SPORT AND EXERCISE SCIENCE Anatomy Muscular Contractions.

1
SPORT AND EXERCISE SCIENCE AnatomyMuscular
Contractions.
2
Learning Outcomes

• By the end of this session you should be able to
• Explain the terms origin and insertion
• Identify at least 4 different roles of muscles
• Explain the terms isotonic, concentric,
  eccentric, isometric and isokinetic contraction

3
Ongoing Task

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

4
Muscle Attachment

• Attached to bones by TENDONS
• Muscles always cross at least 1 joint (some, e.g.
  rectus femoris, cross 2 joints)
• When a muscle contracts, the ends are pulled
  towards each other, exerting a force on the
  attached bones, and producing movement at the
  joints

5
Origin and Insertion

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

6
Example
Insertion
Origin
7
Muscles and Movement

• Muscles can only pull, they cannot push
• They must, therefore, work in pairs in order for
  movement to occur
• Muscles that work together are called
  ANTAGONISTIC PAIRS

8
Roles of Muscles

• AGONIST (prime mover) - the muscle that
  contracts to cause a movement (e.g. the bicep
  muscle contracts to cause the arm to bend)
• ANTAGONIST the opposing muscle to the agonist
  (in the example this would be the triceps)
• Antagonist must relax and lengthen to allow
  movement to occur (i.e. bending the arm)
• Known as RECIPROCAL INNERVATION

9
Roles of Muscles (cont)

• SYNERGIST muscles that help the prime mover to
  produce the desired movement (sometimes called
  neutralisers as they prevent undesired movements)
  (e.g. the brachialis acts as synergist when the
  elbow is bent)
• STABILISER a muscle that stabilises the origin
  of the prime mover (e.g. the deltoid contracts
  (but does not move) to stabilise the origin of
  the biceps)
• FIXATOR muscles that contract to keep other
  joints of the body still

10
Types of Contractions

• Contraction development of tension within the
  muscle
• Isotonic
• Concentric
• Eccentric
• Isometric
• Isokinetic

11
Isotonic Contractions

• Involves movement
• Contractions can be either concentric
  (shortening) or eccentric (lengthening)

12
Concentric Contraction

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

13
Eccentric Contraction

• A muscle contracts but lengthens
• 2 ends of the muscle are drawn apart
• Acts against gravity to control movement (acts
  like a brake)
• (e.g. the biceps that contracted concentrically
  to curl the elbow will be subject to an eccentric
  contraction to control the lowering of the arm
  against the force of gravity)

14
Isometric Contraction

• A muscle contracts (develops tension) but no
  movement occurs, therefore no change in muscle
  length (e.g. curl the arm upwards and then hold
  in that position, or tug of war)
• The tension in the muscle is exactly the same as
  the opposing force
• Fixator muscles often contract isometrically

15
Isokinetic Contraction

• Muscle worked at maximum tension throughout its
  range at a controlled speed
• Requires expensive specialised equipment (often
  used for rehabilitation)

16
Student PracticalWorksheet 40 and 41

• Work in pairs and carry out the following
  exercises
• Press ups
• Sit ups
• Arm wrestle
• Ski squat
• What muscles are being worked?
• What type of contractions are taking place?

17
Learning Outcomes

• By the end of this session you should be able to
• Explain the terms origin and insertion
• Identify at least 4 different roles of muscles
• Explain the terms isotonic, concentric,
  eccentric, isometric and isokinetic contraction