Muscular System
1. What is the muscular system?
The muscular system is made up of muscles that allow the body to move.
Muscles work with the skeletal system to produce movement.
The muscular system is also important for:
Maintaining posture.
Stabilising joints.
Producing heat.
Supporting movement.
Helping the body perform physical activity.
Protecting some internal organs.
There are 3 main types of muscle:
Skeletal muscle.
Cardiac muscle.
Smooth muscle.
For sport and exercise, skeletal muscle is the most important because it produces voluntary movement.
2. The three types of muscle
Skeletal muscle
Skeletal muscles are attached to bones by tendons.
They are responsible for movement of the skeleton.
They are:
Voluntary muscles.
Controlled consciously.
Striated, meaning they have a striped appearance under a microscope.
Usually attached to bones in pairs or groups.
Examples:
Biceps.
Triceps.
Quadriceps.
Hamstrings.
Gastrocnemius.
Pectorals.
Sport example:
When doing a biceps curl, the biceps contracts to move the forearm.
Cardiac muscle
Cardiac muscle is only found in the heart.
It contracts continuously to pump blood around the body.
It is:
Involuntary.
Striated.
Very resistant to fatigue.
Controlled automatically by the nervous system and the heart's electrical system.
Sport example:
During exercise, cardiac muscle contracts more frequently so the heart can pump more blood to working muscles.
Smooth muscle
Smooth muscle is found in the walls of internal organs.
Examples include:
Stomach.
Intestines.
Blood vessels.
Bladder.
It is:
Involuntary.
Not striated.
Controlled automatically.
Smooth muscle helps move substances through the body.
For example, smooth muscle in the digestive system helps move food through the intestines.
3. Skeletal muscle
Skeletal muscle is the main type of muscle involved in sporting movement.
Skeletal muscles:
Attach to bones using tendons.
Contract and relax.
Pull on bones to create movement.
Help maintain posture.
Stabilise joints.
Produce heat.
A muscle can only pull, not push.
This is why muscles often work in pairs.
For example:
Biceps + triceps
Biceps contracts → elbow flexes.
Triceps contracts → elbow extends.
4. Major muscles of the body
You need to know the location and actions of the major muscles.
Deltoid
Location:
Shoulder.
Main action:
Abduction of the arm.
Sport example:
Raising the arm during swimming.
Lifting the arm during a shoulder press.
Pectorals
Location:
Chest.
Main actions:
Horizontal flexion of the shoulder.
Adduction of the arm.
Sport example:
Pushing the arms through the water during swimming.
Pushing movements in resistance training.
Biceps
Location:
Front of the upper arm.
Main action:
Flexion of the elbow.
Sport example:
Pulling the arm during swimming.
Biceps curl.
Triceps
Location:
Back of the upper arm.
Main action:
Extension of the elbow.
Sport example:
Straightening the arm during swimming.
Pushing movements.
Trapezius
Location:
Upper back and neck.
Main actions:
Helps move and stabilise the shoulder blades.
Helps with movement of the neck and shoulders.
Sport example:
Swimming.
Rowing.
Weight training.
Latissimus dorsi
Location:
Large muscle across the middle/lower back.
Main action:
Pulling the upper arm down and backwards.
Sport example:
Pulling the arms through the water during swimming.
Pull-ups.
Abdominals
Location:
Front of the trunk.
Main actions:
Flexion of the trunk.
Stabilisation of the trunk.
Sport example:
Maintaining body position while swimming.
Stabilising the body while horse riding.
Obliques
Location:
Sides of the abdomen.
Main actions:
Rotation of the trunk.
Lateral flexion of the trunk.
Stabilisation.
Sport example:
Turning the upper body.
Maintaining balance during horse riding.
Erector spinae
Location:
Runs along the spine.
Main actions:
Extension of the spine.
Maintaining posture.
Sport example:
Maintaining an upright position while horse riding.
Maintaining posture while lifting.
Gluteals
Location:
Buttocks.
Main actions:
Extension of the hip.
