![]() ![]() Synovial fluid is a thin, but viscous film with the consistency of egg whites. Exercise and stretching may also have a beneficial effect on synovial joints. Most of the joints you use during exercise are synovial joints, which have synovial fluid in the joint space between two bones. Recall the discussion about muscles crossing joints to create movement. ![]() A pulled tendon, regardless of location, results in pain, swelling, and diminished function if it is moderate to severe, the injury could immobilize you for an extended period. Without a proper warm-up, it is possible that you may either damage some of the muscle fibers or pull a tendon. Stretching pulls on the muscle fibers and it also results in an increased blood flow to the muscles being worked. When exercising, it is important to first warm up the muscles. The hamstrings flex the leg, whereas the quadriceps femoris extend it.Įveryday Connections: Exercise and Stretching Quadriceps femoris: group of four muscles in the anterior compartment of the thigh ![]() Hamstrings: group of three muscles in the posterior compartment of the thigh The biceps brachii flexes the forearm, whereas the triceps brachii extends it. ![]() Triceps brachii: in the posterior compartment of the arm Agonist and Antagonist Skeletal Muscle Pairsīiceps brachii: in the anterior compartment of the arm When flexed, the muscle works at extending, adducting and rotating the arm. Elevates, depresses, rotates, and retracts the scapula, or shoulder blade Tilt and turn the head and neck, shrug, steady the shoulders, and twist the arms. Pulls the ribs and the pelvis in and curves the back. Plantar flexes foot – extension or flexion of the foot at the ankle, flexes kneeĬontrol the movement of the arm, create lateral, vertical, or rotational motion. Lateral rotation and abduction of thigh flexion and medial rotation of legįlexes knee, extends hip joint, medially rotates leg at knee Shoulder abduction, flexion and extensionĮxternal rotation and extension of the hip joint, Table 1: Major Muscles of the Human Body and their Actions. In addition, the diaphragm contracts and relaxes to change the volume of the pleural cavities but it does not move the skeleton to do this. There also are skeletal muscles in the tongue, and the external urinary and anal sphincters that allow for voluntary regulation of urination and defecation, respectively. The insertions and origins of facial muscles are in the skin, so that certain individual muscles contract to form a smile or frown, form sounds or words, and raise the eyebrows. For example, there are the muscles that produce facial expressions. There are also skeletal muscles that do not pull against the skeleton for movements. See Table 1 for a list of some agonists and antagonists. If you consider the first action as the knee bending, the hamstrings would be called the agonists and the quadriceps femoris would then be called the antagonists. However, to flex the knee joint, an opposite or antagonistic set of muscles called the hamstrings is activated.Īs you can see, these terms would also be reversed for the opposing action. They control rapid movement, as in shadow boxing without landing a punch or the ability to check the motion of a limbįor example, to extend the knee, a group of four muscles called the quadriceps femoris in the anterior compartment of the thigh are activated (and would be called the agonists of knee extension).They maintain body or limb position, such as holding the arm out or standing erect.Antagonists play two important roles in muscle function: A synergist can also be a fixator that stabilizes the bone that is the attachment for the prime mover’s origin.Ī muscle with the opposite action of the prime mover is called an antagonist. To lift a cup, a muscle called the biceps brachii is actually the prime mover however, because it can be assisted by the brachialis, the brachialis is called a synergist in this action (Figure 1). The brachoradialis, in the forearm, and brachialis, located deep to the biceps in the upper arm, are both synergists that aid in this motion.Īlthough a number of muscles may be involved in an action, the principal muscle involved is called the prime mover, or agonist. ![]()
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