

Naming the various parts of the human body required anatomists to develop a reference position so that structures and areas of the body could be

Chapter 2

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Table 2-1 Anatomical, Directional, and Regional Terms

Term Definition

Anterior (ventral) Toward the front

Posterior (dorsal) Toward the back

Superior Toward the head

Inferior Away from the head

Medial Toward the midline of the body

Lateral Away from the midline of the body

Proximal Toward the attached end of the limb, origin of the structure, or midline of the body

Distal Away from the attached end of the limb, origin of the structure, or midline of the body

Cervical Regional term referring to the neck

Thoracic Regional term referring to the portion of the body between the neck and abdomen; also known as the chest (thorax)

Lumbar Regional term referring to the low back; the portion between the abdomen and the pelvis

Plantar The sole, or bottom, of the feet

Dorsal The top surface of the feet and hands

Term Definition

Palmar The anterior or ventral surface of the hands

Sagittal plane A longitudinal (imaginary) line that divides the body or any of its parts into right and left halves

Mediolateral axis The transverse axis of rotation about which sagittal plane movement occurs; perpendicular to the sagittal plane

Frontal plane A longitudinal (imaginary) section that divides the body or any of its parts into anterior and posterior halves

Anteroposterior axis The front-to-back axis of rotation about which frontal plane movement occurs; perpendicular to the frontal plane

Transverse plane Also known as the horizontal plane; an imaginary line that divides the body or any of its parts into superior and inferior halves

Longitudinal axis The vertical axis of rotation about which transverse plane motion occurs; perpendicular to the transverse plane

Table 2-2 Common Anatomical Terminology

Root Meaning Term Definition

Arthro Joint Arthritis Inflammation in a jointBi Two, both Bilateral On both sidesBrachium Arm Brachialis Muscle of the armCardio Heart Cardiology The study of the heartCephalo Head Cephalic Pertaining to the headChondro Cartilage Chondroectomy Excision of a cartilageCosto Rib Costochondral Pertaining to a rib and its cartilageDermo Skin Dermatitis Inflammation of the skinHemo, hemato Blood Hemorrhage Internal or external bleedingIlio Pelvis or hip Ilium The wide, upper part of the pelvic bone Myo Muscle Myositis Inflammation of a muscleOs, osteo Bone Osteopenia Loss of bone mineralPulmo Lung Pulmonary artery Vessel that brings blood to the lungs Thoraco Chest Thorax ChestTri Three Triceps brachii Three-headed muscle on the arm

described in relation to each other. This

reference is called anatomical position

and refers to a person standing erect

with the head, eyes, and palms facing

forward. Additionally, the feet are

together with the toes pointing forward

and the arms are hanging by the sides.

A representation of anatomical position

is given in Figure 2-1, along with the

anatomical planes of motion.

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thin and typically curved. They include certain bones of the skull, as well as the ribs and sternum. Bones that do not fit into these categories are classified as irregular bones because of their diverse shapes. Examples include hip bones, ver-tebrae, and certain skull bones.

Although the size and shape of the skeleton is genetically determined, it can be greatly affected by loading or impact from physical activity. Ultimately, a bone’s size and shape fits best with its function. In other words, “form follows function.” Wolff’s law indicates that changes in bone structure coincide with changes in bone function. That is, when the skeleton is subjected to stressful forces, such as those that occur with exercise, it responds by laying down more bone tissue, thereby increasing its density. Conversely, when individuals experience prolonged periods of bed rest due to illness or injury, their bones lose mineral and become less dense. Maintaining adequate bone density is an important issue for all adults. Fitness

Skeletal System

The human skeleton is an active, living tissue that performs sev-eral important functions: support,

movement, protection, storage, and the formation of blood cells. The body has a total of 206 bones, most of which are paired (such as the right and left femurs and right and left tibias) (Figure 2-2). The structural functions of bone include giving support to the soft tissues of the body and providing attachment sites for most muscles, which plays an important role in movement. The various shapes of bones determines how they are classified—long, short, flat, or irregular. Long bones are so named because they are longer than they are wide, thereby having a long axis. Most of the bones of the limbs are classified as long bones, including the humerus, radius, ulna, femur, tibia, fibula, and pha-langes. Bones that are approximately the same length and width are called short bones. Examples of short bones include the carpals and tarsals. Flat bones are

Medial Lateral

Ventral (front side)

Dorsal (back side)

Superior

Inferior

Transverse Plane Frontal Plane Sagittal Plane

Figure 2-1Anatomical reference position and planes of motion

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professionals can play a crucial role in helping clients preserve bone tissue by educating them about the importance of exercise and proper nutrition.

