2022 NMES Lecture

Neuromuscular
Electrical Stimulation

– Use in Neurological populations

1

Neuromuscular Electrical Stimulation

• Neuromuscular electrical stimulation (NMES) involves
the administration of an electrical current generated by
a stimulator that travels through leads to electrodes
placed on the skin to depolarize the motor nerve and
produce a muscle contraction.

• NMES uses a safe, non-invasive, low-frequency
current that is applied to the muscles through
electrodes on the skin.

• Electrical stimulation excites the nerves that innervate
desired muscles, causing them to contract. Stimulating
muscles to contract in this way enhances motor
learning, muscle re-education, strength, and

2 endurance.

Functional Electrical Stimulation

• What is it?

• The use of electrical
stimulation of the peripheral
nervous system to contract
muscles during functional
activities (e.g. standing,
walking, reaching, and
grasping etc.)

3

Neuro Clients

NMES can be used with:

⚫ Stroke
⚫ Brain injury
⚫ Spinal cord injury (lesions above T12)
⚫ Cerebral palsy
⚫ Multiple sclerosis
⚫ Parkinson’s Disease
⚫ Familial/hereditary spastic paraparesis

4

Neuro Clients

NMES not to be used with:

✓ Complete peripheral nerve damage
✓ Motor neuron disease*
✓ Guillain-Barre syndrome*
✓ Spinal cord lesions above T6 – needs close

monitoring - autonomic dysreflexia

7 * In minority of cases NMES can be useful

Why NMES?

▪ Increased functional activity

• currents depolarize nerves
• generates sensory & motor responses
• ↑ing muscle strength & control

▪ Increase intensity of rehab

• Train at higher contraction intensities

▪ Strong evidence to support its use

• ‘Another tool in your toolbox’

6

How does NMES work?

I feel
great !

7

‘Magic of Neuroplasticity’:

Neural reorganization and plasticity

• Ascending afferent input from sensory organs in joints,
muscles, tendons and skin as well as the direct effect of
stimulation on the afferent nerves act upon the nervous
system encouraging new synaptic connections.

Neural Reorganization
with NMES

• At the spinal level

• Improved recruitment by
voluntary descending
activity

• Subroutines – synergies /
pattern generators

• Within the brain

• increasing motor and
sensory cortex
expression



Muscle
Facilitation &
Reeducation

Goal: re-establish voluntary
control of body position &
movement after disruption of
motor control mechanisms

Needs to be applied in context of
motor learning

✓ Functionally relevant
activities

✓ Intermittent feedback
✓ Client must be an active

participant

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NMES Paradigms

⚫ NMES Independent Application

– Use of NMES for a finite time period to minimize
impairments, increase strength, and encourage motor
relearning in context of function

– The expectation is that the patient will be weaned off FES

⚫ NMES Dependent Application

– This enables the patient to perform functional activities that
wouldn’t otherwise be possible (e.g., picking up and
carrying a bag) – ‘neuroprosthesis’

THINGS TO REMEMBER:

Active involvement in task performance leads
to a substantial increase in cortical excitability
compared to non-skillful or passive training

Active better Little carry-over

Regaining functional use takes
‘Practice makes permanent’
patterns

⚫ Intensity: neuroplasticity: 900 reach and grasp reps/day –
less you use the paretic arm, the more the unaffected
hemisphere activates

⚫ Patterns:

Central patterns STRETCHING
Synergies…
will it reactivate?

Sensible Not so sensible

Stimulation Parameters

NMES Parameters
• Waveform: symmetric or asymmetric
• Amplitude: 0-100mA adjustable
• Pulse duration: 50-400µsec adjustable
• Frequency: 1-100 Hz adjustable
• Ramp up/down: 1-10 secs adjustable
• On/off time: 1-100 secs adjustable
• Polarity: Smoke over Fire

Do Parameters Matter?

• Recent literature review found no relationship
between stimulus parameters, duration of treatment,
subject characteristics and clinical outcome!

• “Triggered or volitionally activated ES more likely to
yield improvements in motor control than non-
triggered ES”

• Use parameters that encourage active participation
of client

Waveform

Classification of Waveforms

1.Monophasic - single phase,
unidirectional pulse from baseline to either positive OR negative
• Do not confuse this with Direct Current (DC). The similarity is
that one electrode is always positive and one electrode is
always negative, however, pulsed monophasic waves have
interruptions, shorter duration, and less strength than DC
making this wave unable to perform like DC. Monophasic
waveforms do not cause the same magnitude of chemical
changes as DC.

