Kinesiology Chapter 2

Isokinetic's

A type of dynamic exercise using concentric and/or eccentric muscle contractions. Speed (or velocity) of movement is constant. Muscular contraction (ideally maximum contraction) occurs throughout movement. Not another type of contraction, as some have described. Example - Biodex, Cyber. Various exercises may use any one or all of these contraction types for muscle development.

Location and Number of Divisions Example

Biceps Femoris

Location and Attachment Example

Brachioradialis

Two advantages over uni-articular muscles

Can cause and/or control motion at more than one joint. Are able to maintain a relatively constant length due to shortening at one joint and lengthening at another joint.

Role of Agonist Muscles

Cause joint motion through a specified plane of motion when contracting concentrically. Known as primary or prime movers, or as muscles most involved. Some agonist muscles, because of their relative location, size, length, or force generation capacity, are able to contribute significantly more to the joint movement than other agonists. Current joint positions and angle of motion can also change agonists and which of those are the prime mover for a given exercise. Assisters or assistant movers. Agonist muscles that contribute significantly less to the joint motion. Consensus among all authorities regarding which muscles are primary movers and which are weak assistants does not exist in every case.

Concentric Contraction

Causes motion. Muscle develops active tension as it shortens. Occurs when muscle develops enough force to overcome applied resistance. Causes movement against gravity or resistance. Described as being a positive contraction. Force developed by the muscle is greater than that of the resistance. Results in the joint angle changing in the direction of the applied muscle force. Causes the body part to move against gravity or external forces.

Gaster (Belly or Body)

Central, fleshy portion of the muscle that generally increases in diameter as the muscle contracts.

Hip and knee biarticular muscles- Example 1

Concurrent movement pattern occurs when both the knee and hip extend at the same time. If only the knee were to extend, the rectus femoris would shorten and its ability to exert force similar to the other quadriceps muscles would decrease, but its relative length and subsequent force production capability are maintained due to its relative lengthening at the hip joint during extension.

Determination of Muscle Action

Consideration of anatomical lines of pull. Anatomical dissection. Palpation. Models. Electromyography. Electrical stimulation.

Role of True Synergist Muscle

Contract to prevent an undesired joint action of the agonist and have no direct effect on agonist action. Example - Finger flexors are provided true synergy by wrist extensors when grasping an object. Finger flexors originating on the forearm and humerus are agonists in both wrist flexion and finger flexion. Wrist extensors contract to prevent wrist flexion by finger flexors. This allows finger flexors to maintain more of their length and therefore utilize more of their force in flexing the fingers.

Eccentric Contraction

Controls Muscles. Muscle lengthens under active tension Occurs when muscle gradually lessens in tension to control the descent of resistance. Weight or resistance overcomes muscle contraction but not to the point that the muscle cannot control descending movement. Decelerates movement Controls movement with gravity or resistance. Described as a negative contraction. Force developed by the muscle is less than that of the resistance. Results in the joint angle changing in the direction of the resistance or external force. Controls the body part to allow movement with gravity or external forces (resistance). Used to decelerate body segment movement. Referred to as a muscle action instead of a contraction because the muscle is lengthening as opposed to shortening.

Points of Attachment Example

Coracobrachialis, Extensor Hallucis Longus, Flexor Digitorum Longus

Role of Neutralizer Muscles

Counteract or neutralize the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions, which is referred to as neutralizing. Contract to resist specific actions of other muscles. Example 1 - When only the supination action of the biceps brachii is desired, the triceps brachii contracts to neutralize the flexion action of the biceps brachia. Example 2 - Biceps curl - When only the flexion force of the biceps brachii is desired, the pronator teres contracts to neutralize the supination component of biceps.

Hip and knee biarticular muscles- Example 2

Countercurrent movement pattern occurs in kicking. During the lower extremity forward movement phase, the rectus femoris concentrically contracts to flex the hip and extend the knee. These two movements, when combined, increase the tension or stretch on the hamstring muscles both at the knee and hip. Multiarticular muscles act on three or more joints due to the line of pull between their origin and insertion crossing multiple joints. Principles relative to biarticular muscles apply to multiarticular muscles.

Uni-articular Muscles

Cross and act directly only on the joint that they cross. Example - Brachialis, which can only pull the humerus and ulna closer together

Bi-articular Muscles

Cross and act on two different joints. Depending on certain factors, biarticular muscles may contract and cause motion at either one or both of its joints.

Shape Example

Deltoid, and Rhomboid

Action Example

Erector Spinae, Supinator, Extensor Digiti Minimi

Lines of Pull

Exact locations of bony landmarks to which muscles attach proximally and distally and their relationship to joints. Planes of motion through which a joint is capable of moving. Muscle's relationship or line of pull relative to the joint's axes of rotation. As a joint moves the line of pull may change and result in muscle having a different or opposite action than in the original position. Potential effect of other muscles' relative contraction or relaxation on a particular muscle's ability to cause motion. Effect of a muscle's relative length on its ability to generate force. Effect of the position of other joints on the ability of a biarticular or multiarticular muscle to generate force or allow lengthening.

