Slide 1
Electrical Stimulation to Augment
Muscle Strengthening: Guidelines
for Surgical Procedures, Diagnosis
and Co-Morbidities
Tara Jo Manal PT, OCS, SCS:
Director of Clinical Services
Orthopedic Residency Director
University of Delaware Physical Therapy
Department
Tarajo@udel.edu
302-831-8893
Slide 2
Properties of Electrical
Stimulation
Tara Jo Manal PT, OCS, SCS
University of Delaware
Slide 3
Properties of Electric
Stimulation

Voltage

Current
– Voltage represents the driving force that repels
like charges and attracts opposite charges
– Current is the movement of charged particles in
response to voltage
– Ampere represents an amount of charge moving
per unit time
– The higher the voltage, the higher the current
Slide 4
Magnitude of Charge
Flow

Conductance

Resistance
– Relative ease of movement of charged particles
in a charged medium
– If the ease of movement is high, the resistance to
movement is low
– Opposition to movement of charged particles
– Lower resistance provides greater
comfort/tolerance by patient for higher intensity
stimulation since less charge is needed to
penetrate the skin
Slide 5
Ohm’s Law

I = V/R

As the skin resistance decreases, more of
the current can flow, increasing the response
– Current increases as the driving force (V) is
increased or as the Resistance (R) to movement
is decreased
Slide 6
Properties

Impedance
– Opposition to alternating currents
– Higher frequency stimulation can pass with
greater ease
– Impedance is the best word to describe resistance
to flow in human tissue since it is comprised of the
tissue resistance and the insulator (subcutaneous
fat) effects of tissue
– Greater the impedance, greater the intensity
required to achieve therapeutic goal
High frequency stimulation is more comfortable
because impedance is lower
Slide 7
Current Density

Represents the intensity/area under a
stimulation pad
– At fixed voltage
• smaller the electrode the greater the intensity of
the stimulation compared to larger electrode
– Caution in setting intensity level with
smaller electrodes or damaged electrodes
• Very high current density can be related to
biological damage or burns
– Large electrodes
• Can the unit produce sufficient current
intensity?
Slide 8
Current Modulation

Timing

Train
– Altering the time characteristics of stimulation
– a continuous, repetitive series of pulses at a fixed
frequency
Slide 9
Current Modulation

Burst
– a package of train pulses
– delivered at a specified frequency
– e.g. 2 bursts per second
Slide 10
Carrier Characteristics

Carrier frequency
– Pulse duration is 1/f
– To increase pulse duration to improve muscle
force output you would decrease the train
frequency
– 2000Hz = 1/2000 or 500second pulse duration
– 1000Hz = 1/1000 or 1000second (1
millisecond) pulse duration
Slide 11
Frequency and Pulse
Duration
If the f is 5 Hz or 5 cycles/second
The duration is 1/5 or 20milliseconds
Slide 12
Pulse Duration

Increases recruitment of motor units

Improves the muscle contraction

Often labeled “width” or “pulse width”
Slide 13
How to Achieve
High
Force

Activate more
motor units
(recruitment)

Drive the motor
units more quickly
(Rate coding)
Slide 14
NMES – Increasing
Recruitment

How to recruit more motor
units electrically?
– Increase recruitment via
↑ phase charge

How to increase phase
charge
– Increase amplitude
– Increase pulse duration
– Or BOTH
Phase
Charge
Mixed
Nerve
Slide 15
Frequency

Increasing frequency

Tetanic contraction

Force production reaches a
plateau maximum between
50-80 pulses per second

For muscle strengthening
you want 50-80
pulses/second or 50-80
bursts/second
Slide 16
Frequency Controls



Usually labeled “Rate or Pulse Rate”
Set the number of pulses (or AC cycles) delivered
through each channel per second
As frequency is increased, impedance is decreased
Slide 17
NMES – Increasing
frequency

How to achieve high force
– Rate Coding
– Increase the frequency of stimulation
– But… increased frequency  increased fatigue
Slide 18
Quality of Contraction

Goal = strong tetanic contraction
– Stimulation frequency 50-80 pps
Slide 19
Understanding the
Manuals

Presets
– Advantage’s & Disadvantages

Adjustable Controls
– Waveform Selection
– Amplitude Controls
• AC: generally have a maximum of 100 –
200mA
• Independent vs. Shared amplitude control for
multiple channels
Slide 20
Cycle time controls

On & Off Time
– Duration of stimulation and rest
– Rest time dependent on goal of treatment
• Strengthening- Adequate rest to avoid fatigue
Slide 21
Ramp Controls

