2013-2014
Anatomy
Muscle Structure and Exercise Physiology
Objective:
•
When you complete this lab you should be able to:
Understand how several body movements are performed by the interaction of muscles, why
muscle fatigue occurs, and how temperature affects muscle action.
Introduction:
Human athletic performance has been a source of entertainment, admiration, and curiosity since the
dawn of recorded history. Athletes with extraordinary capacities for speed, power, strength,
endurance, and stamina are not only recognized for their physical achievements, but they are also
likely generate puzzled expressions of amazement such as, “Why is that guy so strong?” “How can
she r u n so fast?” and “Could I ever do that?” These questions lie at the very core of human
exercise physiology, a field that seeks to understand the physiological and biochemical events that
occur when a person exercises. As a result of research in this area, we now know a great deal about
why athletic performance varies from one individual to another, about the effect of training on muscle
function, and about the long-term consequences of performance-enhancing drugs such as anabolic
steroids and amphetamines. In this exercise, you will look at several aspects of the musculoskeletal
system. In this lab, you will focus on muscle physiology.
Station I:
MUSCLE FIBER TYPES
Many exercise physiologists believe that one of the most important factors determining athletic
performance is the cellular composition of the contracting muscles. Muscle cells, which are
called fibers, can be broadly classified into categories based on their structural and metabolic
characteristics. Consider the biceps muscle in the upper arm. This muscle tissue is composed of
distinct fiber types that play a critical role in determining the muscle’s performance capacity.
Three main fiber types are commonly identified, although further sub-groupings are known. For our
purposes, we will focus on the three major types described here. White, fast-twitch, glycolytic fibers
(FG) are generally quite large in diameter and can generate energy rapidly for quick, powerful
contractions. White fibers rely on anaerobic metabolism to produce ATP and become fatigued with
the accumulation of lactic acid, a noxious by-product that interferes with muscle contraction.
Consequently, white, fast-twitch fibers are generally activated in short-term sprint or “power”
activities, as they fatigue rapidly. Red, slow-twitch, oxidative fibers (SO) are smaller in diameter,
and generate a greater yield of ATP by aerobic metabolism and without theformation of lactic acid.
As the name implies, red, slow-twitch fibers contract less rapidly and powerfully, but they are not
easily fatigued and are well suited for prolonged exercise. In addition to these two types, a
third intermediate fiber type, fast, oxidative-glycolytic (FOG), shares both the oxidative and
glycolytic pathways and is intermediate in size as well when compared to red and white fibers (it is
sometimes referred to as “pink” fibers). These characteristics are summarized below in Table 1.
2013-2014
Anatomy
Table 1. A Comparison of Muscle Fiber Types.
Fiber color
Predominant
metabolic pathway
Contraction speed
Rate of fatigue
Mitochondria
Slow, Oxidative
Red
Intermediate
Pink - red
Fast, Glycolytic
White
Aerobic
Slow
Slow
Many
Aerobic
Fast
Intermediate
Many
Glycolysis
Fast
Fast
Few
It is widely known among sport physiologists that the “fiber-type”1 of elite, world-class athletes is a
reliable predictor of performance in athletic events. Sprinters, weight-lifters, wrestlers and others
that rely on short, powerful bursts of muscle activity generally have a predominance of
-twitch fibers, whereas marathon runners, cross-country skiers, cyclists, and other
endurance athletes have a greater abundance of
- twitch fibers.
Less widely appreciated is the extent to which these principles of human exercise physiology
apply to other animals and their capacity for exercise. Organisms with predominantly white, fast
twitch fibers (FG) also use anaerobic metabolism during exercise. They are capable of producing
very high levels of muscle power output (e.g., fast sprints and strong bites), but these animals exhaust
quickly. Other animals with a greater abundance of red, slow-twitch fibers (SO), which rely on
aerobic metabolism, are capable of producing a moderate level of power for long periods of time.
The principal disadvantage for “aerobic animals” is that aerobic metabolism is an expensive system
to maintain; it requires a large, active heart, an elaborate vascular system to deliver oxygen, and
numerous mitochondria in the muscle cells to produce large quantities of ATP. The high costs of
maintaining these features are reflected in the higher rates of metabolism when the animal is at rest.
