Muscle Speed and Tone

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Muscle Speed and Tone
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Muscle Fibres

• Muscles are made up of cells called fibres.
• Muscle contract (shorten) because the fibres do.
• All the fibres do not contract at once.
• The number contracting depends on how much force
  is needed.
• You use more muscle fibres to lift 100kg than
  10kg.

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Two types of muscle fibres

• Slow twitch contract slowly, and without much
  force. But they do not tire easily. They are
  suited to endurance activities.
• Fast twitch contract much faster than slow
  twitch fibres, and with much more force. But
  they do tire quickly. They are suited to
  activities that require short bursts of strength
  and power.

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• Every muscle contains a mixture, but
• The mixture is different in different muscles.
• Your gastrocnemius contains a lot of fast twitch
  fibre. Standing on your toes gets tiring.

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• The mixture is different for different people.
• Some distance runners have 80 slow twitch
  fibres while some weight lifters have 80 fast
  twitch fibres.

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• Why the difference?
• Its your parents fault!!
• You inherited the mixture from them and its too
  late to change it now.
• Can you train your muscles to react differently?

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How muscle speed affects performance

• The more fast twitch fibres you have, the more
  suited you are to sports that need bursts of
  strength and power.
• Think About!!
• Suppose two sprinters X and Y are competing.
  They are the same age and weight and at the same
  level of fitness. But X has 75 fast twitch
  fibre in her leg muscles and Y has only 55. So
  X should be able to start faster, accelerate
  faster and sprint faster than Y. She has a
  better chance of winning!

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Muscle Tone

• Even when a muscle is relaxed, a small number of
  its fibres are contracted enough to keep the
  muscle taught but not enough to cause movement.
  This state of partial contraction is muscle tone.
• Without muscle tone you would not be able to
  stand up straight, keep your head up.
• Poor muscle tone leads to poor posture. That is
  why it is important to also train your muscles by
  doing resistance exercises.

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Think about!!

• What muscles are being worked in the following
  exercises
• Press up
• Chin up
• Bench Press
• Leg extension/curl
• Step ups
• Sit ups