Abduction of the hip.
Help stabilise the pelvis.
Sport example:
Running.
Jumping.
Standing up from a squat.
Maintaining position while horse riding.
Hip flexors
Location:
Front of the hip.
Main action:
Flexion of the hip.
Sport example:
Bringing the leg forwards during running.
Lifting the leg while riding.
Quadriceps
Location:
Front of the thigh.
Main action:
Extension of the knee.
Sport example:
Kicking.
Running.
Jumping.
Standing up from a squat.
Hamstrings
Location:
Back of the thigh.
Main actions:
Flexion of the knee.
Extension of the hip.
Sport example:
Running.
Sprinting.
Jumping.
Tibialis anterior
Location:
Front of the lower leg.
Main action:
Dorsiflexion of the ankle.
Sport example:
Pulling the toes upwards while running.
Controlling foot position.
Gastrocnemius
Location:
Calf.
Main action:
Plantarflexion of the ankle.
It also helps with knee flexion.
Sport example:
Pushing off the ground when running.
Jumping.
Swimming.
Soleus
Location:
Lower calf, underneath the gastrocnemius.
Main action:
Plantarflexion of the ankle.
Sport example:
Running.
Jumping.
Maintaining posture.
5. Muscle actions
Muscles create movement by contracting.
Different muscles are responsible for different movements.
Examples:
Muscle | Main action |
|---|---|
Biceps | Elbow flexion |
Triceps | Elbow extension |
Deltoid | Shoulder abduction |
Pectorals | Shoulder horizontal flexion/adduction |
Latissimus dorsi | Shoulder extension/adduction |
Abdominals | Trunk flexion |
Erector spinae | Trunk extension |
Gluteals | Hip extension |
Hip flexors | Hip flexion |
Quadriceps | Knee extension |
Hamstrings | Knee flexion |
Gastrocnemius | Plantarflexion |
Tibialis anterior | Dorsiflexion |
6. How muscles produce movement
Muscles are attached to bones by tendons.
When a muscle contracts, it becomes shorter and pulls on the tendon.
The tendon then pulls on the bone.
This causes movement around a joint.
The basic process is:
Muscle contracts → tendon pulls → bone moves → joint movement occurs
Example:
During a biceps curl:
Biceps contracts → tendon pulls on forearm → elbow flexes → forearm moves upwards
7. Agonist and antagonist muscles
Muscles often work in pairs.
These are called antagonistic pairs.
One muscle contracts while the other relaxes.
Agonist
The agonist is the main muscle responsible for producing a movement.
It is sometimes called the prime mover.
Antagonist
The antagonist produces the opposite movement.
It relaxes or lengthens while the agonist contracts.
8. Example – biceps and triceps
The biceps and triceps form an antagonistic pair.
Elbow flexion
For example, during a biceps curl:
Biceps = agonist.
Biceps contracts.
Triceps = antagonist.
Triceps relaxes.
Elbow flexes.
Elbow extension
When straightening the arm:
Triceps = agonist.
Triceps contracts.
Biceps = antagonist.
Biceps relaxes.
Elbow extends.
Remember:
Biceps = flexion
Triceps = extension
9. Synergist muscles
A synergist is a muscle that helps the agonist produce movement.
It can:
Assist the main muscle.
Reduce unwanted movement.
Help make movement more controlled.
This is particularly important during complex sporting movements.
10. Fixator muscles
A fixator stabilises part of the body while another muscle produces movement.
Fixators are important because they prevent unwanted movement.
Example:
When performing an arm movement:
Some muscles move the arm.
Other muscles stabilise the shoulder and trunk.
This allows the movement to be controlled.
11. Types of muscle contraction
There are 3 important types of contraction:
Isometric.
Isotonic concentric.
Isotonic eccentric.
12. Isometric contraction
An isometric contraction happens when a muscle produces tension but does not change length.
The joint does not move.
Example:
Holding a plank.
Holding a squat position.
Holding a weight still.
During a plank:
The abdominal and other core muscles are working.
