Dance Anatomy and Kinesiology Notes.

Principles and exercises for improving technique and avoiding common injuries, 2nd edition. Clippinger, Karen. Human Kinetics, 2016.

Human anatomy - the science of the structure of the human body

Kinesiology - the science of human motion.

Mechanics - a branch of physics concerned with energy and forces and their effect on bodies and motion. (p. ix)

Chapter 1: The Skeletal System and its Movements

Primary Tissues of the Body

There are four different primary tissue types: muscle, nervous, epithelial, and connective tissues.

Muscle tissue - has the ability to contract and is found in the heart, organs (smooth muscle), and in the skeletal mucles.

Nervous tissue - neurons are cells able to generate and conduct electrical messages; and neuroglia help support neurons.

Epithelial tissue - is composed of cells that fit closely together to form continuous sheets, or membranes, that cover and line surfaces of the body or form glands.

Connective tissue - functions to bind, support, insulate, and protect structures and can be further divided into connective tissue proper, cartilage, bone, and blood.

Organ - a structure that performs a specific function for the body and is composed of two to four of the primary tissues.

System - organs working closely together for a common function.

Skeletal system - composed of all of the bones of the body, related cartilages and ligaments, and the joints that connect these bones together.

Bone Composition and Structure

(pg3)

Bone contains inorganic minerals, mainly calcium salts, in the space between bone cells (extracellular matrix) that give bone its compressive strength (the ability to resist a force that would tend to push together or crush a bone). Bone also contains organic fibrous proteins called collagen fibers that give bone its tensile strength (the ability to resist a pulling force that would tend to pull a bone apart). These combined properties enable bones to support weight and withstand various forces during movement and impact.

• Osteoblasts - build new bone

• Osteoclasts - break down or remove bone

• Resorption - the breakdown or removal of bone

Functions of Bone

• Support: Provides an internal rigid framework for the body that is essential for stability and form.

• Protection: Shields vital organs from injury

• Movement: Bones assist with movement by forming the rigid links (levers) that are moved at joints when muscles contract.

• Blood Cell Production: Some bones contain tissue that is responsible for the production of blood cells.

• Mineral Storage: Various important minerals including calcium are stored within bones. Bone contains 99% of the calcium in the body.

Types of Bone

There are five types of bone that are classified based on their shape. Long bones, short bones, flat bones, irregular bones, and sesamoid bones.

• Long bones - bones that are longer than they are wide (tubular), providing support and facilitating movement by allowing the limbs to move through a large distance, at a fast speed, or both. Femur, tibia, fibula, metatarsals, phalanges, and parallel bones in the upper limbs.

• Short bones - bones that are approximately equal in length and width (cubical), that often articulate with more than one other bone, allowing them to aid with small complex movements and stability. Examples include the carpals in the wrists and the tarsals in the ankles.

• Flat bones - relatively thin and flat, although often curved in shape. They commonly protect important soft underlying structures, and their shape also allows for extensive attachment of muscles. Examples include the upper portion of the pelvis (ilium), some of the bones of the skull, and the ribs, sternum, and scapula.

• Irregular bones - exhibit complex and varied shapes that don’t fit well into other categories. They serve various functions that are often enhanced by their specialized shapes. Examples include the vertebrae and lower portion of the pelvis (ischium).

• Sesamoid bones - are bones that form within a tendon. They help protect the tendons they are within from excessive wear from the underlying bone. They also change the angle of the tendon so that the associated muscle can produce more effective force for movement. An example is the patella.

Structure of Bone

• The structure consists of two types: cortical (compact) bone, which is dense and forms the outer layer, and trabecular (spongy) bone, which is lighter and found within the interior of bones.

• Bones also contain marrow, which is crucial for blood cell production and fat storage.

Bone Development and Growth

Bone Growth and Remodeling

Bone and Physical Activity

Wolff’s law: changes in the internal architecture of bone and the external form of a bone occur in response to the magnitude and direction of forces acting on bones. bone is laid down where it is needed to resist the forces, while it is resorbed from areas where it is not subjected to stress. This principle highlights the importance of regular physical activity, as it stimulates bone density and strength, ultimately enhancing overall skeletal health.

Bone Changes with Aging

In healthy children, bone deposition outweighs bone resorption, resulting in net growth in bones. In young adults, bone resorption and bone deposition proceed at similar rates with bone mass reaching a maximum level between 25 and 30 years of age. In older adults, bone resorption predominates, which results in loss of bone density. Osteoporosis is a disease in which bone mineral density is so reduced that bone becomes fragile and susceptible to fracture.