Axial SkeletonOf the 206 bones that make up

the skeleton, 80 are categorized as the axial skeleton (Table 2-3). Consisting of the skull, vertebral

column, sternum, and ribs, the axial skeleton’s most important functions are to provide the main axial support for the body and protect the central nervous system and organs of the thorax. Fitness professionals should have a fundamental knowledge of the structure of the vertebral column since the mechanics of the spine affect all exercise performance. The vertebral

CraniumSkull Face

Greater tubercle of humerus

Medial epicondyle of humerus

Lateral epicondyle of humerus

Vertebral column

Pelvic girdle

Greater trochanter of femur

Pubis

Ischial tuberosities

Tibial tuberosity

Metatarsals

Phalanges

anterior view posterior view

Shoulder girdle

Clavicle

Scapula

Thorax

Sternum

Ribs

Upper extremity

Humerus

Ulna

Radius

Carpals

Phalanges

Metacarpals

Lower extremity

Femur

Patella

Tibia

Fibula

Spine of scapula

Deltoid tubercle of humerus

Olecranon process of ulna

Vertebral column

Ilium

Sacrum

Lesser trochanter of femur

Lateral condyle of femur

Medial condyle of femur

Ischium

Tarsals

Acromion process of scapula

Figure 2-2Skeletal system

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column consists of 33 vertebrae that are categorized by regions (Figure 2-3). The upper region (neck area) of the spine contains seven cervical vertebrae, which are the smallest and most delicate. The mid-region, under the cervical vertebrae, contains 12 thoracic

vertebrae, which are each attached to a rib. The lower region consists of five lumbar vertebrae, the sacrum (five fused vertebrae), and the coccyx (four fused vertebrae). The lumbar vertebrae are the largest and heaviest vertebrae due to their role in continuously receiving ground reaction forces and supporting the weight of the body.

Appendicular SkeletonThe remaining 126 bones are

categorized as the appendicular skeleton, which includes the bones of the upper and lower limbs and the pectoral (shoulder) and pelvic (hip) girdles (see Table 2-3). The pectoral and pelvic girdles represent the means by which the appendicular skeleton joins together with the axial skeleton. Although the pectoral girdle (i.e., the clavicle and scapula) attaches to the axial skeleton only at the sternum and provides little support for the upper-body structures, the support is sufficient since the upper limbs do not bear the body’s weight. This minimal

Table 2-3 Bones in the Axial and Appendicular Skeletons

Axial Skeleton Number of Bones

Skull Cranium 8 Face 14

Hyoid 1

Vertebral Column 26

Thorax Sternum 1 Ribs 24

(Auditory ossicles)* 6 ______

80

Appendicular Skeleton Number of Bones

Lower Extremity Phalanges 28 Metatarsals 10 Tarsals 14 Patella 2 Tibia 2 Fibula 2 Femur 2

Pelvic Girdle Hip or pelvis (os coxae = ilium, ischium, pubis) 2

Shoulder Girdle Clavicle 2 Scapula 2

Upper Extremity Phalanges 28 Metacarpals 10 Carpals 16 Radius 2 Ulna 2 Humerus 2 ______

126

The auditory ossicles, three per ear, are not considered to be part of the axial or appendicular skeletons, but rather a separate group of bones. They were placed in the axial skeleton group for convenience.

Figure 2-3Vertebral column (lateral view)

Cervical curve (7 vertebrae)

Thoracic curve (12 vertebrae)

Lumbar curve (5 vertebrae)

Sacrum(5 fused vertebrae)

Coccyx (4 fused vertebrae)

7th cervical vertebra

1st thoracic vertebra

Intervertebral disc

1st lumbar vertebra

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connection with the axial skeleton allows the pectoral girdle to express a wide range of movements at the shoulder. In contrast, the pelvic girdle (ilium, ischium, and pubis—known collectively as the os coxae) does support the body’s weight and therefore has more extensive attachments to the axial skeleton through its articulation with the sacrum (see Figure 2-2). Furthermore, each side of the pelvic girdle is united by a strong joint made of cartilage called the pubic symphysis.

