Transcript PPT

1.82 Volts
1 t T 2
m (t )dt
T t
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The Surface
Mechanomyogram
(MMG)
3.44 ms-2

f med
0
S m ( f ) df  

f med
S m ( f ) df
406 μV
55 Nm
I m(t )   
t T
t
0
1
m(t ) dt
2
3 seconds
Mechanomyography (MMG)
Non-invasive technique that
records and quantifies the
oscillations generated by
dimensional changes of the
active skeletal muscle fibers.
Has also been called acoustic
myography, phonomyography,
sound myography, and
vibromyography.
“surface mechanomyogram”
recommended at CIBA
Foundation Symposium, 1995.
Orizio, C. Critical Reviews in Biomedical Engineering. 1993.
force
sound
water
line
muscle
hydrophone
When muscle fibers contract they oscillate or vibrate.
Early MMG studies utilized isolated frog muscle in a sound-insulated
chamber and recorded the oscillations with a hydrophone.
Isometric
muscle
action at
30% MVC
Displacement
Sensor
Accelerometer
Laser
Beam
Bipolar EMG
Electrodes
Force
Transducer
Orizio, C., Gobbo, M., Diemont, B., Esposito,
F., Veicsteinas, A. Eur J Appl Physiol. 2003.
Watakabe, M., Itoh, Y., Mita, K., and
Akataki, K. Med. Biol. Eng. Comput. 1998.
During voluntary contractions, the oscillations
create pressure waves that can be recorded at
the skin’s surface using a crystal contact sensor
or accelerometer.
Over the years, there have been a number of
hypotheses regarding the origin of the MMG signal
that have been ruled out.
Vascular sounds

MMG can be recorded when blood flow is occluded.
Friction between the microphone and skin

MMG can be recorded in a water bath and with air coupled
microphones.
Friction between fascia and muscles


Less MMG activity is recorded over fascia such as the vastus
lateralis.
No MMG activity during passive muscle actions.
Bone oscillations

MMG can be recorded from isolated muscle.
Nerve conduction

Ambient temperature does not affect MMG frequency, but does
affect nerve conduction velocity.
The MMG signal has
three components:
1.
2.
3.
A gross lateral movement
at the initiation of a
contraction generated by a
non-simultaneous
activation of muscle fibers.
Smaller subsequent lateral
oscillations at the resonant
frequency of the muscle.
Dimensional changes of
the active fibers.
Smith, D.B., Housh, T.J.,
Johnson, G.O., Evetovich, T.K.,
Ebersole, K.T., Perry, S.R.
Muscle Nerve. 1998.
The MMG signal is affected by
many factors:
Muscle temperature
Stiffness
Mass
Intramuscular pressure
Viscosity of the intracellular and
extracellular fluid mediums
Perry, S.R., Housh, T.J., Weir, J.P.,
Johnson, G.O., Bull, A.J.,
Ebersole, K.T. J. Electromyogr.
Kinesiol. 2001.
The MMG signal is
low frequency:

Typically bandpass
filtered at 5-100 Hz,
while EMG is 10-500
Hz.
Time and frequency domains of the MMG
signals have been used to examine various
aspects of muscle function including:
Neuromuscular fatigue
Electromechanical delay
Motor control strategies
Muscle fiber type distribution patterns
Diagnose neuromuscular disorders in adult and
pediatric populations
Low back pain
Control external prostheses
Effectiveness of anesthesia
Although we are continually learning
more, our knowledge of the MMG signal
is probably 20-25 years behind that of the
EMG signal.
M. Stokes:

“As knowledge of muscle sounds increases
and the development of more appropriate
methodology occurs, the potential uses and
limitations of [MMG] must be reassessed
continually.”
We have examined the MMG signal in the time
and frequency domains under a number of
conditions in an attempt to both develop and
test hypotheses.
Isometric muscle actions
Concentric muscle actions
Eccentric muscle actions
Passive movements
Cross-talk
Stretching interventions
Resistance training interventions
Isometric and Isokinetic
Force
vs.
MMG and EMG amplitude
and frequency relationships
Coburn, J.W., Housh, T.J., Cramer, J.T., Weir, J.P., Miller, J.M.,
Beck, T.W., Malek, M.H., and G.O. Johnson. Electromyogr clin
Neurophysiol. 2004.
Increase in torque
due only to
increased
recruitment of ST
fibers – no change
in frequency
Torque increase is due
to increased motor
unit firing rate and not
recruitment at > 80%
MVC since MMG
amplitude decreases.
Increased frequency
due to recruitment of FT
fibers at > 50% MVC;
these fibers have
greater frequency than
ST fibers
Subjects:

1.0
Muscle actions:
.9
Normalized MMG rms and MPF
n = 10 (7 male, 3
female).

.8
Leg extension:
Isometric = 45°
Isokinetic = 30°∙s-1
.7
.6
Torque:
.5

.4
10 – 100% MVC.
Parameters:
.3

.2
.1
MMG amplitude and
frequency.
Muscles:
0.0
0
10
20
30
40
50
60
70
Percent Maximal Torque
80
90
100

Vastus medialis.
Coburn, J.W., Housh, T.J.,
Cramer, J.T., Weir, J.P.,
Miller, J.M., Beck, T.W.,
Malek, M.H., & Johnson,
G.O. (2004). J Strength
Cond Res. in press.
Subjects:

n = 7 men
Muscle actions:

Leg extension:
Isometric = 45°
Isokinetic = 30°∙s-1
Torque:

20 – 100% MVC.
Parameters:

MMG & EMG amplitude and
frequency.
Muscles:

Vastus medialis.
Coburn, J.W., Housh, T.J.,
Cramer, J.T., Weir, J.P.,
Miller, J.M., Beck, T.W.,
Malek, M.H., & Johnson,
G.O. (2004). J Strength
Cond Res. in press.
Subjects:

n = 7 men
Muscle actions:

Leg extension:
Isometric = 45°
Isokinetic = 30°∙s-1
Torque:

20 – 100% MVC.
Parameters:

MMG & EMG amplitude and
frequency.
Muscles:

Vastus Medialis
Vastus medialis.
Orizio, C., Gobbo, M., Diemont, B., Esposito, F., A.
Veicsteinas. Eur J Appl Physiol. 2003.
Biceps Brachii
Assignments
Complete all the normalization and graphing for
our experimental data.
Randomly assign the 5 articles posted on the
website tonight



Give a presentation on your article next week.
PPT, 10 min, 5-min Q & A
Discuss the results of your article and how they relate
to our study.
Mid-term exam/lab write-up (take home) due
Monday after spring break (March 21).