Dance Science: Anatomy, Movement Analysis, and Conditioning

By Gayanne Grossman

Winner of:Certificate of Merit, Association of Medical IllustratorsRather than focusing on dance injuries, this book takes a positive approach showing what a dancer can do to dance better, which, in turn, will decrease injury rates. It presents human anatomy and motion in a functional, dance-specific way that teaches the readers to appreciate and take ownership of their bodies through a tour of the musculoskeletal system and movement analysis. The book is divided into three parts. Part one, Anatomy, describes the specific characteristics that affect motion at each individual joint, demonstrated by a variety of hands-on activities for readers to perform. Part two, Movement Analysis, discusses muscles that produce movement and introduces readers to a system of movement analysis. Part three, Conditioning, provides a practical, integrative approach to exercise for enhanced performance. The written material is accompanied by anatomical line drawings commissioned for the book, photographs, and an assortment of experiential activities specifically designed for dancers.

• Language: English
• Publisher: Princeton Book Company
• Release date: Nov 1, 2021
• ISBN: 9780871274038

Book preview

Preface

The purpose of this book is to educate and empower dancers to take ownership of their bodies. This book can be a textbook for dance anatomy and kinesiology courses. Dance teachers will find it helpful to understand their students’ bodies and will be able to add additional training techniques. Male and female dancers will find effective strengthening and myofascial stretching techniques that employ mindfulness. High school students through doctoral candidates will find the material accessible.

Dance science is relatively easy to master with a clear understanding of the fundamental concepts. This book teaches through text, experiential activities for kinesthetic learners, and problem-solving exercises for those aspects of dance science that are well accepted as scientific truth. For example, bone shape and muscle attachments are not likely to change. By contrast, understanding the neuroscience of motor control and its application to dance training is developing every year. These topics are introduced and discussed with the intention of helping the reader gain understanding of what we know, what we don’t know, where to look for information and how to critically assess it, and where the field might be heading. With this knowledge base, readers will be able to explore the varied aspects of dance science independently and with confidence.

Part One explores anatomy and arthrokinematics—how your joints move. We begin by explaining the simple language of anatomy. There is discussion of tissues such as bone and ligament, explaining their strength and how to keep them healthy.

We take the time to describe the architecture and biomechanics of each joint in a joint system in detail because it is important for dancers to understand that bony surfaces have different shapes, that movement is largely dependent on that shape, and that these shapes vary in different people and sometimes different limbs in the same person. This helps dancers spend precious training hours focusing on what can be improved rather than wasting time working toward motion that cannot happen due to the simple biomechanics of joint structure. Bone shape is largely genetic. It is not your fault or a deficit in training. This knowledge can be very liberating when coupled with an understanding of muscle function. Muscles change. They can become stronger, better coordinated, longer, and shorter; there is a training technique to target every skill you need. Once you have the knowledge to design an effective training program you will start to see an improvement in as little as two weeks.

Part Two addresses muscle attachments and actions. We will learn a movement analysis system that discusses a muscle or muscle group’s function as it moves in every direction or holds a position. Then we will discuss the interdependence of joint motion and muscle function. How hip placement effects foot alignment is an example. That knowledge gives you the power to use the information in Part Three—designing effective training protocols and employing these techniques into dance classes. Have you been trying to get your leg higher for years? If your intervention doesn’t show some change within two to six weeks, you may need to explore another intervention. That approach has made many dancers and patients happy over the years!

Clear understanding of the elements in Parts One and Two will help you use the material in Part Three to create quicker and effective interventions and alter training techniques to improve efficiency. Overall, this book will help you embody dance science information, decrease frustration, and open your mind to the wonders of science and its applicability to dance.

Finally, this book is intended to be enjoyable to read and to demystify science. I was a college dance major who learned anatomy: it can be done. Since then, I have taught many dancers and teachers the science of dance movement; and I know you can master the material contained here. Take your time and use your own body as a learning tool. Once you feel confident, and you will, share this knowledge with other dancers. Knowledge is power, truth, liberation, and will help bring about the joy of dancing for many years to come.

Part One

The Anatomy and Biomechanics of Dance

Understanding the function of the bones, collagen, cartilage, ligaments, and joints

1

Introduction to Anatomy

THE LANGUAGE OF ANATOMY

Anatomy has a universal language. Consequently, people of all disciplines including dance scientists, medical professionals, yoga instructors, and everyone who uses anatomy in their day-to-day lives use the same language. The language is very detailed, which enhances understanding between communicating parties.