Controls the rate the amplitude increases
 Provide for more comfortable onset and
cessation of stimulus when very high levels of
stimulation are required

Can adjust if contraction is coming on too
quickly or stopping too quickly
Slide 22
Waveform type

Waveform

Patient dependent

UD PT Clinic
– Delitto Rose PT 1986
– Versastim
– Empi
Slide 23
Stimulation Parameters

What can we modify?
– Pulse Duration
– Pulse Frequency
– Waveform type
– Off time (time between contractions)
– Ramp time
Slide 24
Stimulator Controls

Programmed Stimulation Pattern
Controls
– Found on various stimulation devices,
mostly
– Can be limiting, if user is unable to
program stimulation patterns for a specific
application

Output Channel Selection
– Simultaneous
– Alternate or reciprocal mode
Slide 25
Line vs. Battery Powered
Slide 26
Test The Unit
Empi 300 PV
Slide 27
EMPI 300PV
Empi 300PV
1-800-328-2536
Slide 28
Dose of NMES

Maximal tolerable current and device
dependent- MVIC above blue line
Slide 29
Dose of NMES

Be sure your machine is capable of current
necessary
Slide 30
Test The Electrodes
Slide 31
Electrodes

How to improve the
lifespan
– Proper storage
– Keep them moist
– Placed properly on
plastic
– Improves conductivity
Slide 32
Another Brand of
Electrodes
Slide 33
Same Intensity- Different
Electrodes
Slide 34
Electrodes

Model F216
 Size 3” x 5”
– 8 x 13 cm
– Rectangle

Qty 2

1-800-538-4675
Slide 35
Electrodes

Reflex Tantone 624
 Ref# EC89270
 Size 2in x 2in
– 5.08cm x 5.08cm

Qty 4

Tyco/Heathcare

1-800-328-9454
– Unipatch
Slide 36
Tens Clean Cote

Uni-Patch
 1-800-328-9454
 Function
 Improves conductivity
Slide 37
Pad Placement

Typically include motor points of
muscle of interest
Slide 38
Pad Placement

Relationship between Pad placement
and current- Non-tetanic contraction
Slide 39
Pad Placement

Increase current, contraction becomes
tetanic
Slide 40
Treatment Administration

Patient motivation factors
– Assist your patient in tolerating treatment

Monitor
– set targets, watch output, give article

Blunter
– wear headphones, towel over head, body
relaxation
(Delitto et al PT 1992)
Slide 41
Give the Patient Control

Self trigger if possible

Therapist manually resuming stim

Count down to the stim

Explain to the patient the value of the
modality
Slide 42
What we do when things
are not going well …

General
– Tens Clean Cote
– Change the
waveform
– Decrease pulse
duration
• may need to also
increase the
frequency for
comfort

Specific
– Increase ramp time
– Self trigger
– Increase rest time
• Only if you see
them fatiguing
drastically
Slide 43
Evidence to support the
clinical use of electrical
stimulation for muscle
strengthening
Slide 44
Increased Functional Load

For muscle to hypertrophy and/or gain strength
the overload principle of high weight at low
repetitions is necessary
 Currier and Mann
– Looked at healthy male college students
– Utilized an intensity of at least 60% MVIC paralleling
voluntary exercise protocols for functional overload
– Conclusion: NMES and volitional exercise were
equivalent training stimuli
(Delitto,Snyder-Mackler, 1990)
Slide 45
Increased Functional
Load
Kots

Therapeutic efficacy reported for electrical
stimulation greater than volitional exercise,
when strengthening healthy muscle
– Intensity was 10-30% greater than MVC
– Strength gains of 30-40%
(Delitto,Snyder-Mackler, 1990)
Slide 46
Increased Functional
Load

Conclusions on Overload
– Significant strength gains can be achieved
in healthy muscle with an electrically
augmented training program
• The intensity however needs to be extremely
high (>100%MVIC)
– Electrical stimulation offers equivalent
muscle strengthening effects to voluntary
exercise in healthy subjects
• If intensity level parallels volitional exercise
intensities
(Delitto,Snyder-Mackler, 1990)
Slide 47
Increased Functional
Load

Conclusion on Overload
– Lower loads may still help in muscle recovering
from injury/surgery
• Most studies using subjects other than healthy male
college students demonstrated greater strength gains
in subjects training with NMES compared to volitional
exercise alone
(Delitto,Snyder-Mackler, 1990)
Slide 48
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1991

Purpose: To ascertain the effects of
electrically elicited co-contraction of the thigh
muscles on several parameters of gait and
on isokinetic performance of muscles in
patients who had reconstruction of the ACL
– 2 groups:
NMES + volitional exercise
Volitional exercise only
– Treatment intervention from 3rd to 6th week postop
Slide 49
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1991

