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Dance Anatomy & Kinesiology Karen Clippinger

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1 Dance Anatomy & Kinesiology Karen Clippinger
The Muscular System Dance Anatomy & Kinesiology Karen Clippinger

2 1. Skeletal Muscle Structure & Function
“Muscle cells are the only cells capable of producing active tension and contracting” Contractility – is the unique ability of muscle tissue to shorten It is the property of contractility that generates movement of the human body, as well as allows for movements in the heart and other internal organs There are 3 types of muscle tissue – Smooth Muscle, Cardiac Muscle, Skeletal Muscle Smooth Muscle – forms part of the walls of hollow organs Cardiac Muscle – type of muscle found in the walls of the heart Skeletal Muscle – type of muscle that attaches muscles to bones

3 Skeletal Muscle Structure & Function
Smooth Muscle Bladder, Uterus, Stomach Various systems with hollow tubes – digestive system, circulatory system, respiratory system, reproductive system Contraction of smooth muscle helps move substances through organs Food through stomach; blood through arteries Involuntary muscle movement Cardiac Muscle Helps pump blood via blood vessels to the lungs and body Involuntary muscle movement due to specialized cells is able to contract automatically without stimulation from the nervous system

4 Skeletal Muscle Structure & Function
Influenced by gender, body type & activity Make up 45% of average adults body weight Voluntary muscle contraction Rely on nerve stimulation Important in maintaining: Posture and position, stability of joints, shock absorption, support and protection of internal tissues, control of pressures within cavities and protection of body heat

5 Skeletal Muscle Structure & Function
Properties of Skeletal Muscle Tissue Characterized by: irritability, extensibility & elasticity Irritability is the ability to receive and respond to a stimulus, commonly from an associated nerve -- Reaction is tension or contraction Elasticity is the ability of a muscle to return to its resting length after being stretched Connective tissue associated with muscle has another property, Viscousity. Vioscous or plastic properties is when the elongation produced by force remains after the force is removed – Permanent deformation Extensibility is the ability of a muscle to be stretched or increased in length beyond resting length Average muscle fiber can be stretched 1.5 times its resting length Cannot lengthen on its own, rather a force is required to create elongation This characteristic is key for allowing the dancer to improve range of motion – flexibility Read pg 37 - Viscoelastic

6 2. Microstructure of Skeletal Muscle & Muscle Contraction
Human body contains approximately 270 million muscle cells often called muscle fibers Skeletal muscle fibers grow in both length and diameter from birth to childhood Hypertrophy - Strength training using heavy resistance and low repetitions can also result in substantial increases in muscle cell diameter Read pg 37 for understanding Sarcomere – is a compartment between consecutive Z lines and is the functional unit of muscle contraction

7 2. Microstructure of Skeletal Muscle & Muscle Contraction
The Sliding Filament Theory The filaments (myosin & actin) are the mechanism by which muscles contract The activation of a muscle causes a release of calcium from within the muscle fiber Cross-bridge cycling – the coupling, flexion, uncoupling, retraction and recharging processes are repeated hundreds of times in a second to produce the shortening of the sarcomere associated with muscle contraction. Muscle Fiber Type Type 1 – Slow twitch; allow to remain active for prolonged periods, slower contraction time, produce less tension, higher resistance to fatigue Important for carrying out sustained contractions or repetitive low-intensity muscle contractions like walking, endurance running Type 2 – Fast twitch Type2a – Sometimes termed intermediate Type 2b – fastest contraction time, largest diameter, greatest force production and fatigability Important for carrying out short duration, high intensity muscle contractions such as weight training or sprinting

8 3. Muscle Architecture Muscle Cross-Sectional Area Fiber Arrangement
A muscle with more fibers will be able to produce more force Although complicated a larger muscle will still produce more force because of its larger cross-sectional area Strength training will increase cross-sectional area & allow for greater force Fiber Arrangement Occur in 2 forms – Fusiform & Penniform

9 3. Muscle Architecture Fiber Arrangement
Occur in 2 forms – Fusiform & Penniform Fusiform – fibers run parallel; Penniform – fibers run at an angle to the axis Fusiform relatively few fibers per unit area and offers a disadvantage in force production and advantage in terms of how much shortening the muscle can occur When sarcomeres are contracted, reduce the length of muscle fiber 30%-70%; av. 50% Fusiform muscles – Biceps Brachii, Sartorius, Pectineus, Adductor Brevis Penniform is similar to a feather in design and can produce greater force Greater force production is gained at the cost of reducing speed and range of motion ¾ of the human muscles are in penniform arrangement Penniform muscles – Gluteus Maximus, Gastrocnemus, Tibialis Posterior, Quadriceps Femoris

