1. Unit 1 – Anatomy & Physiology
P4 – Describe the Function of the Muscular System & the Different Fibre Types
Unit 1 – Anatomy & Physiology

3. Function of the Muscular System (skeletal muscle)
= Generate movement
Needs 3 things
Energy (ATP)
Calcium (on/off switch)
Stimulus (signal from brain/spinal cord)

4. Movement Muscles cross joints Muscles contract and pull on the bones
Muscles are ‘ready to go’ always slightly contracted waiting for a message from the nervous system (muscle tone)
Without this we would fall over!
Muscles work ‘all or nothing’
How strong the contraction is depends on how many muscle fibres are used
Muscles use a lot of energy

5. Basic Muscle Rules
Muscles can only pull on their bony attachment – never push
All muscles work in pairs. When 1 muscle contracts (agonist) the other muscle must relax (antagonist) = reciprocal innervation

6. Major Muscle Pairs AGONIST ANTAGONIST Pectoralis Major
Trapezius, Rhomboids
Latissimus Dorsi
Deltoids
Biceps
Triceps
Rectus Abdominus
Erector spinae
Gluteus Maximus
Hip flexors
Gluteus Medius / Minimus
Adductors
Quadriceps
Hamstrings
Gastrocnemius
Tibialis anterior
Soleus

7. Muscles work together!
Agonist – the main muscle generating the movement – prime mover
Antagonist – opposite muscle to the agonist – relaxes to allow the movement to happen
Fixator – the muscle or muscles that contract isometrically to fix a nearby or adjacent joint to prevent any unwanted movement
Synergist – the muscle or muscles that assist the agonist to generate the movement

8. Bicep Curl
Agonist =
Antagonist =
Fixator =
Synergist =

9. Types of Contraction

10. Types of Contractions
Isometric – muscle length stays the same, no movement, static contraction, easy to do but fatigues quickly. e.g. Plank
Concentric – muscle shortens, joint moves, also known as the positive phase of contraction. e.g. Upward part of bicep curl
Eccentric – muscle returning to original length, under resistance, after shortening, muscle works against gravity as a breaking mechanism, known as the negative phase of contraction. e.g. Downward phase of bicep curl
Isokinetic – muscle contracts & shortens at a constant speed, needs specialised equipment that detects the speed of the movement & increases or decreases the load to keep it at the same speed.

11. Isokinetic Training Machine

12. Types of Muscle Fibres
Muscle fibres are classed by the speed of their contraction.
Slow Twitch = Type 1
Fast Twitch = Type 2 (2a & 2b)
All skeletal muscles = different mix of fibres – down to genetics but training can change the characteristics!

13. Types of Muscle Fibres
Muscle fibres are classed by the speed of their contraction.
Slow Twitch = Type 1
Fast Twitch = Type 2 (2a & 2b)
All skeletal muscles = different mix of fibres – down to genetics but training can change the characteristics!

14. Type 1 Muscle Fibres Slow contraction Produce minimal force
Slow to fatigue
Good blood supply
Aerobic
High number of mitochondria
Red in colour
Suited to endurance based aerobic activities

15. Type 2 Muscle Fibres
Type 2a Fast contraction Medium force Slow to fatigue Middle distance Good blood supply Red in colour Aerobic
Type 2b
Fast contraction
High force Quick to fatigue
Short duration/stop go Speed & strength based
Low blood supply
White in colour Anaerobic

16. Muscle Fibres & Sports
Type 1 =
Type 2a =
Type 2b =