Chapter 3: Musculoskeletal System: The Musculature

Chapter 3:Musculoskeletal System:The Musculature KINESIOLOGY Scientific Basis of Human Motion, 10th edition Luttgens & Hamilton Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University

Objectives 1. Describe the structure and properties of the whole muscle, fast and slow twitch muscles fiber, and the myofibril 2. Explain how the relationship of the muscle’s line of pull to the joint axis affects the movement produces by the muscle 3. Describe the relationship between the skeletal muscle’s fiber arrangement and its function 4. Define the roles a muscle may play and explain the cooperative action of muscles in controlling joint actions by naming and explaining the muscle roles in a specified movement

Objectives 5. Define the types of muscular contraction, name, and demonstrate each type pf action 6. Demonstrate an understanding of the influence of gravity and other external forces on muscular action 7. Describe various methods of studying muscle action 8. State force-velocity and length-tension relationship and explain the significance is static & dynamic movements 9. Identify muscle groups active in a variety of motor skills

SKELTAL MUSCLE STRUCTUREProperties of Muscular Tissue • Extensibility and Elasticity: enable the muscle to be stretched, and return to normal length • Tendons are continuations of muscle’s connective tissue, also possess these properties • Contractility: is the ability to shorten and produce tension

The Muscle Fiber (Cell) • Consist of myofibrils held together by sarcolemma (cell membrane), which can propagate nerve impulses Fig 3.1

The Muscle Fiber (Cell)Myofibrils • Are arranged in parallel formation which create alternating dark & light bands that give muscle fiber their striated appearance • Each fiber enclosed by endomysium Fig 3.2

The Muscle Fiber (Cell)Myofilaments Actin & Myosin, when stimulated, slide past each other • Cross-bridges, projections (heads) of myosin attach to actin Fig 3.2

The Muscle Fiber (Cell) Sarcomeres • Myofibril between two Z lines • Functional contractile unit of skeletal muscle Fig 3.2

The Muscle Fiber (Cell) Whole Muscle • Fasiculus (bundle of fibers) enclosed by perimysium • Group of bundles encased within epimysium Fig 3.

Slow and Fast Twitch Fibers • Two major categories pertinent for kinesiology • Most limb muscles contain relatively equal distribution of each fiber type • Posture muscles contain more slow twitch fiber

Slow and Fast Twitch Fibers • Fast fibers are large, pale, and less blood supply than slow fibers • Suitable for intense responses over a short period of time • Slow fibers are small, red, and have a rich blood supply, and greater myoglobin • Highly efficient, do not fatigue easily • Suitable for long duration, posture and endurance events

Muscular Attachments • Muscle attach to bone by connective tissue, which continues beyond the muscle belly to form a tendon • Origin: usually more proximal • Insertion: usually more distal • Contraction produces equal force on the two attachments • Origin usually stabilized by other muscles • Reverse Muscle Action: when distal bone is stabilized and proximal bone moves

Structural Classification of Muscles on the Basis of Fiber Arrangement • Longitudinal: long, strap like muscle with fibers in parallel to its long axis • Sartorius Fig 7.15

Structural Classification of Muscles on the Basis of Fiber Arrangement • Quadrate or Quadrilateral: four sided and usually flat • Consist of parallel fibers • Rhomboids Fig 3.10b

Structural Classification of Muscles on the Basis of Fiber Arrangement • Triangular or Fan-Shaped: fibers radiate from a narrow attachment at one end to a broad attachment at the other • Pectoralis major Fig 5.11

Structural Classification of Muscles on the Basis of Fiber Arrangement • Fusiform or Spindle-Shaped: rounded muscle that tapers at either end • Brachioradialis Fig 6.8

Structural Classification of Muscles on the Basis of Fiber Arrangement • Unipenniform: a series of short, parallel, feather like fibers extends diagonally for side of a long tendon • Tibialis posterior Fig 8.25

Structural Classification of Muscles on the Basis of Fiber Arrangement • Bipenniform: A long central tendon with fibers extending diagonally in pairs form either side of the tendon Fig 7.15

Structural Classification of Muscles on the Basis of Fiber Arrangement • Multipenniform: Several tendons are present, with fibers running diagonally between them • Middle deltoid Fig 5.11

Effect of Muscle Structure on Force • Force a muscle can exert is proportional to its physiological cross section • A broad, thick, longitudinal muscle exerts more force than a thin one • A penniform muscle of the same thickness as a longitudinal muscle can exert greater force • The oblique arrangement of fiber allows for a larger number of fibers than in comparable sizes of other classifications

Effect of Muscle Structure on ROM • Long muscles with fibers longitudinally arranges along the long axis, can exert force over a longer distance • Pennate muscles with their oblique fiber arrange and short fibers, can exert superior force through only a short range

SKELETAL MUSCLE FUNCTIONLine of Pull • Movement that the contracting muscle produces is determined by two factors • Type of joint that is spans • The relation of the muscle’s line of pull to the joint

Line of Pull • Pectoralis major (clavicular) is primarily a flexor, but it also adducts the humerus • When are is abducted, line of pull moves above axis of rotation and contributes to abduction of humerus Fig 3.4

Angle of Attachment • If very shallow, most of the tension will produce a force pulling along the bone • Will tend to stabilize joint • If fairly large, will have a much larger rotary component of force • Many muscles, angle changes throughout ROM • When muscle generates tension at a 900 angle to the bone, it is the most efficient at producing joint motion

