Strategic Muscles and Lever Movement

Strategic muscles supply the power of movement to the levers. The following is a description of the levers in relation to the muscles.

1. The 1st lever, the finger, is powered by 2 sets of muscles.
2. This first set includes the flexors and extensors of the forearm.
3. The 2nd set includes the abductors and the adductors. The flexors are on the palmar side of the hand, with the short flexors attached from the fingertips to the palm of the hand.

Six flexor muscles are found in the palmar side of the forearm.
These long, thin muscles extend through the wrist by means of tendons to insert into the bones of the wrist, palm, and fingers. The

1. flexor carpus radialis ,
2. flexor carpus ulnaris, and
3. palmaris longus

muscles all have their origins on the humerus of the upper arm and insert into the carpals and metacarpals on the palmar side of the hand.
Working together these muscles flex the hand at the wrist. The flexor carpus radialis^[1] also abducts the hand toward the thumb side while the flexor carpus ulnaris adducts the hand toward the little finger side. The other three flexor muscles, 1) flexor digitorum superficialis, 2) flexor digitorum profundus, and 3) flexor pollicis longus extend from the bones of the arm and forearm and insert into the phalanges of the hand to flex the fingers and thumb, respectively.

The extensors usually lift several fingers at once because of the way the tendons are interconnected. It is anatomically impossible for most people to lift one finger by itself without the other fingers moving at all.
The function of the flexor muscles of the forearm is to bring the finger down from the (proximal phalanx and metacarpal head).
The long flexors attach from the fingertip to the elbow. The extensor muscles are on the dorsal ^[2] side of the hand and they are responsible for finger lift. The flexors and extensors exert a dual pull against each other, for if the flexors should pull the finger to an extreme position, the extensors will start to pull in the opposite direction with resultant strain and tension. It is important to keep them in a relationship that is balanced. An important principle is thereby established which applies equally to all sets of muscles. Click on Next to read about the next subject on keeping the limbs in their midrange of movements.

[1] flexor carpus radialis: In anatomy, flexor carpi radialis is a muscle of the human forearm that acts to flex and (radial) abduct the hand. The Latin carpus means wrist, and carpi "of the wrist." Hence flexor carpi is a flexor of the wrist.

[2]dorsal: Dorsal is the back of the hand with fingernails, just as the region in back of the spine is dorsal.