Basic Anatomy and Movement

Transcription

1 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 anatomē, which means dissection or to cut apart. Originally, anatomical understanding came largely from observations of dissected plants and animals. For the purposes of this chapter, basic skeletal muscle anatomy is presented. Primary muscle groups commonly used in fitness programs are described, as well as suggested exercises for working those muscles in an exercise setting. Anatomical Terminology Learning 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

2 Basic Anatomy and Movement 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. Table 2-1 Anatomical, Directional, and Regional Terms Term Definition Term Definition Anterior (ventral) Posterior (dorsal) Superior Inferior Medial Lateral Proximal Distal Cervical Thoracic Lumbar Plantar Dorsal Toward the front Toward the back Toward the head Away from the head Toward the midline of the body Away from the midline of the body Toward the attached end of the limb, origin of the structure, or midline of the body Away from the attached end of the limb, origin of the structure, or midline of the body Regional term referring to the neck Regional term referring to the portion of the body between the neck and abdomen; also known as the chest (thorax) Regional term referring to the low back; the portion between the abdomen and the pelvis The sole, or bottom, of the feet The top surface of the feet and hands 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 joint Bi Two, both Bilateral On both sides Brachium Arm Brachialis Muscle of the arm Cardio Heart Cardiology The study of the heart Cephalo Head Cephalic Pertaining to the head Chondro Cartilage Chondroectomy Excision of a cartilage Costo Rib Costochondral Pertaining to a rib and its cartilage Dermo Skin Dermatitis Inflammation of the skin Hemo, hemato Blood Hemorrhage Internal or external bleeding Ilio Pelvis or hip Ilium The wide, upper part of the pelvic bone Myo Muscle Myositis Inflammation of a muscle Os, osteo Bone Osteopenia Loss of bone mineral Pulmo Lung Pulmonary artery Vessel that brings blood to the lungs Thoraco Chest Thorax Chest Tri Three Triceps brachii Three-headed muscle on the arm 21 ACE Fitness Service Specialist

3 Basic Anatomy and Movement Chapter 2 Superior Dorsal (back side) Ventral (front side) Medial Lateral Inferior Transverse Plane Frontal Plane Sagittal Plane Skeletal System The human skeleton is an active, living tissue that performs several 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 phalanges. 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 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, vertebrae, 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 Figure 2-1 Anatomical reference position and planes of motion ACE Fitness Service Specialist 22

4 Basic Anatomy and Movement Figure 2-2 Skeletal system Skull Cranium Face Greater tubercle of humerus Medial epicondyle of humerus Lateral epicondyle of humerus Vertebral column Pelvic girdle Greater trochanter of femur Pubis Ischial tuberosities Acromion process of scapula Shoulder girdle Clavicle Scapula Thorax Sternum Ribs Upper extremity Humerus Ulna Radius Carpals Phalanges Metacarpals Ischium Spine of scapula Deltoid tubercle of humerus Olecranon process of ulna Vertebral column Ilium Sacrum Lesser trochanter of femur Tibial tuberosity Metatarsals Phalanges Lower extremity Femur Patella Tibia Fibula Tarsals Lateral condyle of femur Medial condyle of femur anterior view posterior view professionals can play a crucial role in helping clients preserve bone tissue by educating them about the importance of exercise and proper nutrition. Axial Skeleton Of 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 23 ACE Fitness Service Specialist

5 Basic Anatomy and Movement Chapter 2 Table 2-3 Bones in the Axial and Appendicular Skeletons Axial Skeleton Skull Cranium 8 Face 14 Hyoid 1 Number of Bones 7th cervical vertebra 1st thoracic vertebra Intervertebral disc Cervical curve (7 vertebrae) Thoracic curve (12 vertebrae) Figure 2-3 Vertebral column (lateral view) Vertebral Column 26 Thorax Sternum 1 Ribs 24 (Auditory ossicles)* st lumbar vertebra Lumbar curve (5 vertebrae) 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 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. 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 Sacrum (5 fused vertebrae) Coccyx (4 fused vertebrae) 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 Skeleton The 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 ACE Fitness Service Specialist 24

6 Basic Anatomy and Movement 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. Articulations The 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) 25 ACE Fitness Service Specialist

7 Basic Anatomy and Movement Chapter 2 Extension Flexion Mediolateral axis (shoulder joint) Mediolateral axis (vertebral column) Mediolateral axis (elbow joint) Flexion Flexion Extension Extension Vertebral column Shoulder joint Elbow joint Mediolateral axis (hip joint) Mediolateral axis (knee joint) Figure 2-4 Segmental 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.) Flexion Knee joint Extension Flexion Extension Hip joint Dorsiflexion Mediolateral axis (ankle) Plantarflexion Ankle joint ACE Fitness Service Specialist 26

