UNIT 4 Muscle: the ultimate force generator in the body Duration 4th week / 3 contact hrs. 5th week / 3 contact hrs. topics Types of muscle contraction (Isometric, Isotonic: Eccentric & Concentric) Role of muscles (agonist, antagonist, stabilizers, synergists, neutralizers) Muscle skeletal stabiliser generating an appropriate amount of force at a given length Muscle morphology: shape and structure Muscle architecture

Types of muscle contraction Concentric contraction Eccentric contraction Isotonic contraction Isokinetic contraction Isoinertial contraction Isometric contraction.

Concentric contraction It is the type of muscle contraction in which the muscle length shortens.

Eccentric contraction It is the type of muscle contraction in which the muscle elongates.

Isotonic contraction It is the type of muscle contraction in which the muscle tone remains constant.

Isokinetic contraction It is the type of muscle contraction in which the angular velocity of the segment remains constant. Variable resistance Possible with dynamometers.

Isoinertial contraction It is the type of muscle contraction in which the resistance to the muscle remains constant.

Isometric contraction It is the type of muscle contraction in which the muscle length remains same.

Functional Role of the muscles Five different roles Agonist. Antagonist. Synergist. Fixators or stabilizer. Neutralizers.

Muscle which acts as a primary mover of the body segment. Agonist Muscle which acts as a primary mover of the body segment. Example: elbow flexion by brachialis.

Muscle which act opposite to the agonist. Antagonist Muscle which act opposite to the agonist. Example: Relaxation of triceps when biceps contract

Synergist Muscle which assist the action of primary mover or agonist. Contraction of rectus femoris during flexion of hip joint by hip flexors.

stabilizers or fixators Muscle which stabilizes the proximal segment of the joint to be moved. Example: stabilization of shoulder joint during elbow flexion

neutralizers Prevents unwanted movement during the desired movement. Examples: the biceps can flex the elbow and supinate the forearm. If only elbow flexion is wanted, the supination component must be ruled out. Therefore, the pronator teres, which pronates the forearm, would contract to counteract the supination component of the biceps, and only elbow flexion would occur. Neutralizers act to cancel out an unwanted movement

Muscle skeletal stabiliser generating an appropriate amount of force at a given length Classification of muscle depending upon the number of joints they cross. One joint muscle. Eg: Deltoid Two joint muscle. Eg: rectus femoris Multiple joint muscle. Eg: Flexor digitorum

Muscle insufficiency with length Passive insufficiency Active insufficiency

Active insufficiency Insufficiency due to exhaustion of muscle to contract further. Happens in multiple joint muscles. MUSCLE CANNOT COMPLETE THE ROM AS THE MUSCLE HAS UNDERGONE FULL CONTRACTION. EXAMPLE: ALL MULTI-JOINT MUSCLES.

Passive insufficiency Insufficiency due to passive tension in the opposite group of muscle. Happens in multiple joint muscles.