Physiotherapy Theory and Practice

An International Journal of Physical Therapy

ISSN: 0959-3985 (Print) 1532-5040 (Online) Journal homepage: http://www.tandfonline.com/loi/iptp20

Efficiency of neuromuscular electrical stimulation:

A comparison of elicited force and subject
tolerance using three electrical waveforms

James W. Bellew, Molly Allen, Austin Biefnes, Sara Grantham, James Miglin &
Dylan Swartzell

To cite this article: James W. Bellew, Molly Allen, Austin Biefnes, Sara Grantham, James Miglin &
Dylan Swartzell (2018): Efficiency of neuromuscular electrical stimulation: A comparison of elicited
force and subject tolerance using three electrical waveforms, Physiotherapy Theory and Practice,
DOI: 10.1080/09593985.2017.1422820

To link to this article: https://doi.org/10.1080/09593985.2017.1422820

Published online: 08 Jan 2018.

Submit your article to this journal

Article views: 14

View related articles

View Crossmark data

Full Terms & Conditions of access and use can be found at

http://www.tandfonline.com/action/journalInformation?journalCode=iptp20
PHYSIOTHERAPY THEORY AND PRACTICE
https://doi.org/10.1080/09593985.2017.1422820

RESEARCH REPORT

Efficiency of neuromuscular electrical stimulation: A comparison of elicited force

and subject tolerance using three electrical waveforms
James W. Bellew, PT, EdD, Molly Allen, SPT, Austin Biefnes, SPT, Sara Grantham, SPT, James Miglin, SPT,
and Dylan Swartzell, SPT
Krannert School of Physical Therapy, University of Indianapolis, Indianapolis, IN, USA

ABSTRACT ARTICLE HISTORY

Objective: Efficacy of neuromuscular electrical stimulation (NMES) is limited by the discomfort of Received 8 September 2016
electrically elicited contractions. Most studies of tolerance to NMES have examined stimulation to Accepted 2 April 2017
maximal tolerance. NMES efficiency is the amount of elicited force at a specific level of tolerance. Revised 14 March 2017
This study is the first to describe and examine such. Design: A repeated measures design was KEYWORDS
used. Electrically elicited force (EEF) was measured using three waveforms: burst-modulated Muscle; strengthening;
alternating current (BMAC), pulsed current (PC), and burst-modulated pulsed current (BMPC). Russian; NMES
EEF at a tolerance rating of 5/10 on a visual analog scale (VAS) was recorded. The dependent
variables were EEF up to 5/10 VAS, current amplitude at 5/10, and percent maximal isometric
force at 5/10. Results: EEF and percent maximal voluntary isometric force were significantly
greater with BMPC versus BMAC (p = 0.001 and 0.004). No differences were noted between PC
and BMAC or BMPC and PC. Amplitude was significantly greater with BMAC compared to BMPC
and PC (p = 0.003 and 0.015). No difference in amplitude was noted between PC and BMPC.
Conclusion: For the same level of discomfort, BMPC yielded one-third greater muscle force than
BMAC and at a lesser current amplitude. These data evidence a greater efficiency for BMPC than
BMAC.