They produce tension.
There is little or no movement at the joints.
Sport example:
A horse rider uses isometric muscle contractions to maintain a stable position while riding.
13. Concentric contraction
A concentric contraction happens when a muscle shortens while producing force.
The muscle is working to create movement.
Example:
During a biceps curl:
The biceps contracts.
The biceps shortens.
The elbow flexes.
The weight moves upwards.
Therefore:
Concentric = muscle shortens
14. Eccentric contraction
An eccentric contraction happens when a muscle produces force while lengthening.
This often happens when controlling or slowing a movement.
Example:
During a biceps curl:
The weight is lowered.
The elbow extends.
The biceps is still working.
The biceps lengthens while controlling the movement.
Therefore:
Eccentric = muscle lengthens while under tension
Another example:
When landing from a jump:
The quadriceps contract eccentrically.
They help control knee flexion.
This slows the body down.
15. Comparing the three contractions
Contraction | What happens to muscle? | Joint movement? | Example |
|---|---|---|---|
Isometric | Stays the same length | No significant movement | Plank |
Concentric | Shortens | Yes | Lifting a weight |
Eccentric | Lengthens | Yes | Lowering a weight |
Easy way to remember:
Concentric = shortens
Eccentric = lengthens
Isometric = same length
16. Sliding filament theory
The sliding filament theory explains how skeletal muscles contract.
Inside muscle fibres are structures called myofibrils.
Myofibrils contain smaller units called sarcomeres.
Sarcomeres contain:
Actin.
Myosin.
These are protein filaments.
The interaction between actin and myosin causes muscle contraction.
17. Actin and myosin
Actin
Thin protein filament.
Myosin
Thick protein filament.
Has small projections called myosin heads.
During contraction:
Myosin heads attach to actin.
They pull the actin filaments.
The actin moves towards the centre of the sarcomere.
The sarcomere becomes shorter.
The muscle fibre shortens.
This produces muscle contraction.
18. Sliding filament theory – step by step
Step 1
A nerve impulse reaches the muscle.
This tells the muscle to contract.
Step 2
Calcium ions are released inside the muscle fibre.
Step 3
Calcium allows the binding sites on actin to become available.
Step 4
Myosin heads attach to the actin.
This is called forming a cross-bridge.
Step 5
The myosin head pulls the actin towards the centre of the sarcomere.
This is called the power stroke.
Step 6
ATP provides energy for the myosin head to detach and reset.
Step 7
The process repeats.
Step 8
The actin and myosin continue sliding past each other.
Step 9
The sarcomere becomes shorter.
Step 10
Many sarcomeres shortening together causes the muscle fibre to shorten.
This produces muscle contraction.
19. ATP and muscle contraction
Muscles need ATP to contract.
ATP stands for:
Adenosine triphosphate
ATP provides energy for:
Myosin heads to work.
Cross-bridge cycling.
Muscle contraction.
Relaxation processes.
The body stores only a small amount of ATP.
Therefore ATP has to be continually resynthesised.
This is why the energy systems are important.
The three main energy systems are:
ATP-PC system.
Anaerobic glycolysis/lactate system.
Aerobic system.
These systems produce ATP at different rates and are covered in more detail in the Energy Systems section.
20. Motor units
A motor unit consists of:
One motor neurone + all the muscle fibres it controls
A motor neurone carries an electrical signal to muscle fibres.
When the motor neurone is stimulated:
The muscle fibres it controls contract.
Force is produced.
21. Motor unit recruitment
The body can increase the force produced by a muscle by recruiting more motor units.
This is called motor unit recruitment.
For a small movement:
Fewer motor units are needed.
For a powerful movement:
More motor units are recruited.
Example:
Picking up a very light object:
Relatively few motor units may be needed.
Lifting a heavy weight:
More motor units are recruited.
Sport example:
A swimmer producing a powerful start from the blocks needs to recruit many motor units in the legs and trunk.
22. All-or-none law
The all-or-none law applies to individual muscle fibres/motor units.