Because that splendidly meticulous language may be unknown or off-putting to some dancers, our book will begin with immersion into the language of anatomy. Much complex sounding anatomic terminology is simply a compilation of prefixes and suffixes.

Our journey into the anatomy of dance begins with vocabulary. The words are really very simple. Always use them as a dancer educated in the science of movement. With this knowledge, you will become empowered to read literature published in the field, teach your current or future students the language so you can empower them as well. Your conversations with medical or somatics professionals will be better understood by all. Your writing will be more precise.

Let’s begin with words or portions of words commonly used in anatomic language.

Vocabulary List: Part One

(Part Two in Chapter 8)

1. Ology: study of, science of, theory of; it is a compound suffix of o meaning of and logy meaning study, science, theory

2. Kinesiology: is the study of human movement; kinesis means movement activity

3. Osteo: bone

4. Neuro: nerve

5. Arth: joint

6. Chondro: cartilage

7. Costa: rib

8. Myo: muscle

9. Ped or pedal: relating to the foot

10. Cep: derivative of caput or head

11. Soma: body separate from the mind

12. Ligament: connects bone to bone

13. Tendon: connects muscle to bone

14. Articulation: a joint, the junction between bones

15. Bi: two

16. Tri: three

17. Quad: four

18. Itis: inflammation

19. Hyper: above normal, excessive

20. Hypo: beneath or below normal, inadequate

21. Mid-sagittal or median plane: divides body into right and left halves

22. Sagittal plane: located anywhere in the body dividing it into right and left portions

23. Frontal or coronal plane: divides body into front and back

24. Transverse plane: divides body into top and bottom

25. Anterior: front

26. Posterior: back

27. Medial: nearer to the median plane

28. Lateral: farther from the median plane

29. Superior: above

30. Inferior: below

31. Proximal: located closer to the trunk

32. Distal: located farther from the trunk

33. Flexion: bending a joint, decreasing the angle of a joint, movement forward from the anatomic position

34. Extension: moving two parts of the body, movement backward from the anatomic position

35. Hyperextension: movement backward beyond the anatomic position

36. Abduction: movement away from the mid-sagittal plane

37. Adduction: movement toward the mid-sagittal plane

38. Medial rotation: rotation of the anterior side of body part in, toward the median plane

39. Lateral rotation: rotation of the anterior side of body part out, away from the median plane

40. Plantar flexion: pointing the foot

41. Dorsiflexion: flexing the foot

42. Fossa: cavity or hollow area

43. Fovea: pit

44. Groove: long channel

45. Foramen: hole

46. Trochanter: large piece

47. Tuberosity: rounded piece

48. Tubercle: small rounded piece

49. Condyle: rounded piece at the end of a bone

50. Epicondyle: smaller piece above the condyle

51. Facet: small flat surface

52. Crest: large ridge

53. Spine: sharp protuberance

54. Range of motion (ROM): your joint’s available movement

FUN WITH WORDS

See if you can answer these word puzzles. The key is on the last page of this chapter.

1. Use two words from the list above to create words that mean:

a. Inflammation of the joints

b. Inflammation of the nerves

c. Inflammation of the muscles

2. Using three words (or parts of three words) from the list above, create a single word that literally means inflammation of the rib cartilages.

3. What do you call the study of …?

a. Bones

b. Joints

c. Nerves

4. A muscle with three heads is called ________.

5. A muscle with two heads is called ______.

6. Synarthosis is a ______.

7. Someone with excessive motion may be ______.

ANATOMICAL POSITION AND PLANES OF ACTION

Anatomical position

Anatomical position is standing in parallel position with your arms at your sides and palms facing forward. Movement is described from this position.

Planes of action

There are three planes on which human movement can occur. These are the sagittal, frontal or coronal, and transverse planes. The sagittal plane divides your body into right and left sides. It’s called the mid-sagittal plane when it is in the very center of your body. The frontal plane divides your body into front and back sides. The transverse plane divides the top of your body from the bottom.¹,² These planes are perpendicular.

Figure 1-1 Anatomical position and plane of action.

Human movement on the planes of action

•Flexion and extension occurs on your sagittal plane.

•Abduction and adduction occurs on your frontal or coronal plane.

•Medial and lateral rotation occurs on your transverse plane.