8 Basic Anatomy and Movement Figure 2-5 Segmental 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 (hip joint) Abduction Anteroposterior axis (shoulder joint) Adduction Abduction Adduction 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 individual. 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 striated muscle. Smooth muscle is found in the walls of hollow organs and tubes, such as the stomach, intestines, and blood vessels, and functions to regulate 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 specialized 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. 27 ACE Fitness Service Specialist

9 Basic Anatomy and Movement Chapter 2 Radionunar joint Longitudinal axis (radioulnar joint) Vertebral Column Longitudinal axis (vertebral column) Left rotation Figure 2-6 Segmental 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.) Right rotation Supination Pronation Transverse rotation (vertebral column) Medial rotation of the humerus Shoulder and hip joints Lateral rotation of the humerus Longitudinal axis (shoulder joint) Longitudinal axis (hip joint) Longitudinal axis (hip joint) Longitudinal axis (shoulder joint) Medial rotation of the femur Lateral rotation of the femur ACE Fitness Service Specialist 28

10 Basic Anatomy and Movement 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 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 Muscles Certain 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 29 ACE Fitness Service Specialist

11 Basic Anatomy and Movement Chapter 2 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 Extremity Although 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 Girdle The 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 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 Shoulder The 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 lowerback (Figure 2-12). It is one of the most ACE Fitness Service Specialist 30

12 Basic Anatomy and Movement Figure 2-7 Select muscles of the shoulder girdle Upper trapezius Middle trapezius Rhomboid minor Lower trapezius Rhomboid major 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 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. Figure 2-8 Shoulder shrug 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 31 ACE Fitness Service Specialist

13 Basic Anatomy and Movement Chapter 2 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. 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 Figure 2-9 Shoulder retraction Muscles of the Trunk The 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- ACE Fitness Service Specialist 32

14 Basic Anatomy and Movement Figure 2-10 Rotator cuff muscles Clavicle Supraspinatus Humerus Supraspinatus Subscapularis Infraspinatus Humerus Anterior view of subscapularis Scapula Posterior view of supraspinatus, infraspinatus, and teres minor Teres minor Figure 2-11 Select muscles of the anterior chest, shoulder, and arm Clavicle Deltoid Pectoralis major (clavicular portion) Pectoralis major (sternal portion) Biceps brachii Brachioradialis Sternum Deltoid (anterior) (middle) (posterior) Humerus Teres major Infraspinatus Latissimus dorsi Figure 2-12 Select muscles of the posterior shoulder and back 33 ACE Fitness Service Specialist

15 Basic Anatomy and Movement Chapter 2 Table 2-6 Select Shoulder Muscles, Primary Actions, and Exercise Examples Muscle Primary Action Exercise Example Rotator cuff Stabilizing the shoulder during different activities Maintaining proper posture throughout all exercises Deltoid Latissimus dorsi Pectoralis major 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) Shoulder extension Shoulder adduction (bringing the arm from an abducted position toward the midline of the body) Shoulder flexion Shoulder adduction Overhead shoulder press (Figure 2-13) Prone rear deltoid pull (Figure 2-14) Lat pull-down (Figure 2-15) Pec fly (Figure 2-16) Figure 2-13 Overhead shoulder press Figure 2-14 Prone rear deltoid pull ACE Fitness Service Specialist 34

16 Basic Anatomy and Movement Figure 2-15 Lat pull-down Figure 2-16 Pec fly Long head Medial head Lateral head Long head Olecranon process Figure 2-17 Three heads of the triceps brachii muscle 35 ACE Fitness Service Specialist

17 Basic Anatomy and Movement Chapter 2 Table 2-7 Select Elbow Muscles, Primary Actions, and Exercise Examples Muscle Primary Action Exercise Example Biceps brachii Elbow flexion (bringing the forearm closer to the upper arm) Biceps curl (Figure 2-18) Figure 2-19 Triceps extension Triceps brachii Elbow extension (moving the forearm away from the upper arm) Triceps extension (Figure 2-19) Figure 2-18 Biceps Curl 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 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 Extremity Compared 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 ACE Fitness Service Specialist 36

18 Basic Anatomy and Movement 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 Hip The hip joint is made up of the head of the femur and the acetabulum (the cup- 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 Figure 2-20 Muscles of the abdominal wall External oblique Rectus abdominis Internal oblique Transverse abdominis (deepest layer) Tendinous inscriptions Figure 2-21 Side-lying torso bridge 37 ACE Fitness Service Specialist