A muscle fibre either:
Contracts fully when sufficiently stimulated, or
Does not contract.
It does not partially contract.
The overall force produced by a whole muscle can still vary because the nervous system can:
Recruit more motor units.
Increase the frequency of stimulation.
23. Muscle fibre types
There are different types of skeletal muscle fibre.
The main types are:
Type I.
Type IIa.
Type IIx.
Different fibres are suited to different types of activity.
24. Type I muscle fibres
Type I fibres are also called slow-twitch fibres.
They are suited to endurance activities.
Characteristics:
Contract relatively slowly.
Produce lower force.
Very resistant to fatigue.
Large number of mitochondria.
High myoglobin content.
Good blood supply.
Use aerobic respiration effectively.
They are useful for:
Long-distance running.
Long-distance swimming.
Cycling.
Endurance activities.
Sport example:
A long-distance swimmer needs muscles that can keep working for a long time without fatiguing quickly.
25. Type IIa muscle fibres
Type IIa fibres are often called fast oxidative fibres.
They have characteristics of both endurance and power fibres.
They:
Contract quickly.
Produce more force than Type I.
Have relatively good fatigue resistance.
Can use both aerobic and anaerobic energy production.
They are useful for:
Middle-distance activities.
Repeated high-intensity activity.
Team sports.
Activities requiring both speed and endurance.
26. Type IIx muscle fibres
Type IIx fibres are fast-twitch fibres.
They are suited to short, powerful activities.
Characteristics:
Contract very quickly.
Produce high force.
Fatigue quickly.
Relatively low aerobic capacity.
Useful for explosive movements.
They are useful for:
Sprinting.
Jumping.
Throwing.
Powerlifting.
Explosive sporting movements.
Sport example:
A sprinter needs to produce a large amount of force very quickly, so fast-twitch fibres are important.
27. Muscle fibre comparison
Type | Speed | Force | Fatigue resistance | Main use |
|---|---|---|---|---|
Type I | Slow | Lower | Very high | Endurance |
Type IIa | Fast | Moderate/high | Moderate | Repeated high-intensity activity |
Type IIx | Very fast | High | Low | Power/sprint |
Easy memory:
Type I = long and lasting
Type II = fast and powerful
28. Muscle fatigue
Muscle fatigue occurs when muscles become less able to produce the required force.
It can occur during prolonged or intense exercise.
Possible causes include:
Reduced energy availability.
Accumulation of metabolites.
Reduced ability of the muscle to contract effectively.
Dehydration.
Reduced glycogen availability.
Fatigue can cause:
Reduced force.
Reduced speed.
Poorer technique.
Reduced performance.
Example:
During the final part of a long swimming session, fatigue can make the swimmer's technique less effective.
29. Muscle cramps
A muscle cramp is a sudden, involuntary and painful contraction of a muscle.
They can occur during or after exercise.
Possible contributing factors include:
Fatigue.
Dehydration.
Electrolyte imbalance.
Exercising beyond normal levels.
Muscle overload.
Examples:
Calf cramp while swimming.
Hamstring cramp during running.
30. Immediate responses of the muscular system to exercise
The muscular system changes immediately when exercise begins.
These include:
Increased muscle temperature
Working muscles produce heat.
This increases muscle temperature.
Warmer muscles can work more effectively.
Increased blood flow
More blood is directed towards working muscles.
This provides:
Oxygen.
Glucose.
Other nutrients.
It also helps remove waste products.
Increased muscle fibre recruitment
More motor units are recruited when greater force is needed.
Increased rate of muscle contraction
During intense activity, muscles may need to contract rapidly.
Increased production of ATP
The energy systems increase ATP production to meet the demands of exercise.
31. Long-term adaptations to resistance training
Regular resistance training can cause adaptations.
Muscle hypertrophy
Hypertrophy means an increase in muscle size.
Resistance training causes the muscles to adapt to repeated overload.
Over time:
Muscle fibres increase in size.