Introduction biphasic, and burst-modulated alternating current

(BMAC), either rectangular or sinusoidal. PC is com-
Neuromuscular electrical stimulation (NMES) is the use
monly administered at 1–120 Hz with a pulse duration
of therapeutic electrical currents to facilitate recovery of
of 100–600 µs (Ward, 2009), whereas BMAC is admi-
muscle strength, to promote muscle reeducation, to pre-
nistered with carrier frequencies from 1 kHz to 10 kHz
vent or attenuate atrophy, and to minimize functional
burst modulated from 1 to 120 Hz and a burst duty
limitations stemming from insult or surgery. Much atten-
cycle of 10% to 50% (Maffiuletti, Minetto, Farina, and
tion has been given to the identification of optimal sti-
Bottinelli, 2011; Ward and Shkuratova, 2002). The two
mulation parameters with emphasis on waveform shape
most commonly used BMACs are Russian current (2.5
(Bellew et al., 2012; Bellew, Sanders, Schuman, and
kHz sinusoidal AC carrier frequency, burst modulated
Barton, 2014; Dantas, Vieira, Siqueira, and Durigan,
at 50 Hz, with 10 ms burst duration and 50% burst duty
2015); pulse duration (Scott, Causey, and Marshall,
cycle) and Aussie current (1kHz rectangular or sinusoi-
2009; Scott et al., 2014); pulse frequency (Fukuda et al.,
dal AC carrier frequency, burst modulated at 50 Hz,
2013; Laufer and Elboim, 2008; Vaz et al., 2012); burst
with 2 ms burst duration and 10% burst duty cycle).
duration and frequency (Bankov, 1980; Laufer and
A lesser known NMES waveform is burst-modulated
Elboim, 2008; Laufer, Ries, Leininger, and Alon, 2001;
pulsed current (BMPC) (VMS-Burst®, Chattanooga Co.,
Moreno-Aranda and Seireg, 1981; Ward, Robertson, and
Hixon, TN, USA) delivered as three symmetrical rectan-
Ioannou, 2004); burst duty cycle (Liebano, Waszczuk, and
gular biphasic pulses with a fixed interphase interval of
Corrêa, 2013; McLoda and Carmack, 2000; Moreno-
100 µs and pulse frequency and duration comparable to
Aranda and Seireg, 1981; Ward, Robertson, and
PC and BMAC. Recent evidence by Bellew, Sanders,
Ioannou, 2004); and interphase intervals (Laufer, 2013).
Schuman, and Barton (2014) and Bellew et al. (2012) has
The most commonly studied NMES waveforms are
shown significantly greater electrically elicited muscular
low-frequency pulsed current (PC), either mono- or
force with BMPC when compared to PC and Russian.

CONTACT James W. Bellew, PT, EdD bellewj@uindy.edu James Bellew 1400 E. Hanna Ave, Indianapolis, IN, USA 46227.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/iptp.
© 2018 Taylor & Francis
2 J. W. BELLEW ET AL.

