Analysis of intramuscular electromyogram signals

It's a quiz!

Dario FarinaRoberto Merletti

Basmajian 1968

What is the term given to describe all of the muscle fibers belonging to one motor unit?

1. Task group

2. Muscle unit

3. Fiber unit

4. Contractile apparatus

What is the term given to describe all of the muscle fibers belonging to one motor unit?

1. Task group

2. Muscle unit

3. Fiber unit

4. Contractile apparatus

Stålberg et al. 1995

Motor Unit 1

Stålberg et al. 1995Stålberg et al. 1995

Motor Unit 2

Motor Unit 3

Volume conductor

Which needle electrode configuration is likely to produce the lower two traces?

1.

2.

3.

4.

Distance from AP

Sign

al a

mpl

itude

Detection volume

Which needle electrode configuration is likely to produce the lower two traces?

1.

2.

3.

4.

Distance from AP

Sign

al a

mpl

itude

Detection volume

All of the following are limitations of intramuscular recordings except:

1. Reflects the activity of only a small number of active motor units

2. The detected APs are not representative of all fibers belonging to the motor unit

3. Permits recording from deep muscles

4. It is difficult to have the same unit in repeated insertions

All of the following are limitations of intramuscular recordings except:

1. Reflects the activity of only a small number of active motor units

2. The detected APs are not representative of all fibers belonging to the motor unit

3. Permits recording from deep muscles

4. It is difficult to have the same unit in repeated insertions

27G needle = 0.41 mm

Muscle fiber = 50 μm

8.2 X

What is one limitation of wire electrodes compared with needle electrodes?

1. Cause less subject discomfort/pain during contraction

2. Ability to be repositioned (in & out of muscle)

3. More stability over long periods of time

4. More stability during movement

What is one limitation of wire electrodes compared with needle electrodes?

1. Less subject discomfort/pain during contraction

2. Ability to be repositioned (in & out of muscle)

3. More stability over long periods of time

4. More stability during movement

Gydikov et al. 1986

Wire 1

Wire 2

Site 1

Site 2a Site 2b

Signal = Wire 1 - Wire 2

Which of the following would NOT improve the signal of the branched bipolar electrode?

1. Reducing the amount of insulation removed and distance between removal sites

2. Placing the electrode parallel to the muscle fibers

3. Closer positioning of the electrode to the muscle fascia

4. Repositioning of the electrode along the muscle belly

Which of the following would NOT improve the signal of the branched bipolar electrode?

1. Reducing the amount of insulation removed and distance between removal sites

2. Placing the electrode parallel to the muscle fibers

3. Closer positioning of the electrode to the muscle fascia

4. Repositioning of the electrode along the muscle belly

1) Triggering single fiber electrode

2) Exposed macroelectrode

Surface

Stålberg et al. 1980

A macro EMG electrode can be used to address all but which of the following:

1. Is the size of motor units of older adults consistent with young adults?

2. Does a particular pathology involve the reinnervation of affected muscle fibers?

3. Are estimates of the number of motor units consistent across age and disease?

4. Does muscle fiber conduction velocity change during eccentric contractions?

A macro EMG electrode can be used to address all but which of the following:

1. Is the size of motor units of older adults consistent with young adults?

2. Does a particular pathology involve the reinnervation of affected muscle fibers?

3. Are estimates of the number of motor units consistent across age and disease?

4. Does muscle fiber conduction velocity change during eccentric contractions?

Example articles:

1. Masakado et al. 1994

2. Ivanyi et al. 1994

3. de Koning et al. 1988

Stålberg & Antoni 1980

Muscle 1) Triggering SFEMG electrode

Investigated corridor

MU territory2) Concentric needle electrode

Stålberg & Antoni 1980

20 increments

What is the length of the MU cross section (mm) and how does this compare to the actual territory size?

1. 10, this is likely an overestimate

2. 1, this is likely an overestimate

3. 10, this is likely an underestimate

4. 1, this is likely an underestimate

What is the length of the MU cross section (mm) and how does this compare to the actual territory size?

1. 10, this is likely an overestimate

2. 1, this is likely an overestimate

3. 10, this is likely an underestimate

4. 1, this is likely an underestimate

What is decomposition?

1. Identification of motor units from an interference EMG signal

2. Classification of a motor unit type from EMG

3. Quantitative description of a motor unit action potential

4. Something best left to the EBIO department

What is decomposition?

