Download 1 I. INTRODUCTION The Myotonometer® measures force

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I. INTRODUCTION
The Myotonometer measures force-displacement characteristics of muscle and other tissues located
beneath the measuring probe. The force applied by the user with the probe is perpendicular to the
muscle. Myotonometric measurements obtained during a muscle contraction are able to quantify
strength because muscle stiffness increases proportionally to muscle activation and torque
production. “Tone,” “compliance,” “hardness,” and “stiffness” are all terms associated with forcedisplacement or length-tension muscle characteristics. Preferred terminology differs among clinicians,
scientists and engineers.
Following are definitions of terms associated with myotonometric
measurements.
Muscle “compliance” is an intrinsic property of muscle in which tension within the muscle increases
during lengthening without a change in the neural drive to the muscle.
“Stiffness” is the magnitude of force necessary to cause tissue displacement (the inverse of
compliance).
“Tone” is defined clinically as a muscle’s resistance to passive stretch.
Muscle tone reflects the
relative influences of the mechanical-elastic characteristics of muscular and connective tissues, and
the reflexive drive to the muscle. “Hypertonia,” an excessive resistance to passive stretch, is one
characteristic of spasticity. “Hypotonia” accompanies other medical disorders and diseases.
“Spasticity” is a motor disorder characterized by velocity-dependent hypertonia and accentuated
tendon reflexes.
“Spastic Paresis” typically infers the presence of spasticity and associated positive and negative
sensorimotor phenomena.
Among the negative phenomena associated with spasticity is muscle
paresis (weakness).
For reading ease, the manual will use the term "tone" rather than compliance, stiffness, or hardness.
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The Myotonometer was developed to quantify muscle tone and paresis. Protocols also permit
quantification of the level of severity of the spastic paretic condition. Valid and reliable quantifiable
measures of muscle tone are obtained easily and quickly.
Clinical trials have shown that
myotonometric measurements can distinguish between injured and non-injured muscles (even years
post injury) and quantify muscle imbalances.
The Myotonometer can also quantify differences
between individuals with upper motor neuron involvement from non-disabled individuals as well as
distinguishing between ipsi- and contra-lesional extremities.
extremely high.
Intra- and inter-rater reliabilities are
Measurements of muscle strength/paresis correlate very well with surface
electromyography (EMG) and joint torque outputs. A summary of these results and a publication list
are available on our website, www.neurogenic.com.
The Myotonometer assesses the amount of resistance a muscle exerts against a probe as the probe
is pushed in a direction perpendicular to the muscle fibers. The amount of resistance is directly
proportional to muscle tone.
Figure 1 shows the general operation of
the probe. The probe is the mechanical
part of the Myotonometer and sends
information pertaining to force and tissue
displacement to the computer. (1) Inner
probe (2) Plexiglas collar (3) Inner shaft
(4) Handle. The user grasps the handle
and
applies
downward
pressure
perpendicular to the muscle. As pressure
is applied, the inner probe pushes into
the muscle whereas the Plexiglas collar
remains relatively motionless on the skin
surface. Specialized transducers monitor
ongoing
pressure
changes
with
the
accompanying changes in displacement
between the inner probe (1) and outer
Рис.
Fig.11
collar (2).
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Figure 2 shows, schematically, the relationship between tissue displacement and its tension/elasticity.
The tissue to be measured consists of the skin layer (s), the muscle (m), and bone (b) (Fig.2A). The
User, by applying downward pressure with the Myotonometer, compresses the underlying tissues.
The depth of penetration (L) (the difference in displacement between the inner probe and the
external Plexiglas collar) is measured at pre-programmed force levels (selected by the User; see
section 3.1.7) (Fig. 2B).
An activated/contracted muscle, which has higher tone than a relaxed muscle would be characterized
by a steep slope when plotted on a length-tension curve (1) because it provides more resistance to
the pressure of the probe. In contrast, a relaxed muscle would be characterized by gently sloping
curve or a curve that "shifts to the right" (Fig. 2C).
Fig. 2
kg
mm
A
B
C
The Myotonometer is programmed to take 8 length-tension measurements per recording.
default setting = force levels from 0 to 2.0 kg in steps of .25 kg.