19 Basic Anatomy and Movement Chapter 2 (Superficial layer) Spinalis cervicis Longissimus cervicis Longissimus capatis (Deep layer) Semispinalis capitis Semispinalis cervicis Figure 2-22 Extensor muscles of the spine Illiocostalis cervicis Spinalis thoracis Longissimus thoracis Illiocostalis thoracis Illiocostalis lumborum Semispinalis thoracis Multifidus Table 2-8 Select Trunk Muscles, Primary Actions, and Exercise Examples Muscle Primary Action Exercise Example Rectus abdominis Internal and external obliques Transverse abdominis Erector spinae Spine flexion (bending forward from the trunk) Spine rotation (twisting the trunk) Spine stabilization Abdominal compression (drawing the navel in toward the spine; sucking in the gut ) Spine and pelvis stabilization Spine extension (bending backward from the trunk) Abdominal curl (Figure 2-23) Side-lying torso bridge (see Figure 2-21) Maintaining proper posture throughout all exercises Trunk extension (Figure 2-24) Birddog (Figure 2-25) Figure 2-23 Abdominal curl ACE Fitness Service Specialist 38

20 Basic Anatomy and Movement Figure 2-24 Trunk extension Adductor longus Adductor brevis Adductor magnus Figure 2-25 Birddog Figure 2-26 Select anterior muscles of the hip and knee 12th rib 5th lumbar vertebra Iliac crest Anterior superior iliac spine Quadriceps Rectus femoris Vastus lateralis Vastus medialis Tendon of quadriceps femoris Patella 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). 12th thoracic vertebra Iliopsoas Figure 2-27 Medial thigh muscles 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 Knee The femur and the tibia and fibula make up the knee joint. The muscles located in the thigh are responsible for movement 39 ACE Fitness Service Specialist

21 Basic Anatomy and Movement Chapter 2 Iliac crest Gluteus medius Gluteus medius Gluteus maximus Hamstrings Gluteus minimus (deep to gluteus medius) Semitendinosus Semimembranosus Long head Short head Biceps femoris Medial head (Gastrocnemius) Lateral head (Gastrocnemius) Figure 2-29 Abductors of the posterior hip. Figure 2-28 Select posterior hip and thigh muscles 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 Ankle The 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, Table 2-9 Select Hip Muscles, Primary Actions, and Exercise Examples Muscle Primary Action Exercise Example Iliopsoas Rectus femoris Adductors Gluteus maximus Gluteus medius and minimus Hamstrings Hip flexion (bringing the knee closer to the chest; decreasing the angle between the pelvis and the upper thigh) Hip flexion Knee extension (straightening the knee) Hip adduction (bringing the thigh toward the midline of the body from an abducted position) Hip extension (bringing the thigh backward behind the body; increasing the angle between the pelvis and the upper thigh) Hip abduction (lifting the thigh outward away from the midline of the body) Hip extension Knee flexion (bending the knee) Squat (Figure 2-30) Lunge (Figure 2-31) Standing cable hip adduction (Figure 2-32) Squat Lunge Hip extension bridge (Figure 2-33) Side-lying leg lifts (Figure 2-34) Squat Lunge Hip extension bridge ACE Fitness Service Specialist 40

22 Basic Anatomy and Movement Figure 2-30 Squat Figure 2-33 Hip extension bridge Figure 2-31 Lunge Figure 2-34 Side-lying leg lifts Figure 2-32 Standing cable hip adduction 41 ACE Fitness Service Specialist

23 Basic Anatomy and Movement Chapter 2 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. Summary This chapter provides a brief regionby-region summary of the basic anatomy and movements of the trunk and upper and lower extremities. With this information, a fitness professional has at his or her disposal a basic overview of specific exercises and physical activities that will safely and efficiently accomplish the goals of most exercise participants. Table 2-10 Select knee muscles and primary actions Muscle Primary Action Exercise Example Quadriceps Knee extension Squat Lunge Leg extension (Figure 2-35) Hamstrings Hip extension Knee flexion Squat Lunge Hip extension bridge Figure 2-36 Select anterior tibial compartment muscles Anterior tibialis Figure 2-35 Leg extension ACE Fitness Service Specialist 42

24 Basic Anatomy and Movement Figure 2-37 Posterior tibial compartment muscles Gastrocnemius origins Popliteus Gastrocnemius Soleus Achilles tendon Calcaneus Table 2-11 Select Ankle Muscles, Primary Actions, and Exercise Examples Muscle Primary Action Exercise Example Anterior tibialis Gastrocnemius Ankle dorsiflexion (lifting the toes upward toward the shin; decreasing the angle between the top of the foot and the shin) Knee flexion Ankle plantarflexion (pointing the toes downward; increasing the angle between the top of the foot and the shin) Toe lifts (Figure 2-38) Heel lifts (Figure 2-39) Soleus Ankle plantarflexion Heel lifts Figure 2-39 Heel lifts Figure 2-38 Toe lifts 43 ACE Fitness Service Specialist

25 Basic Anatomy and Movement Chapter 2 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 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. ACE Fitness Service Specialist 44