The textbook has a list of key terms and word origins for each chapter. Most of these terms will become familiar as the material is covered, but reviewing them, especially the word origins, before reading the chapter can be helpful. Definitions for the key terms are available from the Evolve Website. Just because a group of movers exists does not mean that every muscle of that group necessarily contracts every time the action in question occurs. One or a few muscles can contract to create the action in question. Slide 1 Slide 2 In this illustration, the brachialis is the mover. Name other possible movers of flexion of the forearm at the elbow joint. In the picture on the left, gravity acts as the mover. What is the mover in the picture on the right? In the illustration on the right, the force of the opponent’s pull acts as the mover. The name antagonist literally means antiagonist (antimover). However, the actual definition of an antagonist is a muscle (or other force) that can perform the action that is the opposite of the action in question. In other words, the antagonist must oppose that particular action of the mover. Slide 4 Every muscle that flexes the forearm at the elbow joint is an antagonist, because every elbow joint flexor opposes the action in question. Slide 5 Why is gravity an antagonist in these pictures? Slide 3 Because the motion is upward (flexion of the forearm at the elbow joint). Every extensor of the elbow joint is an antagonist, even if it is not working. Slide 6 When might cocontraction be beneficial? When stabilization of a body part is needed, cocontraction is desirable and often occurs. Slide 7 Since gravity affects every movement in the same basic way (i.e., it’s always pulling down), it provides an effective way to determine which muscle is working in any given situation. Slide 8 Of course, there are exceptions to these rules. We can supplement gravity to move downward more quickly, for instance. Slide 9 What role does gravity play in these two illustrations? Gravity is an antagonist in the scenario depicted on the left, and it is a neutral force in the scenario on the right. Slide 10 What is the role of gravity in this illustration? Gravity is a mover in this picture. Slide 11 Practice flexing your fingers into a fist and simultaneously palpating both your own wrist joint extensor musculature and the common extensor tendon. You can feel the contraction. Why are wrist joint extensors contracting when the fingers flex? They are contracting in order to fix (stabilize) the hand at the wrist joint so that the finger flexor muscles do not also flex the hand at the wrist joint. Slide 12 Slide 13 How can we determine which attachment of the working muscle is fixed? Look at the action in question that is occurring. Whichever body part is moving is the mobile attachment; whichever body part is not moving is the fixed attachment. Slide 14 In the illustration on the right, the posterior deltoid acts as a fixator of the arm by creating a force of extension on the arm at the shoulder joint. This prevents the biceps brachii from flexing the arm at the shoulder joint. Slide 15 Which muscle is acting as the fixator in this figure? The rectus abdominis. Why? It prevents the TFL from anteriorly tilting the pelvis. Slide 16 In any given action, the mobility muscles would tend to be the movers of the joint action. Slide 17 How does core stabilization create stronger and more efficient movements of our body? If we stabilize our core’s axial body, then we can channel all the strength of our muscles’ contractions toward moving our extremities. Slide 18 If the vertebrae in this scenario are not fixed, then they will move every time the arm abducts. This can eventually result in excessive wear and tear and therefore damage to the spine. Slide 19 There are three cardinal planes: sagittal, frontal, and transverse. If we assume that the desired action occurs in one of these planes, we should also recognize that undesired actions might occur in the other two, were it not for the presence of neutralizers. Slide 20 In B (on the right), why is the sternocleidomastoid (SCM) a neutralizer? It is a neutralizer because it cancels out unwanted actions of the right levator scapulae. (Neck flexion cancels out neck extension, and left rotation of the neck cancels out right rotation of the neck.) Slide 21 Which muscle is the neutralizer in the illustration on the left? The pronator teres is the neutralizer because its action of pronation of the forearm at the radioulnar joints cancels out the biceps brachii’s action of supination of the forearm at the radioulnar joints. Slide 22 Table 13-1 provides a more detailed version of the information contained on this slide and the next. Slide 23 Once you have this step-by-step rubric down, you will eventually become proficient at determining the fixators and neutralizers associated with a particular action. Slide 24 Which muscle is the “muscle that is working” in this scenario? The levator scapulae is contracting; it is the “muscle that is working”; it is the mover in this illustration. What is the role of the SCM? The SCM is a neutralizer. What is the role of the lower trapezius? The lower trapezius is a fixator (stabilizer). Slide 25 Slide 26 Slide 27 Support muscles usually work far away from the joint where an action is occurring. Slide 28 Which are the support muscles in the scenario on the left? The left-sided erector spinae musculature supports this action. Why? Its force of left lateral flexion of the trunk at the spinal joints prevents the trunk from falling into right lateral flexion of the trunk at the spinal joints. Slide 29 The biceps brachii and pronator teres both flex the forearm at the elbow joint in the sagittal plane. Therefore they are synergists. Slide 30 In the sagittal plane, these muscles are synergists. In the frontal plane, however, they are antagonists. Slide 31 Why does it take humans so long to become coordinated? The coordination of multiple movements and contractions is enormously complex; the more complex, as in athletics or dance, the longer it takes to achieve proficiency and economy of movement. Slide 32 What is ischemia? It is the loss of arterial blood supply to the tissues of the body. Slide 33 One way to explore the complexity of coordination is to lift a heavy weight in your right hand (as shown in the illustration) and slowly palpate the pronator teres, biceps brachii, posterior deltoid, and left erector spinae. You will be able to feel each of these muscles as they work in concert to lift the weight. Slide 34 In the soccer scenario, what is the role of the support muscle? It is keeping the player from falling to the ground. Slide 35 Abduction of the arm 180 degrees relative to the trunk really consists of two separate coupled joint actions. What are they? The two separate coupled joint actions are abduction of the arm at the shoulder joint and upward rotation of the scapula at the scapulocostal joint.