ArticulationsThe bones of the skeleton come to

together at articulations (joints.) When two bones meet at a junction, they are said to “articulate” with each other (for example, the femur articulates with the tibia). While most joints allow movement between two bones, there are many that permit little, if any, movement. The three main types of joints are fibrous, cartilaginous, and synovial. Fibrous joints are held tightly together by fibrous connective tissue and allow little or no movement. An example of a fibrous joint is an immoveable suture of the skull (see Figure 2-2). In cartilaginous joints, the bones are connected by cartilage and little or no movement is allowed. The junctions between the bodies of adjacent vertebrae are examples of cartilaginous joints (see Figure 2-3).

The most common type of joint in the body are synovial joints, which are freely moveable. Synovial joints move based on the shapes of their bony structures and their articular surfaces. A joint’s axis of rotation allows it to move in various planes where the plane of movement is generally perpendicular to the axis. There are four general groups of movements that occur in synovial joints throughout the body: gliding, angular, circumduction, and rotation.

In gliding, the surfaces of two adjoining bones move back and forth upon each other. An example of a gliding joint is the articulation between the head of a rib and the body of its associated vertebra. Angular movement describes an increase or decrease between two adjoining bones. There are four angular movements defined for synovial joints: flexion, extension, abduction, and adduction.

Flexion describes movement in which the bones comprising a joint move toward each other, decreasing the joint angle between them. An example is bringing the forearm upward toward the upper arm, as in elbow flexion. Extension is the opposite of flexion and causes the angle between two adjoining bones to increase. An example is starting with the calf upward toward the back of the thigh and moving it downward away from the thigh, as in knee extension (Figure 2-4). Abduction occurs when a part of the body is moved away from the midline of the body, such as lifting an arm or leg away from the side of the body. Adduction is the opposite of abduction and refers to movement of a body part toward the midline of the body, such as lowering an arm or leg from an abducted position downward toward the side of the body (Figure 2-5).

Certain joints, such as the shoulder and hip, are capable of incorporating all four angular movements to create one motion called circumduction. That is, the movement is actually a sequential combination of flexion, extension, abduction, and adduction. An easy way to remember circumduction is to picture a swimmer performing arm circles as a warm-up prior to diving in the pool. The circular motion represents circumduction of the shoulder joints.

Rotation describes motion of a bone around a central (longitudinal)

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Figure 2-4Segmental movements in the sagittal plane (Redrawn from Biomechanics, 3rd ed., Kreighbaum, E. & Barthels, K. Copyright © 1990 by Macmillan Publishing Company. Reprinted by permission of Pearson Education, Inc.)

Mediolateral axis (vertebral column)

ExtensionFlexion

Vertebral column

Mediolateral axis (shoulder joint)

Flexion

Shoulder joint

Mediolateral axis (elbow joint)

Flexion

Extension

Elbow joint

Extension

Flexion

Extension Flexion

Hip joint

Mediolateral axis (hip joint)

Mediolateral axis (knee joint)

Knee joint

Dorsiflexion

Plantarflexion

Ankle joint

Mediolateral axis (ankle)

Extension

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axis. From the anatomical position, movement of the anterior surface of the humerus or femur inward is called internal (medial) rotation. Conversely, movement of the anterior surface of humerus or femur outward is called external (lateral) rotation. A specific type of rotation, called pronation and supination, occurs at the radioulnar joint. Rotating the forearm outward so the palm faces anteriorly is supination, whereas rotation of the forearm inward so the palm faces posteriorly is pronation. Anatomical position,

therefore, requires supination of the forearm. Rotation around a longitudinal axis also includes rotation of the spine (Figure 2-6). A summary of all the synovial joint fundamental movements is presented in Table 2-4.

Muscular System

Muscle tissue is categorized into different types based on its function, is controlled both

voluntarily and involuntarily, and is able to produce various levels of force based on its size and shape. One property that all muscle tissue has in common is its ability to contract and develop tension. There are three types of muscle tissue—skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle attaches to the skeleton and, through contraction, exerts force on the bones and moves them. Skeletal muscle is considered voluntary muscle because it is normally under the conscious control of the indi-vidual. When viewed under a microscope, skeletal muscle tissue exhibits alternating light and dark bands, giving it a striped appearance. This characteristic is the reason skeletal muscle is also called stri-ated muscle. Smooth muscle is found in the walls of hollow organs and tubes, such as the stomach, intestines, and blood vessels, and functions to regu-late the movement of materials through the body. It is named smooth muscle because it lacks the striated appearance of skeletal muscle and, because it is not under conscious control, it is considered involuntary. Cardiac muscle forms the wall of the heart and is a very special-ized tissue that functions to maintain the constant pumping action of the heart. Cardiac tissue is involuntary, like smooth muscle, and is striated in appearance, just like skeletal muscle.