OSTEOLOGY

The hardest structure in your body is bone.³ Have you considered its weight? According to Dr. Aydin Tozeren, your head and neck can be seven percent of your total body weight. Your leg can average eighteen percent of body weight.⁴ An arm can average 6.5 percent of body weight.4 This varies by size and bone density. Your muscles are largely responsible for holding, supporting, or lifting that weight.

What does this mean to us as dancers?

Knowing something as basic and important as how much your body parts weigh will help you re-think your dance training program. It may also help you understand some of the challenges dancers face. For example, let’s consider the weight of your head. Imagine standing in parallel first position and rolling down to touch the floor. Your head is pulling on your neck and the rest of your spine. This is like the weight of a bowling ball creating pull or traction on your spine. Now, imagine swinging your bowling ball (head) from side to side with a little force or momentum. What protects your neck from this force? If you said muscular strength, you would be correct.

Have you considered the weight of your leg? Lifting your leg into développé devant (front) or à la seconde (side) as high as you like may be a challenge for some of you. Using easy math, if you weigh one hundred pounds, then your leg weighs eighteen pounds. Your muscles will need to be strong enough to lift that much weight. What you are doing to train those muscles?

BONY SHAPE

Your bones come in many different shapes.²,⁵ These include:

•long bones

•short bones

•flat bones

•irregular bones

Certain bones form within your tendons. These are called sesamoid bones.²,⁵

Figure 1-2 Shapes of bones.

EXTERNAL ANATOMY OF BONE

A long bone has a shaft known as the diaphysis.² The end of the bone is the epiphysis.²

INTERNAL ANATOMY OF BONE

There are two distinct types of bony (osseous) tissue: compact and trabecular bone.³ It is easiest to see this on a long bone.

Compact bone

The shaft of a long bone, called the diaphysis, is comprised of compact bone that is dense and hard.³,⁴

Trabecular bone

The end of your bone, called the epiphysis, also known as cancellous or spongy bone, is comprised of a porous network of bone.³,⁴

PERIOSTEUM: EXTERNAL COVERING OF BONE

Your bones are covered by a fibrous layer of connective tissue known as periosteum.²,³,⁵ It is entwined with blood vessels that nourish bone.3 Additionally, it provides cells creating bone growth in width.⁵

BONE HEALING

Bone is bloody. The shaft and epiphysis of your bone houses bone marrow.³,⁵ Marrow is responsible for the production of red blood cells.³ Your periosteum houses blood vessels. You can see that bone is relatively bloody in nature. Scientifically speaking, bloody tissue tends to be well nourished. Therefore, bone injuries have excellent potential to heal, depending on the fracture, of course. The caveat is this: you must take proper care of your bones when you’re healthy as well as when they are injured.

LAWS RELATED TO BONE GROWTH: WOLFF’S AND ROUX’S LAWS

In the latter part of the nineteenth century, Julius Wolff, a German anatomist and surgeon, suggested, The shape of bone is determined only by static loading.⁶ His institute explains on its website that, the form and structure of bone constantly adapts to mechanical loading and that the adaptation is permanent.⁷ This is known today as Wolff’s Law.

Think of it this way: Wolff believed trabecular bone forms along lines of mechanical stress.⁸

Figure 1-3 Anatomy of bone.

Though his law still influences orthopedics today, many scientists have debated or expanded his theories. This makes sense, of course; he was working before X-ray⁹ was discovered.

Wilhelm Roux, an embryologist, worked closely with Wolff. Roux’s Law is slightly different because his discussion included cellular regulation and functional adaptation to stressors.⁹

Think of Roux’s Law this way: stressors will cause bony changes that can yield normal bony shape or pathologic bone. An excellent example of that process in some dancers is the bunion, a pathological condition. We will discuss this more in Chapter 2.

YOUR APPENDICULAR AND AXIAL SKELETON

The skeleton is divided into two portions.⁵

Your appendicular skeleton is so named because it refers to your appendages, namely your limbs and limb girdles. These are your arms and shoulder girdle, and legs and pelvic girdle.

Your axial skeleton is everything on your central axis. It includes the head, spine, sternum, ribs, sacrum, and coccyx.

Figure 1-4 Appendicular and axial (shaded) skeleton

ARTHROLOGY

Arthrology is the study of joints—where two bones are linked together. Not all joints exhibit movement. Our focus will be on those that do.

Three joint classifications

1. Synarthrotic joints. These joints are considered immovable, ³ though there can be limited movement. ⁶

The junction between these joint surfaces may be fused or is very close together, known as approximated. Examples are closed growth plates and the sutures in your skull. Growth plates (a cartilaginous area that becomes bone between the diaphysis and epiphysis) and sutures (a zigzag line joining the bony plates in your skull) fuse as growth is completed.

