Basic EMG (Muscle Tension) Software Application User Guide
Contents
1. 3 1 What ls EMG As I ve said in the introduction EMG is an electrical correlate of muscle tension measured from the skin It s quite a complex measurement in some ways For practical purposes all you need to know is this you attach three sensors to the skin Two of these are known as the active sensors The software comes up with a number that reflects the muscle tension between the two active sensors This number is changing from moment to moment if you tighten up the number gets bigger and if you relax it gets smaller The active sensors are the white and black cables See the Hardware Set up Guide for more details The rest of this section explains how this number is derived If you are new to the application you can skip over it and return to it later if you feel you need a fuller understanding EMG is actually an oscillating voltage A voltage is always a difference in electric potential between two points In our case the two points are the active sensors The voltage comes not from muscle cells themselves but from the electrical impulses travelling in the nerves that stimulate the muscles The oscillations are quite fast up to several hundred cycles per second or Hertz Figures 3 and 4 show what a raw EMG trace looks like The amplitude of this signal or size in the vertical dimension is what correlates to muscle tension Lv bl lia E a Figure2. to breathing The yellow dotted line is the threshold level see section 4 5 below for more about this The combo boxes below the chart control how the EMG signal is processed and displayed Filter Controls the frequency band from which the EMG measure is derived See section 3 1 for further information There are two options 100 200 Hz and 10 400 Hz The latter may be considered a specialist application for the vast majority of users the former will suffice If you re not sure what frequency band means simply select 100 200 Hz Note that the filter setting applies to all displays in the user interface with the exception of the spectral display see section 4 3 below Average Controls the level of smoothing of the EMG signal With a shorter average you will see all the fine grained changes in muscle tension With a longer average these are smoothed out and the signal will be slightly slower in responding to change For most users a setting of 1 0 or 2 0 seconds will be suitable Range Sets the upper limit of the display The lower limit is always zero Select a larger range if the trace appears to be off the top of the chart If you can t see the trace it probably is off the top Select a lower range as you learn to reduce tension so that the display offers greater sensitivity meaning that even subtle changes in muscle tension can be seen Period This controls the length of time it takes for the trace to traverse the who
3. 3 Raw EMG data This chart show 10 seconds worth of data The voltage is varying so quickly that at this scale the cycles merge into one another The amplitude or height in the vertical direction gives an indication of the muscle tension in this case the tension was relaxed after around 6 5 seconds Basic EMG Application User Guide copyright Glyn Blackett page 4 Figure 4 Raw EMG data At a time scale of 1 second the individual cycles of the oscillating voltage begin to become apparent If we could zoom in even more we would see that the frequency or wavelength is not constant but quite variable For practical purposes we aren t really interested in the oscillation Rather we want to quantify muscle tension as a number that gets larger when we tighten the muscles and smaller when we relax The following is a Somewhat technical description of the steps needed to derive such a number Remember you don t need to understand the details to make practical use of the application The first step is to apply a frequency filter to the raw EMG signal The idea behind this is that a complex oscillation such as EMG does not have a constant frequency or wavelength We could say that it is made up lots of waves or different frequency Applying a filter means that certain frequency components are blocked from passing through in the same way as large particles are blocked f