Fundamentally, skeletal muscles perform their required tasks by pulling on bones to create joint movement.

Figure 2-5Segmental movements in the frontal plane (Redrawn from Biomechanics, 3rd ed., Kreighbaum, E. & Barthels, K. Copyright © 1990 by Macmillan Publishing Company. Reprinted by permission of Pearson Education, Inc.)

Anteroposterior axis (shoulder joint)

Abduction

Adduction

Anteroposterior axis (hip joint)

Abduction

Adduction

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Figure 2-6Segmental movements in the transverse plane (Redrawn from Biomechanics, 3rd ed., Kreighbaum, E. & Barthels, K. Copyright © 1990 by Macmillan Publishing Company. Reprinted by permission of Pearson Education, Inc.)

Longitudinal axis (hip joint) Longitudinal

axis (shoulder joint)

Lateral rotation of the femur

Lateral rotation of the humerus

Longitudinal axis (shoulder joint)

Longitudinal axis (hip joint)

Medial rotation of the femur

Medial rotation of the humerus

Shoulder and hip joints

Right rotation

Transverse rotation (vertebral column)

Left rotation

Longitudinal axis (radioulnar joint)

Supination Pronation

Radionunar joint Vertebral Column

Longitudinal axis (vertebral column)

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That is, when a muscle contracts, its origin and insertion attachments move closer together. In contrast, when a muscle is stretched, its origin and insertion points move further apart. Each joint movement incorporates all of the supporting structures surrounding it. Pairings of muscles called agonists and antagonists help to illustrate this point. A muscle that creates a major movement is called a prime mover, or agonist. The muscle on the opposite side of the joint is called an opposing muscle, or an antagonist. For example, the quadriceps muscle group in the front of the thigh produces knee extension. When the quadriceps contracts to extend the knee, it is

considered the agonist muscle group, whereas the hamstrings (antagonist) group is being stretched on the opposite side of the joint. This type of functional pairing of muscle groups is found throughout the body.

Major Skeletal MusclesCertain criteria are used in the naming

of a muscle such as its shape, size, and location in the body. Familiarizing yourself with these criteria will help you as you go through the process of finding specific muscles and learning their locations.

Shape:• The names of certain muscles include references to their shape. For example, the rhomboids

Table 2-4 Fundamental Movements (From Anatomical Position)

Plane Action Definition

Sagittal Flexion Decreasing the angle between two bones

Extension Increasing the angle between two bones

Dorsiflexion Moving the top of the foot toward the shin (only at the ankle joint)

Plantarflexion Moving the sole of the foot downward; “pointing the toes” (only at the ankle)

Frontal Abduction Motion away from the midline of the body (or part)

Adduction Motion toward the midline of the body (or part)

Elevation Moving to a superior position (only at the scapula)

Depression Moving to an inferior position (only at the scapula)

Inversion Lifting the medial border of the foot (only at the subtalar joint)

Eversion Lifting the lateral border of the foot (only at the subtalar joint)

Transverse Rotation Internal (inward) or external (outward) turning about the vertical axis of bone

Pronation Rotating the hand and wrist medially from the elbow

Supination Rotating the hand and wrist laterally from the elbow

Horizontal flexion From a 90-degree abducted arm position, the humerus is flexed in, toward the midline of the body in the transverse plane

Horizontal extension The return of the humerus from horizontal flexion

Multiplanar Circumduction Motion that describes a “cone”; combines flexion, abduction, extension, and adduction in sequence

Opposition Thumb movement unique to humans and primates

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is supported by muscle tissue. Thus, the main function of shoulder girdle muscles is to anchor the scapulae. When the scapula is immobilized, it serves as a stable point of origin for the muscles that move the humerus. Major muscles that anchor the scapula in the back are the trapezius and rhomboids. The shape of the trapezius allows it to perform several distinct actions. If the upper portion contracts, the scapula is elevated, as in shrugging the shoulders. In contrast, if the lower portion contracts, depression—or lowering—of the scapula occurs. When all parts of the trapezius are working together, they tend to pull upward and adduct the scapulae at the same time. The rhomboid muscles are also responsible for adducting the scapulae (Figure 2-7). Table 2-5 lists select shoulder girdle muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Muscles of the ShoulderThe most mobile joint in the body,