Results:
– Significantly greater average and peak torque of
the quadriceps femoris at both 90°/sec and
120°/sec in the NMES group
– No significant difference in performance of the
hamstring muscles between groups
• Torque produced in the involved hamstrings averaged
80% of the strength in the uninvolved leg
Slide 50
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1991

Conclusions:
– The quadriceps muscles of these patients were
stronger in the eighth post-operative week than
reported averages for similar patients even years
after surgery
Slide 51
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1995

Purpose: To assess the effectiveness of
common regimens of electrical stimulation as
an adjunct to ongoing intensive rehabilitation
in the early postoperative phase after
reconstructions of the anterior cruciate
ligament
Slide 52
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1995

Training Intervention – 4 Groups
– High intensity NMES + volitional exercise
– High level volitional exercise
– Low intensity NMES + volitional exercise
– Combined high & low intensity NMES + volitional
exercise
Slide 53
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1995


High Intensity NMES
–
–
–
–
15 electrically elicited isometric contractions
2500Hz triangular AC current
Burst rate of 75bps
Amplitude to maximal tolerance
Low Intensity NMES
–
–
–
–
–
Portable electrical stimulation
Pulse duration of 300 microseconds
Frequency of 55pps
Amplitude >50mA to maximal tolerance
15 minutes 4 times/day
Slide 54
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1995

High Level Volitional Exercise

High Intensity and Low Intensity Electrical
Stimulation Combined
– 3 sets of 15 repetitions of the quadriceps femoris
– Intensity was maximum effort for 8 seconds
– Visual Feedback provided
All groups followed a standard volitional exercise
protocol beyond the experimental treatment
interventions
Slide 55
Electrical Stimulation for
Strength
Snyder-Mackler et al., 1995
– At least 70% recovery of the quadriceps
by 6 weeks after the operation, vs. 51%
in the groups that did not include high
intensity stimulation
– High intensity electrical stimulation leads to
more normal excursions of the knee joint
during stance
Slide 56
Electrical Stimulation for
Strength
Snyder-Mackler et al,
1995
Conclusion: For
quadriceps
weakness, high-level
NMES with volitional
exercise is more
successful than
volitional exercise
alone
Slide 57
Modified NMES Protocol
for Quadriceps Strength

Fitzgerald et. al.,
2003
– Subjects receiving
the modified NMES
treatment
combined with
exercise
demonstrated
greater quadriceps
strength and higher
ADLS scores than
the comparison
group
Slide 58
Fitzgerald et. al., 2003

Their data support the modified NMES
protocol in clinics without access to a
dynamometer

Option of using a dynamometer
– Authors choose the high intensity NMES protocol
Slide 59
NMES for Strength in the
Early Post-op Phase
Haug et al., 1988

Purpose: Efficacy of NMES of the quadriceps
femoris during CPM following total knee
arthroplasty
– CPM/NMES group
•
•
•
•
•
•
Intensity at maximum tolerance
3 times per day for 1 hour
Pulse width: 300 microseconds
Frequency: 35pps
On 15sec off 20 seconds at 40° setting and 65sec at 90° setting
Ramp time: 2 seconds up and 1 second down
– CPM group
Slide 60
NMES for Strength in the
Early Post-op Phase
Haug et al., 1988

Results: Stimulation group had significant
reduction of extension lag, and spent fewer
days in the hospital
– Intensity level was low compared to the other
studies mentioned

Conclusion: Electrical stimulation combined
with CPM in the treatment of patients with
total knee arthroplasty is a worthwhile
adjunctive therapy
Slide 61
Role of Strength in
Physical Therapy
Management
Strength losses can result in loss of the
ability to perform activities of daily living
 Strength recovery following surgery is often
incomplete
 Strength deficits can place patients at risk of
further injury

(Snyder-Mackler, 1991)
Slide 62
Neuromuscular Electrical
Stimulators

Indication
– Muscular strength deficits
• <80%MVIC
Slide 63
Neuromuscular Electrical
Stimulation
2.5 KHz (400 microsecond pulse duration)
 50-75 bursts per second
 2-5 second ramp
 12-15 seconds on, 50 - 80 seconds off
 Amplitude to maximal tolerance of patient

– With dynamometer feedback
• Minimum of 50% MVIC for ACL reconstruction
• Minimum of 30% MVIC for TKA
Slide 64
NMES for Quad
Strengthening
Slide 65
Procedure Modified
Rehabilitation
Slide 66
NMES Post ACL
Reconstruction