4. YORK BIOFEEDBACK www york biofeedback co uk Glyn Blackett Basic EMG Muscle Tension Software Application User Guide Table of Contents 1 RIG Ce NEE 2 2 Launching the Apnplcaton 3 2 1 Hardware E 3 3 About Electromyography EMG 4 3 1 What Is EM 4 3 2 Working With EMG Biofeedback EEN 6 3 2 1 Wrist Hacement ccc ccc ccccceccccccccecceccecccucececceaseceeneuueaueneeunes 6 3 2 2 Forehead Hlacement T See EE 8 4 1 Standard Controls Start Stop etc 8 4 2 Short Term Displays and CGontrols 9 EE ee 10 4 4 Long Term Display and Controls cccccecceeeceeeeeseeeeeteeseeeeeeeseneees 10 4 5 Threshold Display and in e 4 iiisasciciscnsctccessaienieetsaekspeduiaaanacianieiiaces 11 4 6 Audio Feedback Copnbrols 0c cccccececcececcececcccccecceceaceceacecceeceeas 12 EH e E 13 oye Beieleit 13 5 2 Adding Notes to AIRE DON E 13 5 3 Sample Session REPOST eee ceccecceeceecseeeeeeeeeeeeeeeeegeaeeeeneaeeeegeaeees 14 EE innn E EES EER 15 6 1 Report Ee e E 15 Basic EMG Application User Guide copyright Glyn Blackett 1 Introduction This guide introduces the Basic Electromyography EMG biofeedback application part of York Biofeedback s Mind Body Training Tools suite This set of applications is designed to develop skills in mind body awareness and self regulation particularly in a context of mindfulness and meditation practice The guide has two purposes firstly to explain what EMG actually is and secondly to teach yo
5. aring as green triangles labelled 1 in figure 10 but switching to red squares when the feedback is turned on Each also has an independent volume control sliders labelled 2 in figure 10 graded on a scale of 0 100 Tone and midi feedback use a range parameter which defines what EMG levels correspond to the highest and lowest pitches available A combo control 6 in figure 10 set this range Audio feedback also has a separate average control to allow the greatest flexibility This works just like the average control of the short term display In my experience tone feedback needs at least a couple of seconds worth of averaging applied for aesthetic reasons The threshold level can be applied to tone and midi feedback meaning that they play only when the threshold condition is met Check the controls labelled 3 in figure 10 to apply this feature Tone A tone is played whose pitch varies continuously with the EMG level Midi A musical note is played at regular intervals whose pitch varies with the EMG level Threshold The meeting of the threshold condition triggers the sound of a bell The application plays an audio file named 1 wav and located in the folder media in the EMG file location within the BioEra installation Le generally speaking C Program Files BioEraPro design Y BF EMG You can have the application play sounds of your choice by simply substituting this file with one of your own For example you could record a message
6. ate list of supported hardware please see the York Biofeedback website 2 Launching the Application Ze York Biofeedback Software Mind Body Training Tools Set up iabili Selected Trainee Default U Heart Rate Variability elected Iraimee efault User HEG Neurofeedback Basic EMG Application EMG amp Breathing Application 1 p Start Basic EMG Application Start EMG amp Breathing Application Breathing 2 Es View Basic EMG Session Report View EMG amp Breathing Session Report EMG Muscle Tension 3 Es View Basic EMG Application Report View EMG amp Breathing Application Report GSR amp Skin Temperature Documentation Documentation Capnometry Basic EMG Application User Guide EMG amp Breathing Application User Guide EEG Assessment Impedance Checking EEG Training Start Battery and Impedance Check Application YORK BIOFEEDBACK MIND BODY TRAINING TOOLS www york biofeedback co uk A Figure 1 EMG Tab of the Platform Application Figure 1 above shows the Muscle Tension EMG tab of the Platform program Press the button labelled 1 to launch the application Make sure you have your BioEra licence key dongle inserted into a USB socket After a few seconds a new window will appear on your screen 2 1 Hardware Set up The physical aspects of hardware set up how to connect and use your sensors how to check impedances etc are dependent upon the type of amplifier you are using and are covered in a separat
7. e They should be self explanatory The Epoch control sets the time period at which data is written to the session data file This data file is used to generate session reports which are described in section 6 below For the Basic EMG application only EMG data is written Choosing a lower time period generates more data The setting also controls the level of averaging of the recorded data For example if you select 2 seconds then the application will write to the session data file once every two seconds the average EMG over that two second period The button marked with a red asterisk is a simple event marker You can use it to mark adventitious happenings and changes in session conditions It is particularly useful for coaches and therapists Events thus marked are represented in the long term chart see section 4 4 below by a vertical white line They are also recorded in the session data file and are shown in session report charts as dotted vertical lines see section 5 Note that pressing the escape key during a session has the same effect as pressing the red asterisk with your mouse i e it is an alternative 4 2 Short Term Displays and Controls 141 98 5 P E Finer E gt Average e R 1 2 Figure 6 Short term display and controls This chart shows EMG as it varies over the short term You can see that in figure 6 there is a rhythm in the left most part of the trace This is related