“Anaerobic animals” avoid these energetic costs and have relatively low resting metabolic rates,
leaving more energy available for growth and reproduction. However, they are incapable of
any behavior that entails moderate or high levels of muscle activity for prolonged periods of
time.
Many vertebrate animals possess both fiber types, but usually one type predominates over the
other. This translates into the animal’s ability to be either a sprinter (i.e., moves quickly but can only
do so for short distances) or better at endurance (i.e., is able to travel long distances at steady paces).
You are already familiar with this by the “white meat and dark meat” of chicken and turkey.
A. How frequently do chickens fly? W hat t ype of fi bers do chi cken breasts have?
Ex pl ain wh y you bel i eve this t o be t rue.
B. How much time do chickens spend running around? W hat kind of fibers are i n the
l egs? Expl ain what is going on chemi cally i n t hi s m uscl e t yp e.
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Anatomy
C. What about other birds, such as ducks and geese? Would you expect these birds to have the
same distribution of white and red fibers?
II. Station 2:
MUSCLE ACTION: Muscles of the human body vary in shape and size. While most are
somewhat elongated in shape, others may be trapezoidal and a few circular. The thick fleshy part of
the muscle is called the belly. You can easily relate to this by feeling the muscle of you upper arm
and back of your lower leg. Many (but not all) muscles are directly connected to bones. The tapered
ends of these muscles are connected to bone by tendons (a type of dense connective tissue).
Most muscles of the body work in groups to perform a specific body movement. The area on a bone
where a muscle is firmly attached is called the origin and the point of attachment to the bone it
moves is called the insertion. The contraction of specific muscles results in an action and that action
is often described in terms of “antagonistic pairs” of muscles. The main muscle that is responsible
for a specific movement (or action) is called the agonist (or prime mover); the muscle that opposes it
is called the antagonist. When one muscle contacts to produce a motion, its opposing muscle is
relaxed. This will become clearer as you perform some of the actions listed below. Some basic types
of body movements are flexion/extension (arm or leg), depression/elevation (jaw), and
dorsiflexion/plantar flexion (foot).
B. Muscle Identification: Identify the muscles below on your body. Based on the information in
Table 3, determine the action of the following muscles.
Masseter
Triceps brachii
Tibialis anterior
Temporalis
Orbiularis oculi
Sternocleidomastoid
Biceps brachii
Gastrocnemius
Table 3: Actions of some human skeletal muscles.
Action
Main muscle(s) involved
Tibialis anterior
Gastrocnemius
Biceps brachii
Triceps brachii
Location (bone hints)
Origin: tibia
Insertion: foot bones
Origin: femur
Insertion: heel bone
Origin: scapula
Insertion: radius
Origin: scapula and humerus
Insertion: ulna
2013-2014
Anatomy
Orbicularis oculi*
-------- N/A -----------
Sternocleidomastoid
Origin: sternum and clavicle
Insertion: temporal (mastoid process)
Masseter
Origins: temporal bone;
Temporalis
maxilla & zygomatic arch
Insertions: mandible
* Note this is a sphincter-type muscle.
Station 3:
The Effects of Muscle Fatigue on Muscle Function
Materials:
Hand grip exerciser
Two volunteers in your group can do this activity. Each person will determine the number of
times he/she can completely compress the handgrip until your hand is fatigued. In the table
below, record the number of closures you (and you lab partners) can do.
DATA: The effect of muscle fatigue on hand contractions using a handgrip exerciser.
Your data:
Total # of
compressions
Partner’s data:
Total # of
compressions
Answer the questions that follow.
1. Based on your data, and that of your partner’s and/or classmates, discuss if any of you participate
in activities that require extensive use of the fingers (e.g. typing, play piano or guitar, etc.). Does this
have a relationship to the results?
2. What is the relationship between muscle fatigue and fiber type? Do you think there are more red
(SO) or white (FG) fibers in the hand muscles?