2. Amphiarthrotic joints. These joints are considered slightly movable. The joint surfaces are joined by cartilage. An example is your pubic symphysis, the joint formed in front of your pelvis by the two pubic bones.

Figure 1-5 Types of synovial joints.

3. Diarthrotic or synovial joints. Diarthrotic or synovial joints are highly moveable. These joints will be our primary focus. They are mobile and have a joint capsule.

There are seven subclassifications of synovial joints: hinge, ball and socket, gliding, pivot, condyloid, ellipsoid, and saddle.³,⁶ We will focus our attention on the arthrokinematics (movement of the joint surfaces) of the first four and on the synovial joint capsules. Listed below are the actions possible at each joint. You should know that many actions are not pure because bony surfaces have some translation or displacement with movement.⁶ For example, a rotational motion of the joint surfaces may exhibit some linear movement. An extensive explanation is beyond the scope of this book.

Hinge joints move on one plane, that is, they are uniaxial. They flex and extend on the sagittal plane. An example is the ankle joint.

Ball and socket joints move on three planes, that is, they are triaxial. They flex, extend, abduct, adduct, and rotate. An example is the hip joint.

Figure 1-6 View through a joint capsule.

Gliding joints have surfaces that slide over each other. An example is the facet joints.

Pivot joints move on one plane. They rotate on the transverse plane. An example is the superior radioulnar joint.

Joint capsule

Diarthrotic or synovial joints have a two-layered joint capsule.

The outer layer is fibrous and supportive. It blends with your periosteum—the fibrous covering of your bone. In certain joints it blends with your ligaments. It is integral to joint stability.

The inner layer is the synovial membrane. It secretes synovial fluid. The synovial fluid is both for joint lubrication and to provide nourishment to cartilage to keep it healthy and when it is injured.³,⁶

The synovial membrane can be loose and have folds. Sometimes it can pinch between the articular surfaces just by extending or flexing a joint too fast. No structures within the joint are injured; even so the synovial membrane has been irritated and will respond by secreting additional synovial fluid. The joint capsule is a confined space because the outer layer is fibrous. The additional fluid (swelling or edema) will feel like an injury because of the increased pressure. You can probably avoid a lot of these discomforts by simply repositioning your joint allowing the folds of the joint capsule to better align. In other words, when you feel a little pinch simply shake your limb or move it a bit to allow your synovial membrane to be happy. Understanding tissue principles like this will help you prevent injuries.

CARTILAGE

The purpose of cartilage is to prevent shock and distribute forces.⁴

Cartilage, unlike bone, is usually white and glistens because it has little to no blood supply, known as avascular.²,³,⁴,⁶ Have you ever cleaned a chicken? The white rubbery substance is cartilage. Its avascular nature makes cartilage more difficult to heal than bone. Some believe certain types do not heal.⁴ Therefore, it is helpful to understand the mechanical principles of your cartilage and take good care of it.

Figure 1-7 Types of cartilage.

Cartilage is nourished by diffusion from the synovial fluid.⁴,⁵,⁶ This is enhanced by compression and decompression.⁶ For example, as you walk or move, the bones forming your knee joint move apart and together, compressing and decompressing. This moves the synovial fluid within the joint space delivering nutrients to your cartilage. Too much compression or lack of movement impairs fluid movement and retards the delivery of nutrients. (We will discuss this more in Chapter 3).

The body has three types of cartilage: hyaline, elastic, and fibrous.³

Hyaline cartilage is also known as articular cartilage because it covers the end of your bone where it articulates with the next bone. It is white and smooth. Actually, hyaline means glassy or transparent in Latin. It protects your bony surfaces by decreasing friction thereby helping them move easily over each other.⁴ It also helps with shock absorption.6

Elastic cartilage is more flexible than the other two cartilage types.³ It is found in your ear.

Fibrous cartilage has more fibrous connective tissue, making it dense and very good for shock absorption. Examples are your intervertebral disks, pubic symphysis, and the menisci in your knee.

Figure 1-8 Two-layered tendon sheath.