Despite continuing efforts to identify optimal wave- examined. The number of subjects used was deter-
forms and parameters, tolerance to NMES-induced dis- mined based on previous studies of similar design and
comfort is largely held to be a primary limiting factor in methodology (Dantas, Vieira, Siqueira, and Durigan,
the use and efficacy of NMES (Delitto, Strube, Shulman, 2015; Scott, Causey, and Marshall, 2009; Scott et al.,
and Minor, 1992; Doheny, Caulfield, Minogue, and 2014). No subjects were currently or recently engaged
Lowery, 2010; Lyons, Robb, Irrgang, and Fitzgerald, in regular vigorous strength training, none were cur-
2005; Maffiuletti, Minetto, Farina, and Bottinelli, 2011; rently participating in organized competitive sports,
Petrofsky, 2008; Scott, Causey, and Marshall, 2009; Scott and none had been previously treated with NMES on
et al., 2014). Some people report severe discomfort with the either leg. Subjects with reported aversion to elec-
NMES, while others report none (Abram, Asiddao, and trical stimulation that would preclude electrically eli-
Reynolds, 1980; Bennie et al., 2002; Downie, Leatham, cited muscle activation were not included. Prior to
and Rhind, 1978; Forrester and Petrofsky, 2004). initiation of this study, all subjects offered written
Discomfort can be so significant that many patients informed consent approved by the Institutional
prefer to avoid or not use NMES despite evidence of Review Board of the University of Indianapolis.
therapeutic benefit (Abram, Asiddao, and Reynolds,
1980; Bennie et al., 2002; Forrester and Petrofsky,
Procedure
2004). The literature on tolerance to NMES discomfort
is not clear, with conflicting results regarding differences A single-session repeated measures design was used.
in elicited torque and discomfort when comparing PC For each subject, all data collection was completed in
and BMAC (Aldayel, Jubeau, McGuigan, and Nosaka, a single session and was completed by three clinicians.
2010; Dantas, Vieira, Siqueira, and Durigan, 2015; Da The first operated the stimulator parameters and was
Silva et al., 2015; Fukuda et al., 2013; Liebano and Alves, positioned behind the examination table so that the
2009). No study has reported on NMES-induced dis- stimulator controls were not visible to the subject.
comfort with BMPC. The second operated the data acquisition equipment
Inconsistency in the literature regarding self-per- and was positioned so that no data were visible to the
ceived discomfort with NMES thus led our laboratory subject. The third was responsible for positioning and
to investigate the concept of the efficiency of NMES instrumenting the subject, instructing the patient on
waveforms. If a specific NMES waveform yields greater the use of the visual analog scale (VAS), and obtaining
muscle force at the same specific level of self-perceived the self-perceived rating of discomfort for each trial.
discomfort as another waveform, the initial waveform During the single session, all subjects completed pre-
can be considered more efficient. Previous clinical stu- testing familiarization procedures during which: (1)
dies of NMES and self-perceived discomfort have lar- maximal voluntary isometric force (MVIF) of the self-
gely used protocols assessing force up to maximal reported dominant leg was measured; (2) electrode
tolerance (Dantas, Vieira, Siqueira, and Durigan, 2015; location sites were determined by identifying the mid-
Fukuda et al., 2013; Liebano and Alves, 2009). dle one-third of the quadriceps muscle; and (3) subjects
However, due to poor tolerance, clinical use of NMES experienced submaximal electrically elicited contrac-
at maximally tolerated intensities is likely to lead to tions with the waveform that was determined to be
poor compliance and patient willingness to undergo used first. The order of the three NMES waveforms
repeated applications. To date, no study has examined was determined and administered in rotating order
the efficiency of NMES waveforms defined as force based on the order of subject entry into the study so
elicited for a specific level of self-perceived tolerance. that each of the three currents was administered first,
Therefore, this study was designed to examine the second, or third for a total of five times over the 15
efficiency of PC, BMAC, and BMPC waveforms used subjects.
for NMES. For testing, subjects were positioned supine, with the
knee of the test leg resting on the edge of a standard
padded examination table and the nontest leg flexed 45°
Methods at the hip and 90° at the knee with the foot resting flat
on the table (Bellew et al., 2012; Bellew, Sanders,
Subjects
Schuman, and Barton, 2014). A variable length chain
Fifteen healthy, physically active men and women (8 in series with an Interface SM-1000 load cell and data
female; 7 male; mean ± SD: age 23.5 ± 1.9) without acquisition software was adjusted for each subject to a
cardiovascular, neurologic, or musculoskeletal impair- test angle of 45° knee flexion (Figure 1). The chain was
ment (e.g., ligament or meniscal injuries) were attached to a nonelastic ankle strap positioned just
 PHYSIOTHERAPY THEORY AND PRACTICE 3

Figure 1. Test position for measurement of maximal voluntary isometric force and electrically elicited force.

proximal to the ankle joint. Immediately prior to test- fixed 100 µs interphase and interpulse intervals and was
ing, the subject’s test knee was manually positioned at burst modulated at 50 Hz so that with the selected 200
45° flexion to remove any slack in the chain. Upon µs phase duration, the burst duration was 1.7ms, the
verbal instruction, subjects attempted to extend their burst duty cycle was 8.5%, and the carrier frequency
leg as forcefully as possible for 3 to 4 s. Sixty seconds of was 1667 Hz. This carrier frequency was calculated as
rest was allowed between each repetition. Three repeti- 1/period, with the period being the sum of two phases
tions were performed with the greatest value recorded plus the interphase and interpulse intervals (e.g., the
as the MVIF. period would be 600 µs, considering two phases of 200
For stimulation, two three-inch round self-adhesive µs + 1 interphase interval and 1 interpulse interval; in
electrodes were positioned in a bipolar longitudinal this case, carrier frequency would be 1667 Hz).
arrangement over the middle one-third of the quadri- Waveform characteristics are depicted in Figure 2.
ceps, with one inch spacing between electrodes. The Three trials with each waveform were recorded with
electrode locations were predicated on the motor point the highest value of electrically elicited force (EEF) used
mapping of Botter et al. (2011). The same electrodes for data collection. For each trial, the stimulator opera-
were used for all three waveforms and were not moved tor increased the current amplitude to evoke a quad-
from their initial location. A multiwaveform stimulator riceps contraction and stopped when the subject
(Vectra Genisys, Chattanooga Group, Hixon, TN, USA) reported a discomfort level of 5 out of 10 while viewing
was used to deliver the three waveforms. a 10 cm (11-point) VAS with the end-point descriptors
The PC used was a symmetrical biphasic PC with a of “No Pain” and “Worst Possible Pain.” When the
fixed 100 µs interphase interval (VMS®, Chattanooga subjects indicated that their discomfort level had
Group, Hixon, TN, USA). PC was delivered at 50 Hz reached 5 out of 10 on the VAS, the stimulation inten-
using a 200 µs phase duration. The BMAC used in this sity was reduced to zero and the EEF and correspond-
study was conventional Russian current delivered as a ing VAS score and current amplitude at that VAS score
2.5 kHz carrier frequency burst modulated at 50 Hz were recorded. Sixty seconds were given between trials.
with a phase duration of 200 µs, a burst duration of 10 These procedures were followed for all nine trials. For
ms, and a burst duty cycle of 50%. The BMPC consisted each trial retained for data collection, the VAS score for
of three consecutive symmetrical biphasic pulses with that specific trial was used.
4 J. W. BELLEW ET AL.

