Lab 9 - Introduction to sEMG

pdf

School

University of Ottawa *

*We aren’t endorsed by this school

Course

2315

Subject

Psychology

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by ChefRock10823

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 1 APA 2315 Lab 9 - Introduction to Surface Electromyography **Shorts and a t-shirt are required for this laboratory** OBJECTIVES: 1. To become acquainted with research-based surface electromyography (sEMG); 2. To understand the basic principles of sEMG. INTRODUCTION: In this lab, you will be given an introductory lesson on surface electromyography (EMG). This is a common biomechanical tool used in research, sport, clinical and many other settings. EMG is the technique that is used to collect electrical signals generated by contracting muscles. This technique allows clinicians and researchers to determine which muscles are active during the various phases of a movement. EMG can also be used to determine the percentage of the muscles’ maximum that is being generated during a movement. However, it is important to understand that a higher electrical signal does not result in more force from the muscle. Surface electromyography (sEMG) is the most commonly used type of EMG because of its ease of use and ethical implications. The other type of EMG is known as indwelling or intramuscular electromyography. This process involves inserting electrodes directly into the muscle belly, not simply to the surface of the skin. EMG data are very useful in understanding the roles of specific muscles during complex motions. The data can also help clinicians monitor the progression of patients after various types of procedures and injuries, or to improve athletic performance by corrected muscle recruitment and monitoring maximum contractions. In this lab, you will learn how to use sEMG to collect and analyze data. You will be able to see the timing and level of muscle recruitment in the lower limbs during a participant’s gait cycle. You will become familiar with the proper procedure for preparing a subject for data collection and locating muscle bellies in the lower limb. Hopefully this little description will help clarify some of the concepts involved with EMG: “Imagine you are living in an apartment with rather thin walls and your neighbour is throwing a party. From your apartment it seems like there are groups of conversations next door, and you’re wondering who’s at the party, how many people there are, whether they are men or women, and so on. The conversations closer to the wall are easier to hear, and the voices sound a bit different from those deeper in the room. A radio is playing so it is somewhat difficult to hear the conversations, and as more people enter the party, everything gets louder. The challenge of recording and interpreting electromyographic activity is analogous to the task you face in this thin-walled apartment. If you record from the skin surface (the wall), the superficial muscle fibres nearest the skin (voices closer to the wall) contribute greater activity than those farther from the surface electrodes. Groups of motor units (analogous to groups of human conversations) make unique contributions to the EMG signal. As more motor units participate in the muscle contraction (more people enter the room), the EMG signal increases in amplitude. Numerous sources of noise (like background music) can make the interpretation of the EMG signal difficult” *Excerpt from: Kamen & Gabriel (2010). Essentials of electromyography . Champaign, IL: Human Kinetics.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 2 *** This lab is divided into 3 parts. In Part 1, you will learn how to properly place EMG electrodes. In Part 2, you will learn how to use the Delsys Trigno wireless EMG system. In Part 3 you will learn how to interpret EMG data. To do this, the EMG activity of the i) rectus femoris, ii) gastrocnemius, iii) tibialis anterior and iv) biceps femoris muscles will be measured during natural gait (walking). Force data will also be gathered using force plates. The roles of each of these muscles during brisk walking will be examined. MATERIALS: Delsys Trigno Wireless EMG system, computer equipped with Vicon Nexus software and Trigno Control Utility software, surface electrodes, alcohol pads, electrode adhesives and force plates. PROCEDURES: Part 1: How to place EMG electrodes *You will work in pairs to complete this part of the lab. 1. On your participant, identify the muscle that you will be evaluating. For the purpose of practice, use the biceps brachii. 2. Determine the proper location for electrode placement according to the Seniam Sensor Location Guidelines. Mark this spot using a pen. a) Seniam Guideline : “Electrode needs to be placed on the line between the medial acromion and the fossa cubit at 1/3 from the fossa cubit” b) Confirm that the Seniam location is indeed on the muscle belly (see image of muscle belly below) . If not, adjust it accordingly to fit your participant’s body (the Seniam location is a guideline , not an absolute location). Illustration taken from: De Luca (2002). Surface Electromyography: Detection and Recording, Delsys Incorporated©. 3. If there is hair on the muscle belly, it would need to be shaved off. Since we are just practicing the placement of electrodes, you can disregard this step for now. 4. In the absence of hair, or after shaving, the skin will need to be cleaned using an alcohol pad. This will remove skin oils and dead skin cells. Go ahead and clean the area. muscle belly

