The Surface The Surface Mechanomyogram Mechanomyogram (MMG)(MMG)

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Mechanomyography (MMG)Mechanomyography (MMG)Non-invasive technique that Non-invasive technique that records and quantifies the records and quantifies the oscillations generated by oscillations generated by dimensional changes of the dimensional changes of the active skeletal muscle fibers.active skeletal muscle fibers.Has also been called acoustic Has also been called acoustic myography, phonomyography, myography, phonomyography, sound myography, and sound myography, and vibromyography.vibromyography.““surface mechanomyogram” surface mechanomyogram” recommended at CIBA recommended at CIBA Foundation Symposium, 1995.Foundation Symposium, 1995.

forcesound

water line

musclehydrophone

Orizio, C. Critical Reviews in Biomedical Engineering. 1993.

When muscle fibers contract they oscillate or vibrate.When muscle fibers contract they oscillate or vibrate.Early MMG studies utilized isolated frog muscle in a sound-insulated Early MMG studies utilized isolated frog muscle in a sound-insulated chamber and recorded the oscillations with a hydrophone.chamber and recorded the oscillations with a hydrophone.

Orizio, C., Gobbo, M., Diemont, B., Esposito, F., Veicsteinas, A. Eur J Appl Physiol. 2003.

Displacement Sensor

Laser Beam

Accelerometer

Bipolar EMG Electrodes

Force Transducer

Isometric muscle

action at 30% MVC

Watakabe, M., Itoh, Y., Mita, K., and Akataki, K. Med. Biol. Eng. Comput. 1998.

During voluntary contractions, the oscillations During voluntary contractions, the oscillations create pressure waves that can be recorded at create pressure waves that can be recorded at the skin’s surface using a crystal contact sensor the skin’s surface using a crystal contact sensor or accelerometer.or accelerometer.

Over the years, there have been a number of Over the years, there have been a number of hypotheses regarding the origin of the MMG signal hypotheses regarding the origin of the MMG signal

that have been ruled out.that have been ruled out.

Vascular soundsVascular sounds MMG can be recorded when blood flow is occluded. MMG can be recorded when blood flow is occluded.

Friction between the microphone and skinFriction between the microphone and skin MMG can be recorded in a water bath and with air coupled MMG can be recorded in a water bath and with air coupled

microphones.microphones.

Friction between fascia and musclesFriction between fascia and muscles Less MMG activity is recorded over fascia such as the vastus Less MMG activity is recorded over fascia such as the vastus

lateralis.lateralis. No MMG activity during passive muscle actions.No MMG activity during passive muscle actions.

Bone oscillationsBone oscillations MMG can be recorded from isolated muscle.MMG can be recorded from isolated muscle.

Nerve conductionNerve conduction Ambient temperature does not affect MMG frequency, but does Ambient temperature does not affect MMG frequency, but does

affect nerve conduction velocity.affect nerve conduction velocity.

The MMG signal has The MMG signal has three components:three components:

1.1. A gross lateral movement A gross lateral movement at the initiation of a at the initiation of a contraction generated by a contraction generated by a non-simultaneous non-simultaneous activation of muscle fibers.activation of muscle fibers.

2.2. Smaller subsequent lateral Smaller subsequent lateral oscillations at the resonant oscillations at the resonant frequency of the muscle.frequency of the muscle.

3.3. Dimensional changes of Dimensional changes of the active fibers.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 The MMG signal is affected by many factors:many factors:

Muscle temperatureMuscle temperature

StiffnessStiffness

MassMass

Intramuscular pressureIntramuscular pressure

Viscosity of the intracellular and Viscosity of the intracellular and extracellular fluid mediumsextracellular 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 The MMG signal is low frequency: low frequency: Typically bandpass Typically bandpass

filtered at 5-100 Hz, filtered at 5-100 Hz, while EMG is 10-500 while EMG is 10-500 Hz. Hz.

Time and frequency domains of the MMG Time and frequency domains of the MMG signals have been used to examine various signals have been used to examine various

aspects of muscle function including:aspects of muscle function including:

Neuromuscular fatigueNeuromuscular fatigueElectromechanical delayElectromechanical delayMotor control strategiesMotor control strategiesMuscle fiber type distribution patternsMuscle fiber type distribution patternsDiagnose neuromuscular disorders in adult and Diagnose neuromuscular disorders in adult and pediatric populationspediatric populationsLow back painLow back painControl external prosthesesControl external prosthesesEffectiveness of anesthesiaEffectiveness of anesthesia

Although we are continually learning Although we are continually learning more, our knowledge of the MMG signal more, our knowledge of the MMG signal

is probably 20-25 years behind that of the is probably 20-25 years behind that of the EMG signal.EMG signal.