TENDONS AND TENDON SHEATHS

Tendons connect muscle to bone and are extremely strong.⁵ Clippinger reports one study found that the, Achilles tendon can resist tensile loads equal to or greater than steel.⁵ The strength, however, varies by tendon.⁶

Tendons are comprised of dense parallel fibers of connective tissue that is white and glistens.⁶ They are non-contractile but not completely inelastic, though their ability to elongate is limited.⁶

Tendons are generally poorly vascularized.³ This means there is not a lot of blood flowing into them. Therefore they can be difficult to heal.

Fortunately, your tendons are surrounded by a two-layer tendon sheath.³,⁵,⁶ The outer layer is fibrous. That helps maintain its shape. The inner layer is a synovial membrane. It secretes synovial fluid to nourish your tendon and help it glide over friction points.⁶

Dancers can develop inflammation in the tendon or the tendon sheath. You can protect these structures by understanding that under normal circumstances you shouldn’t feel a sensation in them. Feeling your muscles move or even post-exercise soreness is fine. When you feel a sensation in your tendon, most likely it is a warning sign that it is under strain from too much motion.

It is a good idea then to stop and assess what you are asking it to do. If it has already become inflamed, employ part of the PRICE principle: protect, rest, ice, compress, and elevate for the first twenty-four to seventy-two hours. Protecting, resting and icing may be enough for many injuries:¹⁰

Of these, the most important to dancers are:

Protect: the activity may be too difficult for your current level of strength or it may simply be too much repeated motion.

Rest: stop what you are doing and rest immediately. Longer term rest may require modifying your activities until healed or strong enough.

Ice: if you have pain, heat, redness, or swelling, ice for fifteen to twenty minutes every day or twice a day.

Figure 1-9 Examples of ligaments.

LIGAMENTS

Your ligaments attach bone to bone.⁵ Your ligaments are comprised of dense connective tissue whose fibers run in parallel.³,⁶ Their strength is due to the collagen fibers within the connective tissue.³,⁶ Like tendons, ligaments have only a small degree of extensibility.³,⁶

Therefore, increasing the length of a ligament too much may involve microfailure or tearing of fibers. Whatever strength those fibers contributed is now lost.

What happens when some percentage of your ligament’s ability to hold the bones together is lost? The remaining ligamentous fibers may not be able to stabilize adequately against stress or strain.⁶ In other words, joint stability is impaired.

You can and should protect your ligaments. Just like your tendons, when you feel a sensation in your ligaments, most likely it is a warning sign. Immediately stop what you are doing or the way you are doing it.

Your ligaments and tendons will remain happily doing their job for years to come if you take a little extra care.

BURSA

Your bursa are small synovial sacs like little pillows. They have two layers like joint capsules and tendon sheaths. The outer layer is fibrous and the inner layer is synovial membrane.³

The purpose is to help reduce friction of bones and tendons. They are almost everywhere there is a friction point!

Let’s feel one. Bend your elbow and gently place it on the table or floor in front of you. Put as little weight on it as possible. Now roll it around in tiny circles. That squishy feeling is bursa. You can compare that feeling with another pointy area that has no bursa. Put the tip of your finger on the table and roll that around. Your finger tips do not have bursa, consequently they will feel very different than the tip of your elbow.

Figure 1-10 Fascia.

FASCIA

Your fascia is a fibrous connective tissue network usually formed in sheets.³ Thomas Meyers calls it the fascial net and the fascial system.¹¹ Its function is supportive, ¹¹,¹²,¹³ but it becomes less so with age.¹²,¹³ You can mitigate some age-related change by continuing to exercise.

A healthy fascial network is important for optimal movement. Essentially, this structure winds over, under, and around most structures in your body. It is connected to itself. For example, the fascia in front of your shoulder, is intertwined with the fascia over your belly, it winds its way to your hip, and thigh. This is true on your back too. This means that every part of your body is intertwined and movement in one area will affect another area.

You may be able to sense this phenomenon. Stand up and raise your arm out to the side. Feel the connection between your pinky finger and your opposite hip though the front of your body. Imagine this on your back too. An effective approach is to imagine an X attaching your right shoulder to left hip and left shoulder to right hip. Walk around for a bit. Try to sense the X in the front of your body, the anterior fascia. Then try to sense the X in the back of your body, your posterior fascia.

Fascia is plastic. That means deforming it can permanently transform it. New connective tissue fibers will have to form for it to return to its correct length.

Fascia can restrict motion when there is too much strain in one area because extra cells are deposited creating a denser sheath.¹¹ Your fascial network can become tight and restrict movement or elongate to allow freer movement. Your goal is to have a supportive fascial network that is not too restrictive.

Fortunately, it is easy to work with.