Figure 2. Waveform characteristics.

Pulsed current (PC) and burst-modulated pulsed current (BMPC) with fixed 100µs interphase intervals. BMPC also has fixed 100µs interpulse
intervals. Russian current (BMAC: burst-modulated alternating current). For study, all waveforms had 200µs phase duration. Waveforms
depicted at three pulses or burst per second (50 Hz used for study).

Data analyses the study. There was a statistically significant differ-

ence in EEF scores among the three groups (Chi-
The dependent variables—EEF up to 5/10 VAS, peak
square (2) = 10.80, p = 0.005) and the effect size of
current amplitude at 5/10 VAS (amplitude), and %
d = 1.12 indicated a large effect. The post hoc tests
MVIF at 5/10 VAS (calculated as EEF/MVIF × 100%)
showed a significantly greater force with BMPC com-
—were compared between the three different groups.
pared to Russian (p = 0.001). EEF with BMPC was
Descriptive statistics were conducted to describe the
33.2% greater than EEF with Russian. No difference
data for each group. Normality of the data was
was noted in EEF scores between PC and Russian or
assessed using Shapiro–Wilk test. The EEF data
BMPC and PC (p = 0.061 and p = 0.023, respec-
were not normally distributed; therefore, the data
tively). The repeated measures ANOVA results
were compared using the Friedman’s test and
showed a significant difference in %MVIF scores
Wilcoxon signed-rank post hoc tests with
between the groups [F(2, 28) = 9.54, p = 0.001] and
Bonferroni correction (alpha level = .017).
a large effect size (partial eta-squared = 0.41). The
Amplitude and %MVIF data were normally distribu-
post hoc test showed significantly greater force with
ted, so repeated measures analysis of variance
BMPC compared to Russian (p = 0.004), with the %
(ANOVA) were used to compare the scores along
MVIF being 39% greater. There was not a significant
with Bonferroni-corrected post hoc tests. Data were
difference in %MVIF scores between Russian and PC
analyzed using IBM SPSS Statistics for Windows,
(p = 0.109) or PC and BMPC (p = 0.105). A signifi-
Version 24.0 (IBM Corp., Armonk, NY, USA). All
cant difference was likewise noted in amplitude
comparisons were two tailed and a significance level
among the three groups [F(2, 28), p = 0.001] with a
of <0.05 was considered statistically significant. Effect
large effect size (partial eta-squared = 0.40). A greater
sizes (Cohen’s d for EEF and partial eta-squared for
amplitude was noted between Russian and BMPC
%MVIF and amplitude) were calculated and inter-
(11.8%, p = 0.003) and Russian and PC (11.5%,
preted using formulas and criteria described by
Cohen (1992). For Cohen’s d, a value at least 0.20
Table 1. Outcome measures of the three electrical waveforms.
is considered “small,” at least 0.50 “medium,” and at PC Russian (BMAC) BMPC
least 0.80 “large.” For partial eta-squared, a value at EEF (lb) 24.9 ± 3.9 21.7 ± 4.4 28.9 ± 4.2*
least 0.10 is considered “small,” at least 0.25 “med- % MVIF 27.2 ± 4.2 22.8 ± 3.6 31.7 ± 4.7*
Amplitude (mA) 69.7 ± 2.4 77.7 ± 3.5^ 69.5 ± 3.2
ium,” and at least 0.40 “large” (Cohen, 1992).
EEF = electrically elicited force.
%MVIF = percent of maximal voluntary isometric force (EEF/MVIF × 100%).
Amplitude = peak amplitude at 5/10 VAS score.
Results PC = pulsed current (VMS®).
Russian = burst-modulated alternating current.
BMPC = burst-modulated pulsed current (VMS-Burst®).
All 15 subjects completed the data collection proce- * = significantly greater than Russian (p < 0.01).
dures. Table 1 depicts the main outcome measures of ^ = significantly greater than BMPC (p = 0.003) and PC (p = 0.015).
 PHYSIOTHERAPY THEORY AND PRACTICE 5

