1. SPORT AND EXERCISE SCIENCE Anatomy Muscular 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 Practical Worksheet 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