Name
Lab Section
PEP 300 - Laboratory
Performing a Muscular Analysis – Part 2
Purpose:
To practice performing an in-depth muscular analysis of a movement pattern or skill.
Equipment:
Lab Handout
Video clips of common skills (to be provided by instructor)
Background:
One of the most important principles of training is specificity. This principle teaches us that we should develop
exercise routines based on the needs of the exerciser and on the activity for which s/he is training. Specificity should
address the anatomical, biomechanical, physiological, and neurological demands of the activity. Within these four
areas there are many aspects that must be considered. One of the most important aspects is identification of which
muscles are being used and how those muscles are being used. This constitutes a muscular analysis. We can apply a
muscular analysis in two ways. First, we can analyze the skill or activity that we are training for so that we know
which muscles are being used and how those muscles are being used. Second, we can analyze training and
conditioning exercises to determine which muscles are being used and how those muscles are being used. With
these two pieces of information, we are able to select training and conditioning exercises that are most appropriate
for training for the activity we are interested in.
Procedures to be completed prior to lab:
1.
2.
Read the assigned material listed on your course syllabus.
Review the steps for conducting a muscular analysis as discussed in lecture and outlined on the handout –
Performing a Muscular Analysis.
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Procedures to be completed during the lab session:
1.
Perform a muscular analysis of the vertical jump shown in the video provided by the instructor by answering the
following questions:
a.
Complete the chart below for the shoulder joint for the portion of the vertical jump from the beginning of
the movement to takeoff from the ground. You should identify as many phases as you think appropriate.
Phase
Early
Countermovement
Mid
Countermovement
Late
Countermovement
Execution
Joint
Shoulder
Shoulder
Shoulder
Shoulder
Joint Action
flexion
extension
extension
flexion
Plane/Axis of
Motion
sagittal/ML
sagittal/ML
sagittal/ML
sagittal/ML
Motive Torque
muscle
muscle
inertial force of arm
muscle
Resistive Torque
weight of arm
weight of arm
muscle
inertial force of arm
& weight of arm
Muscle Action
concentric
concentric
eccentric
concentric
shoulder flexors
shoulder extensors
shoulder flexors
shoulder flexors
shoulder flexors
shoulder extensors
shoulder extensors
shoulder flexors
(anterior deltoid,
coracobrachialis,
biceps brachii,
pectoralis major –
clavicular portion)
(posterior deltoid,
latissimus dorsi, pectoralis
major – sternal portion)
(posterior deltoid,
latissimus dorsi, pectoralis
major – sternal portion)
(anterior deltoid,
coracobrachialis, biceps
brachii, pectoralis major –
clavicular portion)
shoulder extensors
shoulder flexors
shoulder flexors
shoulder extensors
(posterior deltoid,
latissimus dorsi,
pectoralis major –
sternal portion)
(anterior deltoid,
coracobrachialis, biceps
brachii, pectoralis major –
clavicular portion)
(anterior deltoid,
coracobrachialis, biceps
brachii, pectoralis major –
clavicular portion)
(posterior deltoid,
latissimus dorsi, pectoralis
major – sternal portion)
FMG
Developing Force
Agonists
(FMG’s and
individual muscles)
Antagonists
(FMG’s and
individual muscles)
b.
Identify and discuss any two examples of rotary stabilization that are occurring during the skill (these do
not have to involve the shoulder joint). Be sure you identify the segment/joint that is being stabilized, the
muscle (individual or group) that is(are) acting as the stabilizers, and the force that is being stabilized
against.
There are not very many examples of rotary stabilization in this skill, most of the segments are moving
throughout the skill. One example would be stabilization of the wrist by the radial and ulnar deviators
against gravity and the inertial forces created during the movement. A second example is that of the trunk.
It is being stabilized by the flexors and extensors of the trunk, again against gravity and the inertial forces
created during the movement.
c.
