Electromyography (Dynamometry)
Motor unit recruitment and fatigue
Data report and evaluation
ELUP students
Experiment was accomplished by:
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Teacher:
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Date:
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Subject 1
Subject 2
name:..................................................
name:........................................................
gender: male / female
gender: male / female
age: ..........................................
age: ..........................................
height: .......................................
height: .......................................
weight: ......................................
weight: .......................................
2
Aims of the practical lesson (brief definition in a few sentences)
Introduction (can be continued on a separate sheet if needed)
1. Regulation and adjustment of muscle contraction strength (summary of the
most important facts with regard to the analysis of the practical data)
2. Methods and materials (schematic enumeration)
3. Technical details of the practical exercises (preparation of the subject, settings of
the recording system, explanation of the exercises)
3
A. Data and calculations
1. Motor unit recruitment
Fill out the following tables using Segment 1 data both from the dominant and from the nondominant
arm. During the evaluation, use the following options in the channel windows: CH1 - force; CH40integrated EMG. Choose the parameter mean in both parameter windows. Using the I-beam cursor,
select an area on the plateau phase of the first clench, read the values and insert them into the table. As
the program shows the extent of muscle contraction as the force exerted by a given weight in [kg],
please transform the force values in the table to [N]! Calculate the quotient force/integrated EMG as
well! Repeat the same procedure with the subsequent peaks - you may not need 6 peaks to reach
maximum clench force.
Attach the analyzed records (printouts) to the lab report and number them accordingly!
Subject 1 (name:....................................................................)
Dominant forearm
(right
left)
Nondominant forearm
number of the attached record:.......................
Mean int.
Mean force
Force/
Mean
int. EMG
[CH1]
EMG
[CH40]
force [N]
[kg]
[mV/s]
[Ns/mV]
(right
left)
number of the attached record:.......................
Mean int.
Mean force
Force/
Mean
int. EMG
[CH1]
EMG
[CH40]
force [N]
[kg]
[Ns/mV]
[mV/s]
1.
2.
3.
4.
5.
6.
Subject 2 (name:....................................................................)
Dominant forearm
(right
left)
Nondominant forearm
number of the attached record:.......................
Mean force
Mean
Force/
Mean int.
force
int. EMG
[CH1]
EMG [CH40]
[kg]
[N]
[mV/s]
[Ns/mV]
(right
left)
number of the attached record:.......................
Mean force
Mean
Force/
Mean int.
force [N]
int. EMG
[CH1]
EMG [CH40]
[kg]
[mV/s]
[Ns/mV]
1.
2.
3.
4.
5.
6.
Create a graph using the force – integrated EMG data pairs (x axis: force; y axis: integrated EMG)!
Plot the data derived from both forearms of both Subjects on the same graph!
Number of the attachment:.....................
4
2. Muscle fatigue
Subject 1 (name:....................................................................)
Mean
force
[CH1]
[kg]
Maximal force
Mean
Mean int.
force
EMG
[CH1]
[CH40]
[mV/s]
[N]
50% of maximal force
Mean
Mean
Mean int.
force
force
EMG
[CH1]
[CH1]
[CH40]
[mV/s]
[kg]
[N]
Fatigue
length
[CH40; T]
[sec]
dominant
(..............) arm
record:...........
nondominant
(...............) arm
record:...........
Subject 2 (name:....................................................................)
Mean
force
[CH1]
[kg]
Maximal force
Mean
Mean int.
force
EMG
[CH1]
[CH40]
[mV/s]
[N]
50% of maximal force
Mean
Mean
Mean int.
force
force
EMG
[CH1]
[CH1]
[CH40]
[mV/s]
[kg]
[N]
Fatigue
length
[CH40; T]
[sec]
dominant
(..............) arm
record:...........
nondominant
(...............) arm
record:...........
B. Summary and discussion of data
a) What does the EMG electrode measure? What determines the amplitude of the integrated EMG
signal?
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b) Does the dominant or the nondominant forearm have higher strength capacity?
Subject 1:
Subject 2:
dominant
dominant
nondominant
nondominant
no difference
no difference
Is there any difference between the subjects in this respect? Explain the observation!
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c) Is there any difference between the subjects’ maximal strength capacity?
yes
no
Explain your observations!
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d) In the „force-integrated EMG” graph, what does the slope (steepness) of the curve indicate?
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Order the curves according to the slope steepness (1: lowest; 4: highest)
___Subject 1 dominant ___Subject 1 nondominant ___ Subject 2 dominant ___ Subject 2 nondominant
Compare the force per EMG unit values during approximately same strength of clench!
(Use the values calculated in the first two tables!)
___Subject 1 dominant ___Subject 1 nondominant ___ Subject 2 dominant ___ Subject 2 nondominant
Explain and interpret the order above! What do these values reflect?
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e) Compare the fatigue length of the forearms! (1: shortest; 4: longest)
___Subject 1 dominant ___Subject 1 nondominant ___ Subject 2 dominant ___ Subject 2 nondominant
Explain the results!
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6
f) How does the EMG activity change during muscle fatigue?
Subject 1:
decrease
no change
increase
Subject 2:
decrease
no change
increase
Explain your observations!
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g) When holding an object, does the number of motor units remain the same? Are the same motor units
used for the whole duration of holding the object?
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h) As you fatigue, the force exerted by your muscles decreases. What physiological processes explain
the decline in strength?
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7
C. Definitions
Motor unit:.............................................................................................................................................
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Muscle tone:...................................................................................................................................................
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Motor unit recruitment:..............................................................................................................................
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Muscle fatigue:.............................................................................................................................................
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Dynamometer:................................................................................................................................................
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