8. e document Hardware Set up Guide Before you start the application you configure the device set up ol x options accessible by clicking a button in the Set up tab of the Platform In the dialog select the type of amplifier biofeedback Device GPR Ei device you are using in the EMG source control Note all the source settings are remembered the next time you start the Platform See the Installation and Set up Guide for further details of device set up Figure 2 amplifier status One of the device options is Simulator In simulator mode you can learn how to use the software without the encumbrance of sensors leads etc The application simply uses recorded data as a source Once you have started the application you should see your device selection reflected in the device status display in the top right corner of the main window see figure 2 The lamp shown as a red square in figure 2 should change to green when you press the play button If you do not see this happen it means that the application has not been able to establish a connection with your device Check it is plugged m and that the batteries are not flat For some devices you ll see a button rather than just text Pressing this button opens up a dialog that allows you to adjust settings related to the device such as COM port The specifics depend on the device see the Hardware Set up Guide for more details 3 About Electromyography EMG
9. edback This section explains how EMG biofeedback is useful particularly within a context of mindfulness meditation practice It also discusses the two most common sensor placements and their relative merits In biofeedback you learn to connect the external feedback to your internal subjective experience particularly bodily experience Muscle tension offers a very useful window on the mind body connection many of our muscles are directly consciously controllable but on the other hand they also respond quite automatically to emotions thoughts and memories Broadly speaking we tend to tighten up in response to emotions such as anxiety and anger even very brief and subliminal emotions Any sense of emotional threat tends to cause us to literally brace ourselves as though it were a physical threat Inner resistance is a term I use for subtle forms of this It means not wanting some aspect of our current experience for example a pain to be within our awareness Inner resistance manifests as tension as though we were attempting to hold the experience at arms length Learning to maintain soft relaxed musculature is a powerful strategy for maintaining open calm and expansive states of mind Relaxing muscle tension is often difficult because it s not necessarily easy to be aware of tension in the first place and also of the effects of your attempts to relax Awareness is a prerequisite for conscious control EMG biofeedback h
10. elps us develop a much more sensitive awareness of the state of our musculature on the basis of which we can develop greater skill in relaxing muscles An important aspect of mindfulness practice 1s to keep the mind stably focused in the present moment If you ve had any experience with mindfulness you ll know that the mind tends to wander off The practice of mindfulness is to keep returning to the object of concentration The key is to notice when the mind has wandered off This is not easy for most people it is common to spend quite a few minutes at a time in distraction Biofeedback can help with mindfulness practice by flagging when we have become distracted at least insofar as distractions are manifested as subtle changes in the body s physiological state In other words it functions as a distraction detector We can characterise different forms of distraction one useful distinction is between low energy slothful and sleepy states versus high energy agitated states The latter may be emotionally arousing distractions such as anxious worrying or resentment or they may be forms of sensual craving or they may be subtle urges to activity such as restlessness or planning what you re going to do later on Whatever the case this kind of high energy distraction tends to manifest as higher muscle tension meaning that EMG biofeedback 1s useful at flagging this kind of state By contrast low energy distractions such as day dreaming or slee
