1. Roles of Muscles From the books of Joseph E. Muscolino, DC 4/16/2017
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY

2. Objectives
Define the key terms of this chapter and state the meanings of the word origins of this chapter.
Describe the relationship between the role that a muscle plays and the action in question.
Compare and contrast the roles of mover and antagonist.
Discuss the concept of cocontraction.
4/16/2017
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.

3. Objectives
State the muscle that is working during the action in question.
Describe the relationship between gravity and joint actions.
Explain the application of tight antagonists to restricted joint motion.
Compare and contrast the roles of fixator and neutralizer.
4/16/2017
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY

4. Mover Muscles Movers: muscles that can do the action in question
Can shorten in two ways:
Concentrically contract and shorten
Relax and shorten
For every joint action, a functional group of movers can contract to make the action happen.
● 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.

5. Mover Muscles (cont’d.)
Most powerful mover = prime mover
Other movers = assistant movers
Movers are also known as agonists.
● In this illustration, the brachialis is the mover.
● Name other possible movers of flexion of the forearm at the elbow joint.
Figure 13-1

6. Mover Muscles (cont’d.)
4/16/2017
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● 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.
Figure 13-1

7. Antagonist Muscles
Antagonists do the opposite action of the action in question.
Can lengthen in two ways:
Eccentrically contract and lengthen
Relax and lengthen
Sometimes called contralateral muscle (opposite side)
● 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.

8. Antagonist Muscles (cont’d.)
Most powerful antagonist = prime antagonist
● Every muscle that flexes the forearm at the elbow joint is an antagonist, because every elbow joint flexor opposes the action in question.
Figure 13-2

9. Antagonist Muscles (cont’d.)
4/16/2017
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● Why is gravity an antagonist in these pictures?
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.
Figure 13-2

10. Antagonist Muscles (cont’d.)
Contraction: when the agonist and antagonist contract at the same time
Not considered healthy
The same as pressing gas and brake pedals simultaneously
● When might cocontraction be beneficial?
When stabilization of a body part is needed, cocontraction is desirable and often occurs.

11. Determining the “Muscle That Is Working”
4/16/2017
Muscle that is working = muscle that contracts during the action in question
Easiest way is to examine gravity’s role in the action in question
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.

12. Determining the “Muscle That Is Working” (cont’d.)
4/16/2017
Three general rules:
Upward movements, movers work and antagonists relax
Horizontal movements, movers work and antagonists relax
Downward movements, antagonists work and movers relax
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● Of course, there are exceptions to these rules. We can supplement gravity to move downward more quickly, for instance.

13. Determining the “Muscle That Is Working” (cont’d.)
4/16/2017
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● 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.
Figure 13-3

14. Determining the “Muscle That Is Working” (cont’d.)
4/16/2017
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● What is the role of gravity in this illustration?
Gravity is a mover in this picture.
Figure 13-3

15. Stopping Unwanted Actions of the “Muscle That Is Working”
4/16/2017
Fixators and neutralizers both stop unwanted actions of working muscle
Fixators stop action at fixed attachment
Neutralizers stop action at mobile attachment
Example: flexion of the fingers into a fist
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.

16. Objectives
Describe the general concept of the relationship between fixators and neutralizers and the muscle that is working.
Give an example of a fixator and a neutralizer relative to a specific joint action.
State the step-by-step method for determining fixators and neutralizers relative to a specific joint action.
4/16/2017
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17. Fixator Muscles
Fixators: stop unwanted action at the fixed attachment of muscle that is working
Also known as stabilizers
Contract isometrically
4/16/2017
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● 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.
Figure 13-4

18. Fixator Muscles (cont’d.)
4/16/2017
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● 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.
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.
Figure 13-4
Figure 13-5

19. Fixator Muscles (cont’d.)
4/16/2017
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● Which muscle is acting as the fixator in this figure?
The rectus abdominis.
● Why?
It prevents the TFL from anteriorly tilting the pelvis.
● Which muscle is acting as the fixator in this figure?
The rectus abdominis.
● Why?
It prevents the TFL from anteriorly tilting the pelvis.
ology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby
Figure 13-6

20. Concept of Fixation and Core Stabilization
4/16/2017
Mobility (phasic) muscles: larger, longer, more superficial
Postural stabilization (tonic) muscles: smaller, deeper, closer to joints
Core stabilization, strength, and efficiency of movement
Core stabilization and spinal health
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● In any given action, the mobility muscles would tend to be the movers of the joint action.

