Question

What is the direction of the fiber / muscle contraction: ( LEFT, RIGHT, UP, OR DOWN )

1. Supraspinatus, infraspinatus & teres minor (three of the four rotator cuff muscles)
2. Biceps brachii & pronator teres
3. Triceps brachii
4. Extensor digitorum, extensor carpi ulnarus & extensor retinaculum
5. Gluteus maximus & gluteus medius
6. Adductor longus
7. Rectus femoris
8. Hamstrings: biceps femoris, semitendinosus & semimembranosus
9. Gastrocnemius
10. Tibialis anterior

Answer 1

Muscle contraction is the form of activation of tension generating sites in the muscle fibers. Muscle contraction does not necessarily mean a shortening of muscles because the muscle tension can be formed without any changes in the length of muscles. Contraction takes place when the thick and acting myofilaments slide each other. The process is driven by cross-bridges in the myosin filament.

The direction of the fiber / muscle contraction:

1. Supraspinatus, infraspinatus & teres minor --outward (external, or lateral, rotation)
2. Biceps brachii & pronator teres-mover of elbow flexion.
3. Triceps brachii---for fine movements, e.g.writing
4. Extensor digitorum, extensor carpi ulnarus & extensor retinaculum--joints movements
5. Gluteus maximus & gluteus medius--rotation of hip
6. Adductor longus-Thigh movement
7. Rectus femoris-Cross the hips
8. Hamstrings: biceps femoris, semitendinosus & semimembranosus-Knee movement
9. Gastrocnemius-Movement of back part of the lower leg
10. Tibialis anterior-invert the foot movement