Identify and discuss two examples of neutralization that are occurring during the skill (these do not have to
involve the shoulder joint). Be sure you identify the muscle whose action is being neutralized, and the
muscle (individual or group) that is(are) acting as the neutralizer(s).
To examine neutralization, examine the specific scenarios that we identified in lecture.
 Does the scapula or pelvis have to be stabilized to provide a firm base from which muscles that move
the femur and humerus can pull? Yes, all of the shoulder flexors and shoulder extensors (except the
sternal pectoralis major) acting in this movement attach proximally to the scapula and/or the clavicle.
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


d.
Because the scapula and clavicle are lighter than the humerus & forearm, they tend to move when any
of these muscles contract. Therefore, we have to keep this from happening. The line of pull of the
proximal attachment sites for each of these muscles probably causes the scapula to protract and
depress. <ENTER> Therefore, we would need to recruit the retractors and the elevators to stabilize
the scapula against these movements. What are the specific muscles that elevate and retract the
scapula? Would all of these muscles be recruited? Other examples of neutralization under this
scenario may be occurring in the lower extremity as well because many of the agonists at the hip and
knee have their proximal attachments on the pelvis. Can you identify any of these examples?
Is there a multijoint muscle in the agonist or antagonist FMG developing force that may be causing
unwanted action at its other joints? Let’s look at the shoulder first. Both the biceps brachii and the
triceps brachii are multijoint muscles that are developing force at various phases in this movement.
The long head of the triceps brachii crosses the shoulder and the elbow joint, causing extension of the
both joints. However, when the shoulder is extending in the movement, the elbow is extending as well,
so there is not an “unwanted” action created by this muscle. This same situation is true for the biceps
brachii in some phases of the skill. The biceps brachii crosses the elbow, shoulder, and radioulnar
joint, causing flexion, flexion, and supination, respectively. During the early countermovement, the
shoulder and elbow flex simultaneously so no neutralization is needed for those movements. However,
the forearm is maintained in a neutral position throughout the skill, so if the biceps brachii is
developing force, then its supination movement must be neutralized. This neutralization may be
accomplished by the pronator quadratus or the pronator teres. Also, in the execution phase, flexion of
the shoulder is occurring, but the elbow maintains an extended position. Therefore, if the biceps
brachii is developing force, then the flexion at the elbow must be neutralized. This neutralization is
probably performed by the anconeus, since force development in the triceps brachii would counteract
the shoulder flexion movement. Of course, the other alternative is that body does not recruit the biceps
brachii at all and simply uses other movers as appropriate at the joints. Other examples of
neutralization under this scenario may be occurring in the lower extremity as well, since many of those
muscles are multijoint muscles (sartorius, gracilis, semimembranosus, semitendinosus, biceps femoris
– long head, rectus femoris, gastrocnemius). Can you identify any of these examples?
Is the humerus being elevated in this movement so that stabilization of the humerus by the rotator cuff
would be necessary? Yes, during the execution phase. The rotator cuff must develop force to stabilize
the humeral head against the superior shear created by contraction of the deltoid muscle.
Other? Are there any other undesired actions of the agonists that need to be neutralized? Well, if we
list all the actions of the active FMGs during each phase, we are able to examine this further. There
are numerous possibilities here since movement is occurring at most of the joints in the body. Let’s just
identify one case as an example. At the shoulder, the anterior deltoid is part of the active FMG in
several phases of the skill. When the anterior deltoid contracts, not only does it attempt to flex the
shoulder but it also causes medial rotation. Since medial rotation does not occur during this skill, then
that action must be neutralized by at least one other muscle. None of the other muscles in the shoulder
flexor FMG are lateral rotators, so there is no synergistic action within the FMG. Therefore, the likely
source of neutralization is a lateral rotator. There are several possibilities. The posterior deltoid could
neutralize the medial rotation but since it is antagonistic to the flexion being caused by the anterior
deltoid, it is not a likely candidate. Two other lateral rotators are the infraspinatus and the teres
minor. We have already identified these rotator cuff muscles as being recruited to stabilize the humeral
head against the superior pull of the deltoid, so these muscles are likely candidates for neutralization
of medial rotation. Can you identify other examples of neutralization at other joints under this
scenario?