Muscles can produce more force.
Strength can increase.
Example:
A person completing regular resistance training may develop larger and stronger quadriceps.
Increased muscular strength
Regular resistance training can increase the ability of muscles to produce force.
This can occur through:
Muscle hypertrophy.
Improved motor unit recruitment.
Improved coordination of muscle activation.
Increased muscular endurance
Training can improve the ability of muscles to continue working for longer.
This is important for:
Swimming.
Running.
Cycling.
Horse riding.
Team sports.
32. Adaptations to endurance training
Endurance training can produce changes that improve the muscles' ability to use oxygen and produce energy aerobically.
These can include:
Increased mitochondrial density.
Increased myoglobin.
Improved capillarisation.
Improved ability to use oxygen.
Greater ability to use aerobic energy production.
This helps delay fatigue during endurance exercise.
33. Tendon adaptations
Tendons connect muscles to bones.
Regular training can increase tendon strength and stiffness over time.
This can help tendons:
Transmit force from muscle to bone.
Cope with repeated loading.
Support movement.
However, tendons generally adapt more slowly than muscles.
This is one reason training should progress gradually.
34. Muscles and posture
Muscles help maintain posture.
Postural muscles work continuously to keep the body in position.
Examples:
Abdominals.
Erector spinae.
Gluteals.
Muscles around the shoulders.
During horse riding, many muscles work to maintain:
Balance.
Trunk position.
Hip position.
Leg position.
The rider needs muscular endurance because the muscles may need to work for a long period.
35. Muscles and swimming
Swimming uses many muscle groups.
Upper body
Pectorals.
Latissimus dorsi.
Deltoids.
Biceps.
Triceps.
Trapezius.
Core
Abdominals.
Obliques.
Erector spinae.
Lower body
Gluteals.
Quadriceps.
Hamstrings.
Gastrocnemius.
Soleus.
The exact muscles used depend on the swimming stroke.
For example:
During front crawl:
Latissimus dorsi helps pull the arm through the water.
Pectorals help with arm movement.
Deltoids help move the arm.
Triceps help extend the elbow.
Core muscles stabilise the body.
Leg muscles help produce the kicking action.
36. Muscles and horse riding
Horse riding requires the rider to maintain a stable position while responding to the horse.
Important muscles include:
Abdominals.
Obliques.
Erector spinae.
Gluteals.
Quadriceps.
Hamstrings.
Hip flexors.
Calf muscles.
The rider needs:
Muscular endurance.
Core strength.
Postural control.
Hip stability.
Leg strength.
Example:
The core muscles help keep the rider's trunk stable.
The quadriceps and hamstrings help control the position of the legs.
The calf muscles can be used to communicate with the horse.
37. Muscles and running
Running requires repeated contractions of the lower-body muscles.
Important muscles include:
Gluteals.
Quadriceps.
Hamstrings.
Hip flexors.
Gastrocnemius.
Soleus.
Tibialis anterior.
The muscles:
Produce force.
Control movement.
Stabilise joints.
Absorb impact.
Propel the body forwards.
During sprinting, a large amount of force must be produced quickly.
During distance running, the muscles need to resist fatigue for a longer period.
38. Muscles and jumping
Jumping requires explosive force.
Important muscles include:
Gluteals.
Quadriceps.
Hamstrings.
Gastrocnemius.
Soleus.
Before take-off:
The muscles produce force against the ground.
During take-off:
Hip, knee and ankle extend.
This is sometimes described as triple extension.
The result is:
Force against the ground.
The body is propelled upwards.
39. Muscles working together
Sporting movements rarely use only one muscle.
Many muscles work together.
For example, a jump uses:
Gluteals.
Quadriceps.
Hamstrings.
Calf muscles.
Core muscles.
Some muscles act as:
Agonists.
Antagonists.
Synergists.
Fixators.
This allows movement to be:
Powerful.
Controlled.
Stable.
Coordinated.
40. Nervous system and muscular system
The muscular system works closely with the nervous system.