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 3 5. Once the skin has been prepared, place one of the round stickers provided over the muscle belly (draw an arrow on the sticker before applying it to your subject); this sticker will act as an electrode for the purpose of practicing. NOTE : The arrow on the sticker should face in the direction of the muscle fibres, so be sure to check which way the fibres run on your muscle. You may need to refer to an anatomy textbook. 6. Repeat these practice steps for the following muscles: a) Triceps brachii (lateral head) Seniam Guideline: Electrode needs to be placed at 50% on the line between the posterior crista of the acromion and the olecranon at two finger widths lateral to the line. b) Semitendinosus Seniam Guideline: Electrode needs to be placed at 50% on the line between the ischial tuberosity and the medial epicondyle of the tibia. c) Rectus Femoris Seniam Guideline: Electrode needs to be placed at 50% on the line from the anterior spina iliaca superior to the superior part of the patella. d) Gastrocnemius (medial head) Seniam Guideline: Electrode needs to be placed on the most prominent bulge of the muscle.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 4 e) Tibialis anterior Seniam Guideline: Electrode needs to be placed at 1/3 on the line between the tip of the fibula and the tip of the medial malleolus. f) Biceps femoris Seniam Guideline: Electrode needs to be placed at 50% on the line between the ischial tuberosity and the lateral epicondyle of the tibia. g) Iliocostalis Seniam Guideline: Electrode needs to be placed one finger width medial from the line from the posterior spina iliaca superior to the lowest point of the lower rib, at the level of L2.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 5 *** In the next part of the lab, you will learn how to use the Delsys Trigno wireless EMG system. The data collection will involve placing electrodes on four muscles of the lower limb and having a participant walk across force plates. The data gathered will provide information regarding the activity of the different muscles during gait. The terms gait and walking are often used interchangeably. Gait analysis is the study of human walking. “ The gait cycle is defined as the time interval between two successive occurrences of one of the repetitive events of walking ” (Whittle, 2007). Often two successive “initial contacts” (also called “heel strikes”) are used to define a gait cycle, but any event may be chosen. Refer to the images below for information pertaining to gait events. Positions of the legs during a single gait cycle by the right leg (gray). (From Whittle, MW: Gait Analysis: An Introduction, 4 th ed.2007, Elsevier ).

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 6 The major events during the gait cycle are: 1. Initial contact 2. Opposite toe off 3. Heel rise 4. Opposite initial contact 5. Toe off 6. Feet adjacent 7. Tibia vertical (1. Initial contact). These events split the gait cycle into seven periods and two phases. During the stance phase (also known as the support phase or contact phase), the foot is in contact with the ground. This phase lasts from initial contact to toe off, and the four periods of this phase are: 1. Loading response 2. Mid-stance 3. Terminal stance 4. Pre-swing. During the swing phase, the foot is moving through the air. This phase lasts from toe off to the next initial contact, and its three periods are: 1. Initial swing 2. Mid-swing 3. Terminal swing Timing of gait events, periods, and phases as a percentage of the gait cycle. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation , ed 2, St Louis, 2010, Mosby).