Are there any potential force production problems in the movement related to the force-length relationship
(you should especially consider multi-joint muscles)? How can the performer overcome these problems or
is the performance limited by these problems? Explain your answer.
If we examine the multijoint muscles developing force, there does not appear to be a situation where one of
the multijoint muscles is placed in an extremely short or extremely long position. For example, in the lower
extremity, there are several multijoint muscles developing force. The hamstring group is the active FMG
throughout the movement, both eccentrically and concentrically. However, when that muscle group is
lengthened across the knee, it is shortened across the hip, avoiding an extremely long or short position that
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would place it in a disadvantageous position on the force-length curve. An analysis of most of the multijoint
muscles in the lower extremity would produce the same result. You might identify one exception in the
sartorius, which is a knee flexor and a hip flexor. When the hip and knee are flexed simultaneously as
occurs at the bottom of the countermovement, then the sartorius is in a very short position. However, the
hip flexors and the knee flexors are not developing force at this point in the movement, so there is not a
force output problem.
2. Complete a muscular analysis of the push-up exercise under two conditions – one with hands placed
greater than shoulder width apart, and one with hands placed just less than shoulder width apart
(keeping the elbows in). Use the questions below to help you with your analysis.
a. Complete the charts below for each exercise.
Joint
Joint Action
Motive Torque
Resistive Torque
Muscle Action
FMG Developing Force
Agonists (FMG)
Antagonists (FMG)
Wide Hand Placement
Down Phase
Shoulder
Elbow
horizontal
flexion
abduction
weight
weight
muscle
muscle
eccentric
eccentric
horizontal
extensors
adductors
horizontal
flexors
abductors
Up Phase
Shoulder
Elbow
horizontal
extension
adduction
muscle
muscle
weight
weight
concentric
concentric
horizontal
extensors
adductors
horizontal
extensors
adductors
horizontal
adductors
horizontal
abductors
extensors
flexors
Joint Action
Narrow Hand Placement
Down Phase
Shoulder
Elbow
extension
flexion
Up Phase
Shoulder
Elbow
flexion
extension
Motive Torque
weight
weight
muscle
muscle
Resistive Torque
muscle
muscle
weight
weight
Muscle Action
eccentric
eccentric
concentric
concentric
FMG Developing Force
flexors
extensors
flexors
extensors
Agonists (FMG)
extensors
flexors
flexors
extensors
Antagonists (FMG)
flexors
extensors
extensors
flexors
Joint
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a.
Compare and contrast the ROMs used at the shoulder and elbow joints in the two exercises. Are
there any force-length effects that cause muscle involvement to be different between the primary
muscle groups in the two exercises?
ROM of the elbow is very different between the two exercises. The working ROM in the wide hand
placement is 0-90°, while the working ROM in the narrow hand placement is 0-140°. Since the
elbow extensors are the active FMG in both of these exercises, then we should examine forcelength effects of these muscle (the anconeus and the triceps brachii). Let’s focus on the triceps
brachii since it is the major force producer in this group. During the wide hand placement
exercise, the medial and lateral heads of the triceps brachii are extremely short at the top of the
movement when the elbow is fully extended (0°), limiting force production in these heads.
However, the long head is not compromised in this position because even though it is shortened
across the elbow, it is placed in a lengthened position across the shoulder, placing it in a fairly
optimal position on the force-length curve. At the bottom of the movement, none of the triceps
heads are compromised as the elbow joint angle is approximately 90°, or in the midpoint in the
ROM, again placing it in an optimal position on the force-length curve.
In the narrow hand placement exercise, the same is true for the top of the movement as we
described in the wide hand placement. However, at the bottom of the movement, all three heads of
the triceps are in an extremely lengthened position, compromising their force output due to their
length. The long head does not reach its maximal length since the shoulder is not completely
hyperextended, which would actually be advantageous since it is a multijoint muscle. Therefore, at
the bottom of the movement when concentric force is necessary to raise the body, the triceps
brachii force output is compromised, making this exercise much more difficult with respect to the
elbow extension portion.
b.