p = 0.015). No difference in amplitude was noted tolerate great current amplitude with Russian current
between PC and BMPC (p = 0.949). up to a VAS rating of 5/10, the lesser elicited force with
Russian current makes its selection inferior to BMPC.
Because our study only assessed force elicited at a
Discussion
VAS discomfort rating of 5/10, it is speculative to
Our study is the first to use the term “NMES effi- suggest that our findings would hold true at other
ciency,” which we operationally defined as the amount VAS ratings. However, with our preselected tolerance
of elicited muscle force at a given level of discomfort level of 5/10, the %MVIF values for the three wave-
(selected as 5 out of 10 for our study). This level of forms ranged from 22.8% (Russian) to 31.7% (BMPC).
discomfort was selected because it represents 50% of Previous studies of NMES have shown a positive rela-
maximum tolerance and is a level of discomfort empiri- tionship between the amount of force elicited and gains
cally found to be acceptable to patients when using in muscle strength (Selkowitz, 1985; Snyder-Mackler,
NMES in a clinical setting. NMES efficiency takes into Garrett, and Roberts, 1989). Accordingly, Scott, Causey,
account the physical and subjective experience patients and Marshall (2009) suggested that the primary goal
endure with clinical NMES protocols. The concept of with NMES is elicitation of the greatest muscle force
NMES efficiency was born out of the observation that possible so as to result in optimal increases in strength.
patient willingness to endure high levels of discomfort, NMES training intensities as low as 5% MVIF have
as often used in previous studies, threatens the contin- demonstrated efficacy in maintaining muscle mass dur-
ued clinical use of NMES. Furthermore, the concept of ing immobilization (Gibson, Smith, and Rennie, 1988)
NMES efficiency attempts to answer the clinical ques- and for increasing muscle strength in healthy subjects
tion, “if NMES is indicated, and the patient is willing to (Stefanovska and Vodovnik, 1985). Considering that
endure some discomfort, then which waveform will there is not clear evidence or even consensus regarding
yield the greatest muscle force for a given level of self- minimal clinically useful contraction intensity when
reported discomfort?” using NMES (Maffiuletti, 2010; Maffiuletti et al.,
Previous literature comparing muscle force produc- 2008), the %MVIF values in our study appear suitable
tion and tolerance to NMES-induced discomfort is for promoting strength at 50% of maximal NMES-
conflicting. Fukuda et al. (2013) reported no difference induced discomfort. However, when considering effi-
in muscle torque when comparing PC and Russian ciency of the three waveforms, the greater force elicited
current despite lesser discomfort with the Russian cur- with BMPC provides strong evidence for the selection
rent. In contrast, Dantas, Vieira, Siqueira, and Durigan of BMPC over Russian.
(2015) compared torque and discomfort using PC and To date, muscle force production with NMES has
Russian and Aussie currents (both BMAC) and largely been studied with stimulus intensities to max-
reported no difference in discomfort despite signifi- imal tolerance (Dantas, Vieira, Siqueira, and Durigan,
cantly less torque elicited with Russian. Still differing, 2015; Scott, Causey, and Marshall, 2009; Scott et al.,
a systematic review with meta-analysis of BMAC (sinu- 2014). With increasing current amplitudes, greater
soidal and rectangular) and PC waveforms by Da Silva muscle force is produced, but discomfort also increases
et al. (2015) reported no significant difference in (Adams, Harris, Woodard, and Dudley, 1993; Binder-
evoked torque and, among studies comparing self- Macleod, Halden, and Jungles, 1995; Gorgey and
reported discomfort, no difference was found Dudley, 2008). With the transcutaneous administration
(Aldayel, Jubeau, McGuigan, and Nosaka, 2010; of NMES, nociceptive free nerve endings located above
Dantas et al., 2015; Liebano and Alves, 2009). the fatty tissue are depolarized (Petrofsky, 2008; Vaz
Likewise, Laufer and Elboim (2008) reported no differ- et al., 2012). This discomfort can result in decreased
ence in discomfort or elicited force between Russian tolerance and consequently minimize the continued use
current and PC. and efficacy of NMES. Laufer and Elboim (2008) and
Our study presents novel findings to the literature Laufer, Ries, Leininger, and Alon (2001) reported that
which suggest that at a level of self-reported discomfort maximal tolerance levels to NMES have been shown to
of 5/10, BMPC is more efficient than the more com- be achieved between 30 and 38% of MVIF. Our levels
monly used Russian current. This is evidenced by the of %MVIF were below these and are likely the result of
33% greater EEF and 39% greater %MVIF elicited by terminating the stimulus amplitude at a submaximal
BMPC versus Russian current. Furthermore, that 10.5% discomfort rating of 5/10.
less current amplitude was required with BMPC versus Although the early studies of Russian current from
Russian further substantiates our finding of greater the 1970s reported greater comfort and elicited force
NMES efficiency with BMPC. While our subjects did (Ward and Shkuratova, 2002), more recent evidence
6 J. W. BELLEW ET AL.