the shoulder joint consists of the articulation of the head of the humerus with the scapula. The support and stability of the shoulder joint comes mainly from a group of four muscles called the rotator cuff (supraspinatus, infraspinatus, subscapularis, and teres minor). They can be remembered using the acronym SITS (Figure 2-10). The deltoid is a large muscle that forms a cap over and around the shoulder (Figure 2-11). Because its fibers pass in front of, directly over, and in back of the shoulder, the deltoid’s actions are varied, with some of the actions being antagonistic to each other. The deltoid muscle produces shoulder flexion, abduction, or extension, depending on the position of the upper arm during the movement. The latissimus dorsi muscle is located in the mid- to lower-back (Figure 2-12). It is one of the most

muscles resemble the geometric shape of a rhomboid.Action:• Some muscle names include references to their actions in the body. For example, the levator scapula muscle elevates the scapula (shoulder blade).Location: • Certain muscles can be located by a reference to location in their names. For example, the anterior tibialis muscle is located on the front side of the tibia.Attachments:• The points of origin and insertion of some muscles can be deciphered in their names. For example, the brachioradialis muscle originates on a bone in the brachium—which means upper arm—and inserts on the radius bone.Number of divisions:• Muscle names sometimes refer to the number of divisions that make up their structure. For example, the triceps brachii muscle is so named because it is an arm muscle consisting of three heads.Size relationships:• A description of a muscle’s size in relation to other muscles is sometimes found in muscle names. For example, the gluteus maximus is a larger muscle than the gluteus minimus.

Muscles of the Upper ExtremityAlthough this is not a complete review

of every muscle in the upper extremity, this section covers a selection of commonly used major muscle groups that contribute to movement at the scapula, shoulder, and elbow.

Muscles of the Shoulder GirdleThe shoulder girdle consists of the

clavicles, sternum, scapulae, and heads of the humerus (see Figure 2-2). The muscles that act on the scapulae are those of the shoulder girdle. Since the scapulae have no bony articulation with the rib cage, the scapulothoracic “joint”

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Muscles of the Elbow

The articulations of the humerus with the radius and ulna comprise the elbow joint. Additionally, the articulation of the radius and ulna with each other must also be considered since these two bones are responsible for pronation and supination of the forearm. Actions that occur at the elbow joint primarily come from contractions of muscles located

important, powerful extensor muscles of the upper arm. The pectoralis major is a large, fan-shaped muscle that lies on top of the chest wall (see Figure 2-11). Its position allows it to effectively work together with the latissimus dorsi to adduct the arm from a raised, abducted position. Table 2-6 lists select shoulder muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Table 2-5 Select Shoulder Girdle Muscles and Primary Actions

Muscle Primary Action Exercise Example

Trapezius Elevate the scapula (slide shoulder blade upward)

Adduct the scapula (slide shoulder blade toward the spine)

Shoulder shrug (Figure 2-8)

Shoulder retraction (Figure 2-9)

Rhomboids Adduct the scapula

Shoulder retraction

Upper trapezius

Middle trapezius

Lower trapezius

Rhomboid minor

Rhomboid major

Figure 2-7Select muscles of the shoulder girdle

Figure 2-8Shoulder shrug

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in the upper arm. The front upper-arm muscle—the biceps brachii—and the back upper-arm muscle—the triceps brachii—are responsible for powerful forearm movements (see Figure 2-11; Figure 2-17). The biceps brachii flexes the elbow, whereas the triceps brachii extends the elbow. The brachioradialis, the bulk of which is located in the forearm, also acts to flex the elbow. Table 2-7 lists select elbow muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Muscles of the TrunkThe major muscles of the trunk

that support, stabilize, and move the spine are presented in this section. These include the muscles of the abdominal wall (rectus abdominis, external obliques, internal obliques, and transverse abdominis) and the muscles that are located on the posterior surface of the spine (erector spinae). The abdominal wall has no skeletal structures to support it and therefore must rely on strength from the multidirectional layers of muscles comprising it. The rectus abdominis is a superficial, flat muscle located on the front of the abdominal wall that primarily flexes the trunk forward (Figure 2-20). The external obliques make up the outermost layer of the abdominal wall, whereas the internal obliques lie just deep to the external oblique (see Figure 2-20). The oblique muscles work together in rotation of the trunk. That is, rotation of the trunk to the right involves simultaneous contraction of the right internal oblique and the left external oblique. Although rotating the trunk is a primary movement of the obliques, another important role they play is to stabilize the spine. In fact, a safe and effective approach to exercising the abdominal obliques is to perform stability exercises such as the side-