The
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II. DEVICE SPECIFICATIONS
The Myotonometer allows users to:
-
select desired procedure (resting tone, contraction, fixed force) to measure muscle properties
-
reject measurements when appropriate
-
obtain statistical characteristics of measured values
-
store and analyze information
-
obtain quantifiable measures of resting tone
-
obtain quantifiable measures of muscle paresis
-
obtain quantifiable measures that can indicate relative levels of spasticity
-
group data together (e.g. combine pre-drug trials from various testing days)
-
export data to other programs such as Excel, Paint and Systat
Technical specifications of the device:
Electric current (mA):
in measuring mode...........…………………………………………………………......................15
in "off" mode………........………………………………………………………….....................….0.001
The precision of measuring mechanical values:
pressure (kg)............................…………........………………….……….................... ± 0.05
displacement (mm)...........................................……………….……………………...... ± 0.1
Computer Requirements
computer processor 80486DX4 or higher
RAM 8 MB
hard disk 0.6 GB
screen 800X600 High Color(16 bit)
Windows 95/98
free serial or USB port.
data format…………………….........................……………………………………..................RS232;
Electrical safety:
in accordance with ICO-601-1 (Medical electrical equipment, Part 1, General safety
requirements).
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III.
MYOTONOMETER OPERATION
1. Connection of the Device to the Computer.
1.1 The probe cable is permanently connected to the electronic casing. The cable from the electronic
casing has a 9-pin connection to the serial or USB port of the computer (port COM1 or COM2). With
desktop-computers the mouse often occupies the COM1 port. You may need to manually change to
the COM2 port, if the computer does not automatically recognize the device. Do not connect the
device until you have installed the software.
2. Software installation.
2.1. Insert CD-ROM into the computer. If the CD does not initiate automatically, Press "Start" in the
left-hand bottom corner of the screen:
-
choose the lower line: "Run"
enter the letter of your CD-ROM drive (e.g. D:\ or E:\) followed by the following:
D:\myotonometer\setup.exe
The installation procedure will start automatically. The view of the screen in the process of installation
is shown in Figure 3. The program will cue you to insert all necessary program disks. After program
installation, select “Start”; “Programs”; “Myotonometer”; “Myotonometer” (Fig.4).
2.2. Connect the cable from the electronic casing to the USB-port of your computer. See calibration
procedures in section 2.4.
2.3. Initiate the program operation from Programs menu, as shown on Figure 4 (Start – Programs
– Myotonometer – Myotonometer). On initial program starting, if the computer recognizes the
presence of the Myotonometer on the COM-port, a screen appears (Fig.5), prompting the user to
calibrate the unit to ensure that the Myotonometer has not been damaged during shipping.
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Fig.
Fig.4.
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Fig. 3.
2.4. Calibration:
This screen (Fig. 5) allows the user to calibrate the Myotonometer. For this
purpose, the enclosed mouse-pad is to be used. Place the Myotonometer probe on the top of the
pad. Place one hand on top of the probe so that you can exert downward pressure and hold the
Plexiglas collar steady. Press downward gently until the sound signal is generated. This procedure
must be repeated three times.
After each testing cycle, a blue graph is plotted, as shown on Figure 6 (1). If the graph does not
Fig. 5
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extend beyond limits, shown by red dash lines, the condition of the sensors has not changed since
manufacturer's testing. If the generated graph exceeds limits (see Fig. 6[2]) this would indicate either
testing procedure error or damage to the Myotonometer during shipping. If errors are detected (Fig.
7), the test procedure is to be repeated carefully several times.
Make sure the Plexiglas collar
remains in contact with the mouse-pad at all times and the inner probe returns all the way to the
collar following each testing session. (See calibration procedures for further details.) If errors persist
after 3 to 4 testing attempts, the unit needs to be returned to Neurogenic Technologies®, Inc .
Fig.6
Fig. 7
Fig. 8
2.5.
In rare cases, if a computer configuration differs
from established standards, the program will not be able
to recognize the device. If this occurs an error window
appears (Fig.8) after a time delay of 15 – 30 seconds.
You will then need to manually select the desired
Comport.
Click on desired Comport and select "Detect
Again.' Opening window will then appear (Fig. 9). Click
the left mouse button and the Main Window (Fig. 10) will appear. You are now ready to begin
taking Myotonometer measurements
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3. Selecting Patient and Measurement Conditions
Fig. 9
3.1
Patient Information Data collection begins with the entering of patient/subject information.
