1. Properties of Skeletal Muscle
Skeletal muscles interact with the skeleton to provide movement.
Extensibility – ability for muscles to lengthen whilst contracting.
Elasticity – ability for the muscles to return to their normal resting length once stretched.
Contractility – muscle contracts/shortens.
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example

2. Functions of Skeletal Muscle
Movement – attach to bones and when they contract they pull to cause movement.
Support & Posture – muscles usually in a state of contraction. To remain upright muscles are contracting (also know as Muscle Tone).
Heat Production – contracting muscles involves energy production – heat is released. Voluntary or involuntary (shivering) movement.
Storage - of Glycogen for energy
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example

3. Muscle Fibres
Muscles are made up of thousands and thousands of individual muscle fibres.
Muscle fibres differ in physiological make-up – this difference distinguishes between a Sprinter and a Marathon runner
Fibres types tend to be inherited
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example

4. Muscle Fibres Three types of muscle fibre:
Slow-twitch (Type 1) – long periods of low-intensity exercise. Aerobic exercise. Small force.
Fast oxidative glycolytic (FOG) (Type 2a) – Fairly high intensity exercise and relatively short in duration. Anaerobically. Fatigue easily.
Fast-twitch glycolytic (FTG) (Type 2b) – Very high intensity and strong contractions. Large & thick. Anaerobically. Fatigue easily.
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example

5. Fast oxidative glycolytic - FOG (Type 2a)
Slow twitch
(Type 1)
Fast oxidative glycolytic - FOG (Type 2a)
Fast glycolytic - FTG (Type 2b)
Structural Characteristics
Colour
RED
PINK
WHITE
Size
SMALL
LARGE
Capillaries
HIGH
MODERATE
LOW
Mitochondria No.
Myoglobin Content
PC Stores
Glycogen Stores
Triglyceride Stores

6. Fast oxidative glycolytic - FOG (Type 2a)
Slow twitch
(Type 1)
Fast oxidative glycolytic - FOG (Type 2a)
Fast glycolytic - FTG (Type 2b)
Functional Characteristics
Contractile speed
SLOW
FAST
Contractile force
LOW
HIGH
Fatigue resistance
RESISTANT
LESS RESISTANT
EASILY FATIGUED
Aerobic capacity
MEDIUM
Anaerobic capacity
Activity suited
Marathon
1500m
110m Hurdles

7. Muscle Fibre Recruitment
Fibre type recruitment is based on the intensity of the exercise
The proportion of muscle fibre types differs within individual muscles
Most muscles have both fibre types
Postural? Arms? Legs?

8. Training Responses
It’s important to know how training can affect muscle fibres. What type of activities should a marathon runner do? A footballer? A Sprinter? A Javelin thrower?
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example

9. Connective Tissue
Connective tissue surrounds individual muscle fibres and encases the whole muscle forming TENDONS.
Tendons
Attach skeletal muscle to bone and transmit the pull of the muscle to the bone to cause movement.
Tendons vary in length (examples?) and composed of fibres called collagen.
Can withstand high levels of stress
Learning Objectives
Know what is meant by connective tissue and the types of muscle contraction
Understand the role of antagonistic muscle action
Be able to identify types of muscle contraction in an antagonistic muscle action

10. Connective Tissue cont.
Points of attachment are called:
Origin or Insertion
Origin
Point of attachment of muscle onto the stationary bone.
Insertion
Point of attachment of a muscle onto the bone that moves
Complete the ‘Movement Analysis Homework’ sheet.
Learning Objectives
Know what is meant by connective tissue and the types of muscle contraction
Understand the role of antagonistic muscle action
Be able to identify types of muscle contraction in an antagonistic muscle action

11. Antagonistic Muscle Action
Muscles work in groups or pairs to create movement
Agonist/Prime Mover
The muscle that contracts and is responsible for the movement
Antagonist
Muscle that relaxes and lengthens which is the opposite to the agonist and enables the movement to occur.
Fixator
Muscle that stabilises the origin of the agonist
Synergist – S for stabilises the joint
Muscles that prevent and undesired movement during muscular contraction
Learning Objectives
Know what is meant by connective tissue and the types of muscle contraction
Understand the role of antagonistic muscle action
Be able to identify types of muscle contraction in an antagonistic muscle action

12. What are the 3 types of muscle fibres
What are the 3 types of muscle fibres? Slow oxidative, fast oxidative glycolytic, fast glycolytic.
What has the biggest influence on muscle fibre type: training or genetics? Genetics, although training does have an influence
What would be the number of mitochondria in slow oxidative fibres? High
What would be the contractile speed of fast glycolytic fibres? Fast
What is the anaerobic capacity of fast glycolytic fibres? High
Are the number of capillaries at fast oxidative glycolytic fibres high, intermediate or low? Intermediate

13. How do muscles contract??
Skeletal muscles can only contract when stimulated by an electrical impulse sent from the CNS
Motor Unit made up of:
Motor neuron
Axon
Motor end plate
Muscle fibres
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

