MuscleMuscle

What are muscles?What are muscles?

MachinesMachines– purpose of machines is to help us do work.purpose of machines is to help us do work.

Characteristics of Muscle TissueCharacteristics of Muscle Tissue

ExtensibilityExtensibility ElasticityElasticity ContractilityContractility IrritabilityIrritability AmplitudeAmplitude ViscosityViscosity

What is a muscle contraction?What is a muscle contraction?

Types of ContractionsTypes of Contractions

Concentric ContractionConcentric Contraction

Static ContractionStatic Contraction

Eccentric ContractionEccentric Contraction

Isometric and Isotonic ContractionsIsometric and Isotonic Contractions

Concentric ContractionsConcentric Contractions

development of tension within a muscle development of tension within a muscle with consequent shortening of the muscle.with consequent shortening of the muscle.

the movement is caused by the muscle.the movement is caused by the muscle.

Static ContractionStatic Contraction

development of tension within a muscle development of tension within a muscle with no change in the overall muscle length.with no change in the overall muscle length.

goal is usually to maintain a position.goal is usually to maintain a position.

Eccentric ContractionEccentric Contraction

development of tension within a muscle development of tension within a muscle resulting in lengthening of the muscle.resulting in lengthening of the muscle.

movement is caused by another force movement is caused by another force contracting muscle tries to control the contracting muscle tries to control the

movement.movement.

Mechanical FactorsMechanical Factorsdetermining specific movementsdetermining specific movements

structure of the joint or joints muscle structure of the joint or joints muscle crossescrosses

the orientation of the muscle’s line of pull the orientation of the muscle’s line of pull to the axis or axes around which movement to the axis or axes around which movement is permittedis permitted

Line of PullLine of Pull

the direct line between the centers of the the direct line between the centers of the muscle’s attachmentsmuscle’s attachments

one origin, one insertionone origin, one insertion

one origin, multiple insertionsone origin, multiple insertions

Mechanical AxisMechanical Axis

the straight line drawn connecting the the straight line drawn connecting the centers of the joints at each end of the centers of the joints at each end of the specific bone, or specific bone, or

from the center of the joint where the from the center of the joint where the movement is occurring to the center of the movement is occurring to the center of the distal end of the limb, if the limb is moving distal end of the limb, if the limb is moving as a unitas a unit

Axis of RotationAxis of Rotation

the angle formed by the line of pull and the the angle formed by the line of pull and the mechanical axis.mechanical axis.

Muscle RolesMuscle Roles

Individual muscles take on a variety of roles Individual muscles take on a variety of roles at different times and under different at different times and under different circumstances.circumstances.

there are six roles a muscle can assumethere are six roles a muscle can assume

Muscles and their RolesMuscles and their Roles

Muscles are not selective when stimulated Muscles are not selective when stimulated to contract.to contract.

Resulting actions are partially determined Resulting actions are partially determined by functions performed by other muscles by functions performed by other muscles attendant to the agonist.attendant to the agonist.

Muscle RolesMuscle Roles

AgonistAgonist AntagonistAntagonist FixatorFixator RegulatorRegulator NeutralizerNeutralizer SynergistSynergist

AgonistAgonist

Prime MoverPrime Mover causes a concentric contractioncauses a concentric contraction

AntagonistAntagonist

refers to a muscle whose function is refers to a muscle whose function is opposite to that of some muscle tending to opposite to that of some muscle tending to cause a movement.cause a movement.

Three different functions:Three different functions:– relax throughout the movementrelax throughout the movement– relax initially, but contract toward the end of relax initially, but contract toward the end of

the movement to prevent injurythe movement to prevent injury– contract throughout the movementcontract throughout the movement

FixatorFixator

any muscle that contracts to anchor or any muscle that contracts to anchor or steady the position of a particular bonesteady the position of a particular bone

Two categories of fixators:Two categories of fixators:– Stabilizing role - Stabilizing role -

– Supporting role -Supporting role -

RegulatorRegulator

used to identify a muscle contracting used to identify a muscle contracting eccentrically to control a movement caused eccentrically to control a movement caused by an external force.by an external force.