When the Main Window appears (Fig. 10) select "New Client". You will then see the
window "Client" (Fig.11) and the window "Body" (Fig.12). The blinking cursor within
"Name" makes it possible to enter the patient's name or subject code number from the
keyboard. It is recommended that you avoid long words as it can create later difficulties while
working with the database.
3.2
Any additional information (e.g. condition,
date etc.) can be entered and stored in
"Notes".
3.3
It is then necessary to select the muscles
and conditions you wish to measure. Move
the cursor to the red silhouetted figure in
the window and click with the left mouse
button.
This will activate the “Body”
window (Fig. 12).
Fig. 10.
3.4.
Selection
of
muscles
and
conditions: First, choose the muscle to be measured by clicking on the appropriate gray
box associated with the muscle (Fig. 12).
3.5.
After choosing the part of the body, (e.g. Arm right), a window with a more detailed
picture of a particular body part will be shown (Fig.13). Select the specific muscle.
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Fig. 11
Fig. 12
3.6. After choosing the muscle, the window "Muscle Dialog" appears (Fig. 14). There are three
possible conditions:
“Activation" = muscle contraction (a maximal voluntary contraction is recommended)
"Relaxation" = resting muscle tone
"Fixed Force" is selected if you wish to obtain a measurement at a known and pre-prescribed
level of muscle contraction.
For instance, the patient could hold a 5-pound weight or could
isometrically contract against a hand-held dynamometer to a certain force level. If this option is
selected, you must also enter the value in the box to the right.
Fig. 13.
Fig. 14.
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Use the left mouse button to click on the desired conditions. A check mark will appear for each
selected condition.
Upon completing the description of the conditions, press "OK". The "Client"
window will appear (Fig. 15) and in the section "Muscles" the name of the muscle and condition will
be listed. If needed, choose the next muscle for investigation by clicking on the red-silhouetted
figure and repeat the procedure described above. In this way you will be able to compile a list of
muscles to be measured. The section "Muscles" will then show the list of muscles and conditions
(Fig.15).
Fig. 15
3.7
Fig. 16
Selection of Probe Forces: The User can set the amount of maximum pressure exerted
by the probe during testing. This is done within the Force section of the Client window
(Fig. 15). The default setting is 2 kg in .25 kg steps. In some instances (e.g. children,
debilitated individuals) the 2 kg force is too high and can be uncomfortable. In these
cases, enter values of 1 or 1.5 kg in the Force window. It is important to note that
measurements obtained during different force values (e.g. 1.0 and 2.0 kg)
cannot be combined or compared in the Analysis portion of the program.
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Fig. 18.
3.8 After you have completed all your selections
within the Client window, left mouse click "Save."
The information you have entered (patient name,
notes, list of muscles and conditions, and test
force) will be stored in the database. The same
window will re-appear with the "Measure" button
Fig. 17
highlighted (Fig.16). By clicking on it you will
progress to the measurement mode. But, if you wish just to make a preliminary list of muscles and
conditions without immediately performing any measurements, click "Close", after which the window
"Client" will disappear and the “Main Window” will appear. After that you can exit the program or
insert information about another patient.
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Measurement Procedures
4.1. If you want to initiate a measurement session directly after entering patient information, click
"Measure" in the window "Client" (Fig.16). The window "Measure" will open (Fig.17). Patient
information will be displayed.
4.2. Click “Measure”
A window with a table and a chart will appear on the screen (Fig. 19). The
title above the window indicates the name of the muscle, and the condition (relax, contract…) in
which it is to be measured.
4.3. Use of the Probe:
Before initiating a measurement with the probe, the patient is asked to
contract or relax the muscle (dependent on desired condition).
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The
probe
should
be
gently
pressed against the surface of the
skin overlying the desired muscle.
Pressure
should
be
exerted
perpendicular to the muscle. It is
recommended that the user apply
the pressure within a 2-3 second
time period. When the pressure
reaches 2 kg a sound will occur
signaling
the
end
measurement.
of
the
Several
repetitions are needed for each
measurement in order for an
Fig. 19
average
to
be
calculated.
A
minimum of 5 to 8 repetitions is
recommended. Any number of repetitions can be selected with the “Options” button within the
"Main Menu" window (Fig.10). You must exit out of the program and re-enter to set and save any
changes made in this window
4.4.
After each probe measurement, the table and graph will immediately display the results. The
table displays the depth of the plunging rod (mm) at 8 different pressures (e.g. from 0.25 kg to 2.0
kg). The graph reflects these numbers. After every measurement a new line of the table and an
additional curve is displayed. The red curve is the average of all measurements taken during the
session; black curves – of each individual measurement.