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 7 The periods generally take place during the following intervals of the gait cycle: Loading response: 0-10% of gait cycle Midstance: 10-30% of gait cycle Terminal stance: 30-50% of gait cycle Pre-swing: 50-60% of gait cycle Initial swing: 60-73% of gait cycle Mid swing: 73-87% of gait cycle Terminal swing: 87-100% of gait cycle The phases generally take place during the following intervals of the gait cycle: Stance phase: 0-60% of gait cycle Swing phase: 60-100% of gait cycle Prior to completing the EMG data collection, work together in small groups to hypothesize which muscles will be active during the following events and periods of the gait cycle: heel strike (initial contact), loading response, midstance, heel rise, toe off, initial swing, mid-swing, and terminal swing . The muscles of interest are: biceps femoris, rectus femoris, tibialis anterior, and gastrocnemius. A hypothesis, often referred to as an educated guess, proposes an explanation for an occurrence based on existing scientific knowledge. For this lab, you should base your hypotheses on the known actions of each muscle . You may want to refer to a functional anatomy textbook. To help you frame your hypotheses, fill out the missing information in the following tables. Muscle Action (e.g. thigh/hip flexion) Biceps femoris Rectus femoris Tibialis anterior Gastrocnemius Gait cycle event Thigh position Leg position Foot position Initial contact (“heel strike”) Opposite toe off Heel rise Opposite initial contact Toe off Feet adjacent Tibia vertical *You may want to get up and walk to get a better idea of limb positioning during the gait events.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 8 Gait cycle event or period Hypothesis regarding which muscles are activated Initial contact (“heel strike”) Loading response Midstance Heel rise Toe off Initial swing Mid-swing Terminal swing *** Part 2: How to use the Delsys Trigno Wireless EMG system Below are the detailed steps for collecting EMG data using the Delsys Trigno Wireless EMG system. You need to understand the methods for gathering EMG data, but you do not need to know the specific computer steps. 1. Select a volunteer to be your participant. This person will wear have EMG electrodes applied to their leg muscles and perform a walking task in front of the group. 2. Turn on the electrodes which will be used in this analysis (Channels 1-4), by pressing the button on top of them. 3. Apply the electrode adhesive on the back of the electrode. 4. Place electrodes following the Seniam Sensor Location Guidelines on the clean muscle belly of the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius (medial head). The arrow on the sensor should face the direction of the muscle fibres. Be sure to prepare the skin by shaving the hair and cleaning the area with alcohol pads. Make note of which electrode is on which muscle. You will need to know this for your analysis.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 9 5. System preparation & Signal check a) Trigno Control Utility i. Open the Trigno Control Utility software program (on the desktop) and confirm that the four sensors of interest are activated. ii. Click Start Analog once all 4 channels are active. b) Vicon Nexus software i. Open the Vicon Nexus 2.8.2 software (on the desktop). ii. In the Communications pane (at the bottom of the screen) under the Data Management tab, select your course APA 2315 – APA 2715 (green circle). Select EMG (yellow circle) then create your lab section (gray circle). iii. Click Go Live . iv. You should see the work “ LIVE ” in the View pane. v. Select 5 MX cameras + 4 force plates + 4 NewEMG from the drop down menu in the System tab of the Resources pane. This is your system configuration. vi. Still in the System tab, expand the Devices nodes ( ) and ensure that the Delsys Trigno EMG system and force platforms are listed. vii. To confirm that the EMG system is collecting data, select Graph from the drop down menu on the top left corner of the View pane and select the first four channels of the Delsys Trigno EMG system in the Devices portion of the Resources pane (under the System tab). This can be done by expanding the Delsys Trigno EMG node ( ) and expanding the Voltage node, then holding down Ctrl on the keyboard as you click on each of the four channels. viii. Ask your participant to contract and relax each of the muscles under investigation. If the EMG system is set up properly, you should see spikes in the signals when your participant contracts. These spikes indicate muscular activity. If this is not the case, reposition your sensors and repeat this step. ix. To confirm that the force plates are collecting data, select Graph from the drop down menu on the top left corner of the View pane and select the F z channels of force plates #2 and #4 in the Devices portion of the Resources pane. This can be done by expanding the node ( ) for each of the two force plates of interest and expanding the Force nodes, then holding down Ctrl on the keyboard as you click on each F z channel. x. Ask your participant to walk across each force plate under investigation. If the force plates are set up properly, you should see a mountain-like spike in the signal when your participant is in contact with the force plate. If this is not the case, troubleshoot the force plates. c) Video data on a smartphone i. To help you visualize the movements and determine the roles of the muscles, set up a camera to record the trial as well.