NeutralizerNeutralizer

acts to prevent the undesired action of acts to prevent the undesired action of another contracting muscle without another contracting muscle without interfering with the desired function of that interfering with the desired function of that other muscleother muscle

two typestwo types– mutual neutralizer -mutual neutralizer -

– true neutralizer -true neutralizer -

SynergistSynergist

usually assigned to the synchronous action usually assigned to the synchronous action of two joint musclesof two joint muscles

2 types2 types– Concurrent pattern - Concurrent pattern -

– Countercurrent pattern - Countercurrent pattern -

Control of MovementControl of Movement

Coordination is an orchestrated sequencing Coordination is an orchestrated sequencing of binary impulsesof binary impulses

Reciprocal Innervation (Sherrington’s Reciprocal Innervation (Sherrington’s Principle)Principle)– inhibition of one member of antagonistic pairinhibition of one member of antagonistic pair

CorollaryCorollary– inhibition of muscle is inhibitedinhibition of muscle is inhibited

Conditions for Co-contractionConditions for Co-contraction

when an exact amount of tension or when an exact amount of tension or accurate placement of a limb is neededaccurate placement of a limb is needed

deceleration of limb deceleration of limb to stabilize the wrist for precise hand to stabilize the wrist for precise hand

movements or for a powerful gripmovements or for a powerful grip

Ballistic MovementsBallistic Movements

Three phases:Three phases:– Acceleration-Acceleration-

– Inertial-Inertial-

– Deceleration-Deceleration-

Ballistic MovementsBallistic Movements

muscle initially contracts to move the limb, muscle initially contracts to move the limb, but then the limb is carried through space but then the limb is carried through space due to momentumdue to momentum

antagonistic muscles fire to slow down the antagonistic muscles fire to slow down the speeding limbspeeding limb

Stretch ReflexStretch Reflex

occurs in skilled ballistic movementsoccurs in skilled ballistic movements muscle is stretched quickly, resulting in a muscle is stretched quickly, resulting in a

stronger contraction stronger contraction

Olson’s PrinciplesOlson’s Principles

Dealt with free weights only and Dealt with free weights only and considered:considered:– direction of direction of movementmovement relative to the line of relative to the line of

gravitygravity– the type of contractionthe type of contraction– the muscle group usedthe muscle group used

Olson’s 1st PrincipleOlson’s 1st Principle

If the If the movementmovement is against the line of is against the line of gravity:gravity:– the muscle causes the movementthe muscle causes the movement– the contraction is concentricthe contraction is concentric– the muscle group that should perform the the muscle group that should perform the

action, performs the actionaction, performs the action

Olson’s 2nd PrincipleOlson’s 2nd Principle

If the If the movementmovement is through the line of is through the line of gravity:gravity:– the muscle causes the movementthe muscle causes the movement– the contraction is concentricthe contraction is concentric– the muscle group that should perform the the muscle group that should perform the

action, performs the actionaction, performs the action

Olson’s 3rd PrincipleOlson’s 3rd Principle

If the If the movementmovement is toward is toward the line of the line of gravity:gravity:– the the resistanceresistance causes causes the movementthe movement– the contraction is the contraction is eccentriceccentric– the muscle group that is opposite to the joint the muscle group that is opposite to the joint

movement acts to control the movement movement acts to control the movement

Ulibarri’s Corollaries toUlibarri’s Corollaries toOlson’s PrinciplesOlson’s Principles

These corollaries restate Olson’s Principles These corollaries restate Olson’s Principles relative to the:relative to the:– direction of the weight (resistive force)direction of the weight (resistive force)– type of muscle contractiontype of muscle contraction– muscle group usedmuscle group used

Ulibarri’s 1st CorollaryUlibarri’s 1st Corollary

If the weight (resistive force) moves against If the weight (resistive force) moves against the line of gravity:the line of gravity:– the muscular force causes the movementthe muscular force causes the movement– the contraction is concentricthe contraction is concentric– the muscle group that should do the action, the muscle group that should do the action,

performs the actionperforms the action

Ulibarri’s 2nd CorollaryUlibarri’s 2nd Corollary

If the weight (resistive force) moves toward If the weight (resistive force) moves toward the line of gravity:the line of gravity:– the resistive force causes the movementthe resistive force causes the movement– the contraction is eccentricthe contraction is eccentric– the muscle group that is opposite to the joint the muscle group that is opposite to the joint

action acts to control the movementaction acts to control the movement