Unfortunately, in older adults the loads associated with exercise do not have as potent an effect as in the growing skeleton, and bone may become desensitized to repetitive loading that occurs in a habitual manner. However, shorter periods of vigorous exercise that apply novel loading appear to reduce bone loss and may be helpful for prevention of osteoporosis.

Bone Health and the Female Athlete Triad

• The Female Athlete Triad refers to a syndrome characterized by three interrelated conditions: energy deficiency (with or without disordered eating), menstrual dysfunction, and decreased bone mineral density.

• Energy availability relates to insufficient dietary caloric intake relative to the calories expended with exercise (with or without disordered eating) and appears to negatively affect reproductive health and bone health (and increased risk of fractures).

• One preventative measure is to emphasize eating a nutrient-dense diet with adequate caloric and calcium content.

Stress Fractures

A stress fracture is a microscopic fracturing of the bone resulting in a thin crack that is so small it is not even initially apparent on an X-ray. When the bone undergoes excessive repetitive submaximal stress, it will weaken due to an increase in osteoclast activity that breaks down bone before laying down a stronger new bone matrix. This period of breaking down bone leaves it weaker and more susceptible to fractures. During this period if the stress on the bone is too much, then the outer portion of the bone may crack, creating a stress fracture. To help prevent stress fractures dancers should incorporate sound training principles and avoid overtraining, ensure they are eating a healthy and nutrient dense diet with adequate calcium intake, avoid smoking, and take swift medical referral when menstrual irregularities are present.

The Human Skeleton

The Axial and Appendicular Skeleton

Axial skeleton - forms the central upright axis of the skeleton and includes the skull, vertebral column, sternum, and 12 ribs.

Appendicular skeleton - includes the bones of the limbs (appendages) and can be subdivided into the paired upper extremity and paired lower extremity. The upper extremity includes the bones of the shoulder girdle, the clavicle, and the scapula, as well as the humerus, radius, ulna, and the bones of the hand. The lower extremity consists of the pelvic girdle (os coxae), femur, patella, tibia, fibula, and the bones of the foot.

Bony Landmarks

Bony landmarks are names given to distinguishing features or markings on a given bone. Bony landmarks can be important for body alignment evaluation, sites of muscle or ligament attachment, and the formation of joints.

Table 1.1 (pg 9)

Joint Architecture and Classification

Articulation - the connection between adjacent bones or cartilage of the human skeleton (joint). Function: they bind the skeleton together and provide mobility.

Classifications of joints:

Fibrous joints - hold adjacent bones tightly together by fibrous connective tissue such as the very short fibers found in sutures or the sheet-like arrangements found in interosseous membranes. Examples: sutures found in the skull (little movement, only give), and the interosseous membranes between the bones of the forearm (middle radioulnar joint) (hold the bones together with slight movement, allowing for rotation of the forearm).

Cartilaginous joints - these joints allow more movement between bones than fibrous joints but still restrict motion compared to synovial joints. They are connected entirely by cartilage (fibrocartilage or hyaline cartilage), which provides flexibility and shock absorption. Examples include the joints between the vertebrae (intervertebral discs) that permit limited movement and the pubic symphysis that allows some flexibility during childbirth.

Synovial Joints - these are the most movable type of joint in the body, characterized by a synovial/joint cavity filled with synovial fluid, which reduces friction and allows for smooth movement. They are surrounded by a joint capsule and often include ligaments for stability. Examples of synovial joints include the knee (hinge joint), elbow (hinge joint), hip (ball-and-socket joint), wrist, ankle, and shoulder (ball-and-socket joint), all of which provide a wide range of motion.

General Structure of a Synovial Joint:

• Joint cavity: A space that contains synovial fluid, allowing for lubrication between articulating surfaces.

• Articular cartilage: A smooth layer of (hyaline) cartilage that covers the ends of bones, facilitating low-friction movement and aiding in shock absorbency. Articular cartilage has the ability to adapt to stress - actually exuding some of its fluid in response to loading, spreading the load, and markedly reducing stress at any contact point.

• Joint capsule: A fibrous structure that surrounds the joint, providing stability and support while maintaining the integrity of the joint cavity. It is composed of an outer layer of dense (fibrous) connective tissue and an inner synovial membrane, which secretes synovial fluid to nourish the articular cartilage and further facilitate movement.

• Synovial membrane: A lining that produces synovial fluid to nourish and lubricate the joint.

• Ligaments: Strong bands of (fibrous) connective tissue that bind articulating together, providing stability and support.

