Lab 9 - Introduction to sEMG

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 1 APA 2315 Lab 9 - Introduction to Surface Electromyography Jeremiah Zephir 300130890 **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, wheth er 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

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 2 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. *** 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.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 4 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.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 5 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. *** 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.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 7 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). 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

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 8 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 Extension at the hip, and knee flexsion Rectus femoris Flexion at the hip, knee extention Tibialis anterior Dorsiflexion of the foot Gastrocnemius Plantar flexion at the foot Gait cycle event Thigh position Leg position Foot position Initial contact (“heel strike”) Slight flexion Fully extended Dorsiflexion Opposite toe off Slight flexion Slight flexion Plantar Heel rise Slight flexion Slight flexion Plantar Opposite initial contact Slight flexion Fully extended dorsiflexion Toe off Slight flexion Slight flexion Plantar Feet adjacent Slight flexion Slight flexion Plantar Tibia vertical Slight flexion Neutral Neutral *You may want to get up and walk to get a better idea of limb positioning during the gait events. Gait cycle event or period Hypothesis regarding which muscles are activated Initial contact (“heel strike”) Rectus femoris (major), tibialis anterior (slight), bicep femoris Loading response Rectus femoris, tibialis anterior Midstance Gastrocnemius Heel rise Gastrocnemius Toe off Rectus femoris Initial swing Rectus femoris

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 10 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. 6. Data collection i. Zero the force plates (hardware and software zero).

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 11 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.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 13 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. *****graphs were unable to be completed, I had great difficulty in figuring it out, I did thorough research in learning which and how each muscle is active, I hope this is sufficient. General analysis of how each muscle attributes during each step of the gait cycles. Gait Cycle Bicep femoris Rectus femoris Tibialis anterior Gastrocnemius Initial contact (“heel strike”) Minimal activation, as it primarily functions in hip extension, not heavily involved in heel strike. Hypothesis states this would be slightly active as it used for initiation in hip flexion. Limited activation, as it primarily acts on the hip and knee and may not be highly engaged at this stage. Hypothesis states this would be most active. This is not the case. Limited activation, as it primarily acts on the hip and knee and may not be highly engaged at this stage. Hypothesis states slight activity, this was the case. Minimal activation, as the foot is flat on the ground. Loading Response: Hypothesis states no activity. Loading response Limited activation as weight is transferred to the loaded limb. Hypothesis states no activity. Engagement to stabilize the knee and control flexion. Hypothesis states major activity here. This was correct. Continues to be active to control dorsiflexion. Hypothesis states major activity here. This was correct. Activation increases to control ankle plantarflexion. Hypothesis states no activity. This wasn’t the case. Midstance Minimal activation, focusing on weight-bearing. Maintains some level of activation to stabilize the knee. Becomes less active as feet move into full contact. Continues to be active to maintain ankle plantarflexion.

APA 2315 – Introduction to the Biomechanics of Human Movement University of Ottawa 14 Hypothesis states no activity. There was minimal Hypothesis states no activity. There was minimal. Hypothesis states no activity. There was slight activity. Hypothesis states major activity. This was the case Heel rise Initiates activation as the heel begins to lift. Hypothesis states no activity. This wasn’t the case, there is slight activity. Engaged to assist with knee extension. Hypothesis states no activity. This wasn’t the case, there is slight activity. Decreases activation as the foot lifts. Hypothesis states no activity. This was the case. Becomes highly active to initiate plantarflexion. Hypothesis states major activity. This was the case Toe off Engages further to assist with hip extension. Hypothesis states no activity. This wasn’t the case, there is slight activity. Continues to be active for knee extension. Hypothesis states major activity, this was the case. Minimal activation as the foot leaves the ground. Hypothesis states no activity. This wasn’t the case, there is slight activity. Remains highly active for plantarflexion. Hypothesis states no activity. This wasn’t the case, there is major activity. Initial swing Active to assist with hip flexion. Hypothesis states no activity. This wasn’t the case, there is major activity. Engages to flex the hip. Hypothesis states major activity, this was the case. Minimal activation as the foot swings forward Hypothesis states no activity. This wasn’t the case, there is slight activity. Active to control dorsiflexion and prepare for the next heel strike. Hypothesis states no activity. This wasn’t the case, there is major activity. Mid-swing Active in hip flexion. Hypothesis states no activity. This wasn’t the case, Engaged in hip flexion. Hypothesis states no activity. This wasn’t the case, Limited activation during swing. Hypothesis states major activity, this Moderately active to control dorsiflexion. Hypothesis states no activity. This wasn’t the case,