For each exercise, identify two examples in which rotary stabilization is performed by muscles.
Compare and contrast this stabilization between exercises.
Rotary stabilization occurs at several joints in this skill, because most of the segments are not moving and
yet muscular torque is necessary to keep them from rotating. Examples of rotary and linear stabilization
are described below. In each bullet, a specific scenario is examined as we identified in lecture.
 Rotary stabilization by muscles often occurs at joints in which no rotation is occurring. This case is
usually the simplest case of rotary stabilization to identify. You should ask whether the lack of
movement (rotation) at a joint is because there are no forces acting to rotate the joint, or because two
or more forces are acting in such a way that the net torque is zero, and rotation does not occur. If the
latter, and if muscle is one or both of the forces acting, then muscles are acting as rotary stabilizers.
Three examples of this case are identified below:
o Hyperextension of the lumbar and thoracic trunk tends to occur due to the force of gravity. The
trunk flexors must contract to prevent this hyperextension.
o Flexion of the knee tends to occur due to the force of gravity. The knee extensors must contract to
prevent this flexion.
o Dorsiflexion of the ankle tends to occur due to the force of gravity. The ankle plantar flexors must
contract to prevent this dorsiflexion.
 Rotary stabilization also occurs when a multijoint muscle in the agonist or antagonist FMG is
developing force that may be causing unwanted action at adjacent joints. Let’s look at the wide hand
placement push-up first. The FMGs for this exercise include the horizontal adductors and the elbow
extensors. The only multijoint muscle in those FMGs is the triceps brachi, which is an elbow extensor.
The long head of the triceps brachii crosses the shoulder and the elbow joint, causing extension of the
both joints. While elbow is extension is desired in the movement, shoulder extension is not. So, the
shoulder extension must be offset so that the shoulder does not move (is stabilized). This stabilization
is easily accomplished by any of the agonist horizontal adductors, all of which are shoulder flexors as
well. Therefore, the agonists stabilize against the unwanted shoulder extension of the triceps brachii.
The same is true in the narrow hand placement push-up. The shoulder flexors stabilize against the
shoulder extension created by the triceps brachii-long head.
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

Linear stabilization occurs when the scapula or pelvis has to be stabilized to provide a firm base from
which muscles that move the femur and humerus can pull. In these exercises, the muscles that cause
horizontal adduction (anterior deltoid, pectoralis major, coracobrachialis) during the wide hand
placement push-up attach to the scapula/clavicle and would tend to cause shoulder girdle protraction,
so it appears that the scapula would need to be stabilized against the pull of these agonist muscles.
However, it is important to recognize that movement of the shoulder girdle (protraction) must occur to
accompany and facilitate the horizontal adduction of the shoulder. So, technically, there is no
stabilization of the scapula (the scapula is not fixed in place), but instead, this is considered a dynamic
stabilization that occurs in the shoulder girdle. The concept of dynamic stabilization is beyond the
scope of this course at this time. It is important that you recognize that technically, there is no scapular
stabilization as we have defined stabilization (fixation). The same concept (dynamic stabilization)
holds true for the narrow hand placement push-up.
Linear stabilization also occurs when the humerus is being elevated in a movement. In this movement,
stabilization of the humerus by the rotator cuff would be necessary.In both exercises, the rotator cuff
must develop force to stabilize the humeral head against the superior shear created by contraction of
the anterior deltoid muscle, which is a member of the FMGs in both exercises.
These examples of stabilization occur in both exercises. Stabilization does not differ across the
two exercises.
c.
For each exercise, identify two examples in which neutralization is performed by muscles.
Compare and contrast this neutralization between exercises.
