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A presentation put together for my weekly lab meeting based on the recent publication "Analysis of intramuscular electromyogram signals" (pubmed: http://tinyurl.com/b4mryy).Concepts highlighted in the manuscript are reviewed with multiple choice questions mixed in between.
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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