4.5.
The User should look at the graph after each probe measurement. Measurements
that deviate substantially from pervious measurements might indicate a source of error. For instance,
perhaps the patient's condition has changed (e.g. they contracted the muscle during a relaxed trial)
or the probe head slipped off the muscle.
4.6.
Deleting Measurements: If a measurement differs greatly from previous measurements,
results should be deleted. There are several ways to accomplish this:
1) Pressing the button at the top of the probe will delete only the last trial taken.
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2) Left mouse click on "Reset Measure" will also delete last measure.
3) Clicking "Reset All Measures" will delete all measurements taken to that point.
4) At the end of a testing session the window "Save Measure" will appear. If many errors
have occurred, select "Remeasure" and all trials will be deleted and program will
automatically put you back in measure mode to repeat your measurements.
4.7.
Automatic Deletion of Trials:
It is possible to have the program automatically delete
individual measurements that deviate + 2 standard deviations from the average. This is done
by left clicking on "Exclude" located above the table (Fig.19) prior to taking measurements.
4.8.
If there are long time delays between measurements after the initiation of the measuring
mode, the program will produce intermittent sound signals. This is done to remind the
user that the unit is still on and using power.
Exiting measurement mode as soon as
measurements are completed will ensure long battery life. Batteries should last for one year
of intensive work.
4.9.
After completing a cycle of measurements, a window will appear (Fig.19) asking if the data
are to be saved (“Save”) or deleted ("Remeasure").
4.10.
After data have been saved, another measurement window will appear with the next muscle
or condition listed. Measurement procedures are then repeated.
4.11.
A tone will signal the end of the testing session. Results are automatically saved and the user
can either exit the program or immediately analyze and printout the results by opening the
Analysis part of the program.
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5 Analysis
5.1. The Analysis program allows:
-
data analysis in numerical and graphical form for a particular muscle or for a group of muscles.
-
calculation of statistical parameters of a chosen muscle or group.
-
summation of data from groups of muscles or conditions
-
calculation of percent differences between tonograms of selected measurements.
-
calculation of “Area Under the Curve” of any length-tension curve.
-
the saving of data as text (table) or graph.
-
Printout of data as text or graph.
-
exporting of data files in formats for import into other software packages (e.g. Excel, Systat,
Paint)
-
importing of data for analysis from other Myotonometer™ units and computers
5.2.
It is not necessary to have the Myotonometer™ connected while doing data analysis. At the
start of the program (Fig. 8), select “ Work without device" if this is what you wish to do.
When this mode is chosen the button “Measure” in Main Window is not activated.
5.3.
In order to initiate analysis, left click on “ Analysis” in the Main Window. The “Analysis”
window (Fig.20) will appear. The User will be cued to select either "Display Measurements" or
"Display Groups of Measurements" "Display Measurements' is used when you have no need to
combine data into a different group name. "Display Groups of Measurements allows the User to
merge data files and create a new group name for analysis (e.g. combining pre or post treatment
intervention data).
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5.4. "Display Measurements" Left mouse clicking on "Display Measurements" (Fig.20) will bring
up another window, "Measurements for Analysis." From here it is necessary to choose the file for
analysis and drag it into the right-sided window. To do this, highlight the desired file, then, while
keeping the left mouse button depressed, use your mouse to move the file icon into the right
window. Once the icon is located anywhere within the window, release the left mouse button and the
file will be rewritten into this window. The file to be analyzed can come from any level within the
“tree” of file: names (e.g. patient name; part of the body; muscle; condition). Once you have done
this, a smaller window "Analysis of Measurements" (Fig.21) will be displayed.
Fig. 20
Fig.21
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5.4.1 "Analysis of Measurements" (Fig.21) window allows you to select the desired analysis
function and display.
"Display Graph of Selected Muscles" Left clicking this button will display your selected
data files in graph format (Fig.22).
"Display Table of Selected Muscles" will display data in table format with averages given
of each force measurement. Area Under the Curve (AUC) calculation is also given for each line. See
Figures 24 and 25.
"Calculate % of Difference of Area" will compare each set of data and calculate the %
difference between each (e.g. the % difference between relaxed biceps brachii vs. contracted biceps
brachii). This window will also provide a statistical comparison of the % differences.
