Muscle Fatigue
Teacher Copy
Purpose:
Our human body is a complex system of bones, muscles, organs, nerves, etc… Students will experience
and observe the function of muscle contraction, and observe how temperature and fatigue impact
muscle function and performance.
Background Information:
Bones and organs are moved by contractile muscle tissue, of which there are three types: skeletal,
smooth, and cardiac. Skeletal muscles, those responsible for moving parts of the body that are under
voluntary control, are made up of muscle fibers. Each muscle fiber is an elongated, multinucleated cell
crossed by dark and light striations, and the fibers are grouped into bundles called fascicles.
Generally, the muscle fibers span the length of the muscle and are woven into connective tissues like
tendons at the end of the muscle. The tendons attach the muscle to the bone, allowing it to function
as a biological lever that can exert force on the bone it attaches to. The more fibers a muscle has, the
more powerful the muscle is: for example, the quadriceps has a huge number of fibers, so it is one of
the most powerful muscles in the body.
Every skeletal muscle is supplied with at least one nerve, one artery, and one vein. This is to ensure
that every muscle can receive incoming nerve impulses while being fueled by fresh blood from the
arteries. The veins are needed to export deoxygenated blood containing metabolic wastes and other
byproducts. Active muscles require energy, and therefore require a continuous supply of oxygen and
nutrients. For fuel, muscles rely on glucose form the bloodstream, glycogen stored in the muscle
fibers, or fat molecules during vigorous, prolonged exercise. When energy availability fails to keep
pace with the demands being placed on the muscle, the muscle will lose its physiological abillity to
contract in a controlled fashion due to ATP depletion. Even though the muscle may still receive nerve
stimulation to move, muscle fatigue sets in.
Equipment:
For each lab group:


Economy Force Sensor with rubber attachment
500 or 750 Interface:



Beaker of cold water
Ice
Digital Thermometer
Software Setup:
1.
Load the DS Muscle Fatigue program until the laptop under My Documents.
2.
Open Data Studio.
3.
Select Open Activity
4.
Select My Documents and the Muscle Fatigue lab
Experimental Procedure:
Data Recording:
1.
Place the ice into the container of cold water, and let stand until the water temperature is
about 4 degrees Celsius.
2.
Grip the Force Sensor and place your thumb on the rubber bumper.
3.
Click the Start button (
4.
Begin squeezing the Force Sensor until the DataStudio graph display reads 40N or above.
5.
Continue to hold the Force Sensor at or above 40N as long as possible.
6.
Click the Stop button (
7.
Submerse the same hand into the container of ice water for 30 seconds or more.
8.
Repeat steps 2-6.
) to begin collecting data.
) once the display begins to drop below 40N.
Data Analysis:
1.
Examine the graph display to view your data, using the Scale to Fit button (
toolbar to resize the axes.
) in the Graph
2.
Determine the length of time for each endurance test.
3.
Examine how steady the graph of Force vs. Time is -- was the test subject able to exert a
fairly constant force? Or were there oscillations in the graph?
Conclusions and Extensions:
1.
Which of the two endurance tests were longer in length of time?
2.
What factors may have caused different results?
3.
What effect did the ice water have on the action of the student’s hand muscles? Why?
4.
Discuss how this experiment relates to the experience of drowning victims who succumb in
very cold water as opposed to warmer waters.
Teacher Hints:
1.
An alternative to this experiment is to have a student use their weak hand (left, if they’re
right handed) first, and submerse their dominant hand into the ice water.
2.
An additional experiment is to have a student press down the rubber bushing for 45 seconds
at 40N. Repeat this step 9 more times, each time noting the number of seconds the student
can maintain 40N.
Trial
Time (seconds) 50N is
maintained
1
2
3
4
5
6
7
8
9
10
3.
Notice how the time decreases with every run.
4.
What effect did fatigue have on the student’s hand muscles?
5.
Challenge students to exert a continuous steady force on the sensor -- staying within a 5-N
range, for example. On repeat trials, challenge students to stay within a more narrow range -within 2 N for instance.
Muscle Fatigue
Opening the program
5.
6.
7.
8.
Load the DS Muscle Fatigue program until the laptop under My
Documents.
Open Data Studio.
Select Open Activity
Select My Documents and the Muscle Fatigue lab
Experimental Procedure:
Data Recording:
9. Place the ice into the container of cold water, and let stand until the water
temperature is about 4 degrees Celsius.
10. Grip the Force Sensor and place your thumb on the rubber bumper.
11. Click the Start button (
) to begin collecting data.
12. Begin squeezing the Force Sensor until the DataStudio graph display
reads 40N or above.
13. Continue to hold the Force Sensor at or above 40N as long as possible.
14. Click the Stop button (
40N.
) once the display begins to drop below
15. Submerse the same hand into the container of ice water for 30 seconds or
more.
16. Repeat steps 2-6.
Data Analysis:
4. Examine the graph display to view your data, using the Scale to Fit button
( ) in the Graph toolbar to resize the axes.
5. Determine the length of time for each endurance test.
6. Examine how steady the graph of Force vs. Time is -- was the test subject
able to exert a fairly constant force? Or were there oscillations in the
graph?
Conclusions and Extensions:
5. Which of the two endurance tests were longer in length of time?
6. What factors may have caused different results?
7. What effect did the ice water have on the action of the student’s hand
muscles? Why?
8. Discuss how this experiment relates to the experience of drowning victims
who succumb in very cold water as opposed to warmer waters.