MUSCLE PHYSIOLOGY REPORT
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School
Texas State University *
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Course
3421
Subject
Mathematics
Date
Apr 3, 2024
Type
docx
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3
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MUSCLE PHYSIOLOGY REPORT
Answers should be in complete sentences. Graphs should have axes and units clearly labeled. Point
values for each item are in gray. Spelling, grammar, punctuation, and formatting are worth 3 points overall.
Delete this note and delete the written question portions so that your final document just has tables,
graphs, and answers. Leave the numbers to help your lab instructor grade. Be sure to use consistent
formatting throughout – reports should be neat and professional looking.
A. EMG and Grip Strength
1. Complete the table with your data. Remember to keep data neat and consistent in all tables.
(1)
Dominant Forearm Circumference (cm): Relative Grip
Strength
Absolute Area of
EMG Activity
Absolute Area Under
Force Curve
Lowest
Higher 1
Higher 2
Highest
2. Make a line graph of your own data, plotting the absolute area of the EMG signal (Y) as a function of the absolute area of muscle force (X) for each muscle contraction. Always give graphs a clear title at the top and be sure to label axes and include units. (In this one case only, absolute area does not require units. Be sure to include units on your other graphs.)
Insert your graph here. (3)
3. Is there a linear relationship between EMG activity and muscle force? Using what you know about physiology, why or why not? (A linear relationship would be shown as a perfectly straight line through the data, with the X variable increasing or decreasing exactly in proportion to the Y variable.)
(2)
4. Thinking through the concepts you have learned, what might contribute to these graded contractions? In other words, the muscle fibers in your forearm didn’t contract in an all-or-
none fashion, but rather performed four contractions of different strengths. What are at least two reasons this is able to happen? (2)
B. EMG and Muscle Fatigue
5. Complete the table with your own data. (1)
Maximum Muscle
Force (kg)
Half-Max Muscle
Force (kg)
Half-Max Fatigue
Time (sec)
6. We cannot sustain maximum muscle force indefinitely. What are some factors involved in muscle fatigue and how do they cause it? Include at least three factors and how they cause fatigue. (3)
C. Combining Data
7. Complete the table with data from the rest of the class, adding rows as needed. (1)
Subject
Forearm
Circumference (cm)
Maximum Muscle
Force (kg)
Half-Max Fatigue
Time (sec)
1
2
3
4
5
8. Create a scatter plot graph showing the relationship between muscle size (X) and max muscle force (Y). Insert your graph here. (3)
While adding your line of best fit, Excel will give you the option to display the R-
squared value. R
2
is the "coefficient of determination:" the square of the correlation between two variables. These values will help determine whether there are strong correlations between muscle size and force or fatigue. In general, an R
2
value of 1.0 = 100% correlation between variables, while a score of 0.0 = 0% correlation, which is another way of saying no correlation at all. So an R
2
value of 0.3 might suggest that the independent variable accounts for about 30% of the dependent variable. While the R
2
value is a statistical description of correlation, it is not a p-value and cannot be used to determine statistical “significance.” 9. Create another scatter plot showing the relationship between muscle size (X) and fatigue time (Y). Be sure to add your line of best fit and display the R-squared value. Insert your graph here. (3)
10. How is the maximum muscle force related to the size of the muscles involved? How is the
time to fatigue to half-maximum strength related to the size of the muscles involved (i.e. arm circumference)? Mention your R
2
values and what it suggests in each case. (R
2
values tell us about correlation, but not “significance.”)
(2)
11. If muscle size and muscle force or muscle fatigue are not always perfectly correlated (e.g.
two people with about the same sized forearms can have different forces or fatigue), what variable could account for this? Explain how this variable can affect force or fatigue. (2)
12. What is the circumference of your non-dominant forearm and how does it compare with your dominant forearm? Do you predict that your maximum muscle force and half-maximum fatigue time would be the same, or different, for your non-dominant arm? Why? (1)
13. Do you think measuring the circumference of a forearm is a perfect estimate of forearm muscle mass? If not, why not? (1)
14. What are at least two possible errors you may have encountered in this experiment? How
could you avoid those errors in the future? (2)
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