11

SPORT AND EXERCISE SCIENCE SPORT AND EXERCISE SCIENCE AnatomyAnatomy

Muscular Contractions. Muscular Contractions.

22

Learning OutcomesLearning Outcomes

By the end of this session you should By the end of this session you should be able to:be able to:

Explain the terms origin and insertionExplain the terms origin and insertion Identify at least 4 different roles of Identify at least 4 different roles of

musclesmuscles Explain the terms isotonic, Explain the terms isotonic,

concentric, eccentric, isometric and concentric, eccentric, isometric and isokinetic contractionisokinetic contraction

33

Ongoing TaskOngoing Task

Try to complete worksheet 38 and 39 Try to complete worksheet 38 and 39 as we go through the lecture.as we go through the lecture.

44

Muscle AttachmentMuscle Attachment

Attached to bones by TENDONSAttached to bones by TENDONS Muscles always cross at least 1 joint Muscles always cross at least 1 joint

(some, e.g. rectus femoris, cross 2 (some, e.g. rectus femoris, cross 2 joints)joints)

When a muscle contracts, the ends When a muscle contracts, the ends are pulled towards each other, are pulled towards each other, exerting a force on the attached exerting a force on the attached bones, and producing movement at bones, and producing movement at the jointsthe joints

55

Origin and InsertionOrigin and Insertion

The fixed attachment point is called The fixed attachment point is called the ORIGIN point of the muscle (i.e. the ORIGIN point of the muscle (i.e. the end of the muscle attached to a the end of the muscle attached to a bone that does NOT move)bone that does NOT move)

The moving end is called the The moving end is called the INSERTION point of the muscle (i.e. INSERTION point of the muscle (i.e. the end of the muscle attached to a the end of the muscle attached to a bone that does move)bone that does move)

66

ExampleExample

OriginInsertion

77

Muscles and MovementMuscles and Movement

Muscles can only pull, they cannot Muscles can only pull, they cannot pushpush

They must, therefore, work in pairs in They must, therefore, work in pairs in order for movement to occurorder for movement to occur

Muscles that work together are Muscles that work together are called ANTAGONISTIC PAIRScalled ANTAGONISTIC PAIRS

88

Roles of MusclesRoles of Muscles

AGONIST (prime mover) - the muscle that AGONIST (prime mover) - the muscle that contracts to cause a movement (e.g. the contracts to cause a movement (e.g. the bicep muscle contracts to cause the arm bicep muscle contracts to cause the arm to bend)to bend)

ANTAGONIST – the opposing muscle to the ANTAGONIST – the opposing muscle to the agonist (in the example this would be the agonist (in the example this would be the triceps)triceps)

Antagonist must relax and lengthen to Antagonist must relax and lengthen to allow movement to occur (i.e. bending the allow movement to occur (i.e. bending the arm)arm)

Known as RECIPROCAL INNERVATIONKnown as RECIPROCAL INNERVATION

99

Roles of Muscles (cont)Roles of Muscles (cont)

SYNERGIST – muscles that help the prime SYNERGIST – muscles that help the prime mover to produce the desired movement mover to produce the desired movement (sometimes called neutralisers as they prevent (sometimes called neutralisers as they prevent undesired movements) (e.g. the brachialis acts undesired movements) (e.g. the brachialis acts as synergist when the elbow is bent)as synergist when the elbow is bent)

STABILISER – a muscle that stabilises the STABILISER – a muscle that stabilises the origin of the prime mover (e.g. the deltoid origin of the prime mover (e.g. the deltoid contracts (but does not move) to stabilise the contracts (but does not move) to stabilise the origin of the biceps)origin of the biceps)

FIXATOR – muscles that contract to keep other FIXATOR – muscles that contract to keep other joints of the body stilljoints of the body still

1010

Types of ContractionsTypes of Contractions

Contraction = development of tension Contraction = development of tension within the musclewithin the muscle

IsotonicIsotonic• ConcentricConcentric• EccentricEccentric

IsometricIsometric IsokineticIsokinetic

1111

Isotonic ContractionsIsotonic Contractions

Involves movementInvolves movement

Contractions can be either concentric Contractions can be either concentric (shortening) or eccentric (shortening) or eccentric (lengthening)(lengthening)

1212

Concentric ContractionConcentric Contraction

A muscle actively A muscle actively shortens and shortens and thickens, creating thickens, creating movement around movement around a joint (e.g. the a joint (e.g. the biceps biceps concentrically concentrically contracts to allow contracts to allow the elbow to bend)the elbow to bend)

1313

Eccentric ContractionEccentric Contraction

A muscle contracts but lengthensA muscle contracts but lengthens 2 ends of the muscle are drawn apart2 ends of the muscle are drawn apart Acts against gravity to control movement Acts against gravity to control movement

(acts like a brake)(acts like a brake)

(e.g. the biceps that contracted (e.g. the biceps that contracted concentrically to curl the elbow will be concentrically to curl the elbow will be subject to an eccentric contraction to subject to an eccentric contraction to control the lowering of the arm against the control the lowering of the arm against the force of gravity)force of gravity)

1414

Isometric ContractionIsometric Contraction

A muscle contracts (develops tension) but A muscle contracts (develops tension) but no movement occurs, therefore no change no movement occurs, therefore no change in muscle length (e.g. curl the arm in muscle length (e.g. curl the arm upwards and then hold in that position, or upwards and then hold in that position, or tug of war)tug of war)

The tension in the muscle is exactly the The tension in the muscle is exactly the same as the opposing forcesame as the opposing force

Fixator muscles often contract Fixator muscles often contract isometricallyisometrically

1515

Isokinetic ContractionIsokinetic Contraction

Muscle worked at maximum tension Muscle worked at maximum tension throughout its range at a controlled throughout its range at a controlled speedspeed

Requires expensive specialised Requires expensive specialised equipment (often used for equipment (often used for rehabilitation)rehabilitation)

1616

Student PracticalStudent PracticalWorksheet 40 and 41Worksheet 40 and 41

Work in pairs and carry out the following Work in pairs and carry out the following exercises:exercises:• Press upsPress ups• Sit upsSit ups• Arm wrestleArm wrestle• Ski squatSki squat

What muscles are being worked?What muscles are being worked? What type of contractions are taking What type of contractions are taking

place?place?

1717

Learning OutcomesLearning Outcomes

By the end of this session you should By the end of this session you should be able to:be able to:

Explain the terms origin and insertionExplain the terms origin and insertion Identify at least 4 different roles of Identify at least 4 different roles of

musclesmuscles Explain the terms isotonic, Explain the terms isotonic,

concentric, eccentric, isometric and concentric, eccentric, isometric and isokinetic contractionisokinetic contraction