Direction of Fibers Example

External Abdominal Oblique

Parallel Muscles

Fibers arranged parallel to the length of the muscle. Produce a greater range of movement than similar-sized muscles with a pennate arrangements.

Pennate Muscle- Unipennate Muscle

Fibers run obliquely from a tendon on one side only. Example- Biceps femoris, Extensor Digitorum Longus, Tibalis Posterior

Pennate Muscles- Bipennate Muscle

Fibers run obliquely on both sides from a central tendon. Example- Rectus femoris, Flexor Hallucis Longus

Tendon

Fibrous connective tissue, often cordlike in appearance, that connects muscle to bones and other structures. Two muscles may share a common tendon. Example- Achilles tendon of gastrocnemius and soleus muscle. A muscle may have multiple tendons connecting it to one or more bones. Example- Three proximal attachments of the tricep brachii.

Size Example

Gluteus Maximus, Teres Minor

Pennate Muscles- Multipennate Muscle

Have several tendons with fibers running diagonally between them. Example- Deltoid

Pennate Muscles

Have shorter fibers. Arranged obliquely to their tendons in a manner similar to a feather. Arrangement increases the cross-sectional area of the muscle, thereby increasing the power.

Isotonic Contractions

Involve the muscle developing active tension to either cause or control joint movement. Dynamic contractions. The varying degrees of tension in muscles result in joint angles changing. Are either concentric or eccentric on the basis of whether shortening or lengthening occurs.

Role of Antagonist Muscles

Located on the opposite side of joint from the agonist. Have the opposite concentric action. Known as contralateral muscles Work in cooperation with agonist muscles by relaxing and allowing movement (reciprocal inhibition). When contracting concentrically, they perform the joint motion opposite to that of the agonist. Example - Quadriceps muscles are antagonists to hamstrings in knee flexion.

Muscle's ability to shorten

Longer muscles can shorten through a greater range. More effective in moving joints through large ranges of motion.

Parallel Example- Strap Muscle

More uniform in diameter with essentially all fibers arranged in a long parallel manner. Can focus their power on small, bony targets. Example- Sartorius

Muscle Tissue Properties- Irritability or Excitability

Muscle property of being sensitive or responsive to chemical, electrical, or mechanical stimuli.

Shape and Fiber Arrangements Affects:

Muscles ability to exert force and Range through which the muscle can effectively exert force onto the bones.

Muscle Nomenclature

Muscles are usually based on their; visual appearance, anatomical location, and function.

Aggregate Muscle Action

Muscles work in groups than independently to achieve a given joint motion.

Role of Force Couple Muscles

Occur when two or more forces are pulling in different directions on an object, causing the object to rotate about its axis. Coupling of muscular forces together in the body can result in a more efficient movement. Example - Middle trapezius, lower trapezius, and serratus anterior each pull on the scapula from a different direction to produce the combined result of upward rotation.

Extrinsic

Pertaining usually to muscles that arise or originate outside of (proximal to) the body part on which they act. Example- Forearm muscles that attach proximally on distal humerus and insert on the fingers.

Intrinsic

Pertaining usually to muscles within or belonging solely to the body part on which they act. Example- Small intrinsic muscles found entirely within the hand or feet.

Action and Shape Example

Pronator Quadrates

Amplitude

Range of muscle fiber length between maximal and minimal lengthening.

Location Example

Rectus Femoris, Palmares Longus

Electrical Muscle Stimulation

Reverse approach of electromyography. Uses electricity to cause muscle activity. Surface electrodes are placed over muscle and the stimulator causes muscle to contract. Joint actions may then be observed to see the effect of the muscle's contraction.

Innervation

Segment of the nervous system responsible for providing a stimulus to muscle fibers within a specific muscle or portion of a muscle. A muscle may be innervated by more than one nerve, and a particular nerve may innervate more than one muscle or portion of a muscle.

Shape and Location Example

Serrates Anterior

Muscle Tissue Properties

Skeletal muscle tissue has four properties related to its ability to produce force and movement about joints. Irritability or excitability, Contractility, Extensibility, and Elasticity.

Action

Specific movement of a joint resulting from a concentric contraction of a muscle that crosses the joint. Example- Bicep brachii, which has the action of flexion at elbow.

Parallel Example- Fusiform Muscle

Spindle-shaped with a central belly that tapers to tendons on each end. Can focus their power on small, bony, targets. Example- brachialis and bicep brachii

Insertion

Structurally, the distal attachment or the part that attaches farthest from the midline or center of the body. Functionally and historically, the most movable part is generally considered the insertion

Origin

Structurally, the proximal attachment of a muscle or the part that attaches closest to the midline or center of the body. Functionally and historically, the least movable part or attachment of the muscle

Role of Stabilizer Muscles

Surround the joint or body part. Contract to fixate or stabilize the area to enable another limb or body segment to exert force and move. Known as fixators. Essential in establishing a relatively firm base for the more distal joints to work from when carrying out movements. Example - Biceps curl.

