Muscle contractions

Types of Muscle Contractions

• Isometric contractions: muscle tension is increased but the length does not change. These contractions are used to maintain body posture.

• Isotonic contractions: in these contractions, the tension remains the same while the muscle length changes.

• Concentric contractions: a subtype of isotonic contractions where the muscle shortens during the contraction, pulling on another structure to produce movement and reduce the angle at the joint.

• Eccentric contractions: another subtype of isotonic contractions, but this time the muscle elongates while contracting. This type of contraction resists the force of gravity on the body.

Muscle Fibres

• Fast Twitch Fibres (Type II): These fibres are suited for short, intense bursts of power. They fatigue quickly and are utilised in activities such as sprinting or weight lifting.

• Slow Twitch Fibres (Type I): These fibres are more efficient at using oxygen to produce energy and are suited for endurance activities. They show resistance to fatigue and are used in prolonged activities such as long-distance running.

Contractions and Movement

• Muscles work in pairs and during a movement, while one muscle contracts, the other relaxes.

• The agonist is the main muscle that contracts to produce a movement.

• The antagonist is the muscle that relaxes to allow the movement to occur.

• The fixator is the muscle that stabilises the origin of the agonist and the joint that the origin spans (moves over) in order to help the agonist work effectively.

• The synergist muscle aids the agonist by providing additional force to perform the movement.