Specialized Structures of Synovial Joints:

• Fibrocartilage disc: A type of cartilage that acts as a cushion between the bones in a joint, enhancing stability and absorbing shock during movement. In some joints this fibrocartilage structure is shaped more like a circumferential ring than a disc and is called a labrum. They are present only in select synovial joints, including the knee (meniscus), and shoulder (glenoid labrum).

• Fat pad: A localized collection of adipose tissue found in and around some synovial joints, which provides cushioning, reduces friction, and fills the space created by joint movement.

• Bursa: A small, fluid-filled sac that reduces friction between tissues, such as bone and tendons, or bone and skin in synovial joints. Bursae are strategically positioned throughout the body, particularly in areas that experience repetitive movements, providing additional protection and support to the joints.

• Tendon sheath: A tubular structure that surrounds a tendon, providing a barrier and reducing friction as the tendon moves, particularly in areas where tendons pass through narrow spaces or over bony prominences. Tendon sheaths are filled with synovial fluid to facilitate smooth movement and protect the tendon from wear and tear.

• Retinaculum: A band of connective tissue that holds tendons in place during joint movement, ensuring proper alignment and function. Retinacula are essential for stabilizing tendons as they traverse over joints, preventing displacement and maintaining efficiency during dynamic activities.

• Muscles: muscles can aid the joint capsule and ligaments in maintaining joint stability by limiting excessive separation or translation of joint surfaces. Because the stability provided by muscles requires active tension in muscles, it is sometimes termed dynamic stability, while the stability offered by the joint capsule and ligaments is termed passive stability.

Body Orientation Terminology

Center of Mass

The point in a body or system where the mass is evenly distributed in all directions, often considered the balance point of the body; understanding its location helps in analyzing movements and postures in dance. (Center of Gravity)

Anatomical Position and Other Positional Terminology

• Anatomical position: The standard position of the body used as a reference in anatomical terminology; the body stands upright, facing forward, arms at the sides with palms facing forward, and feet together.

• Prone: lying on the front with the face downward

• Supine: lying on the back with the face upward

Directional Terminology:

used to describe the location of a given structure with reference to other structures or in relation to anatomical position.

• Superior: Above or toward the head

• Inferior: Below or toward the feet

• Anterior: Front side or in front of

• Posterior: Back side or in back of

• Medial: Closer toward the midline

• Lateral: Farther from the midline or toward side

• Proximal: Closer to root of limb or center of body

• Distal: Farther from root of limb or center of body

• Superficial: Closer to or on the surface of body

• Deep: Farther from the surface of body

• Palmar: Anterior aspect of hand in anatomical position

• Dorsal (for hands and feet): Posterior aspect of hand in anatomical position; top aspect of foot during standing in anatomical position

• Plantar: Bottom aspect of foot when standing in anatomical position.

Body Segments and Rotary Motion

• Head, neck, and trunk comprise the central axis of the body.

• Arm: the segment between the shoulder and the elbow joints

• Forearm: the segment between the elbow and wrist joints

• Thigh: the segment between the hip and knee joints

• Leg: the segment between the knee and the ankle joints

• Foot: the segment distal to the ankle joint

• Rotary motion: the rotation of a bone in relation to the adjacent bone when force is applied.

• Axis of rotation: the line (axis) that passes through the center of a joint and around which the movement of the bones occurs, allowing for various degrees of freedom in motion.

Anatomical Planes and Axes

Plane: flat, two-dimensional surface and can be thought of as an imaginary sheet of cardboard that passes through the body in a given direction.

• Cardinal planes: the three imaginary reference planes in anatomical position that are perpendicular to each other and that pass through the center of mass of the body. Sagittal, frontal, and horizontal planes.

• Sagittal (median or midsagittal) plane: A vertical plan dividing the body into right and left portions

• Median plane: the midsagittal plane dividing the body into equal right and left portions

• Frontal plane: a vertical plan dividing the body into front and back portions

• Horizontal (transverse) plane: a transverse plane dividing the body into upper and lower portions.

• Anatomical planes: sagittal, frontal, and horizontal planes dividing the body into unequal portions.

Basic Anatomical Axes

Joint Movement Terminology

Basic Movements

• Flexion: bringing the anterior surface of a body segment toward the anterior surface of an adjacent body segment (except knee, which approximates posterior surfaces).