Anatomy
2013-2014
3. What insights can you develop about fiber typing of the muscles involved? Which of your
classmates appears to have a higher concentration of red (oxidative) fibers and which appear to have
predominantly white (glycolytic) fibers?
Station 4:
The Effects of Heat and Cold on Muscle Function:
Materials:
Ice
Pen or pencil
Water bath
towel
1. Write your signature 3 times under the column labeled “Normal”.
2. Obtain a handful of ice (as if you were going to make a snowball) and a plastic tray
(to catch the melting ice). Hold the ice in your writing hand for a few minutes then write
your signature 3 times under the column labeled “Cold”.
3. Place your hands in the water bath for a few minutes. Massage your hands and write
your signature 3 times under the column labeled “Warm”.
NORMAL
COLD
WARM
•
What did the changes in temperature do to your hand muscles?
•
How do you explain this effect?
•
Why do you think dancers wear leg warmers and major league pitchers wear
jackets before pitching?
Station 5:
Testing Your Grip Strength and Muscle Fatigue
OBJECTIVES
In this experiment, you will

Obtain graphical representation of the force exerted by your hand while gripping.


Observe the change in hand strength during a continuous grip over time.
Observe the change in hand strength during rapid, repetitive gripping.
MATERIALS
computer
Vernier computer interface
Logger Pro
Vernier Hand Dynamometer
PROCEDURE
Select one person from your lab group to be the subject.
Part I Muscle Strength with Continuous Grip
1. Connect the Hand Dynamometer to the Vernier computer interface. Open
the file “17a Grip Strength Fatigue” from the Human Physiology with
Vernier folder.
2. Zero the readings for the Hand Dynamometer.
a. Hold the Hand Dynamometer along the sides, in an upright position
(see Figure 2). Do not put any force on the pads of the Hand
Dynamometer.
b. Click the Zero button,
.
Figure 2
3. Have the subject sit with his/her back straight and feet flat on the
floor. The Hand Dynamometer should be held in the dominant hand.
The elbow should be at a 90° angle, with the arm unsupported (see
Figure 3).
4. Have the subject close his/her eyes, or avert them from the screen.
5. Instruct the subject to grip the sensor with full strength and click
to begin data collection. The subject should exert maximum
effort with each grip throughout the duration of the experiment.
6. At 90 s, the lab partner(s) should encourage the subject to grip even
harder. Data will be collected for 100 s.
7. Determine the maximum force exerted during different time intervals.
Figure 3
Position the cursor at 0 s and click and drag to highlight 0−10 s on the graph.
Click the Statistics button, , to see the Statistics box.
Record the maximum force during the interval in Table 1, rounding to the nearest 0.1 N.
Move the brackets to highlight the 20−30 s period on the graph. As you move the brackets,
the statistics in the Statistics box will be updated based on the data between the brackets.
e. Record the maximum force during this interval in Table 1, rounding to the nearest 0.1 N. f.
Repeat this process for the time intervals: 40−50 s, 60−70 s, and 80−90 s.
g. Close the Statistics box by clicking the  in the corner of the box.
a.
b.
c.
d.
Part II Muscle Strength with Repetitive Grip
10. Open the file “17b Grip Strength Fatigue” from the Human Physiology with Vernier folder.
11. Have the subject sit with his/her back straight and feet flat on the floor. The Hand
Dynamometer should be held in the dominant hand. The elbow should be at a 90° angle, with
the arm unsupported (see Figure 2).
12. Have the subject close his/her eyes, or avert them from the screen.
13. Zero the readings for the Hand Dynamometer.
a. Hold the Hand Dynomometer along the sides, in an upright position. Do not put any force
on the gray pads of the Hand Dynamometer.
b. Click the Zero button,
.
14. Instruct the subject to rapidly grip and relax his/her grip on the sensor (approximately twice
per second). Click
to begin data collection. The subject should exert maximum effort
throughout the duration of the experiment.
15. At 90 s, the lab partner(s) should encourage the subject to grip even harder. Data will be
collected for 100 s.