Knee stabilized
isometrically at 60°
degrees of knee flexion
 Single Channel two
electrode placement
– Below the AIIS
– Vastus medialis

Target 50% MVIC
– Minimum Intensity
Slide 67
Various Surgical Grafts

Hamstring Autograft/Allograft

Bone-Tendon-Bone Autograft
– Positioned at 60° of knee flexion
– Positioned in most comfortable angle
• flexion position > 40°
Slide 68
NMES Post ACL
Reconstruction

Amplitude to minimum of 50% MVIC
– Patient encouraged to increase the intensity to
maximum tolerated
– Dose-response curve demonstrates greater
intensities lead to greater strength gains
(Snyder-Mackler et al., 1994)
Slide 69
NMES for Muscle
Strengthening
On time- sufficient for strong tetanic
contraction 10-15 seconds
 Off time- sufficient for rest/recovery before
next contraction 30-90 seconds
 Ramp time- as needed for comfort
 Dose- maximal tolerable (no less than that
needed for strength gains to be seen)
 Frequency 2-3 times/week until strength
recovers

– Average 18 visits
Slide 70
NMES for Quadriceps
Strengthening

Following injury or surgery to the knee,
quadriceps weakness can be major
impairment

We utilize electrical stimulation on all patients
who demonstrate quadriceps weakness of
80% involved/uninvolved ratio or less
Slide 71
Post Operative Modification
to ACL Protocol for Other
Knee Problems

PCL
 MCL
30° Knee Flexion
30°-60° Knee Flexion

Meniscal Excision/ Repair None
 Chondroplasty
None

Post surgical intervention- follow soft tissue healing
8wks to protect surgical site or 12 weeks for bony
healing
Slide 72
Knee Flexion Angle

If Pain if limiting toleration – use most comfortable
angle

If Range of motion is limiting toleration – use most
comfortable angle

As long as modification does not risk surgical
procedure

Perform with support from the referring physician
Slide 73
Patellofemoral Joint
Syndrome

We perform burst superimposition testing on all
PFJ evaluations
– Identify “true” maximal force generating capability
– Identify presence or absence of “inhibition”
• Central activation deficit

NMES is performed at the most comfortable knee
joint angle
 Tape is often applied for pain control
 When necessary, treatments to calm irritated
structures are added
Slide 74
Patellofemoral Joint
Syndrome

Joint angle adjusted to patient comfort

Subluxing Patella
– Determined by volitional contraction
– Joint angle adjusted to increase
congruency to prevent subluxation
• Greater than 70°
– Patella taped medially
Slide 75
Proximal-Distal Patellar
Realignment

Knee stabilized
isometrically at 30
degrees of knee
flexion

Patella taped medially

Electrodes over the
proximal quadriceps/
distal pad is moved
central and superior
(avoiding the VMO)
Slide 76
Proximal/Distal
Realignment Precautions

Initiate 1st Week of Treatment
Precautions
 Proximal Realignment
– No MVIC for 8 weeks

Proximal/Distal Realignment

Dosage is maximal tolerable rather than %
MVIC
– No MVIC for 12 weeks
Slide 77
Why NMES following TKA?

Strength deficits can be profound

Quad weakness decreased by 60% following
surgery

Impaired ability to perform ADL’s

Increased fall risk
Stevens et al JOR 2003
Wolfson et al 1995 J Gerontol A: Biol Sci Med
Chandler et al 1998 Arch Phys Med Rehab
Slide 78
Goal of NMES
Quality muscle contraction
 Quantity sufficient enough to produce
strength gains
 Strength gains reflect intensity tolerated
 Therefore …
 Ultimate goal is to generate the greatest
tolerable force output

Slide 79
Total Joint Arthroplasty

Amplitude targeted at
a minimum of 30%
MVIC (Snyder-Mackler et
al., 1994)


Ramp time, frequency
adjusted to increase
comfort and tolerance
for higher intensity
stimulation
Modification of pulse
duration by
decreasing frequency
to 2000Hz or 1500Hz
(inc. pulse duration
from 400 to 500 or 666
microseconds)
Slide 80
NMES for Quadriceps
Strengthening Cannot Do It
Alone

Weakness can lead to compensation
strategies for daily activities
COMPENSATIONS MUST
BE PREVENTED!!!
Slide 81
Compensation Strategies

Unweighting
involved leg for sit to
stand
Slide 82
Compensation Strategies

Shifting weight in
standing to
uninvolved leg
Slide 83
Compensation Strategies

Not utilizing full
extension during
stance phase of gait
Slide 84
Lack of use can lead to...