10 Fusiform Penniform

11 Muscle Attachments to Bone
Connective tissue, endomysium, perimysium and epimysium, is intimately related to muscle tissue and is key For providing form For attaching muscles to bones Individual muscle cells are covered by a very fine sheath termed the endomysium While bundles of about muscle fibers (fascicles) are covered by a dense connective sheath termed perimysium The whole muscle itself is covered by another membrane called the epimysium Muscle Belly – The central part of the muscle, the thicker part and where the contractile cells predominate. Go through figure 2.6

12 Muscle Attachments to Bone
Continued… Towards the end of the muscle belly the muscle cells but the connective tissue coverings continue to attach the muscle to the bone Via the cordlike or flat band called a tendon Or via a sheetlike structure of fibrous tissue called aponeurosis (we won’t focus on) Tendons are the most common form of attachment Serve to concentrate the pull of the muscle to a small area on the bone are very strong Their tensile strength has been estimated to be 4,169 pounds per square inch The Achilles tendon can resist tensile loads equal to or greater than steel of similar dimensions

13 Muscle Attachments to Bone
Origin & Insertion These connective tissue attachments have been termed Origin & Insertion Origin – generally stays stationary Insertion – moves Have also been called – Proximal Attachment & Distal Attachment Good for describing extremities Read passage 43/44

14 On reading and vocabulary so far
Quiz on Tuesday On reading and vocabulary so far

15 Muscle, Levers and Rotary Motion
1st Class Levers – the Axis is in the middle and the effort and resistance are on opposite sides. EX. The atlanto-occipital joint – Your head on your neck EX. Seesaws, scissors, and crowbars 2nd Class Levers – the Resistance is between the axis and the effort No actual form exists in the body EX. Wheelbarrow, nutcracker, lug nut wrench 3rd Class Levers – the Effort lies between the resistance and axis EX. Most human muscles EX. Tweezers, baseball bats, rackets, paddle

16 Muscle, Levers and Rotary Motion
Torque (or movement of force) – the capacity or effectiveness of a force to produce rotation Torque can be calculated by multiplying the amount of force times the perpendicular distance from the line of action Moment Arm: The perpendicular distance from the line of force to the axis of rotation Key: its not just the amount of force but how far away from the axis

17 Muscle, Levers and Rotary Motion
Mechanical Advantage – The relation of the movement arm of the effort to the movement arm of the resistance Large forces have to be generated by muscles to overcome much smaller resistances In human movement the presence of 3rd class levers represents a grave disadvantage in mechanical advantage and has important implications for injury predisposition However, this arrangement does foster a large range of motion of the end of the lever and a potential advantage in terms of speed of movement of the distal segment

18 Muscle, Levers and Rotary Motion
Equilibrium Versus Movement If the torque of a muscle is equal to the resistance, the system is in equilibrium and no movement net will occur If the torque of a muscle is greater than the torque of the resistance, joint rotation will occur in a the direction of the muscle’s pull If torque of the resistance is greater than that of the muscle, joint rotation will occur in the direction of the resistance. Let’s all try Concept Demonstration 2.2 on page 49

19 Muscle, Levers and Rotary Motion
Angle of Muscle Attachment While the movement arm of the resistance is key in determining resistance torque, the effectiveness of the muscle force in producing desired rotation is greatly influenced by the angle of the muscle’s attachment relative to the bone. The muscles force or effort has a direction determined by how hard the muscle is contracting, and hence is a vector Key Vectors: result in vertical or perpendicular components – rotary component Result in horizontal or parallel components – parallel components Less than 90º: part will contribute to rotation, and part to stabilization Perpendicular to 90º: all effort contribute to joint rotation Greater than 90º: part will contribute to rotation, and part to dislocation