16. Determine the maximum force exerted during different time intervals.
a. Position the cursor at 0 s and click and drag to highlight 0−10 s on the graph.
b. Click the Statistics button, , and record the maximum force during that interval in
Table 2, rounding to the nearest 0.1 N.
c. Move the brackets to highlight the 20–30 s period on the graph. As you move the brackets,
the statistics in the Statistics box will be updated based on the data between the brackets.
d. Record the maximum force during this interval in Table 1, rounding to the nearest 0.1 N.
e. Repeat this process for the time intervals: 40–50 s, 60–70 s, and 80–90 s and then close
the Statistics box by clicking the  in the corner of the box.
17. Calculate the difference between each maximum value and the next and record these values
in Table 2.
18. Position the cursor at 0 s. Click and drag to highlight 0–90 s on the graph. Click the Linear fit
button, , and record the slope in Table 3.
8. Calculate the difference between each maximum value and the next and record these values
in Table 1.
9. Position the cursor at 0 s. Click and drag to highlight 0−90 s on the graph. Click the Linear fit
button, , and record the slope (round to the nearest 0.01) in Table 3.
Part II Muscle Strength with Repetitive Grip
10. Open the file “17b Grip Strength Fatigue” from the Human Physiology with Vernier folder.
11. Have the subject sit with his/her back straight and feet flat on the floor. The Hand
Dynamometer should be held in the dominant hand. The elbow should be at a 90° angle, with
the arm unsupported (see Figure 2).
12. Have the subject close his/her eyes, or avert them from the screen.
13. Zero the readings for the Hand Dynamometer.
a. Hold the Hand Dynomometer along the sides, in an upright position. Do not put any force
on the gray pads of the Hand Dynamometer.
b. Click the Zero button,
.
14. Instruct the subject to rapidly grip and relax his/her grip on the sensor (approximately twice
per second). Click
to begin data collection. The subject should exert maximum effort
throughout the duration of the experiment.
15. At 90 s, the lab partner(s) should encourage the subject to grip even harder. Data will be
collected for 100 s.
16. Determine the maximum force exerted during different time intervals.
a. Position the cursor at 0 s and click and drag to highlight 0−10 s on the graph.
b. Click the Statistics button, , and record the maximum force during that interval in
Table 2, rounding to the nearest 0.1 N.
c. Move the brackets to highlight the 20–30 s period on the graph. As you move the brackets,
the statistics in the Statistics box will be updated based on the data between the brackets.
d. Record the maximum force during this interval in Table 1, rounding to the nearest 0.1 N.
e. Repeat this process for the time intervals: 40–50 s, 60–70 s, and 80–90 s and then close
the Statistics box by clicking the  in the corner of the box.
17. Calculate the difference between each maximum value and the next and record these values
in Table 2.
18. Position the cursor at 0 s. Click and drag to highlight 0–90 s on the graph. Click the Linear fit
button, , and record the slope in Table 3.
DATA
Table 1−Continuous Grip
Time interval
Maximum force (N)
∆ Maximum force (N)
0–10 s
20–30 s
40–50 s
60–70 s
80–90 s
Table 2−Repetitive Grip
Time interval
Maximum force (N)
∆ Maximum force (N)
0–10 s
20–30 s
40–50 s
60–70 s
80–90 s
1. Examine your graph and the data in Table 1. What conclusion can you draw about the
number of individual muscle fibers that are firing in the last 10 s compared with the first
10 s?
2. Is the change in number of muscle fibers that contract occurring at a constant rate?
3. Use your knowledge of fast, slow, and intermediate skeletal muscle fibers to hypothesize
which fibers are contracting in the first, third, and final 10 s intervals.
Station 6:
Isometric vs. Isotonic
1. Read through directions at station.
2. In your lab book, write in your own words the definitions of isometric and isotonic. Give
an example of each.
3. Read the article and perform the activities at the station.
4. Which of the contractions would best promote joint stability?
5. Which of these contracts would best promote muscle strength?
Station 7:
Muscle Stimulation
1. After getting shocked by your teacher, please diagram why the electrical current causes
the muscle to contract. You may need to do some “googling.”