Parallel Example- Sphincter or Circular Muscles

Technically endless strap muscles. Surrounded openings and function to close them upon contraction. Example- Orbicularis oris- surrounding the mouth

Actions actually performed depend upon several factors

The motor units activated. Joint position at the time of contraction. Planes of motion allowed in the joint. Axis of rotation possible in the joint. Muscle length. Relative contraction or relaxation of other muscles acting on the joint.

Muscle Contractions can be used to cause, control, or prevent joint movement

To initiate or accelerate the movement of a body segment. To slow down or decelerate the movement of a body segment. To prevent the movement of a body segment by external forces

Numbers of Divisions Example

Triceps Brachia

Palpation

Using the sense of touch to feel or examine a muscle as it contracts. Limited to superficial muscles. Helpful in furthering one's understanding of joint mechanics. Long rubber bands may be used as models to simulate muscle lengthening or shortening as joints move through ranges of motion.

Parallel Example- Flat Muscle

Usually thin and broad, orienting from broad, fibrous, sheet-like aponeuroses. Allows them to spread their forces over a broad area. Example- Rectus abdomins and external oblique

Electromyography (EMG)

Utilizes either surface electrodes which are placed over muscle or fine wire/needle electrodes placed into muscle. As the subject moves the joint and contracts muscles, the EMG unit detects the action potentials of muscles and provides an electronic readout of contraction intensity and duration. Most accurate way of detecting the presence and extent of muscle activity.

Contraction

When tension is developed in a muscle as a result of a stimulus. The term muscle contraction may be confusing because in some contractions the muscle does not shorten in length. As a result, it has become increasingly common to refer to the various types of muscle contractions as muscle actions instead.

Active and Passive Insufficiency

-Active insufficiency is reached when the muscle becomes shortened to the point that it cannot generate or maintain active tension. The muscle cannot shorten any further. -Passive insufficiency is reached when the opposing muscle becomes stretched to the point where it can no longer lengthen and allow movement

Skeletal Muscles

-Responsible for movement of the body and all its joints. -Muscle contraction produces the force that causes joint movements. -Provide protection. -Provide dynamic stability of joints. -Contribute to posture and support. -Produce a major portion of total body heat.

Cross-Section Diameter

A factor in muscles ability to exert force. Keeping all other factors constant, a muscle with a greater cross-section diameter will be able to exert a greater force.

Reversal of Muscle Function

A muscle group described to perform a given function can contract to control the exact opposite motion.

Fascia

A sheet or band of fibrous connective tissue that envelopes, separates, or binds together parts of the body such as muscles, organs, and other soft-tissue structures of the body. In certain places throughout the body, such as around joints like the wrist and ankle, fascial tissue forms a retinaculum to retain tendons close to the body

Aponeurosis

A tendinous expansion of dense fibrous connective tissue that is a sheet or ribbon like in appearance and resembles a flattened tendon. Serves as a fascia to bind muscles together or as a means of connecting muscle to bone.

Muscles with Multiple Agonist Actions

Attempt to perform all of their actions when contracting. Cannot determine which actions are appropriate for the task at hand.

Muscle Tissue Properties- Extensibility

Ability of muscle to be passively stretched beyond its normal resting length.

Muscle Tissue Properties-Contractility

Ability of muscle to contract and develop tension or internal force against resistance when stimulated.

Muscle Tissue Properties-Elasticity

Ability of muscle to return to its original length following stretching.

Isometric Contraction

Active tension is developed within the muscle but joint angles remain constant. Also thought of as static contractions. Significant amount of tension may be developed in a muscle to maintain the joint angle in a relatively static or stable position. May be used to prevent a body segment from being moved by external forces.

Action and Size Example

Adductor Magnus

Parallel Example- Radiate Muscles

Also described sometimes as being triangular, fan shaped, or convergent. Have combined arrangement of flat and fusiform. Originate on broad aponeuroses and coverage onto tendon. Example- Pectoralis major, trapezius

Angle of Pull

Angle between the line of pull of the muscle and the bone on which it inserts (angle toward the joint). With every degree of joint motion, the angle of pull changes. Joint movements and insertion angles involve mostly small angles of pull. Angle of pull decreases as the bone moves away from its anatomical position through the local muscle group's contraction. Range of movement depends on the type of joint and bony structure. Most muscles work at angles of pull less than 50 degrees. Amount of muscular force needed to cause joint movement is affected by the angle of pull. Rotary component (vertical component) - Component of muscular force that acts perpendicular to the long axis of the bone (lever).

Role of Synergist Muscles

Assist in the action of agonists. Not necessarily prime movers for the action. Known as guiding muscles. Assist in refined movement and rule out undesired motions. They may be helping synergists or true synergists. Helping synergists: Have an action in common but also have actions antagonistic to each other. Help another muscle move the joint in the desired manner and simultaneously prevent undesired actions. Example - Anterior and posterior deltoid. Anterior deltoid acts as an agonist in glenohumeral flexion, while the posterior deltoid acts as an extensor. Helping each other, they work in synergy with the middle deltoid to accomplish abduction.