20 Types of Muscle Contraction (Tension)
Dynamic Muscle Contraction occurs when there’s a change of length of the involved muscle and accompanying observable joint movement There are two types “concentric” & “eccentric” Concentric Contraction – involves a shortening of the muscle and resultant visible joint movement in the direction of the action of the primary muscle Loosely means ‘towards center’ Both attachments of the muscle will tend to be pulled toward each other as the muscle shortens Concentric contractions are commonly uses on the up-phase of movements in dance such as rising from a plie’, the takeoff phase of a jump, or raising the arms overhead

21 Types of Muscle Contraction (Tension)
Eccentric Contraction – involves a “lengthening” of the muscle as visible joint motion is occurring. Loosely means “away from the center” The resistance is lengthening the muscle while the muscle is contracting to control the effect of the resistance In most cases the muscle is not actually lengthening beyond resting length, but rather decreasing the degree of contraction from its shortened contracted position toward its resting length In human movement this is used to Control the effects of gravity, to decelerate body segments, and to help shock absorb (some examples in the book)

22 Types of Muscle Contraction (Tension)
Static (Isometric) Muscle Contraction – involves partial or complete contraction of a muscle where no visible joint movement occurs Loosely means “equal length” Use to maintain posture. In dance, they play a vital role in preventing undesired compensations of the body as well as maintain desired postions EX. When a dance is working at the barre, isometric contractions commonly used to maintain desired positions of the support leg, torso, and the arm on the barre.

23 Vocabulary 21-40 Distal Lever Axis Effort Resistance Torque
Dynamic Muscle Contraction Concentric Muscle Contraction Eccentric Muscle Contraction Isometric Contraction Agonist/Mover Antagonist Synergist Stabilizer Force Couple Uniarticulate Muscle Biarticulate Muscle Multiarticulate Muscle Active Insufficiency Static Stretching

24 Upcoming September 29 – Discuss Muscular Considerations, Vocabulary due October 1 – Test 1 on all Muscles PowerPoint will be posted on my Wiki on September 29th for your review

25 Muscular Considerations in Whole body movement
In most functional movement there is well-orchestrated contribution of many muscles at many joints. Some additional important considerations include use of the stretch- shortening cycle, the different roles muscles can play when they are acting simultaneously, how muscles can work as force couples, and the unique challenges that arise with muscles that cross multiple joints.

26 Muscular Considerations in Whole body movement
Stretch-Shortening Cycle A muscle is used eccentrically immediately preceding use of the same muscle concentrically When an active muscle is stretched, mechanical energy is stored in the elastic component of the muscle, which is then released during the immediately following shortening contraction, resulting in greater force. Ex. Stretching a spring coil Use of Stretch-Shortening Cycle has been shown to allow for lower energy requirements in a given movement Example on Page 54 (quick demi-plie’ prior to a jump)

27 Muscular Considerations in Whole body movement
There are 4 primary roles muscles play when working together at the same time: mover (agonist), antagonist, synergist, or stabilizer Mover or Agonist: is a muscle or muscles whose contraction actually produces the desired movement Antagonist: is a muscle or muscles with an action opposite to the action of the prime mover Synergist: is the muscle that works together with the agonist(s) to help achieve the movement goal. Stabilizer: is a muscle that contracts isometrically to support to steady a body part against forces related to muscle contraction, gravity, soft tissue constraints, momentum, or recoil from the movement Force Couple: two forces that are equal in magnitude and opposite in direction and are located at a distance from the axis such that they produce rotation

28 Muscular Considerations in Whole body movement
Special Considerations with Multijoint Muscles Muscles can cross one or more joints and dramatically influence the muscles contribution to movement Single-joint/Uniarticulate Muscle – crosses only 1 joint Can produce movement only at the joint it crosses Ex. Gluteus Maximus Two-joint/Biarticulate Muscle – crosses 2 joints Can produce movement in both joints Ex. Rectus Femoris Multijoint/Multiarticulate – crosses 2 or more joints Can produce movement at all the joints it crosses Ex. Sartorius, Gastronemius, Hamstrings

29 Muscular Considerations in Whole body movement
Active Insufficiency occurs when active contraction of the muscle is unable to produce as much range of motion as could be produced if an external force was responsible for the movement. View Concept Demonstration 2.4 on page 57 View muscles on 60 & 61

30 Unit Test on Oct 1 1. PowerPoint will be posted on my wiki which can be found through the CMS website or on your syllabi 2. Review your quiz, vocabulary, notes 3. Possible Study guide will be post – check wiki periodically

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