"Calculate Area Under the Curve" will calculate area under the curve (AUC) for each
measurement selected.
"Summate Selected Muscles" will combine all selected measurements and display as
summated data (a single line on a graph with standard deviations and a table) (Fig.28). For instance,
the data displayed in Figure 27 was summated and then automatically displayed as Figure 28. You
are limited to displaying and summating 10 individual trials. When more than 10 tonograms are
entered, the message “Too many graphs" appears.
"Cancel" will bring you back to "Analysis" window (Fig.20).
Fig. 23
Fig.22
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Fig. 24
Fig. 25
5.5 All of the windows allow switching among the windows by clicking on the buttons located
at the bottom of each window. Buttons to save or printout data are also located at the bottom of
each window. When the button "Save" is pressed, a window appears (Fig.23) that will allow you to
save your data. It is recommended that you place your data in a folder designated "Data." The
graphic files will be saved in .BMP format and table/text files in .TXT format. You will not be able to
pull these data up again from within the Myotonus program.
Fig. 26
Fig. 27
Fig. 28
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5.6 "Display Groups of Measurement" allows the user to merge data files and create a new
group name for analysis (e.g. combining pre or post treatment intervention data). First, click and
drag all files to be combined into the right window. For instance, you might want to combine all
muscle activation patient data taken prior to a treatment intervention. Once all files are listed in the
right window, click "Add Group" located on the far right of the window. An example is shown in
Figure 29.
Once this is done, the "Analysis of Groups of Measurements" window becomes active and all
operations necessary for analysis are the same as described above.
5.7
“Remove group" To remove a group from your list in the right window it is necessary to
highlight the file to be deleted by left mouse clicking on it. Then, press the button “Remove
group”.
5.7.1 “Remove All Groups” will remove all groups. Highlighting is not necessary
Fig. 29
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6.1 Exporting Files: It is possible to export data to another user or another computer by using the
"Export" button located on the
Fig. 30
Main
Window
(Fig.30).
First,
highlight the desired file to be
exported. Then, left mouse click
on "Export." The "Saving" window
will appear and you can designate
the location where you would like
the file to be saved. Clicking on
"Save" completes the procedure.
Fig. 31
Fig. 31
6.2 Importing Files: To import Myotonometer™ data from another source, click "Import" and then
highlight and "Open" desired. The file will automatically be listed on the Main Menu.
6.3
If a duplicate file name exists, the program will automatically assign the same name but a
different number to the data file. For instance, you might try to import a file named "test" from a
floppy disk but you already have a file named "test" listed on your Main Menu. The program will
import the data from the floppy and assign the new name "test1."
7.1.1 Options: Located within the Main Menu is the "Options" button. This allows the user to
change certain settings within the program.
7.1.2 "Switch X-Y Axis in Analysis" By selecting this option the user determines whether "Force"
or "Displacement" measures will be displayed on the X or Y axes (see Figures 33 and 34). The
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program typically defaults to having "Force," the independent variable, located on the X-axis. The
option to switch X and Y axes is also available within the Analysis program. There is an
arrow box located on the top right of the graph which, when activated, will switch the
axes.
7.1.3 "Number of Measures" Typically it is recommended that the user obtain the average of 3 to
5 measurements for each condition (i.e. you press the probe onto the muscle 5 times to get the
measurement of muscle tone during relaxation and 5 times during contraction). But, this number can
be changed by the user.
7.1.4 "Units" Clicking the right arrow key allows the user to select the unit of measurement to be
used during Force measurements.
7.1.5 "Port" The Communication Port to be used is typically detected automatically during setup. If
subsequent changes are made to the computer configuration it might be necessary to manually
change the ComPort.
7.1.6 "Use external printing program" This option is selected if the user wants data sent to a
graphics editor installed on their computer (MS Paint, Imaging, PhotoShop, Corel Draw, MS Word or
any other using .BMP file structures). Click "external printing program" box and use "Browse" to
select appropriate path to your graphics editor.
7.1.7 Please note that you must exit out of the program and re-enter before any of your
"Options" selected will become effective.
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8.1 Main Window Options/Procedures:.
8.1.1 If you are taking measurements from a patient for which the muscle list has already been
established and saved all you need to do is highlight the patient's name in the Main Window and
click "Measure." The "Client" window will appear with the information about the patient and with
the list of previously listed muscles and conditions.
