1. The Surface Mechanomyogram (MMG)
3.44 ms-2
1.82 Volts
55 Nm
seconds 3 1 2
406 μV
The Surface Mechanomyogram (MMG)

2. 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.

3. 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.

4. Isometric muscle action at 30% MVC
Orizio, C., Gobbo, M., Diemont, B., Esposito, F., Veicsteinas, A. Eur J Appl Physiol
Displacement Sensor
Laser Beam
Accelerometer
Bipolar EMG Electrodes
Force Transducer
Isometric muscle action at 30% MVC

5. Watakabe, M. , Itoh, Y. , Mita, K. , and Akataki, K. Med. Biol. Eng
Watakabe, M., Itoh, Y., Mita, K., and Akataki, K. Med. Biol. Eng. Comput
During voluntary contractions, the oscillations create pressure waves that can be recorded at the skin’s surface using a crystal contact sensor or accelerometer.

6. Friction between the microphone and skin
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.

7. The MMG signal has three components:
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

8. The MMG signal is affected by many factors:
Muscle temperature
Stiffness
Mass
Intramuscular pressure
Viscosity of the intracellular and extracellular fluid mediums

9. The MMG signal is low frequency:
Perry, S.R., Housh, T.J., Weir, J.P., Johnson, G.O., Bull, A.J., Ebersole, K.T. J. Electromyogr. Kinesiol
The MMG signal is low frequency:
Typically bandpass filtered at Hz, while EMG is Hz.

10. 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

11. Although we are continually learning more, our knowledge of the MMG signal is probably 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.”

12. Isometric muscle actions Concentric muscle actions
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

13. Isometric and Isokinetic Force vs
Isometric and Isokinetic Force vs. MMG and EMG amplitude and frequency relationships

14. Coburn, J. W. , Housh, T. J. , Cramer, J. T. , Weir, J. P. , Miller, J
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
Increase in torque due only to increased recruitment of ST fibers – no change in frequency
Increased frequency due to recruitment of FT fibers at > 50% MVC; these fibers have greater frequency than ST fibers
Torque increase is due to increased motor unit firing rate and not recruitment at > 80% MVC since MMG amplitude decreases.
Subjects:
n = 10 (7 male, 3 female).
Muscle actions:
Leg extension:
Isometric = 45°
Isokinetic = 30°∙s-1
Torque:
10 – 100% MVC.
Parameters:
MMG amplitude and frequency.
Muscles:
Vastus medialis.
1.0 .9 .8 .7 .6
Normalized MMG rms and MPF .5 .4 .3 .2 .1
0.0 10 20 30 40 50 60 70 80 90
100
Percent Maximal Torque

15. Coburn, J. W. , Housh, T. J. , Cramer, J. T. , Weir, J. P. , Miller, J
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.

16. Coburn, J. W. , Housh, T. J. , Cramer, J. T. , Weir, J. P. , Miller, J
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

17. Orizio, C. , Gobbo, M. , Diemont, B. , Esposito, F. , A. Veicsteinas
Orizio, C., Gobbo, M., Diemont, B., Esposito, F., A. Veicsteinas. Eur J Appl Physiol
Biceps Brachii

18. 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).