Chapter 11: The Muscular System Lab
Name: ___Jazmin Franks____
The unique characteristic of muscle as a tissue is the ability to actively develop tension.
Skeletal muscle is the motor and active force generator within the musculoskeletal system to
control limb movement and joint stiffness. The structure and function of skeletal muscle
(sarcomere, fiber, and fascicle) and connective tissue (mysia and tendon) are introduced in this
chapter and made relevant to the characteristics of muscle. The three forms of muscle activity
(concentric, isometric, and eccentric) are covered with reference to the concepts of work and
energy introduced in chapter 4 and serve as an introduction to the possible roles of muscle
(agonist, antagonist, stabilizer, and neutralizer). The theory of muscle activation is introduced,
and factors affecting the generated tension (physiological cross-sectional area, fiber arrangement,
length–tension relationship, force–velocity relationship) are presented. The torque-generating
capability of muscle, introduced in chapter 5, is revisited.
Objectives
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Describe the three types of muscle tissue: smooth, skeletal, and cardiac
Discuss the functions of skeletal muscle
Describe the microstructure of skeletal muscle
Describe the macrostructure of skeletal muscle
Discuss the three different types of muscular actions: concentric, eccentric, and
isometric
Describe the roles that muscles can assume
Discuss the factors that influence the force developed during muscular activity
Understand the relationship between power output and velocity of contraction of a
muscle
Key Terms
agonist
antagonist
aponeuroses
concentric contraction
eccentric contraction
endomysium
epimysium
fascicle
isometric contraction
muscle fiber
neutralizer
perimysium
sarcolemma
sarcomere
stabilizer
synergy
tendons
type I muscle fibers
type IIA muscle fibers
type IIB muscle fibers
Lab Activity
Straight Arm
Neutral:
The subject will grasp a handgrip dynamometer in a neutral position with their
dominant arm. The subject’s arm should be down by their side with a joint angle
of 180 degrees at the elbow. The subject should then perform a MVC (Pull on the
handle of the dynamometer as hard as they can for 3 sec) in this neutral position.
Record the result.
Wrist Flxn/Extn:
The subject should then flex their wrist (towards their side) and repeat the
contraction. Record the result.
The subject should then extend their wrist (away from their side) and repeat the
contraction. Record the result.
90 Degrees of Elbow Flexion
Neutral:
The subject will then flex the elbow to 90° with the wrist in a neutral position and
perform an MVC. Record the result.
Pronation/Supination:
The subject should then pronate their wrist and repeat the contraction. Record the
result.
The subject should then supinate their wrist and repeat the contraction. Record the
result.
Use the chart found on the next page to answer the following discussion
questions.
Subject
FS001
FS002
FS003
FS004
FS005
FS006
FS007
FS008
FS009
Mean
SD
Handgrip EMG Extensor Carpi Radialis Amplitude (mV)
Neutral Position Wrist Flexed Wrist Extended 90° Elbow Neutral 90° Elbow Supination 90° Elbow Pronation
1.8
2.0
1.9
2.2
1.7
1.8
2.1
1.9
2.0
1.8
1.7
1.9
1.7
1.8
1.6
1.9
1.7
1.8
2.0
2.2
2.1
2.3
2.0
2.1
1.9
2.0
1.8
1.7
1.9
2.0
2.2
1.7
1.9
2.1
2.0
1.8
1.8
2.1
2.0
1.9
2.2
1.7
1.6
1.9
1.7
1.8
1.6
1.7
2.0
2.2
1.8
2.1
2.3
2.0
1.90
1.98
1.87
1.98
1.90
1.87
0.18
0.16
0.15
0.19
0.23
0.13
Subject
FS001
FS002
FS003
FS004
FS005
FS006
FS007
FS008
FS009
Mean
SD
Handgrip Flexor Digitorum Superficialis EMG Amplitude (mV)
Neutral Position Wrist Flexed Wrist Extended 90° Elbow Neutral 90° Elbow Supination 90° Elbow Pronation
2.1
1.9
2.2
2.0
2.3
2.1
1.8
1.7
1.9
1.6
1.8
2.0
2.0
2.1
2.2
2.3
2.1
2.0
1.9
2.0
1.8
1.7
1.9
2.0
2.2
2.3
2.1
2.2
2.0
2.1
1.7
1.8
1.6
1.7
1.9
1.8
2.1
2.0
2.2
1.9
2.1
2.0
1.6
1.7
1.5
1.6
1.8
1.7
2.0
2.1
2.3
2.0
2.2
2.1
1.93
1.96
1.98
1.89
2.01
1.98
0.19
0.19
0.27
0.24
0.17
0.13
Discussion
1. Why are there differences in grip strength between the joint angles?
Muscle orientation changes as they lengthen and shorten from the position it is placed;
this can restrict or generate greater force production of a muscle.
2. What are the agonist and antagonist forearm muscles involved with the ‘Neutral grip’
contraction? Agonist -flexor digitorum superficialis. Antagonist-extensor carpi radialis
Do these change when the wrist is extd/flxd?
They will change due to shortening or lengthening of flexors and extensor
muscles associated with the movement. With wrist extended, the agonist muscle is the extensor
carpi radialis; the muscle is contracting therefore shortening due to different joint angle.
3. What kind of muscular contraction is involved in this lab activity? Explain.
A concentric muscular contraction is involved. As the grip tightens, the flexor muscles of the
forearm and fingers are active as flexion takes place. Tension is developed on the 3 second hold
as muscle activity is shortening.
4. During which contraction did the flexor digitorum superficialis have the most muscular
activation (EMG Activity)?
90 deg. Elbow supination
a) extensor carpi radialis?
Wrist flexed and 90 deg. elbow neutral
5. What physiological factors influence maximal force production?
A position that changes the joint angle to flex elbow at 90 degrees supinated or with a
flexed wrist in which activates other muscles to contract such as biceps brachii.