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Presenter: Sana Rai (MPT 1st Year)
Guide: Dr. Suvarna Ganvir (PhD)
Department of Neurophysiotherapy
D.V.V.P.F’s College of Physiotherapy, Ahmednagar
• Concepts of EMG
• Different types of electrodes.
• Clinical EMG.
1. Normal potential
2. Abnormal potential.
• EMG findings in different conditions.
• Clinical implication.
• Electromyography tests the integrity of the entire motor
system, which consists of upper and lower motor
neurons, the neuromuscular junction, and muscle.
• Electromyography (EMG) is used to evaluate the scope
of neuromuscular disease or trauma, and kinesiological
electromyography is used to study muscle function.
• As the examination procedure, clinical EMG involves the
detection and recording of electrical potentials from skeletal
• Electromyographer must first learn physiologic mechanisms of
normal muscle contraction to understand the various
abnormalities that characterize disorders of the motor system.
• Multiple factors affect the outcome of recordings.
1. age of patients.
2. the particular properties of the muscle under study.
3. the electrical specifications of the needle electrodes and
Concepts of Electromyography
• EMG is the recording of the electrical activity
of muscles and in essence, the study of motor
• The single axon conducts an impulse to all its
muscle fibers, causing them to depolarize at
relatively the same time.
• This depolarization produces electrical activity that is
manifested as a motor unit action potential (MUAP) and
recorded and displayed graphically as the EMG signal.
• Instrumentation for recording EMG potentials requires a
1. An input phase: electrode electrical potentials from
2. Processor phase: small electrical signal is amplified.
3. Output phase: electrical signal visual/ audible signal
Instrumentation and Signal
Ø Detecting the EMG signals: Electrodes
• An electrode is a transducer ; a device for converting one
form of energy into another.
• Types of electrodes:
1. Surface electrodes.
2. Fine wire indwelling electrodes.
3. Needle electrode.
4. Ground electrode.
• Surface Electrode are used frequently when
performing a NCV test and in some kinesological
• They are generally considered adequate for
monitoring large superficial muscle or muscle group.
• The simplest surface EMG electrode is a small metal
disc, commonly made of silver/ silver chloride, which
is typically 3 to 5 mm in diameter.
• Fine Wire Indwelling Electrode were introduced in
the early 1960 for kinesiological study of small and
• Fine wire electrodes are necessary for monitoring
activity from deep muscles, such as the soleus, or
small or narrow muscle , such as the fingers flexors.
• They mat not be as useful for large muscles because
they sample motor unit activity form such a small
area of the muscle.
• They are inappropriate for use in clinical EMG
because the examiner has either good control over
placement of the electrode, nor the ability to move the
electrode within the muscle once it is placed.
• Ultrasound imaging has recently been used with great
success in helping to guide the placement of fine wire
electrodes in deeply situation muscles, such as the
• A Needle Electrode is required for clinical EMG, so
that single motor unit potentials can be recorded from
difference parts of a muscle.
• The 1st studies of motor unit activity were done in
1929 by Adrian and Bronk who used a concentric
• The bare tip of the platinum wire is considered to be
the active electrode and the cannula acts as the
• Another commonly used approach for clinical EMG
involves the use of a Monopolar Needle Electrode,
which is composed of a single fine needle, insulated
except at the tip.
• These electrodes are less painful than concentric
electrodes because they are smaller in diameter.
• Monopolar configurations record much larger
potentials than bipolar.
• In addition to a recording electrode (either surface or
needle), a ground electrode must be applied to provide a
mechanism for canceling out the interference effect of
external electrical noise such as that caused by
fluorescent lights, broadcasting facilities, elevators and
other electrical apparatus.
• The Ground Electrode is a surface electrode that is
attached to the skin near the recording electrodes, but
usually not over muscle.
• The EMG Examination: testing usually involves
observation of muscle action potentials form several
muscles in different stages of muscle contraction.
• The EMG signals is only part of a complete
examination, however which will include a thorough
understanding of the patients history and clinical
• Insertional Activity: initially, the patient is asked to
relax the muscle to be examined during insertion of the
• At this time, a spontaneous burst of potentials is
observed, which is possibly caused by the needle
breaking through muscle fiber membranes.