M. Stokes: M. Stokes: ““As knowledge of muscle sounds increases As knowledge of muscle sounds increases

and the development of more appropriate and the development of more appropriate methodology occurs, the potential uses and methodology occurs, the potential uses and limitations of [MMG] must be reassessed limitations of [MMG] must be reassessed continually.”continually.”

We have examined the MMG signal in the time We have examined the MMG signal in the time and frequency domains under a number of and frequency domains under a number of

conditions in an attempt to both develop and conditions in an attempt to both develop and test hypotheses.test hypotheses.

Isometric muscle actionsIsometric muscle actions

Concentric muscle actionsConcentric muscle actions

Eccentric muscle actionsEccentric muscle actions

Passive movementsPassive movements

Cross-talkCross-talk

Stretching interventionsStretching interventions

Resistance training interventionsResistance training interventions

Isometric and Isokinetic Isometric and Isokinetic Force Force

vs. vs. MMG and EMG amplitude MMG and EMG amplitude

and frequency relationshipsand frequency relationships

Coburn, J.W., Housh, T.J., Cramer, J.T., Weir, J.P., Miller, J.M., 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. Beck, T.W., Malek, M.H., and G.O. Johnson. Electromyogr clin Electromyogr clin

NeurophysiolNeurophysiol. 2004.. 2004.

Subjects: Subjects: n = 10 (7 male, 3 n = 10 (7 male, 3

female).female).

Muscle actions: Muscle actions: Leg extension:Leg extension:

Isometric = 45Isometric = 45°°Isokinetic = 30°∙sIsokinetic = 30°∙s-1-1

Torque: Torque: 10 – 100% MVC.10 – 100% MVC.

Parameters: Parameters: MMG amplitude and MMG amplitude and

frequency.frequency.

Muscles: Muscles: Vastus medialis.Vastus medialis.

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.

Percent Maximal Torque

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Coburn, J.W., Housh, T.J., Coburn, J.W., Housh, T.J., Cramer, J.T., Weir, J.P., Cramer, J.T., Weir, J.P., Miller, J.M., Beck, T.W., Miller, J.M., Beck, T.W., Malek, M.H., & Johnson, Malek, M.H., & Johnson, G.O. (2004). G.O. (2004). J Strength J Strength Cond ResCond Res. . in pressin press..

Subjects: Subjects: n = 7 menn = 7 men

Muscle actions: Muscle actions: Leg extension:Leg extension:

Isometric = 45Isometric = 45°°Isokinetic = 30°∙sIsokinetic = 30°∙s-1-1

Torque: Torque: 20 – 100% MVC.20 – 100% MVC.

Parameters: Parameters: MMG & EMG amplitude and MMG & EMG amplitude and

frequency.frequency.

Muscles: Muscles: Vastus medialis.Vastus medialis.

Vastus Medialis

Coburn, J.W., Housh, T.J., Coburn, J.W., Housh, T.J., Cramer, J.T., Weir, J.P., Cramer, J.T., Weir, J.P., Miller, J.M., Beck, T.W., Miller, J.M., Beck, T.W., Malek, M.H., & Johnson, Malek, M.H., & Johnson, G.O. (2004). G.O. (2004). J Strength J Strength Cond ResCond Res. . in pressin press..

Subjects: Subjects: n = 7 menn = 7 men

Muscle actions: Muscle actions: Leg extension:Leg extension:

Isometric = 45Isometric = 45°°Isokinetic = 30°∙sIsokinetic = 30°∙s-1-1

Torque: Torque: 20 – 100% MVC.20 – 100% MVC.

Parameters: Parameters: MMG & EMG amplitude and MMG & EMG amplitude and

frequency.frequency.

Muscles: Muscles: Vastus medialis.Vastus medialis.

Orizio, C., Gobbo, M., Diemont, B., Esposito, F., A. Orizio, C., Gobbo, M., Diemont, B., Esposito, F., A. Veicsteinas. Veicsteinas. Eur J Appl PhysiolEur J Appl Physiol. 2003.. 2003.

Biceps Brachii

AssignmentsAssignments

Complete all the normalization and graphing for Complete all the normalization and graphing for our experimental data.our experimental data.

Randomly assign the 5 articles posted on the Randomly assign the 5 articles posted on the website tonightwebsite tonight Give a presentation on your article next week.Give a presentation on your article next week. PPT, 10 min, 5-min Q & APPT, 10 min, 5-min Q & A Discuss the results of your article and how they relate Discuss the results of your article and how they relate

to our study.to our study.

Mid-term exam/lab write-up (take home) due Mid-term exam/lab write-up (take home) due Monday after spring break (March 21).Monday after spring break (March 21).