Fig.32
8.1.2 The "Edit" button allows the user to change the list of muscles by using "Add" or "Delete."
The window will cue the user regarding whether your intention is to make a permanent file change,
or just a change for this particular measurement session (Fig.18).
You can also delete muscles to be measured from your list by clicking on the small square window
with the sign to the left of the name of the muscle. After completing the editing process, select "OK".
Again the "Measure" button will be activated—click on it and the "Measure" window will appear
(Fig.17).
Fig.33
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Sample Protocol for Testing of Muscle Injury or Muscle Imbalance
The following protocol describes a procedure for assessing the muscle health of the knee
extensors during or following anterior cruciate ligament (ACL) surgery rehabilitation.
Resting Muscle Tone: The athlete is positioned in a supine position with legs extended or flexed
over the edge of the treatment table. Myotonometric measurements are then taken of the desired
muscles for each leg (legs must be positioned similarly). The Myotonometer probe is pressed onto
the muscle perpendicularly until an audible tone is heard. The probe is then lifted off the muscle and
re-positioned to take the next measurement. Five probe measurements are suggested. This requires
less than one minute for data acquisition. For knee extensors the rectus femoris, vastus lateralis and
vastus medialis can be measured separately. The athlete can then be asked to move into a prone
position with legs extended and the biceps femoris tested if desired.
Muscle Strength: Muscle strength is assessed using a maximal voluntary isometric contraction. The
athlete does not have to be in the same position during assessment of muscle strength as they were
for resting muscle tone. For instance, the athlete can be sitting at the edge of the treatment table
with knees flexed or they can be positioned in isokinetic dynamometer equipment. The athlete is
asked to maximally contract against an immovable force (e.g. cable attached to treatment table,
examiner’s resistance etc.). The examiner asks the athlete to maximally contract the muscle to be
tested. While the athlete contracts the muscle, the examiner presses the Myotonometer probe
perpendicularly onto the muscle. A hand-held or computerized dynamometer can be used to ensure
consistency of effort between trials if this is an issue. Dynamometry will measure total joint torque
production but not provide information about individual muscles. Myotonometric measurements will
provide information about individual muscle contribution to torque output.
Analysis: Several types of analyses are possible following the above outlined testing protocol.
Resting muscle tone of the various muscles can be compared between the right and left legs. The
resting tone should be the same. Stiffness of different muscles of the same leg should not be
expected to be identical. Muscle stiffness during muscle contraction should show a significant
difference from resting tone. In addition, muscle stiffness during contraction should be symmetrical
between both legs. If myotonometric measurements were taken pre-injury or pre-surgery, they can
be used to assess the rehabilitation and progress of specific muscles.
The graph on the following page was generated by Myotonometer computational software and
depicts data collected from the vastus medialis of an athlete three years following ACL surgery. The
athlete tested normal during computerized isokinetic testing.
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VMO Weakness s/p ACL Surgery
Myotonometer measurements of vastus medialis (VMO) of an athlete who had ACL surgery three
years prior. Red line shows resting muscle tone. The green line shows the stiffness obtained from
the non-surgical leg during a maximal voluntary contraction. The blue line shows the stiffness of the
surgical leg during a maximal voluntary contraction.
The small difference between stiffness of the surgical VMO during contraction (blue line) from resting
stiffness indicates weakness of this muscle (despite the fact that computerized isokinetic
dynamometry indicated equal strength of both legs). This assessment of weakness is further verified
by the inability of the surgical VMO to generate as much stiffness during contraction as the
nonsurgical VMO (green line).
(Note that the legend [generated from the computer’s clock] indicates that all data were acquired in
less than two minutes).
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Sample Protocol for Testing Muscle Tone, Paresis and Level of Severity of Spastic Paresis
Biceps Brachii Testing
Tone measurements are taken while the subjects’ muscles are relaxed and during a
maximal voluntary contraction (MVC). It is recommended that at least 3 trials of 5
measurements each be taken (required testing time is less than 1 minute).
The area over the flexor surface of the arm is tested with the subject in a sitting or
supine position. The elbow is extended with the forearm supinated (putting muscle at end
range). The area of application of the Myotonometer probe for the biceps is located (e.g.
equidistant between the lateral aspect of the acromion process and the most inferior part of
the olecranon). This point is marked with an ink pen. Measurements are then be taken with
the muscle relaxed.