1. Identification of motor units from an interference EMG signal

2. Classification of a motor unit type from EMG

3. Quantitative description of a motor unit action potential

4. Something best left to the EBIO department

Decomposition

Put the steps of decomposition in the correct order:

1. Detection or segmentation – how does information differ from noise signal

2. Identification and classification of an “ideal” MUAP

3. Verification of Identified MUAP's

4. Recognition or Classification

Put the steps of decomposition in the correct order:

1. Detection or segmentation – how does information differ from noise signal

2. Identification and classification of an “ideal” MUAP

3. Verification of Identified MUAP's

4. Recognition or Classification

1

2

3

4

Put the steps of decomposition in the correct order:

1. Detection or segmentation – how does information differ from noise signal

2. Identification and classification of an “ideal” MUAP

3. Verification of Identified MUAP's

4. Recognition or Classification

−Generally 1 and 2 are combined in one step

1

2

3

4

Identification of MUAP's

Peak to peak

Voltage

# of phases, turns

Duration

Fourier transformation coefficients

Coefficients from other transformations

Time sample of filtered signal

Wavelet characteristics

Merletti and Farina 2008

Wavelet vs. Fourier Transform

Meyer Mexican Hat

What is not a limitation to Decomposition?

1. No ideal waveform available

2. Must come from intramuscular EMG

3. Inaccurate past ~50% MVC

4. Can only readily identify 3-8 MU's

What is not a limitation to Decomposition?

1. No ideal waveform available

2. Must come from intramuscular EMG

3. Inaccurate past ~50% MVC

4. Can only readily identify 3-8 MU's

How are waves decomposed?

Peel off method Modeling method

http://www.ling.umd.edu/~idsardi/sinewave/

MATLAB based EMGLAB resolved superimpositions with which method?

1. Modeling approach

2. “Best match” or “peel off” method

MATLAB based EMGLAB resolved superimpositions with which method?

1. Modeling approach

2. “Best match” or “peel off” method

MATLAB based EMGLAB resolved superimpositions with which method?

1. Modeling approach

2. “Best match” or “peel off” method

Which is more powerful? difficult?

Stashuk 2001

Modelling vs. Peel Off

Which is not a method of verifying a decomposed signal?

1. Comparison with ideal waveform characteristics

2. Cross verification from two different locations

3. Mathematical reference signal

4. Expert Operator verification

Which is not a method of verifying a decomposed signal?

1. Comparison with ideal waveform characteristics

2. Cross verification from two different locations

3. Mathematical reference signal

4. Expert Operator verification

Which is not true with regards to decomposition in a clinical setting?

1. Done using interference EMG signal

2. Uses same methodology as in research setting

3. Impractical for clinical use

4. True decomposition is beyond the realm of clinicians

Which is not true with regards to decomposition in a clinical setting?

1. Done using interference EMG signal

2. Uses same methodology as in research setting

3. Impractical for clinical use

4. True decomposition is beyond the realm of clinicians

First dorsalinterosseus

Amplifier(EMG)

Triggerunit

Averager

Amplifier

Surface electrodearray

Muscle fiberconduction

velocity

Farina et al. 2002

If the time between averaged waveforms is 1.28 ms and the CV is 3.9 m*s-1, how far apart are

the electrodes on the array in mm?

1) 5

2) 0.39

3) 7.5

4) 0.5

If the time between averaged waveforms is 1.28 ms and the CV is 3.9 m*s-1, how far apart are

the electrodes on the array in mm?

1) 5

2) 0.39

3) 7.5

4) 0.5

First dorsalinterosseus

Amplifier(EMG)

Triggerunit

Amplifier

Averager

Forcetransducer

Torquecontribution

Stålberg & Falck 1997

Patient 1 Patient 2

Signal A Signal B

Which detection system (intramuscular or surface) is used to diagnose pathologies and why?

1. Intramuscular, lower frequencies are preserved

2. Intramuscular, features of individual APs are preserved

3. Surface, you record from more fibers

4. Surface, the signal bandwidth allows for analysis of the number of turns in AP shape

Which detection system (intramuscular or surface) is used to diagnose pathologies and why?

1. Intramuscular, lower frequencies are preserved

2. Intramuscular, features of individual APs are preserved

3. Surface, you record from more fibers

4. Surface, the signal bandwidth allows for analysis of the number of turns in AP shape

References*Adrian & Bronk 1929

Basmajian 1963

Basmajian & Stecko 1962

Buchthal at el. 1957

de Koning et al. 1988

De Luca & Forrest 1972

Farina et al. 2002

Gydikov et al. 1986

Haig et al. 2003

Ivanyi et al. 1994

Masakado et al. 1994

Stålberg & Antoni 1980

Stålberg & Falck 1997

Stålberg et al. 1980

Stålberg et al. 1995

Stashuck 2001

*Click on each study to view record on journal website