• Extension: moving from a flexed position toward the anatomical position or beyond

• Abduction: Moving away from the midline of the body

• Adduction: Moving toward the midline of the body

• External rotation: turning anterior surface outward

• Internal rotation: Turning anterior surface inward

Specialized Movements

• Right lateral flexion (spine): side-bending of the trunk to the right or moving from a position of left lateral flexion toward anatomical position

• Left lateral flexion (spine): side-bending of the trunk to the left or moving from a position of right later flexion toward anatomical position

• right rotation (spine): turning the anterior surface of the head or trunk to the right

• left rotation (spine): turning the anterior surface of the head or trunk to the left

• Pronation (forearm): turning the palm backward

• Supination (forearm): turning the palm forward

• Horizontal abduction (shoulder and hip): movement of the arm or thigh away from the midline in a horizontal plane

• Horizontal adduction (shoulder and hip): movement of the arm or thigh toward the midline in a horizontal plane

• Dorsiflexion (ankle-foot): bringing the top of the foot up toward the shin

• Plantar flexion (ankle-foot): bringing the top of the foot away from the shin.

Joint Movements in the Sagittal Plane

• Flexion & Extension

• Hyperextension: movements in the direction of extension beyond anatomical position.

• Dorsiflexion & Plantar flexion

Joint Movements in the Frontal Plane

• Abduction & Adduction

• right lateral flexion & left lateral flexion

Joint Movements in the Horizontal Plane

• External rotation & Internal rotation

• right rotation & left rotation

• pronation & supination

• Horizontal abduction & horizontal adduction

Complex Movement in Multiple Planes

Many complex movements use multiple planes and often involve planes between the sagittal, frontal, and horizontal planes. For example, circumduction. This movement pattern combines flexion, extension, abduction, and adduction. In circumduction, one end of the body segment makes a circle while the other end stays relatively stationary.

Subclassification of Synovial Joints

(pg. 23)

There are six types of synovial joints classified according to shape and configuration. The number of axes a joint has parallels the number of planes in which that joint allows motion.

Uniaxial Joints

• Hinge joints: a spool-shaped or convex surface fits into a concave surface generally allowing flexion-extension. For example: elbow and knee joints

• Pivot joints: a rounded surface or process pivots in an arch- or ring-shaped surface generally allowing rotation. For example, upper radioulnar joint (upper forearm), and lower radioulnar joint (lower forearm), contributing to the specialized movements of pronation-supination of the forearm.

Biaxial Joints

• Condyloid joints: an oval-shaped condyloid fits into an elliptical cavity, allowing for flexion-extension (in the sagittal plane about a ML axis) and abduction-adduction (in the frontal plane about an AP axis). For example: the wrist joint (radiocarpal joint) permits movement in multiple directions; and the knuckles (metacarpophalangeal joints) of the hands.

• Saddle joints: each joint surface is shaped like a saddle (in opposite direction), allowing for similar movements as the condyloid joint but with increased stability. The carpometacarpal joint of the thumb is a prime example, enabling grasping and opposition.

Triaxial Joints

• Ball-and-socket joints: a spherical head fits into a concave socket generally allowing flexion-extension, abduction-adduction, and external rotation-internal rotation. Examples: shoulder and hip joints.

Nonaxial Joints

• Gliding joints: flat or slightly curved surfaces come together allowing slight sliding motions that do not occur around an axis. Examples: acromioclavicular joint, and many of the joints between the tarsals of the feet and carpals of the hands.

Skeletal Considerations in Whole-Body Movement

Three key considerations to keep in mind when examining the contribution of bones and joints to functional movements, such as those in dancing.

Joint Stability and Mobility

• Joint stability: the ability of a joint to withstand forces and avoid being separated (disarticulated) without injury.

• Joint mobility: the range of motion that is allowed at a given joint.

Flexibility is the functional capacity of joints to move through a full range of motion.

Close-Packed and Loose-Packed Position of Joints

• Close-Packed Position: This is the position in which a joint is most stable and offers maximal surface area contact, generating the highest degree of stability; in this position, the ligaments and joint capsules are tight and provide strong support.

• Loose-Packed Position: In contrast, this position allows for greater movement and flexibility within the joint, where there is less tension in the surrounding ligaments and capsules, enabling a wider range of motion despite decreased stability.

Closed and Open Kinematic Chain Movements

• Kinematics: the branch of mechanics that describes the spatial and temporal components of movement such as the change in position (displacement), velocity, or acceleration of the body or its parts without consideration for the forces associated with the movement.

• Kinematic chain: series of joints that link successive body segments or bones. Most commonly used with reference to the limbs.

• Closed Kinematic Chain Movements: These involve movements where the distal segment is fixed, allowing for more stability and force production.

• Open Kinematic Chain Movements: In these movements, the distal segment is free to move, leading to increased mobility and a focus on muscle isolation.