Muscles

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Muscles
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Learning Objectives

• By the end of this unit you will
• Know the names, positions and roles of the major
  muscles
• Understand how muscles work to create movement
• Be able to apply this knowledge to different
  sporting actions

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Major muscles of the body
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Active Challenge

• Work in groups of 3 or 4 and nominate one person
  to be a body
• Take 3 or 4 sheets of flip chart paper and put
  them on the floor so the body can lay on them
• Use a marker pen to draw around the outline of
  the body.
• Use your knowledge of the position of the muscles
  to label your picture.
• You can use the following to say if the muscle is
  
• A (Anterior) the front of the body
• P (Posterior) the back of the body
• L (Lateral ) the side of the body

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Types of muscle
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What is muscle made up of?

• Muscles consist of lots of tiny, thread-like
  fibres that are packed together in bundles.
• In voluntary muscles they come together at the
  end of the muscles to form the tendon.

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Muscle Fibres

• Slow-twitch fibres
• good oxygen supply
• work for a long time
• cant work very fast,
• used in all types of exercise, especially ones
  that need cardiovascular fitness like distance
  running.

• Fast-twitch fibres
• poor oxygen supply
• tire quickly
• strong
• work very quickly
• used for movements that need to be fast and
  powerful like sprinting and jumping.

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How these muscle fibres work

• Our muscles are usually a mixture of slow-twitch
  and fast-twitch fibres. In low intensity
  exercise, the slow-twitch fibres do more of the
  work, but as the intensity increases, the
  fast-twitch fibres begin to kick in. At maximum
  intensity, both sets will be working flat out.

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How many slow-twitch and fast-twitch fibres do we
have?

• The ratio of slow-twitch to fast-twitch fibres in
  our muscles is partly determined by genetics. A
  person with more slow-twitch fibres is likely to
  be better at sports needing good cardiovascular
  fitness. Someone with more fast-twitch fibres is
  likely to be better at anaerobic activity
  throwing and jumping.

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How do muscles work?

• Muscles work in two main ways
• 1)   Isometric Contraction
• 2)   Isotonic Contraction

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Different types of contraction

• Isometric contraction is where the muscle is
  tensed (contracted) but it does not change
  length.

• Isotonic contraction is where the muscle tenses
  (contracts) and its length changes. There are two
  types eccentric and concentric

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Active Challenge -Static press up

• Get into this position on the floor and dont
  move!
• Ask your partner to feel your biceps and triceps
  muscles.
• How do they feel? Are they under similar tension?
• Is this contraction isotonic or isometric?

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Isotonic Contraction

• Concentric muscle contraction is where the muscle
  fibres shorten as they contract. The ends of the
  muscle move closer together.

• Eccentric muscle contraction is where the muscle
  fibres lengthen. The ends of the muscles move
  further apart.

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Active Challenge-Bicep Curl
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• Try this task (using one weight, not two).
• Feel your biceps muscle as you perform the bicep
  curl
• What is the difference in muscle size when you
  lift the weight, compared to when you lower it?
• Is the contraction concentric or eccentric?

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How are our muscles attached to bones? - Origin

• Muscles are normally attached to two or more
  different bones.
• The end of the muscle that is attached to the
  fixed bone is called the origin.

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How are our muscles attached to bones? - Insertion

• The other end is called the insertion and it is
  attached to the moving bone.
• As the muscle contracts the insertion moves
  closer to the origin.

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How does muscle attach to bone?

• Tendons are very strong cords of fibrous tissue,
  which attach muscle to bone.
• They can stretch a little much less than
  ligaments, and can get bruised or torn in some
  situations.
• E.g. Achilles tendon

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How do our muscles work together?

• Muscles can only work by pulling. They take on
  different roles depending on what kind of
  movement is being attempted.
• Flexors these contract to bend (flex) the
  joint
• Extensors these contract to straighten
  (extend) the joint
• Prime movers (agonists) these contract to
  start off a movement
• Antagonists these relax to allow another
  muscle to do its job.

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How do our muscles work in pairs?

• When a prime mover contracts, the antagonist
  relaxes so that the movement can take place.
• In isometric muscle contraction both muscles
  contract at the same time so no movement is seen.

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Active Challenge

• Working with a partner, perform the following
  actions, and see if you can work out which
  muscles are acting as the prime movers and which
  are acting as the antagonists.
• Squat onto a chair
• A biceps curl

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Did you get it right?

• Squat
• Prime mover hamstrings (cause flexion at the
  knee)
• Antagonist quadriceps (contract eccentrically
  (lengthen) to allow flexion at the knee and
  control the action)
• Biceps Curl
• Prime mover biceps (cause flexion at the elbow)
• Antagonist triceps (relax to allow flexion at
  the elbow)
• What would happen if the actions were reversed,
  e.g. standing up from a squat or extending the
  arm in a biceps curl?

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Muscle Tone

• Even when you are standing still your muscles are
  still partly contracted.
• This state of partial contraction is called
  muscle tone. Without it you'd collapse in a heap.
  
• In partial contraction, groups of fibres take
  turns to contract, so muscles don't get too tired.

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Muscles and Exercise

• We can make our muscles stronger by exercising,
  but if we stop exercising the principle of
  reversibility is applied.
• If we dont use it, we lose it!
• Hypertrophy is when the muscles get larger and
  stronger.
• Atrophy is when the muscles get smaller and
  weaker.
• Weight training is most commonly used to increase
  muscle strength, but most forms of exercise,
  repeated often enough, will have a positive
  effect on the muscles involved.