Waveform

Classification of Waveforms

2. Biphasic - two phase, bidirectional wave with one positive phase and
one negative phase.
• Like Alternating Current in that the electrodes change polarity
• Can be symmetrical (identical phases that cancel each other out) or
asymmetrical (non-identical phases that can be either balanced with
no net charge or unbalance yielding a net charge )

3. Polyphasic - bidirectional wave with three or more phases in bursts
• All polyphasic pulses are bursts but not all bursts are polyphasic

Waveform Clinical Considerations

Waveform Comfort

• Symmetrical biphasic waveforms are most often reported to be most
comfortable.

• Symmetrical biphasic was preferred to stimulate large muscle groups.
• No biphasic preference for stimulation of smaller muscle groups.
• Preference varied by person and another waveform tried if one is not tolerated

well.

•

• Waveform Selection

• All waveforms are capable of activating peripheral nerves.
• Symmetrical biphasic waveforms pose the least risk for skin reaction.
• Monophasic waveforms are most appropriate for wound healing.
• Asymmetrical balanced biphasic waveforms may be more useful to stimulate

small muscle groups.
• Monophasic and symmetrical biphasic waveforms generate greater torque with

muscle contraction and were less fatiguing than polyphasic waveforms.

Current Characteristics

Pulse Duration / Width

Pulse width and pulse duration are terms used interchangeably and refers to the
length of time each group of pulses of stimulation is set to, measured in microseconds
(µs); or milliseconds on devices offering EMS for peripheral nerve damage (ms). It is
common to see EMS devices offering ranges between 200-300us. Pulse width on
some devices will be pre-set and on others can be adjusted.
• A short pulse width can be more comfortable for some patients, but a longer pulse

width may recruit more motor neurones and thus improve the muscle contraction
produced.

Amplitude

• Amplitude (sometime referred to as intensity) refers to the
strength of the stimulation delivered, measured in milliamps
(mA).

• The amplitude needs to be high enough to evoke the desired affect
while still remaining comfortable.

• Adjustment of this parameter is always available as amplitude may
not always be set to the same level at each treatment session.

• Balancing the amplitude and the pulse width can help to
optimize both the muscle contraction produced and the
comfort for the patient

• a wider pulse duration may mean the amplitude can be reduced
offering more comfort.

Frequency

• Frequency refers to the number of stimulation pulses
delivered per second, measured in Hertz (Hz).

• At a low frequency (1-10Hz), a weak muscle twitch or flutter
will be generated. As frequency is increased (more pulses
delivered per second), so does the strength of the
contraction created up to around 60-70Hz, at which point
the frequency has more effect upon the sensory rather than
motor neurons and the power of the muscle contraction
reduces.

• EMS devices will offer a frequency within a set range (0-
70Hz), some devices may only provide one set level of
frequency, others will provide the option to adjust the
frequency within a pre-set range.

On:Off Cycle

• This refers to the ratio between the time that the
stimulation is on and off.

• During the on time the NME stimulator will deliver a train
of electrical impulses at the set frequency of impulses per
second.

• To prevent the muscle fibers becoming over-
fatigued, the off time or rest phase will allow the
motor units (consisting of a motor neuron and
innervated muscle fibers) to repolarize and recover.

• This off time should always be at least equal to that of the
on phase.

On:Off Cycle Clinical Note

Ramping

• Ramping is a gradual increase in the intensity at the
start of each phase of stimulation. A ramp may also
be applied at the end of the on time.
• During the ramp the level of stimulation will not
produce a contraction of the muscles.

• If this phase is very long it will reduce the overall
therapeutic time for the stimulation.

It takes 9 full
seconds to
receive 7 sec
of treatment

Where do we apply NMES?