Patellar baja

Lack of superior patellar migration with
quadriceps contraction

Quad dysplasia
Slide 85
Functional Use of
Quadriceps
Use of quadriceps during daily activities
must be relearned in order to eliminate
compensation strategies.
 If it gets to this point…you are in a hole!

Slide 86
Use of Strength in Daily
Activities

Composite overview of muscle performance

Observation of compensatory patterns
– Functional Testing
– Avoidance patterns
• Lack of progress with a strengthening program
• Re-education in order to retain strength gains
Slide 87
Case Report

17 y/o female soccer player 4 months
s/p ACL reconstruction

Quad Index (involved/uninvolved)
– Pre-operative = 77% (533 N)
– 2 month post-operative = 87% (601 N)
– 4 month post-operative = 29% (200 N)
Slide 88
Patient Examination

KOS-ADLS: 66% pre-operative
53% 4 months postoperative

Severe pain at infrapatellar tendon and
medial border of patella

Compensations to avoid use of involved
leg with functional activities secondary
to anterior knee pain
Slide 89
Patient Examination

No quadriceps inhibition with burst
superimposition test

Decreased superior migration of patella with
quad set and superior patellar hypomobility
Slide 90
Treatment Intervention

Superior patellar mobilizations

Pain control modalities
Quadriceps strengthening
 Quadriceps re-education

– Biofeedback
– Education to avoid compensation strategies
Slide 91
Quadriceps Re-education

Two 4 x 6 inch pads
over distal VMO and
proximal bulk of quad

Intensity = maximum
contraction patient can
tolerate
Slide 92
Exercises with Electrical
Stimulation

Sit to Stand
Slide 93
Exercises with Electrical
Stimulation

Standing Terminal
Knee Extensions
Slide 94
Exercises with Electrical
Stimulation

Seated Knee
Extensions
Slide 95
Quad Index



Pre-operative
2 month post-operative
4 month post-operative
QI = 77%
QI = 87%
QI = 29%

6 months post-op (16 visits) QI = 51%

7 months post-op (28 visits) QI = 72%

8 months post-op (37 visits) QI = 98%
Slide 96
Patient’s Strength Over
Time
MVC from 8-19-99 to 12-5-01
1400
MVC R
1200
MVC L
800
600
400
200
12/5/01
3/21/01
12/13/00
10/18/00
4/4/00
3/14/00
2/7/00
12/22/99
10/20/99
0
8/19/99
Newtons
1000
Slide 97
Return to Soccer
Progression
 Self-management
 Coaching support

Slide 98
Rotator Cuff
Strengthening

Patient Position
– Involved arm belted to
the body with the
elbow at 90° for
isometric contraction
– Forearm is blocked to
avoid rotation during
the contraction
Slide 99
Rotator Cuff Repair

Parameters
– NMES Protocol
– Current Intensity:
Maximal tolerable with
visible contraction
causing movement of
the arm against the
restraint
Slide 100
Slide 101
Achilles Tendon Repair

Early Phase - Tendon Gliding

Patient prone, knee resting in >50° of flexion
and ankle in full plantar flexion

Single Channel on the
medial/lateral gastroc

Current Intensity
– 10days – 4wks
– Modified surgical procedure (loop tightens under
tension)
– Visible tendon gliding
Slide 102
Achilles Tendon Repair

Late Phase – Muscle
Contraction
– >10weeks post op

Patient prone with knee
extended and ankle in
resting position

Can increase to
isometric against the
wall
Slide 103
Achilles Tendon Repair

Current Intensity

Continue treatment
until patient has full
active plantar flexion
– Look for visible
contraction
– Maximal tolerable
contraction by the
patient
Slide 104
Lumbar Rehabilitation

Patient Positioning Isometric Prone over
pillows
– Pelvis strapped to the
table in posterior
pelvic tilt
– Assess movement to
active lumbar
extension and tighten
as necessary
Slide 105
Lumbar Rehabilitation

High Intensity Electrical
stimulation

A single channel is
placed on the right and
left side of the spine
Slide 106
Lumbar Rehabilitation
Look for visible
contraction
Slide 107
Current Intensity

Maximal tolerable
contraction by the
patient
Slide 108
Thank You
Noel Goodstadt PT, OCS, CSCS
 Laura Schmitt PT, DPT, OCS, SCS, ATC
 Airelle Hunter PT
 Faculty, Residents, and Staff at UD
 Patients who endure e-stim at UD
 Tarajo@udel.edu
 302-831-8893
 www.udel.edu/PT/manal/estim