11. functions as a warning that you have drifted away from your desired state or drops below in which case the feedback serves as a reward Select gt for the former and lt for the latter Average The threshold control has its own level of averaging which works in just the same way as the average control in the short term display section 4 2 This was done in order to offer the greatest flexibility in usage Duration This control allows you to say that feedback should be triggered only if the threshold condition is met for a certain period of time This is a way of in effect filtering out discrete events of brief duration for example if you swallow or briefly move your hand In such cases the muscle tension may rise above the threshold limit but will drop back below again very quickly so that the feedback is not triggered The control sets the length of time needed to trigger feedback The lamp displays 7 and 8 allow you to discriminate lamp 7 lights up as soon as the signal crosses the threshold while lamp 8 will only light up if the signal exceeds the threshold continuously for the required duration 4 6 Audio Feedback Controls 1 2 3 y y y Tone re tr J Apply Thr Midi me Ern l Apply Thr Thr keen M invert Audio Avg HIE Range fa T A A A 4 5 6 Figure 10 Audio feedback controls There are three forms of audio feedback available tone midi and audio file Each has an on off button appe
12. in your own voice There are lots of programs that you can use to do this including some freeware applications Your recording needs to be saved in WAV format The value of using the threshold is that the feedback is generally less intrusive freeing you to focus on your direct experience The feedback only comes in when you ve drifted out of your desired psychophysiological zone You can set some options for midi feedback notably the instrument piano by default from the Platform i e before starting the application See the Installation and Set up Guide for further details 5 Session Reports The application records data so that you can generate a report for your sessions The report contains summary data and graphs showing the progression of the feedback parameter over the whole session To generate and open a session report click the button labelled 2 in figure 1 A dialog window opens in which you can select various options see figure 11 The software creates the report in html format It will be opened using your computer s default web browser e g Internet Explorer Note that a live internet connection is not needed The html file is saved so you can for example email it to someone See the Installation and Set up Guide for details of file storage 5 1 Report Options Most of the options should be self explanatory If you change your mind about options on seeing your report you can regenerate the report by clicking the
13. ion of the EMG over a longer time scale up to 30 minutes The two combo boxes 1 and 2 in figure 8 control the horizontal and vertical ranges LT Period Controls how long it takes the trace to traverse the whole chart from right to left Range Controls the upper limit of the chart in the same way as the equivalent range control does in the short term display 4 5 Threshold Display and Controls The essence of threshold based feedback is that a discrete feedback event is triggered whenever muscle tension exceeds some limit For example the feedback event could be the playing of a sound file The threshold limit is shown and controlled by the bar labelled 5 in figure 9 To change this limit simply click your mouse over the bar and drag it to the desired location The range of the bar graph is controlled by 5 the range combo control described in section 4 2 above In other words the bar graph and the short term display being 4 adjacent to each other will always be matched in terms of range RI SG S The numeric display 6 shows the current 1 2 3 7 EMG while 4 shows the setting of the threshold bar 8 The exact behaviour of the threshold based feedback depends upon the settings of three Figure 9 Threshold controls controls combos 1 2 and 3 in figure 9 Condition 1 in figure 9 Feedback can be triggered when the EMG signal either goes above the threshold in which case the feedback
14. le chart from right to left or in other words the horizontal range 4 3 Spectral Display T5 100 125 150 175 Figure 7 Spectral display For the majority of users this display shown in figure 7 above is not really relevant or useful but for those interested the following is an explanation of what it does It can of course be skipped over As discussed in section 3 1 above EMG in its raw form is a complex oscillation It doesn t have a single fixed frequency but rather is a mixture of frequencies We can use a mathematical method called Fourier analysis or spectral analysis to decompose the complex EMG into component frequencies The spectral display shows the results of this analysis In the chart frequency varies along the horizontal axis represents The height of the graph at each point represents the size of the contribution of that frequency The spectral display always shows the full frequency range up to 400 Hz regardless of the setting of the filter control described in section 4 2 above One way this chart can be useful is in recognising electrical interference You will see a prominent bar at the mains frequency 50 Hz in the UK and perhaps at multiples thereof 100 Hz 150 Hz etc these are known as harmonics 4 4 Long Term Display and Controls 240 Fall 300 LT Penod Je min Range i2uv 1 2 Figure 8 Long term display and controls The long term display figure 8 shows the variat