• This is called insertional activity and normally lasts less
• Insertional activity can be describe as normal, reduced,
absent, increased, or prolonged.
• The Muscle At Rest: following cessation of insertional
activity, a normal relaxed muscle will exhibit electrical
silence, which is the absence of electrical potentials.
• It is often difficult for the patient to relax sufficiently to
observe complete electrical silence.
• However, the potential seen will be distinct motor unit
potential, whereas spontaneous potential can be
differentiated by their distinct characteristics related to
amplitude, shape, frequency, waveform and sound.
• Normal Motor Unit Action Potential: after observing
the muscle at rest, the patient is asked to contract the
• This weak voluntary effort should cause individual
motor unit to fire.
• These motor unit potential are examined with respect
to amplitude, duration, shape, sound, and frequency.
• Spontaneous Activity: a normal muscle at rest exhibits
electrical silence, any activity seen during the relaxed
state can be considered abnormal.
• Such activity is termed as spontaneous because it is not
produced by voluntary muscle contraction.
• 4 types of spontaneous potentials have been
1. Fibrillation potential.
2. Positive sharp waves.
3. Fasciculation potential.
4. Repetitive discharge.
Positive Sharp Waves Myotonic And Complex
It is observed in denervated muscle
lesion of the anterior horn cell and
peripheral nerves , and with
Biphasic waves . Regular and repetitive waveform.
Amplitude: 50µV to 2mV
Frequency: 2 to 100 per sec
Duration: 100 msec
Amplitude: : 50µV to 1mV
Frequency: 50 to 100 per sec
Duration: 100 msec
Muscle dystrophy and polymyositis. Myotonic dystrophy as well as
• Amyotrophic lateral sclerosis: It is motor neuron disease (MND),
is a specific disease which cause death of the neurons controlling
• Muscle dystrophy: It is a group of muscle diseases that results in
increasing weakening and breakdown of skeletal muscles over
Electrodiagnosis in Amyotrophic Lateral Sclerosis
Nanette C Joyce, D.O., M.A.S.1 and Gregory T Carter, M.D., M.S.
PM R. 2013 May; 5(5 0): S89–S95.
For the evaluation of LMN findings in ALS, the clinical and electrophysiological
abnormalities have equal diagnostic significance in any given body region.
However, two EMG features are required for confirmation of neurogenic change
consistent with a diagnosis of ALS:
1. Evidence of chronic neurogenic change.
2. Evidence of acute denervation.
To support a diagnosis of ALS, the needle electrode examination should reveal
decreased motor unit recruitment with rapid firing of a reduced number of motor
units, and/or large amplitude, long duration MUP with or without evidence of
remodeling (increased number of phases) in combination with abnormal
spontaneous activity including positive sharp waves (PSWs), fibrillations, and/or
fasciculation potentials (FP).
Electrophysiology of Myopathy Approach to the Patient With
Myopathy in the EMG Laboratory
Nithi S. Anand and David Chad
• An increase in insertional activity is the first EMG clue to the presence of
abnormal spontaneous potentials in the muscle.
• The four abnormal spontaneous potentials to look for in a patient with myopathy
comprise: fibrillation potentials, positive sharp waves (PSWs), myotonic
potentials, and complex repetitive discharges (CRDs).
• Fibrillation potentials are the most common abnormal insertional/spontaneous
activity observed in myopathies.
•They seem to arise spontaneously from either a single muscle fiber or a few
muscle fibers and are not associated with visible contractions. They are biphasic
or triphasic waves with an initial positive deflection. They are usually 1 to 2 ms in
duration and less than 100 µV in amplitude.
Assessment of Low Back Muscle by Surface EMG
Adalgiso Coscrato Cardozo and Mauro Gonçalves
• Introduction : Surface electromyography (EMG) is wide used to
analyze back muscle activity.
• This tool is a non-invasive technique that allows the evaluation of
• The aim of the chapter is to provide a global understand of EMG
parameters used to access low back muscle.
