AS Level Muscles Contractions

1
AS Level Muscles Contractions

• Isometric
• Isotonic Concentric
• Isotonic Eccentric

2
Isometric Contractions

• An isometric contraction occurs in the muscle
  when the muscle is working but there is no
  movement of the joint.
• Examples
• Tugowar
• Rugby scrum
• Handstand

3
Isometric Contractions

• Note the following points in the photo.
• All the contractions in this balance are
  Isometric.
• Ankle-Plantar Flexion (Agonist is the
  Gastrocnemius.).
• Knee- Extension. (Quadriceps).
• Hips- Extension (Gluteus Maximus).
• Shoulders- Flexion/Abduction (Anterior and Middle
  Deltoids).
• Elbow- Flexion (Bicep Brachii).
• Wrist- Pronation(Pronator Quadratus).

4
Isometric Contractions Statements

• Isometric contractions occur when the joint moves
  at a constant speed
• Isometric contraction can be concentric or
  eccentric
• Isometric contraction only takes place when the
  joints do not move

True?
True?
True?
5
No !!!!!!!!!!

• Youre thinking of Isotonic contraction.
• Only isotonic contractions are concentric or
  eccentric.
• Isometric contraction only occurs when there is
  no movement!

6
YES!!!!!!!!!

• Well done!
• Now you need to make sure you know about isotonic
  contractions.
• With isotonic contractions the muscle changes
  length as the muscle contracts.

7
Isotonic Concentric Contraction

• With isotonic concentric contractions the muscle
  gets shorter as it contracts. This causes
  movement at a joint.
• i.e. when you contract your bicep brachii
  concentricaly the muscle gets shorter and so
  there is flexion at the elbow.
• The runner in this picture has the following
  joint actions and contractions-.
• Right Leg.
• Flexion at the hip- Isotonic Concentric
  contraction of the Illiopsoas muscle.
• Flexion at the knee- Isotonic Concentric
  contraction of the hamstrings.
• Plantar Flexion at the ankle- Isotonic Concentric
  contraction of the gastrocnemius.

8
Joint Analysis- Isotonic Concentric Contractions

• Analysis of Left Leg.
• Extension at the hip- isotonic concentric
  contractions of the Gluteus Maximus.
• Extension at the knee - isotonic concentric
  contraction of the quadriceps.
• Plantar flexion of the ankle- isotonic concentric
  contraction of the Gastrocnemius.

9
Isotonic Concentric Contractions

• When moving the body the opposite way to the pull
  of gravity the muscles work with Concentric
  contractions.
• From the starting position the Bicep Brachii
  contracts to cause Flexion at the elbow.
• The Bicep Brachii is getting shorter during this
  contraction so it must be a concentric
  contraction.

10
Isotonic Eccentric Contractions

• At the start of the movement all the Joints are
  static so there are isometric contractions

• Gravity is pulling the body down so this needs to
  be controlled to prevent the body crashing to the
  ground.
• The Tricep Brachii are working hard to slowly
  allow the body to lower to the final position.
  There is clearly flexion taking place at the
  elbow so the Tricep Brachii is getting longer
  even though it is contracting.
• This is therefore an isotonic ECCENTRIC
  contraction

End