15. of our mental and emotional state Chest based breathing 1s suggestive of the kind of emotionally defensive states I ve alluded to whereas abdominal breathing is more open and calm For many people chest based breathing has become an ingrained habit but one which can quite easily move towards more natural abdominal breathing with mindfulness practice To get a meaningful measure the arms should be loose and by the sides with the hands probably on the lap Holding the arms up or clenching the hands will give much higher readings Fully relaxing all these muscle groups will give an EMG reading of around 1 microvolt but not much less A typical everyday state might give around 3 6 microvolts Higher readings 10 20 microvolts are common and may reflect stress and emotional tension If you re using gel free snaps see the Hardware Set up Guide for more about this bear in mind that the readings are less accurate so interpret the numbers more loosely 3 2 2 Forehead Placement All three sensors are placed on the forehead with the ground in the middle This placement picks up tension from anywhere in the head the jaw being an especially powerful contributor Even the tongue can contribute However breathing makes no significant contribution With this placement the numbers are generally smaller compared to the wrist to wrist placement Fully relaxing all the muscles of the head will give a reading of around 0 5 microvolts perhaps sligh
16. pen an application report click the button labelled 3 in figure 1 A dialog window opens in which you can select various options see figure 12 As with session reports the software creates the application report in html format It will be opened using your computer s default web browser e g Internet Explorer Note that a live internet connection is not needed The html file is saved so you can for example email it to someone See the Installation and Set up Guide for details of file storage Report Options Show Max 7 Min EMG v Mark data points EMG axis from zero Maximum EMG Amplitude 72 yy Figure 12 Report options 6 1 Report Options The application report options dialog is an adapted version of the session report options dialog Many of the options are the same and should be self explanatory See section 5 1 above As with all of the application reports in the suite there is a chart for each of the main parameters tracked in the application in the case of the Basic EMG application that means only EMG amplitude For each chart you can opt for line graphs for the maximum minimum mean and standard deviation The line graphs have one point per session
17. piness don t create muscle tension Sensor location is a key decision in EMG biofeedback Different placements can bring out different aspects of the mind body relationship The two placements I commonly use are 1 wrist placement and 11 forehead placement 3 2 1 Wrist Placement Placing one active sensor on each wrist picks up tension in the arms hands and shoulders especially the latter two Also tension in the upper chest and neck has an influence The third sensor or ground can go on either wrist See the Hardware Set up guide for more information Emotional defensiveness inner resistance and wariness can all subtly manifest as tightness in these areas mostly commonly around the shoulders but also in the hands and any of the muscles detected with this placement With the wrist to wrist placement rhythmic patterns related to the breathing typically show up This is because the shoulders and upper chest are often involved with breathing Figure 6 shows an example This makes the wrist placement very useful for practising mindfulness of breathing The more the upper chest and shoulders are involved the more prominently the rhythm shows up in the EMG Conversely relaxed abdominal breathing shows as a much smaller variation This makes sense because movements of the diaphragm and lower intercostal muscles which are active in abdominal breathing are not really picked up picked up by this placement The breath is subtly reflective