Figure 2-9Shoulder retraction

a. Maintain neutral spine and pull the scapulae toward the spine, keeping the elbows straight and arms hanging down

b. Maintain neutral spine and pull the scapulae together with the elbows slightly bent and the wrists neutral

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Supraspinatus

Humerus

Subscapularis

Supraspinatus

Infraspinatus

Scapula

Humerus

Teres minor

Posterior view of supraspinatus, infraspinatus, and teres minor

Anterior view of subscapularis

ClavicleFigure 2-10Rotator cuff muscles

Figure 2-11Select muscles of the anterior chest, shoulder, and arm

Clavicle

Deltoid

Pectoralis major (sternal portion)

Biceps brachii

BrachioradialisSternum

Pectoralis major (clavicular portion)

Figure 2-12Select muscles of the posterior shoulder and back

Deltoid (anterior)

(middle)

(posterior)

Humerus

Teres major

Infraspinatus

Latissimus dorsi

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Figure 2-13 Overhead shoulder press

Figure 2- 14 Prone rear deltoid pull

Table 2-6 Select Shoulder Muscles, Primary Actions, and Exercise Examples


Rotator cuff Stabilizing the shoulder during different activities Maintaining proper posture throughout all exercises

Deltoid Shoulder flexion (bringing the arm forward in front of the body)Shoulder abduction (bringing the arm out to the side of the body)Shoulder extension (bringing the arm backward behind the body)

Overhead shoulder press (Figure 2-13)Prone rear deltoid pull (Figure 2-14)

Latissimus dorsi Shoulder extensionShoulder adduction (bringing the arm from an abducted position toward the midline of the body)

Lat pull-down (Figure 2-15)

Pectoralis major Shoulder flexionShoulder adduction

Pec fly (Figure 2-16)

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Figure 2-16Pec fly

Figure 2-15Lat pull-down

Long head

Medial head

Lateral head

Long head

Olecranonprocess

Figure 2-17Three heads of the triceps brachii muscle

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transverse abdominis acts to compress the abdominal cavity, stabilize the lower back and pelvis, and assist in forced exhalation. Because its fibers are oriented horizontally, their contraction reduces the diameter of the abdomen (“suck in the gut”). The back muscles that run vertically from the sacrum to the skull are known as the erector spinae (Figure 2-22). Table 2-8 lists select trunk muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Muscles of the Lower ExtremityCompared to the musculature of the

upper limbs, the muscles of the lower extremity tend to be bulkier and more powerful to serve their functions in

Table 2-7 Select Elbow Muscles, Primary Actions, and Exercise Examples


Biceps brachii

Elbow flexion (bringing the forearm closer to the upper arm)

Biceps curl (Figure 2-18)

Triceps brachii

Elbow extension (moving the forearm away from the upper arm)

Triceps extension (Figure 2-19)

Figure 2-18Biceps Curl

Figure 2-19Triceps extension

lying bridge (Figure 2-21). The deepest muscle of the abdominal wall is the transverse abdominis, which has fibers that run horizontally, encircling the abdominal cavity (see Figure 2-20). The

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shaped space created by the adjoining of the three pelvic bones—the ilium, ischium, and pubis). A front view of the hips and pelvis reveals the iliopsoas, rectus femoris, and adductor group. A back viewpoint shows the gluteus maximus, gluteus medius, gluteus minimus, and the hamstrings muscles.

Most of the muscles that act at the hip arise from the pelvis. One muscle, the iliopsoas, originates from the lumbar vertebrae and the pelvis (Figure 2-26). The iliopsoas is primarily responsible for flexing the hip. The rectus femoris muscle is part of the quadriceps femoris muscle group and is the only one that acts at both the hip and the knee (the other quadriceps

standing and weightbearing activities. The muscles of the lower limbs are somewhat less moveable than those of the upper limbs, but they provide relatively more strength and stability. Additionally, the pelvis is fully supported by the skeleton, whereas the shoulder girdle relies more on soft-tissue structures for stability and strength. Although this is not a complete review of every muscle in the lower extremity, this section covers a selection of major muscle groups that contribute to movement at the hip, knee, and ankle.