14. The Motor Unit
Motor Neurons A nerve cell which conducts a nerve impulse to a group of muscle fibres.
Motor Unit
A motor neuron and the muscle fibres that are stimulated by its Axon.
Its function is to carry nerve impulses from the brain & spinal cord to the muscle fibres – resulting in muscular contraction
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

15. Action Potential
Nerve impulses being sent to the muscle fibres is an electrochemical process
This relies on ACTION POTENTIAL
Action Potential
Positive electrical charge inside the nerve and muscle cells which conducts a nerve impulse down the axon to the motor end plates
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

16. Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

17. Neuromuscular Junction
Neuromuscular Junction The point where the Axon meets the muscle fibre – there is a gap called Synaptic Cleft Action Potential cannot cross Synaptic Cleft gap without a Neurotransmitter called Acetylcholine (Ach)
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

18. Neurotransmitter
Neurotransmitter A chemical (Acetylcholine) is produced and secreted by the neuron in the Synaptic Cleft to help the nerve impulse across the gap – where a muscle action potential is created. When the Action Potential reaches a threshold charge ALL muscle fibres (within motor unit) contract at maximum force – this is called the All-or-None Law. If the Action Potential does not reach threshold charge = no contraction.
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

19. Know what a motor unit is Understand the All-or-None Law
1) Nerve impulse initiated in motor neuron cell body
2) Nerve impulse conducts down Axon by Action Potential to neuromuscular junction
3) Neurotransmitter (Acetylcholine) is secreted in Synaptic Cleft and helps the nerve impulse across the gap
4) If electrical charge is above Threshold, then muscle fibres will contract
5) This is an all-or-none law
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

20. All-or-Nothing Law
Depends on whether the stimulus from the motor unit creates an action potential that is above threshold.
All muscle fibres will completely contract or no contraction at all
ALL or NOTHING
Learning Objectives
Know what a motor unit is
Understand the All-or-None Law
Be able to explain a skeletal muscle contraction

21. Homework: The basics Motor Neurone Disease:
Motor neurone disease (MND) is a uncommon condition that affects the brain and nerves. It causes weakness that gets worse over time.
It's always fatal and can significantly shorten life expectancy, but some people live with it for many years. There’s no cure, but there are treatments to help reduce the impact it has on your daily life.
Early symptoms can include:
weakness in your ankle or leg – you might trip, or find it harder to climb stairs
slurred speech, which may develop into difficulty swallowing some foods
a weak grip – you might drop things, or find it hard to open jars or do up buttons
muscle cramps and twitches
weight loss – your arms or leg muscles may have become thinner over time
difficulty stopping yourself crying or laughing in inappropriate situations

22. (Notes) Motor Neurone Size
Small motor neurones stimulate relatively few small muscle fibres. This motor unit would produce a small amount of force over a prolonged period of time and resist fatigue well (maintaining posture)
Large motor neurones stimulate many large muscle fibres. The motor unit produces a large amount of force rapidly, however they fatigue quickly (Jumping)

23. Recovery rates
SO fibres provide the energy for sub maximal aerobic work and have low contractile force
An individual fibre can recover quite quickly and be available for recruitment in 90seconds
Work to rest ratio is low. 1:1 or 1:05 (work: rest ratio) for example: Ten, three minute moderate intensity running intervals with 90 seconds rest between
Fibre damage is not associated with aerobic training so training can be done on a daily basis

24. FG fibres muscle fibres are recruited in the last 2-20 seconds of contraction, near muscle exhaustion or maximal efforts are needed quickly
Accompanied by eccentric muscle fibre damage which causes DOMS (24-48 hours after activity). Take longer to recover
Maximal weight training work:rest ratios are high. 1:3+ is common for each muscle worked with 3-5mins of rest between sets of 2-6reps
4-10 days to recover when used to exhaustion
A minimum of 48 hours before using the same muscle group again

25. Questions???
Account for the difference in the speed of contraction between slow and fast twitch fibres (4 marks)
High Glycogen content of fast twitch fibres
High levels of phosphocreatine stores in fast twitch fibres
More developed sarcoplasmic reticulum in fast twitch fibres which means more Ca++ available and improved transportation system for nutrients like glucose
Fast twitch have large motor neurones for fast conduction
Explain the differences in recovery rate between slow and fast twitch fibres (4 marks) 2 each from
Slow twitch fibres can recover relatively quickly 90 seconds
1:1 ratio (example)
Can train on a daily basis
Fast twitch fibres take longer to recover hours
1:3+ ratio (example)
Minimum 48 hours rest before using the same muscle

26. Answer the questions for revision
Look at the timetable for the 2016 Olympics
Is the schedule appropriate for what we’ve just learned regarding recovery?
Would it affect times/distances?
Think about the football world cup.
Is that schedule appropriate based on muscle recovery rates?

27. Prevision Refresh your knowledge on the structure of the heart
How does it beat?
What is the cardiac cycle?
What is HR, SV, Q?
How does the HR respond to exercise?
What is venous return?
Learning Objectives
Know the name, properties and function of the skeletal muscles
Understand the difference between fast-twitch and slow twitch muscle fibres
Be able to identify fast-twitch and slow-twitch muscle fibres in a practical example