18. report button 2 in figure 1 then checking Overwrite existing report Setting a maximum EMG amplitude is a basic way of excluding artefacts for example if you changed your posture during the session Data points exceeding the maximum value are excluded 5 2 Adding Notes to a Report You can choose to write some notes for your session report Checking Add notes to report top right of the dialog allows you to do this You may wish to add notes after having first seen the report In this case simply click the button 2 in figure 1 again and check the Add notes option This will regenerate the report with your added notes Report Options Overwrite existing report Add notes to report EMG v Mark data points EMG axis from zero Maximum EMG Amplitude 72 yy Figure 11 Report options 5 3 Sample Session Report Training Session Report Training Application Basic EMG User Name Default User Session Date 28 03 12 22 01 EMG Amplitude in Microvolts os N dy n dy ho dy Ww EMG Muscle Tension EMG Summary Data Parameter Value Max Reading 3 0 uV Min Reading 0 8 uV 10 Session Time in Minutes Basic EMG Application User Guide copyright Glyn Blackett 15 20 page 14 6 Application Report An application report summarises all the sessions for the currently selected user in charts and a table To generate and o
19. rom passing through an ordinary filter such as a sieve In our case both high and low frequencies are blocked unlike a sieve which only blocks large particles from passing Frequency filtering allows us to exclude certain sources of interference artefacts that would otherwise contaminate our measure of muscle tension and it also helps us to in some sense standardise the measurement The application offers you a choice of two frequency windows 1 e two settings of the frequency filter One is a wide frequency band 10 400 Hz while the other is narrower 100 200 Hz See section 4 2 below for how to change the setting The narrow band is generally much more usable practically speaking and I anticipate that most users will only ever use that one The next step is to rectify the signal which means to turn a reading which oscillates either side of zero and thus whose average is zero into a set of positive only values It amounts to flipping all parts of the trace that are below the zero line above it The final step is to average out the signal so we get something that varies smoothly rather than jumping rapidly up and down The application allows you to choose the time period of this averaging Choosing a longer averaging period makes the signal smoother but the trade off is that it is less responsive asic EIVIG App lication User Guide LOUNT oht I hi l UTN D anl att nage s onl OLY DIacKetl DAYO J 3 2 Working With EMG Biofe
20. tly less Everyday states are typically around 1 2 microvolts Again stress and emotions are likely to be reflected in higher tension at this placement Facial expression is a natural part of emotion Even fleeting and barely noticed emotions so called micro emotions can be detected The forehead placement also throws useful light on thought processes Inner dialogue seems to involve subliminal use of the speech muscles those in the jaw lips and even the tongue Activity in these muscles is easily registered with the forehead placement To an extent fully relaxed facial musculature is incompatible with maintaining inner dialogue 4 User Interface 1 Standard controls 2 Short term display and controls Q l 05 02 ze Epoch 23 Yo Biofe pack wwwyork biofeedback co uk Simulator Dy BioEra A7 EMG_Main 5 Threshold l LR e S display Filer 100 200Hr Average 205 Range euv Period imin Thr gt g 205 Duration jos 350 11 98 i Op Eeer Y T Tone gt n Apply Thr Midi gt Jya Apply Thr Thr re ant 360 376 dMi Audio Aug feos r Range fe uv Sem 3 Spectral display 4 Long term display 6 Audio controls Figure 5 User Interface Figure 5 above shows the user interface for the EMG application 4 1 Standard Controls Start Stop etc A set of buttons Play Stop and Pause are the same in all the applications in the suit
21. u how to use the software though it is more of a reference than a tutorial Other training material is available on the York Biofeedback website address above EMG 1s an electrical correlate of muscle tension It 1s easy to appreciate that the state of muscle tension 1s reflective of your subjective state of mind EMG biofeedback is a means of developing greater sensitivity to this mind body relationship and of transforming your state of mind by changing the underlying physiology EMG is measured using sensors in contact with the skin By selecting the placement of the sensors we can choose to monitor different sets of muscles This guide discusses the most commonly used placements In keeping with others in the suite the Basic EMG application was designed to support your aims not to supplant them Achieving low muscle tension is not necessarily the most important thing Biofeedback should enhance or expand your subjective awareness rather than detract from it Note that other applications m the suite namely EMG amp Breathing and Capnometry with EMG contain much of the functionality of the Basic EMG application and extend it by also monitoring breathing and by relating the EMG feedback to breathing They are covered in a separate user guides The guide assumes that you have read the Software Installation and Set up Guide and therefore know how to start the application The application works with several devices For an up to d
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