• Low back muscle fatigue during isometric contractions: Dolan
et al. (1995) developed an alternative protocol called “Frequency
• In their study thirty-five health volunteers pulled upward with
constant force on a handlebar attached to the floor while the EMG
signal from the erector spinae was recorded at the levels T10 and
• The power spectra were divided into 10 frequency bands between
5Hz and 300Hz.
• Conclusion: EMG techniques and its application to
the assessment of low back muscle.
• It was shown that the surface EMG has a good
reliability in its parameters, and is a good tool to
access muscle fatigue.
The clinical significance of electromyography normalisation
techniques in subjects with anterior cruciate ligament injury
during treadmill walking.
Benoit DL1, Lamontagne M, Cerulli G, Liti A.
Gait Posture.2003 Oct; 18(2):56-63.
• This study investigated the clinical interpretation of three electromyographic
(EMG) normalisation techniques to detect neuromuscular alterations in
patients diagnosed with anterior cruciate ligament knee injury during treadmill
• The EMG signal was normalised using the mean value during the gait cycles
(MEA), the maximum value during the gait cycles (MAX), and a maximum
voluntary isometric contraction (MVC) test in 16 male and female subjects.
• The MAX method detected an increase in total muscle activity in
the injured limb rectus femoris (11.6%; P=0.02) while the MVC
method detected decreased injured limb gastrocnemius medialis
(GM) overall muscle activity (34.4%; P=0.02). The MAX method
identified decreased GM activity in three portions of the gait cycle.
• This study indicates the importance of choosing the appropriate
normalisation technique since its choice will change outcome
measures and subsequent clinical interpretation.
The Effects of Upper-Limb Training Assisted with an
Electromyography-Driven Neuromuscular Electrical
Stimulation Robotic Hand on Chronic Stroke
Chingyi Nam,1 Wei Rong,1 Waiming Li,1 Yunong Xie,1 Xiaoling
Hu,1,* and Yongping Zheng1
Impaired hand dexterity is a major disability of the upper limb after stroke. An
electromyography (EMG)-driven neuromuscular electrical stimulation (NMES)
robotic hand was designed previously, whereas its rehabilitation effects were not
A clinical trial with single-group design was conducted on chronic stroke
participants (n = 15) who received 20 sessions of EMG-driven NMES-robotic
hand-assisted upper-limb training.
The training effects were evaluated by pre training, post training, and 3-month
follow-up assessments with the clinical scores of the Fugl-Meyer Assessment
(FMA), the Action Research Arm Test (ARAT), the Wolf Motor Function Test, the
Motor Functional Independence Measure, and the Modified Ashworth Scale
(MAS). Improvements in the muscle coordination across the sessions were
investigated by EMG parameters, including EMG activation level and Co-
contraction Indexes (CIs) of the target muscles in the upper limb.
The upper-limb training integrated with the assistance from the EMG-driven
NMES-robotic hand is effective for the improvements of the voluntary motor
functions and the muscle coordination in the proximal and distal joints.
Furthermore, the motor improvement after the training could be maintained till
3 months later.
• Concepts of EMG
• Instrumentation and signal characteristics.
1. Different types of electrodes.
2. EMG examination.
3. Normal potential.
4. Abnormal potential.
• Different conditions
• Clinical implication.
1. Physical Rehabilitation 5th Edition. By: Susan B.O’sullivan.
Thomas J. Schmitz.
2. Electrodiagnosis in Diseases of Nerve And Muscle: Principles
and Practice. By: Jun Kimura
3. Electrodiagnosis in Amyotrophic Lateral Sclerosis, Nanette C
Joyce et al, PM R. 2013 May; 5(5 0): S89–S95.
4. Electrophysiology of Myopathy Approach to the Patient With
Myopathy in the EMG Laboratory , Nithi S. Anand et al.
5. The clinical significance of electromyography normalisation
techniques in subjects with anterior cruciate ligament injury
during treadmill walking. Benoit dl et al. Gait posture. 2003 oct;
6. The effects of upper-limb training assisted with an neuromuscular
electrical stimulation robotic hand on chronic stroke. Chingyi
Nam et al.
7. Applications of EMG in clinical and sports medicine : Edited by