The nervous system:
Detects information.
Sends electrical impulses.
Controls muscle contraction.
Basic process:
Brain/nervous system → motor neurone → muscle → contraction → movement
This allows the body to control sporting movements.
Example:
A swimmer decides to move their arm.
The nervous system sends signals to the relevant muscles.
The muscles contract.
The arm moves.
41. Neuromuscular junction
A neuromuscular junction is the point where a motor neurone communicates with a muscle fibre.
The process is:
An electrical impulse travels down the motor neurone.
The impulse reaches the end of the neurone.
A chemical neurotransmitter called acetylcholine is released.
Acetylcholine crosses the small gap between the nerve and muscle.
It binds to receptors on the muscle fibre.
This starts an electrical signal in the muscle.
Calcium is released.
The actin and myosin interaction begins.
The muscle contracts.
42. Age and the muscular system
The muscular system changes with age.
As people get older:
Muscle mass can decrease.
Muscle strength can decrease.
Muscle power can decrease.
Recovery can become slower.
Flexibility can decrease.
Reaction speed can decrease.
This is partly associated with sarcopenia, which is the age-related loss of muscle mass and strength.
Regular physical activity and resistance training can help maintain muscular function.
43. Children and young athletes
Children are still developing physically.
Their:
Muscles are developing.
Bones are developing.
Coordination is developing.
Neuromuscular control is developing.
Training should therefore be appropriate for:
Age.
Development.
Experience.
Ability.
Technique and safe progression are particularly important.
44. Short-term vs long-term muscular responses
It is important not to confuse these in an exam.
Short-term responses
These happen during or immediately after exercise.
Examples:
Increased muscle temperature.
Increased blood flow.
Increased motor unit recruitment.
Increased ATP production.
Muscle fatigue.
Long-term adaptations
These occur after regular training over time.
Examples:
Muscle hypertrophy.
Increased strength.
Increased muscular endurance.
Increased mitochondrial density.
Increased myoglobin.
Stronger tendons.
Easy way to remember:
Short-term = what happens during exercise
Long-term = what happens because you keep training
45. Key muscular system terms
Skeletal muscle
Muscle attached to bones that produces voluntary movement.
Cardiac muscle
Muscle found in the heart.
Smooth muscle
Involuntary muscle found in internal organs.
Tendon
Connects muscle to bone.
Agonist
Main muscle producing a movement.
Antagonist
Muscle that produces the opposite movement.
Synergist
Muscle that assists the agonist.
Fixator
Muscle that stabilises a body part.
Concentric
Muscle shortens while producing force.
Eccentric
Muscle lengthens while producing force.
Isometric
Muscle produces tension without changing length significantly.
Actin
Thin protein filament involved in muscle contraction.
Myosin
Thick protein filament involved in muscle contraction.
Sarcomere
Functional unit of a muscle fibre where actin and myosin interact.
Motor unit
One motor neurone and all the muscle fibres it controls.
Hypertrophy
Increase in muscle size.
Muscle fatigue
Reduced ability of a muscle to continue producing the required force.
Type I fibre
Slow-twitch, endurance-oriented muscle fibre.
Type IIa fibre
Fast muscle fibre with relatively good fatigue resistance.
Type IIx fibre
Fast, powerful muscle fibre that fatigues quickly.
46. Easy muscle action memory list
Upper body
Biceps → flexes elbow
Triceps → extends elbow
Deltoid → abducts shoulder
Pectorals → horizontal flexion/adduction of shoulder
Latissimus dorsi → extension/adduction of shoulder
Trunk
Abdominals → flex trunk
Obliques → rotate/laterally flex trunk
Erector spinae → extend trunk
Lower body
Hip flexors → flex hip
Gluteals → extend hip
Quadriceps → extend knee
Hamstrings → flex knee
Tibialis anterior → dorsiflex ankle
Gastrocnemius → plantarflex ankle
Soleus → plantarflex ankle
47. Example exam question
Explain how the muscular system allows a swimmer to perform front crawl.
