the muscular system dance anatomy & kinesiology karen clippinger

THE MUSCULAR SYSTEMDance Anatomy & Kinesiology

Karen Clippinger

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

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


• Skeletal Muscle• 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


• 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

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

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

3. MUSCLE ARCHITECTURE

• Muscle Cross-Sectional Area• 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

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

PenniformFusiform

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 100-200 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


• 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


• 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

QUIZ ON TUESDAYOn reading and vocabulary so far

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


• 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


• 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


• 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


• 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

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


• 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)


• 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.

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

UPCOMINGSeptember 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

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.


• 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)


• 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


• 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


• 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

UNIT TEST ON OCT 11. 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

the muscular system dance anatomy & kinesiology karen clippinger

Documents

muscle cell diameter

nervous system slide

protection of body heat

contraction elasticity

viscoelastic slide

circulatory system

respiratory system

body type activity