muscle contractions

Topic: Antagonistic Muscle Action

Agonist (Prime Mover)

The primary instigator of a joint movement. The contraction of an agonist causes the movement of a joint’s related limb.

Antagonist

This muscle opposes the motion of the agonist, acting as its pair. Contraction of this type restores the limb to its starting position.

Fixator Muscles

These control and stabilise the origin of the agonist muscle to make movement as efficient as possible.

Synergist Muscles

These aid the movement of the agonist and ensure movement is within the range of movement, preventing injury through overstretching.

Topic: Types of Muscular Contraction

Isotonic Contraction

A contraction where the muscle changes length. This is split into concentric and eccentric.

Concentric Contraction

A type of isotonic contraction where the muscle becomes shorter as it undergoes contraction (e.g., lifting a weight).

Eccentric Contraction

A type of isotonic contraction where the muscle lengthens under tension (e.g., lowering a weight).

Isometric Contraction

A contraction where there is no change in the muscle's length while it exerts force (e.g., holding a plank).

Topic: Integration of Action and Contraction

How do agonists use Isotonic contractions?

During the lifting phase of a movement, the agonist performs a concentric contraction. During the controlled lowering phase, the same agonist performs an eccentric contraction.

Movement Analysis: Bicep Curl (Upward Phase)

• Agonist: Biceps performing a concentric contraction.
• Antagonist: Triceps (relaxes).

Movement Analysis: Bicep Curl (Downward Phase)

• Agonist: Biceps performing an eccentric contraction to control weight against gravity.
• Antagonist: Triceps (relaxes).

Movement Analysis: The Squat (Downward Phase)

• Agonist: Quadriceps performing an eccentric contraction to control the descent.
• Antagonist: Hamstrings.

Movement Analysis: The Squat (Upward Phase)

• Agonist: Quadriceps performing a concentric contraction to extend the knee.
• Antagonist: Hamstrings.

Contraction type for Fixator muscles

Fixator muscles usually perform isometric contractions to stabilize the bone or origin point while the agonist moves.

Synergist Muscles

These aid the movement of the agonist and ensure movement is within the range of movement, preventing injury through overstretching.

Topic: Types of Muscular Contraction

Isotonic Contraction

A contraction where the muscle changes length. This is split into concentric and eccentric.

Concentric Contraction

A type of isotonic contraction where the muscle becomes shorter as it undergoes contraction (e.g., lifting a weight).

Eccentric Contraction

A type of isotonic contraction where the muscle lengthens under tension (e.g., lowering a weight).

Isometric Contraction

A contraction where there is no change in the muscle's length while it exerts force (e.g., holding a plank).

Topic: Integration of Action and Contraction

How do agonists use Isotonic contractions?

During the lifting phase of a movement, the agonist performs a concentric contraction. During the controlled lowering phase, the same agonist performs an eccentric contraction.

Movement Analysis: Bicep Curl (Upward Phase)

• Agonist: Biceps performing a concentric contraction.
• Antagonist: Triceps (relaxes).

Movement Analysis: Bicep Curl (Downward Phase)

• Agonist: Biceps performing an eccentric contraction to control weight against gravity.
• Antagonist: Triceps (relaxes).

Movement Analysis: The Squat (Downward Phase)

• Agonist: Quadriceps performing an eccentric contraction to control the descent.
• Antagonist: Hamstrings.

Movement Analysis: The Squat (Upward Phase)

• Agonist: Quadriceps performing a concentric contraction to extend the knee.
• Antagonist: Hamstrings.

Contraction type for Fixator muscles

Fixator muscles usually perform isometric contractions to stabilize the bone or origin point while the agonist moves.