A good answer could include:
The muscular system works with the skeletal system to produce movement.
The latissimus dorsi helps pull the arm through the water.
The pectorals and deltoids help move the arm.
The triceps help extend the elbow.
The abdominal and back muscles stabilise the trunk.
The quadriceps, hamstrings and calf muscles help produce the kicking action.
Muscles contract by the sliding filament mechanism.
Actin and myosin interact inside the muscle fibres.
ATP provides energy for contraction.
Different muscles act as agonists, antagonists, synergists and fixators to make movement controlled.
48. Example exam question – contractions
Explain the different types of muscle contraction using a biceps curl.
A good answer:
During the lifting phase, the biceps acts as the agonist.
The biceps contracts concentrically.
It shortens while producing force.
This causes elbow flexion.
During the lowering phase, the biceps contracts eccentrically.
It lengthens while still producing force.
This controls the lowering of the weight.
If the weight is held still, the biceps can contract isometrically.
The muscle produces tension but does not significantly change length.
49. Example exam question – muscle fibre types
Explain why different muscle fibre types are useful for different sports.
A good answer:
Type I fibres are slow-twitch fibres.
They are resistant to fatigue and suited to endurance activities.
They are useful for long-distance swimming or running.
Type IIa fibres contract faster and can produce more force.
They are useful for repeated high-intensity activities.
Type IIx fibres contract very quickly and produce high force.
They are suited to explosive activities such as sprinting and jumping.
Therefore, different sports place different demands on the muscles.
50. The muscular system in one chain
Remember this overall process:
Nervous system
↓
Motor neurone sends impulse
↓
Neuromuscular junction
↓
Muscle fibre stimulated
↓
Calcium released
↓
Actin + myosin interact
↓
Sarcomeres shorten
↓
Muscle contracts
↓
Tendon pulls on bone
↓
Joint moves
↓
Sporting movement occurs
51. What you need to know for the exam
Make sure you can:
Name the 3 types of muscle.
Explain the difference between skeletal, cardiac and smooth muscle.
Identify the major skeletal muscles.
State the main action of each major muscle.
Explain agonists and antagonists.
Explain synergists and fixators.
Explain concentric contraction.
Explain eccentric contraction.
Explain isometric contraction.
Explain the sliding filament theory.
Know the roles of actin and myosin.
Explain the role of ATP.
Explain motor units.
Explain motor unit recruitment.
Understand the all-or-none law.
Know Type I, Type IIa and Type IIx fibres.
Explain muscle fatigue.
Explain muscle cramps.
Know immediate responses of the muscular system.
Know long-term adaptations to training.
Understand muscle hypertrophy.
Understand how muscles work with the skeletal system.
Apply muscular system knowledge to sporting examples.
Be able to use swimming, horse riding, running and jumping as examples.
52. Quick revision page
Muscle types
Skeletal = voluntary movement
Cardiac = heart
Smooth = internal organs
Contractions
Concentric = shortens
Eccentric = lengthens
Isometric = same length
Muscle pairs
Biceps = elbow flexion
Triceps = elbow extension
Fibre types
Type I = endurance
Type IIa = speed + endurance
Type IIx = power + speed
Contraction
Nerve impulse → calcium → actin/myosin → ATP → sarcomere shortens → muscle contracts
Long-term training
Training → overload → adaptation → stronger/larger/more efficient muscles
Muscular system + skeletal system
Muscle → tendon → bone → joint → movement
53. Big picture
The muscular system does not work on its own.
It works together with several other body systems.
Nervous system
→ controls muscle contraction.
Muscular system
→ produces force.
Skeletal system
→ provides bones and joints for movement.
Cardiovascular system
→ delivers oxygen and nutrients to muscles and removes waste.
Respiratory system
→ supplies oxygen and removes carbon dioxide.
Energy systems
→ provide ATP for muscle contraction.
Therefore:
Nervous system + muscular system + skeletal system + cardiovascular system + respiratory system + energy systems = sporting movement and performance.