An Electrode placement and lead attachment

Lab 1 Electromyography I
Purpose
1) To observe and record skeletal muscle tonus as reflected by a basal level of electrical activity associated with the muscle in a resting state.
2) To record maximum clench strength for right and left hands.
3) To observe, record, and correlate motor unit recruitment with increased power of skeletal muscle contraction.
4) To listen to EMG “sounds” and correlate sound intensity with motor unit recruitment.

Procedure

1. Subject preparation. Clean the skin with rubbing alcohol to make sure the gel electrodes remain adhered to the skin securely during the EMG recording time. Place gel electrodes on your dominant arm and set up the lead/cable connection by following Figure 1. The cable should be plugged in Channel 1 (“CH 1”) of the Biopac data acquisition module, Figure 2. Turn on Biopac MP36; double click “BIOPAC BSL4.0 MP36” to open up the software; select “Record or Analyze a BIOPAC Lesson” and “L01 - Electromyography (EMG) I”, and “OK”.

Figure 1 Electrode placement and lead attachment (dominant arm first and then non-dominant)

Figure 2 Cable and headphone plug in CH1 and OUT1 of Biopac MP36, respectively.

2. Calibration.
   1) Click “Calibrate” to start the Calibration recording.
   2) Clench fist as hard as possible, as shown in Figure 3, then release.

Figure 3 Clench fist for Calibration

3) Wait for Calibration to stop. Calibration will last 8 seconds and stop automatically, let it run its course. At the end of the 8-second Calibration recording, the screen should look like Figure 4, i.e. a zero baseline and a burst (when Subject clenched).
4) If not, redo calibration by clicking “Redo Calibration” and repeat the entire calibration sequence (double check and make sure the electrodes are making good contact before redo calibration).

Figure 4 Calibration

3. Data recording.
   Dominant arm
   1) Click Record. When you click Record, the recording will begin and an append marker labeled “Dominant arm” will automatically be inserted. Subject performs a series of four Clench (hold for 2 sec.)-Release-Wait (for 2 sec.) cycles, beginning with a weak clench, and then trying to increase strength in approximately equal increments so the fourth clench is at maximum.
   2) Click Suspend. Data should look similar to Figure 5 below. If not, click Redo and repeat.

Figure 5 Clench, Release, Wait, Repeat (4 times)

Non-dominant arm
1) Prepare the other arm the same way as the dominant arm and repeat the procedure mentioned above.
2) Data should look similar to Figure 5, except that the height of each plateau (the strength) is smaller.

4. Listen to EMG signal
   1) Subject puts on the headphones.
   2) Click Listen. Experiment by changing the clench force as you watch the screen and listen.
   3) Clicking Stop will end listening to the EMG. Or click Redo, if you want to listen again.
   4) If your teammates want to listen to your EMG, switch the headphones from Subject to the new person and click Redo.
5. Data analysis
   1) Enter the Review Saved Data mode and choose the correct file and open it. Data should look like Figure 6 (top).
   2) There are two channels in your data recording, EMG (CH 1) and integrated EMG (CH 40), and the value displayed in the Mean (the average value in the selected area) box of CH 40 will be your EMG measurement. These are shown in Figure 6 (bottom).

Figure 6 EMG data (top) and channel designations and measurement box settings (bottom)

3) Use the I-Beam cursor to select an area on the plateau of the first EMG cluster, Figure 7 (top), and the tonus between the first and second EMG clusters, Figure 7 (bottom). The measurements you read from the CH 40 Mean box for cluster and tonus are to be entered in Table 1 and 2 of your lab report, respectively.
4) Select other clusters and tonuses and fill out the rest of the blanks of Table 1 and 2 with your measurements.
5) Repeat the above procedure for your Non-dominant arm data.

Figure 7 EMG cluster (top) and tonus (bottom) selection

EMG I Lab Report
Student’s Name: _ Lab Section: Date:
I. Data and Calculations (28 pts total, report 3 significant figures;)
Subject Profile
Name ____ Height_____________ Gender: Male / Female
Age_______________ Weight _ Dominant arm: Right / Left
Data set_________________
Table 1 EMG Measurements (10 pts)

Cluster # Dominant arm Non-dominant arm

1
2
3
4
Note: "Clusters" are the EMG bursts associated with each clench.

• Use the mean measurement from the table above to compute the percentage increase in EMG activity recorded between the weakest clench and the strongest clench of Forearm 1. (10 pts)

Calculation:

Answer: _ %

Table 2 Tonus Measurements (8 pts)
Between Clusters # Dominant arm Non-dominant arm

1-2
2-3
3-4

II. Questions (72 pts total)

1. (14 pts) Compare the mean measurement for the right and left maximum clench EMG cluster.
   1) Are they the same or different? __ Same Different
   2) Which one suggests the greater clench strength? Right Left Neither
   3) Explain your answer.
2. (12 pts) What factors in addition to sex contribute to observed differences in clench strength?
3. (12 pts) Does there appear to be any difference in tonus between the two forearm clench muscles?
   Yes _____No
   Would you expect to see a difference? Does Subject’s gender influence your expectations? Explain.
4. (12 pts) Explain the source of signals detected by the EMG electrodes.
5. (8 pts) What does the term “motor unit recruitment” mean?
6. (8 pts) Define skeletal muscle tonus.
7. (6 pts) Define electromyography.

Comments from Customer
Do you have BSL analysis software installed on your compure? the data set is in a format that can be opened with the software only. if you have not yet installed the software use this step by step to download and install the BSL analysis biopac.

1. Use this Website:
   https://www.biopac.com/support/bsl-analysis-student-rsd-download/
2. swipe the website a little down where you can see the title written in blue that says "CURRENT
   RELEASE"
3. Below the current release you can find "BSL Analysis 4.1 – Mac"
4. Click on "Mac"
5. It will take you to a new page so swipe down a little in the new page
6. click on "BSL Analysis 4.1.3 for macOS"
7. Sign up in the website or if you already have an account simply sign in.
8. The ZIP file will automatically starts to download

Sample Solution