Types of Contraction • Contract literally means to “draw together” • Muscle contraction occurs whenever muscle fibers generate tension which may occur while the muscle is actually shortening, remaining the same length, or lengthening

Concentric or Shortening Contraction • When tension by the muscle is sufficient to overcome a resistance and move the body segment • The muscle actually shortens Fig 3.5c

Eccentric or Lengthening Contraction • When a muscle slowly lengthening as it gives in to an external force that is greater than the contractile force it is exerting • Muscle is acting as a “brake” Fig 3.5a

Isometric or Static Contraction • Isometric means “equal length” • Tension of the muscle without any appreciable change in length • Occurs under two conditions 1. Antagonistic muscles contract with equal strength 2. Muscle is held against another force

Isotonic and Isokinetic Contraction • Isotonic means “equal tension” and the tension remains constant while muscle shortens or lengthens • Isokinetic means “equal or same motion” • Maximum muscle effort at the same speed • “Accommodating resistance”

Influence of Gravity • Movements may be in the direction of gravitational forces (downward), opposing gravity (upward), or perpendicular to gravity (horizontal) • Horizontal motion is not affected by gravity • Lifting against gravity is a concentric contraction of the agonist • Slower lowering with gravity is an concentric contraction of the same muscle

Influence of Gravity • A forceful downward motion uses antagonist muscles is a concentric contraction, since gravitational pull is being exceeded Fig 3.6

Length-Tension Relationship • Optimum length is the length at which a muscle can exert maximum tension • It is slight greater than resting length 1. Passively stretched 2. Total tension 3. Developed tension Fig 3.7

Force-Velocity Relationship • As speed of contraction increases, the force it is able to exert decreases • At maximum velocity of contraction the load is zero Fig 3.8

Stored Elastic Capabilities • When concentric contraction is preceded by a phase of active stretching, elastic energy, stored in the stretch phase, is available for use in the contractile phase. • This enhanced potential for work is attributed to a combination the series elastic components and the stretch reflex

COORDINATION OF THE MUSCULAR SYSTEM • Movements of the body considerable muscular activity in addition to those muscles directly responsible for the movement itself • Muscles causing the movement must have a stable base • Bones not engages in the movement must be stabilized by other muscles

Roles of Muscles • Movers, or Agonists: directly responsible for producing a movement • Prime movers: large impact on movement • Assistant movers: only help when needed • This distinction between the various muscles that contribute to a movement is an arbitrary one

Roles of Muscles • Synergists: cooperative muscle function • Stabilizing, Fixator, & Support Muscles Fig 3.9

Roles of Muscles • Synergists: cooperative muscle function • Neutralizers – prevent undesired action Fig 3.10

Roles of Muscles • Antagonists: have an effect opposite to that of movers, or agonists • Check ballistic movements • First antagonists must relax to permit movement • Second it acts as a brake at completion of movement

Cocontraction • The simultaneous contraction of movers and antagonists • Neutralizers and Stabilizers may need to cocontract to counteract as additional function of a mover

Action of Bi-Articular Muscles • Muscles that pass over and act on two joints • Whether muscles flex joints in the same direction or opposite direction, they are not long enough to permit complete movement in both joints at the some time • Resulting tension of one muscle being transmitted to the other • These muscle can continue to exert tension without shortening

Action of Bi-Articular Muscles • Concurrent Movements: Simultaneous flexion or extension of the hip and knee joints Fig3.11a

Action of Bi-Articular Muscles • Countercurrent Movement: one muscles shortens rapidly at both joints its antagonists lengthens correspondingly and thereby gains tension at both ends Fig3.11b

Types of Bodily Movements • Passive: no effort on the part of the person involved • Active: movement is produced by the subject’s own muscular activity • In Slow movements muscular tension is maintained throughout ROM • In rapid movements, tension could be maintained throughout ROM, but it is an inefficient way of performing

Ballistic Movement • Movements that are initiated by vigorous contraction and completed by momentum • Throwing, striking, & kicking • Early stages of learning a ballistic skill should concentrate on form rather that accuracy

Terminating Ballistic Movements 1. By contracting antagonistic muscles - forehand drive in tennis 2. By allowing the moving part to reach the limit of motion, stopped by passive resistance of ligaments, or other tissues • Throwing motion 3. By the interference of an obstacle • Chopping wood

METHODS OF STUDYING THE ACTION OF MUSCLES • Conjecture & Reasoning: Using knowledge of location and attachments, and nature of joints, one can deduce a muscle’s action • Muscle attachments & line of pull determine possible movements Fig 3.12

METHODS OF STUDYING THE ACTION OF MUSCLES • Dissection: meaningful basis for visualization of muscle’s potential movements • Inspection & Palpation: valuable method for superficial muscles • Models: used for demonstration • Muscle Stimulation: contraction of individual muscles

METHODS OF STUDYING THE ACTION OF MUSCLES • Electromyography (EMG): based on the fact that contracting muscles generate electrical impulses • Reveals both intensity & duration of a muscle’s action Fig 3-13

MUSCULAR ANALYSIS • Description of muscular involvement is added to previously completed analysis of joint and segment involvement • Muscular action is identified for each joint movement and recorded next to the joint action on the chart (table 1.2) • Main Muscle Groups Active • Kind of Contraction

Chapter 3: Musculoskeletal System: The Musculature