Muscles of the HipThe hip joint is made up of the head of

the femur and the acetabulum (the cup-

Figure 2-20Muscles of the abdominal wall

External oblique

Internal oblique

Rectus abdominis

Transverse abdominis(deepest layer)

Tendinous inscriptions

Figure 2-21Side-lying torso bridge

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Table 2-8 Select Trunk Muscles, Primary Actions, and Exercise Examples


Rectus abdominis Spine flexion (bending forward from the trunk)

Abdominal curl (Figure 2-23)

Internal and external obliques

Spine rotation (twisting the trunk)Spine stabilization

Side-lying torso bridge (see Figure 2-21)

Transverse abdominis Abdominal compression (drawing the navel in toward the spine; “sucking in the gut”)Spine and pelvis stabilization

Maintaining proper posture throughout all exercises

Erector spinae Spine extension (bending backward from the trunk)

Trunk extension (Figure 2-24)Birddog (Figure 2-25)

Figure 2-22Extensor muscles of the spine

Longissimus capatis

Spinalis cervicis

Longissimus cervicis

Illiocostalis cervicis

Spinalis thoracis

Illiocostalis lumborum

Longissimus thoracis

Illiocostalis thoracis

Semispinalis capitis

Semispinalis cervicis

Semispinalis thoracis

Multifidus

(Superficial layer) (Deep layer)

Figure 2-23Abdominal curl

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Figure 2-27Medial thigh muscles

Adductor brevis

Adductor longus

Adductor magnus

Muscles that are observed when looking at the pelvis from the back include the three gluteal muscles. The gluteus maximus is the largest and most superficial hip muscle and is primarily responsible for extending the hip (Figure 2-28). Underneath the gluteus maximus is the smaller gluteus medius. Underneath the gluteus medius is the still smaller gluteus minimus (Figure 2-29). The gluteus medius and minimus muscles function to abduct the hip. The hamstrings muscles are located in the back of the thigh and are considered both hip and knee muscles because they have functions at both joints (see Figure 2-28). The hamstrings mainly work to extend the hip and flex the knee. Table 2-9 lists select hip muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Muscles of the KneeThe femur and the tibia and fibula make

up the knee joint. The muscles located in the thigh are responsible for movement

muscles act only at the knee) (see Figure 2-26). The rectus femoris functions to flex the hip and extend the knee. Another group of hip muscles that can be seen when looking at the body from the front is the adductor group. As the name indicates, they act primarily to adduct the hip (Figure 2-27).

Figure 2-24Trunk extension

Figure 2-25Birddog

12th rib

5th lumbar vertebra

Iliac crest

Anterior superior iliac spine

Quadriceps

Rectus femoris

Vastus lateralis

Vastus medialis

Tendon of quadriceps femoris

Patella

12th thoracic vertebra

Iliopsoas

Figure 2-26Select anterior muscles of the hip and knee

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Table 2-9 Select Hip Muscles, Primary Actions, and Exercise Examples


Iliopsoas Hip flexion (bringing the knee closer to the chest; decreasing the angle between the pelvis and the upper thigh)

Squat (Figure 2-30)

Rectus femoris Hip flexionKnee extension (straightening the knee)

Lunge (Figure 2-31)

Adductors Hip adduction (bringing the thigh toward the midline of the body from an abducted position)

Standing cable hip adduction (Figure 2-32)

Gluteus maximus

Hip extension (bringing the thigh backward behind the body; increasing the angle between the pelvis and the upper thigh)

SquatLungeHip extension bridge (Figure 2-33)

Gluteus medius and minimus

Hip abduction (lifting the thigh outward away from the midline of the body)

Side-lying leg lifts (Figure 2-34)

Hamstrings Hip extensionKnee flexion (bending the knee)

SquatLungeHip extension bridge

Semitendinosus

Semimembranosus

Medial head(Gastrocnemius)

Iliac crest

Gluteus medius

Gluteus maximus

Hamstrings

Long head

Short head

Lateral head(Gastrocnemius)

Biceps femoris

Figure 2-28Select posterior hip and thigh muscles

Figure 2-29Abductors of the posterior hip.