For the contraction phase, subjects are instructed to perform a maximal isometric
contraction (MVC) of the elbow flexors. To ensure limited movement of the extremity, a
strap can be placed at the wrist for resistance. A hand-held force dynamometer, placed
at the distal aspect of the forearm, should be used to gauge the force of the isometric
contraction of the upper extremity. For this protocol, subjects should reproduce
similar force output for each trial during MVC testing.
Myotonometer Measurement Procedures
The Myotonometer contains a linear array of transducers that measure: 1) the amount
of displacement of a probe as it is pushed onto the skin overlying the tested muscle and 2)
the amount of force required per millimeter of tissue displacement. Measurements are taken
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every .25 kg of force up to 2.0 kg. Computational software generates force/displacement
curves for each condition (relaxed; contracted). The percent difference at each .25 kg
of force between the relaxed and contracted conditions can be computed. The
smaller the difference in measurements between the two conditions, the more
severe the spastic condition (figs 1-3). Percent difference scores correlate with the
modified Ashworth scale but Myotonometer measurements are more sensitive to smaller
changes. In addition, this protocol will enable the clinician and researcher to determine the
extent to which changes in muscle tone or paretic changes within a muscle contribute to a
disability.
Fig. 1
GROUP 1: CONTROLS
BICEPS BRACHII
Displacement (mm)
12
10
8
Rest
6
4
2
Contracted
0
0
0.25
0.5
0.75
1
Force (kg)
1.25
1.5
1.75
2
26
Fig. 2
GROUP 2: INVOLVED EXTREMITY
BICEPS BRACHII
12
Displacement (mm)
10
8
Rest
6
Contracted
4
2
0
0
0.25
0.5
0.75
1
1.25
Force (kg)
1.5
1.75
2
Fig. 3
GROUP 3: UNINVOLVED EXTREMITY
BICEPS BRACHII
12
Displacement (mm)
10
8
Rest
6
4
Contracted
2
0
0
0.25
0.5
0.75
1
1.25
Force (kg)
1.5
1.75
2
27
Myotonometer Reference List
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28
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29
References Establishing Relationship Between Muscle Stiffness, Muscle Activation and
Torque Production During Contraction
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Kato G, Andrew PD, Sato H. (2004) Reliability and validity of a device to measure muscle hardness.
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Leonard, C., Brown, J., & Price, T. (2002). Comparison of surface electromyography and
myotonometric measurements during isometric contractions. Archives Phys Med and Rehabil,
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Academic Press.
30
Sport-related Myotonometer References
Bizzini M, and Mannion AF. (2003) Reliability of a new, hand-held device for assessing skeletal muscle
stiffness. Clinical Biomechanics, 459-461.
Coon, T., Ikeda, E., Lamb, J., & Sebastian, D. (2002). The effects of strain-counterstrain on muscle
hardness and tenderness in subjects with neck pain. Journal of Orthopedic and Sports
Physical Therapy, 32(1), A29.
Ditto, K., Fischer, M., Fehrer, S., & Leonard, C. (2002). Myotonometer assessment of changes in the
triceps surae musculotendinous unit following a stretch intervention. Journal of Orthopedic
and Sports Physical Therapy, 32(1), A33.
Kato G, Andrew PD, Sato H. (2004) Reliability and validity of a device to measure muscle hardness.
Journal of Mechanics in Medicine and Biology, 4(2): 213-225.
Leonard, C., Brown, J., & Price, T., Queen SA, Mikhailenok EL. (2004). Comparison of surface
electromyography and myotonometric measurements during isometric contractions. Journal
of Electromyography and Kinesiology. (In press).
Leonard, C., Deshner, W., Romo, J., Suoja, E., Fehrer, S., & Mikhailenok, E. (2003). Myotonometer
intra and inter-rater reliabilities. Arch Phys Med Rehabil, 84, 928-932.
Leonard, C., Brown, J., & Price, T. (2004). Comparison of surface electromyography and
myotonometric measurements during isometric contractions. EMG and Kinesiology,
14(6):709-714.
Murayama, M., Nosaka, K., Yoneda, T., & Minamitani, K. (2000). Changes in hardness of the human
elbow flexor muscles after eccentric exercise. European Journal of Applied Physiology and
Occupational Physiology, 82, 361-367.
Shchurova EN, Shchurov VA, Grebenyuk LA. (2004). Age-related changes in contractile
capacity of lower extremity muscles caused by inadequate blood supply. Human
Physiology, 30(2): 209-215.