27

Electrode Placements

Shoulder Flexion and Abduction Scapular Retraction

Anterior Middle Rhomboids
Deltoid Deltoid

Serratus
Anterior

https://www.axelgaard.com/

Electrode Placements

Shoulder Flexion and Abduction Dual Channel

Rhomboids Anterior Middle
Deltoid Deltoid

Serratus
Anterior

https://www.axelgaard.com/

Electrode Placements

Elbow Flexion Elbow Extension

Anterior Middle Rhomboids
Deltoid Deltoid

Serratus
Anterior

https://www.axelgaard.com/

Electrode Placements

Pronation

Rhomboids Anterior Middle
Deltoid Deltoid

Serratus
Anterior

https://www.axelgaard.com/

Electrode Placements

• Supination

https://www.axelgaard.com/

Electrode Placements

Finger Flexion Finger Extension

https://www.axelgaard.com/

Electrode Placements

Thumb Abduction Thumb Extension

https://www.axelgaard.com/

Electrode Placements

• Power Grasp with 2 channels

https://www.axelgaard.com/

Electrode Placements

Wrist Flexion Wrist Extension

https://www.axelgaard.com/

What does it all mean?

Increased
functional
activity

Remember: Combine ES with
active exercise or functional
tasks

Remember…

Stimulation parameters must be tailored to treatment goal and client

Post Stroke – facilitating
voluntary control and wrist
ROM – not a problem if finger
extensors are activated

Post-SCI –
development/maintenance of
tenodesis grip – MUST avoid
finger extension with wrist
extension to avoid
overstretching flexors

Abnormal Tone in Neuro Clients

Observed changes in tone due to pathological
conditions

⚫ Depends on remaining input (reduced &/or
altered) to muscle’s alpha motor neuron
⚫ Low muscle tone (hypotonicity)

• Results from loss of normal input to alpha motor neuron or
damage to alpha motor neurons → loss of input to muscle
fibers

⚫ High muscle tone (hypertonicity)

• Results from abnormally high excitatory input compared to
inhibitory input to intact alpha motor neuron

Spasticity – in CVA

Spasticity:
What is role of NMES?

▪ NMES combined with other intervention modalities
can be considered as a treatment option that
provides improvements in spasticity and range of
motion in patients after stroke
▪ There is strong evidence that ES decreases
spasticity in chronic stroke.

45

Problems with NMES

• Risk of raising unrealistic expectations
• Difficulty in predicting outcome
• Insufficient evidence for duration and dosage of

treatment
• Consistent electrode placements can be tricky

Avoid using electrical stimulation if client has:

• A change in tissue sensation

• Impaired mental status

• Presence of an implanted electrical device (the e-stim

could interfere with pacemakers or implanted pain

stimulators)

• Malignant tissue

• Wounds that are too moist

42 • An injured area near the eyes, carotid sinus, front of your
neck, or over reproductive organs

Absolute Contraindications

• If client has lower motor neuron damage or
denervated muscle (ie. cauda equina, peripheral
neuropathies, polyneuropathies, Guillain Barre
Syndrome)

• Contraindications to NMES use

• cardiac demand pacemaker –
• may interfere with sensing portion of pacemaker

• Pregnancy – effects of NMES on unborn child are unknown
• unhealed fracture in the area – may displace fracture
• Near another stimulator (eg. Phrenic nerve/bladder stim)
• Near arterial/venous thrombus
• Over carotid sinus
• Over areas of skin breakdown

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Relative Contraindications

• Severe spasticity
• Heterotopic ossification
• Severe osteoporosis
• Dysesthesia pain syndrome
• Open sores in the area of treatment
• Malignancy in the area of treatment
• Spastic response to electrical stimulation
• Uncontrolled autonomic dysreflexia
• Obesity

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Relative contraindication means that caution should be taken when
using NMES procedures.

• It is acceptable to do so if the benefits outweigh the risk.

Precautions

Prevention: What if skin looks like this after
treatment:
• Keep skin clean
Cure:
• Clean electrodes with
water after each use • Stop stimulation until marks clear
• Change to ‘better’ electrodes
• Do not shave - trim • Change to symmetrical biphasic output
hairs with scissors • Re-educate your patient about

• Replace electrodes as skin / electrode hygiene
recommended

• Replace carbon rubber
electrodes

• if dull adhesive
• if dry

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NMES Summary Treatment Chart
(M Cameron)

MVIC: Max Voluntary Isometric Contraction

1. NMES is easy to apply if you understand
basics

2. NMES contributes to neural reorganization
& plasticity

3. NMES should be combined with active
movement

4. Best practice guidelines support use of
NMES for hemiplegic shoulder, gait & UE
function – apply NMES to hemiplegic
shoulder early as preventative.