Gluteus medius

Gluteus minimus (deep to gluteus medius)

at the knee, with the exception of the gastrocnemius, which is located in the calf. The front of the thigh contains the quadriceps femoris muscle group, which is primarily responsible for extending the knee—except for the rectus femoris, which functions to both extend the knee and flex the hip (see Figure 2-26). The back part of the thigh contains the hamstrings (see Figure 2-28). These muscles were mentioned earlier for their functions at both the hip and knee joints. Table 2-10 lists select knee muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Muscles of the AnkleThe ankle joint, which is composed

of the tibia, fibula, and talus, acts as hinge that allows only dorsiflexion and plantarflexion. The muscles contained in the lower leg control movements at the ankle. The front compartment of the lower leg contains the anterior tibialis,

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Figure 2-30Squat

Figure 2-31Lunge

Figure 2-32Standing cable hip adduction

Figure 2-33Hip extension bridge

Figure 2-34Side-lying leg lifts

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which mainly works to dorsiflex the ankle (Figure 2-36). The muscles of the calf include the gastrocnemius and soleus, which both function to plantarflex the ankle (Figure 2-37). The gastrocnemius and soleus make up the bulk of the calf and share a common insertion, the Achilles tendon. Table 2-11 lists select ankle muscles and their primary actions, as well as exercise examples for each muscle or muscle group.

Table 2-10 Select knee muscles and primary actions


Quadriceps Knee extension SquatLungeLeg extension (Figure 2-35)

Hamstrings Hip extensionKnee flexion

SquatLungeHip extension bridge

Anterior tibialis

Figure 2-36Select anterior tibial compartment muscles

Figure 2-35Leg extension

Summary

This chapter provides a brief region-by-region summary of the basic anatomy and movements of the

trunk and upper and lower extremities. With this information, a fitness profes-sional has at his or her disposal a basic overview of specific exercises and physi-cal activities that will safely and efficiently accomplish the goals of most exercise participants.

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Table 2-11 Select Ankle Muscles, Primary Actions, and Exercise Examples


Anterior tibialis Ankle dorsiflexion (lifting the toes upward toward the shin; decreasing the angle between the top of the foot and the shin)

Toe lifts (Figure 2-38)

Gastrocnemius Knee flexionAnkle plantarflexion (pointing the toes downward; increasing the angle between the top of the foot and the shin)

Heel lifts (Figure 2-39)

Soleus Ankle plantarflexion Heel lifts

Figure 2-37Posterior tibial compartment muscles

Gastrocnemius

Soleus

Achilles tendon

Calcaneus

Gastrocnemius origins

Popliteus

Figure 2-39Heel lifts

Figure 2-38Toe lifts

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straight line, thereby increasing the angle of the joint, such as straightening the elbow; opposite of flexion.

Fibrous joints Immoveable joints joined together by dense connective tissue.

Flexion Movement about a joint in which the bones on either side of the joint are brought closer to each other; opposite of extension.

Ground reaction forces Forces exerted by the ground on a body in contact with the ground.

Lumbar vertebrae The five vertebrae in the low back, just below the thoracic vertebrae and just above the sacrum.

Prime mover A muscle responsible for a specific movement.

Pronation Internal rotation of the forearm causing the radius to cross diagonally over the ulna and the palm to face posteriorly.

Sacrum Part of the axial skeleton; five vertebrae just below the lumbar vertebrae that are fused together into one bone.

Supination External rotation of the forearm (radioulnar joint) that causes the palm to face anteriorly.

Synovial joint Specialized form of articulation permitting more or less free movement; the union of the bony elements being surrounded by an articular capsule enclosing a cavity lined by a synovial membrane.

Thoracic vertebrae The 12 vertebrae to which the ribs are attached.

Wolff’s law Principle stating that bone is capable of adjusting its strength in proportion to the amount of stress (or repeated exercise) to which it is exposed.

Glossary

Abduction Movement of a body part away from the midline of the body; opposite of adduction.

Adduction Movement of a body part toward the midline of the body; opposite of abduction.

Agonist A muscle that directly engages in contraction; opposes the action of antagonist muscles.

Anatomical position Standing erect with the feet and palms facing forward; a reference point for anatomical locations and movements.

Antagonist A muscle that act in opposition to the action produced by agonist muscles.

Appendicular skeleton The 126 bones that form the extremities.

Articulation The point of contact or connection between bones or between bones and cartilage; also called a joint.

Axial skeleton The bones of the head, neck, and trunk.

Axis of rotation The imaginary line or point about which an object, such as a body or lever, rotates.

Cartilaginous joints Joints in which the bones are united by cartilage, providing either slight flexible movement or allowing growth.

Cervical vertebrae The seven vertebral bones of the neck.

Circumduction The active or passive circular movement of a joint; a combination of flexion, abduction, extension, and adduction movements.

Coccyx The four small vertebral bones making up the “tailbone.”

Extension Movement at a joint that brings two parts into, or toward, a

basic anatomy and movement - ace · basic anatomy and movement connection with the axial skeleton...

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