21. Concept of Fixation and Core Stabilization (cont’d.)
4/16/2017
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● 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.
Modeled from Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby
If we stabilize our core’s axial body, then we can channel all the strength of our muscles’ contractions toward moving our extremities.

22. Concept of Fixation and Core Stabilization (cont’d.)
4/16/2017
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● 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.
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.
Figure 13-8

23. Neutralizer Muscles
Neutralizers stop unwanted action at the mobile attachment of the muscle that is working.
They create a contraction force equal in strength but opposite in direction to the force of the unwanted action.
4/16/2017
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● 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.
● 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.

24. Neutralizer Muscles (cont’d.)
4/16/2017
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.)
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.)
Figure 13-9

25. Neutralizer Muscles (cont’d.)
4/16/2017
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● 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.
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.
Figure 13-10
Figure 13-11

26. Step-by-Step Method for Determining Fixators and Neutralizers
4/16/2017
Determine the action in question.
Determine the muscle that is working and its role.
Determine the fixed and mobile attachments.
List all actions of the muscle that is working, and state whether the actions are desired or undesired.
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● Table 13-1 provides a more detailed version of the information contained on this slide and the next.

27. Step-by-Step Method for Determining Fixators and Neutralizers (cont’d
4/16/2017
Determine the action of each fixator at the fixed attachment.
Choose a muscle that can do the action determined for each fixator.
Determine the action of each neutralizer at the mobile attachment.
Choose a muscle that can do the action determined for each neutralizer.
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.

28. Step-by-Step Method for Determining Fixators and Neutralizers (cont’d
4/16/2017
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● 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).
Figure 13-12

29. Objectives Describe the role of a support muscle.
4/16/2017
Describe the role of a support muscle.
Explain the two ways in which a synergist can be defined.
Compare and contrast synergists and antagonists for a given joint action.
Explain the concept of coordination as it relates to the role of muscles.
Describe the possible clinical effects of isometric contractions.
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY

30. Objectives Define and give an example of a 2nd-order fixator.
Explain why it is difficult to isolate a specific muscle contraction; further, explain and give an example of how muscle contractions tend to spread through the body.
Discuss and give an example of the concept of coupled actions in the body.
4/16/2017
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31. Support Muscles
Hold another part of the body in position while the action in question is occurring
Do not work directly at the joint
Oppose the force of gravity on a body part
Contract isometrically
● Support muscles usually work far away from the joint where an action is occurring.
● Support muscles usually work far away from the joint where an action is occurring.

32. Support Muscles
4/16/2017
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● 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.
The left-sided erector spinae musculature supports this action.
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.
Figure 13-13
Figure 13-14

33. Synergists
Synergists: muscles or forces that work with the muscle that is contracting
Example #1: Biceps brachii and pronator teres
● The biceps brachii and pronator teres both flex the forearm at the elbow joint in the sagittal plane. Therefore they are synergists.
Figure 13-15

34. Synergists
Example #2: Right external abdominal oblique and left internal abdominal oblique
● In the sagittal plane, these muscles are synergists. In the frontal plane, however, they are antagonists.
In the sagittal plane, these muscles are synergists. In the frontal plane, however, they are antagonists.
Figure 13-15

35. Coordinating Muscle Roles
4/16/2017
Muscles rarely act in isolation.
A number of muscles may contract for any given joint action.
Coordination is the co-ordering of muscles in the body in their various roles to create smooth and efficient movement.
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● 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.

36. Coordinating Muscle Roles
4/16/2017
Clinical effects of isometric contractions
Close off veins for the entire length of contraction
Buildup of toxic waste products
Waste products irritate nerves
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● What is ischemia?
It is the loss of arterial blood supply to the tissues of the body.

37. Coordinating Muscle Roles
2nd-order fixators
Fixators that fix attachments of fixator or neutralizer muscles
4/16/2017
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.
TCCD MASSAGE THERAPY PROGRAM MSSG 2014 KINESIOLOGY
● 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.
Figure 13-16

38. Coordinating Muscle Roles
4/16/2017
In the soccer scenario, what is the role of the support muscle?
It is keeping the player from falling to the ground.
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● In the soccer scenario, what is the role of the support muscle?
It is keeping the player from falling to the ground.
Figure 13-17

39. Coupled Actions
Two separate joint actions that must occur simultaneously
● 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.
● 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.
Figure 13-18