To examine neutralization, you should ask whether there are any undesired actions of the agonists that
need to be offset. Well, if we list all the actions of the active FMGs during each phase, we are able to
examine this further. For the elbow, the only unwanted action of the individual muscles in the FMGs
(triceps brachii and anconeus) is the shoulder extension that we have already discussed. At the shoulder,
the anterior deltoid and the pectoralis major are also medial rotators. However, in the wide grip hand
placement, the position of the humerus is already medially rotated to some extent, and, therefore, the line of
pull for the pectoralis major is direct and does not create a medial rotation torque. The line of pull for the
anterior deltoid may produce a slight medial rotation torque, but this torque is easily neutralized by the
two of the rotator cuff muscles (teres minor and infraspinatus) which produce a lateral rotation torque. In
the narrow grip hand placement, the humerus is not medially rotated, therefore, the line of pull of the
anterior deltoid and pectoralis major-clavicular is not direct and exerts a medial rotation torque at the
shoulder. This medial rotation must be neutralized, and again, the only lateral rotators that are candidates
are the infraspinatus and the teres minor. The posterior deltoid is a lateral rotator, but it is not recruited
since it would act antagonistic to the anterior deltoid. Therefore, rotator cuff strength is another
requirement for performance of the narrow hand placement push-up. Weakness in these muscles is one
reason people perform this exercise incorrectly, with the shoulder medially rotated and the elbow pointed
at to the sides
d.
Given your answer to ‘c’, are there any individual muscles in the FMG that you identified in the
chart that would not necessarily be involved in the performance of this exercise?
The biceps brachii is probably not recruited as a shoulder flexor in the narrow push-up since it is
antagonistic to the elbow extensors. One could also argue that the long head of the triceps brachii
may not be as active in these exercises, since it has an undesirable action at the shoulder. A more
sophisticated, quantitative analysis would need to be done to determine whether this is true or not.
e.
Use the chart and your answers to the questions above to summarize the muscle involvement in
the two exercises. Note where they are similar and where they are different.
The primary difference between these exercises is in the shoulder joint actions and active shoulder
FMGs. In the wide hand placement, the shoulder FMG is the horizontal adductors, which includes
the pectoralis major, the anterior deltoid, and the coracobrachialis. In the narrow hand
placement, the shoulder FMG is the flexors, which includes the pectoralis major-clavicular, the
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anterior deltoid, and the coracobrachialis. The rotator cuff muscles probably play a more
important role in the narrow push-up, and the strength requirements of triceps brachii are
demanded throughout the entire elbow ROM in the narrow push-up as compared to the wide push
up.
f.
The narrow hand width position is considered to be more difficult than the wide hand width
position. Based on your analysis, can you support this statement?
Yes. The narrow hand placement exercise is more difficult for three reasons. First, the shoulder flexion
movement is not as strong a movement as the shoulder horizontal adduction movement simply because
there is not as much active muscle mass in the shoulder flexors. The shoulder horizontal adductors include
the pectoralis major – sternal portion which is a large muscle capable of producing a large amount of
force. This muscle is not part of the shoulder flexor FMG, making this a much weaker movement. Second,
in the narrow hand placement exercise, the triceps brachii force production is severely compromised at the
bottom of the movement when the muscles must act concentrically to raise the body. This compromise
occurs because of the large ROM at the elbow which places the muscle in a poor position on the forcelength curve. This does not occur in the wide hand placement exercise. Third, the rotator cuff muscles,
especially the infraspinatus and the teres minor, appear to play a more significant role in the narrow pushup. They must neutralize the medial rotation of the humerus caused by the agonists during shoulder flexion,
and they must neutralize against the superior shear created by the shoulder agonists as well. Since these
muscles are small, the increased torque demand of the exercise makes strength in these muscles very
important. The first two factors result in a much lower muscle torque output during the narrow hand
placement exercise, making it much more difficult, since the resistance (body weight) is the same in both
exercises. The increased torque demand on the relatively small muscles of the infraspinatus and teres
minor also makes the narrow hand placement exercise more difficult.