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 10 6. Data collection i. Zero the force plates (hardware and software zero). ii. In the Next Trial Setup section of the Capture tab ( ) in the Tools pane of Vicon Nexus 2.8.2 , name your trial [e.g. walking _ (insert your lab section)]. Then press Start to begin your data collection and Stop when finished that trial. Be sure to start and stop recording on the smartphone as well. iii. Beginning with nothing on the force plates, collect a couple of dynamic trials of your participant carrying out normal walking. In this walking trial, your participant must step on force plates #4 and #2 with their left foot while walking across the catwalk. Be sure to give your participant a chance to practice walking naturally while ensuring they step on the desired force plates. *If you were doing a research project now, you would want to collect a minimum of 5 trials of each condition being explored. Since this is an introductory lab, you may collect just one trial of walking. iv. Load your file by out by selecting (double-clicking) the new trial you captured in the Communications window and waiting a few seconds for the file to load. v. With the View pane set to Graphs , select the four channels of the Delsys Trigno EMG system in the Devices portion of the Resources pane (under the System tab), as well as the F z channels of force places #2 and #4. vi. Play the trial. You may modify the speed by clicking on more.../Replay speed under the Play button. A speed of 1 indicates the real speed. You can also use the arrows on the keyboard to move one frame at a time. vii. Look at the data for one gait cycle (from heel strike on FP4 to heel strike on FP2 for the left leg) and use this information to determine the roles of the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius (medial head). Cropping your data to approximately one gait cycle will make this analysis easier. To crop your data, drag the grayed area by clicking on the blue triangle and dragging it. 7. Export your data. i. Run the Export ASCII pipeline by selecting it from the drop down menu under Current Pipeline in the Pipeline tab ( ) of the Tools pane . Hit Play ( ). Save your trial. ii. Open your exported data file in Microsoft Excel. You may want to delete any superfluous data columns to make your data analysis easier. The only data you need to keep is the time data, the force plate data (FP#2 and FP#4), and the EMG data for the channels you used during your data collection (channels 1-4). Your TA will email your data file to your lab section. Note: the data being considered in this lab is the raw data for the trial. In research, this data would be processed (e.g. filtered, rectified, and linear envelope applied) to allow for further analyses. Refer to image below for examples of EMG data processing. You do not need to know these steps for this lab.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 11 Part 3: Interpreting EMG signals After each small group has written out their hypotheses and the data collection has taken place, gather as a group and use the EMG data to verify your hypotheses. Lab Assignment Answer the following discussion questions. 1. What did you hypothesize regarding the activity of the biceps femoris during the various events of the gait cycle? Explain the reasoning behind your hypotheses. Were your hypotheses in line with what the data showed? How were they the same? How were they different? 2. What did you hypothesize regarding the activity of the rectus femoris during the various events of the gait cycle? Explain the reasoning behind your hypotheses. Were your hypotheses in line with what the data showed? How were they the same? How were they different? 3. What did you hypothesize regarding the activity of the tibialis anterior during the various events of the gait cycle? Explain the reasoning behind your hypotheses. Were your hypotheses in line with what the data showed? How were they the same? How were they different? 4. What did you hypothesize regarding the activity of the gastrocnemius during the various events of the gait cycle? Explain the reasoning behind your hypotheses. Were your hypotheses in line with what the data showed? How were they the same? How were they different? Be sure to include graphs of your EMG and force plate data. The graphs will help you with your analysis. It is up to you how you would like to present the data graphically.

Lab 9 - Introduction to sEMG

Related Documents