comparing Russian and PC have not substantiated torque in the biceps brachii (Bankov, 1980), finger
these findings. Several studies have shown no difference flexors (Moreno-Aranda and Seireg, 1981), quadri-
in elicited force when comparing Russian and PC ceps (Liebano, Waszczuk, and Corrêa, 2013;
(Delitto and Rose, 1986; Grimby and Wigerstad- McLoda and Carmack, 2000), and wrist extensors
Lossing, 1989; Holcomb, Golestani, and Hill, 2000; (Ward, Robertson, and Ioannou, 2004) and produce
Snyder-Mackler, Delitto, Stralka, and Bailey, 1994), less discomfort (Moreno-Aranda and Seireg, 1981;
whereas other studies reported greater force with PC Ward, Robertson, and Ioannou, 2004). However,
(Laufer and Elboim, 2008; Laufer, Ries, Leininger, and there is inconsistency in the literature regarding dis-
Alon, 2001; Lyons, Robb, Irrgang, and Fitzgerald, 2005; comfort when using varying burst duty cycles. Ward,
Ward, Oliver, and Buccella, 2006). Only Bellew et al. Robertson, and Ioannou (2004) reported the greatest
(2012) have compared BMPC and Russian reporting discomfort with 100% burst duty cycle and least with
significantly greater torque with BMPC. 20–25%, with greater force elicited at 20–25%. In
As the response of skeletal muscle to NMES is contrast, Liebano, Waszczuk, and Corrêa (2013)
dependent upon the specific parameters of the elec- reported no difference in discomfort when using
trical stimulus, differences among the three wave- burst duty cycles of 20%, 35%, and 50% despite
forms must be considered (Bellew et al., 2012; greater elicited force at 20% and 35% burst duty
Bellew, Sanders, Schuman, and Barton, 2014; cycles. Bellew et al. (2012) compared Russian current
Butikofer and Lawrence, 1979; Gorgey, Black, Elder, to BMPC using the same phase duration (200 µs),
and Dudley, 2009; Scott, Causey, and Marshall, 2009; burst frequency (50 Hz), and current amplitude
Ward, Robertson, and Ioannou, 2004). Since its (100 mA) and reported 75% greater elicited force
introduction in the 1970s, Russian current has been with BMPC. However, different among the currents
one of the most commonly used NMES waveforms was carrier frequency (2500 Hz for Russian, 1667 Hz
and it remains the most recognized BMAC (Ward for BMPC), burst duty cycle (50% for Russian and
and Shkuratova, 2002). Conventional Russian current 8.5% for BMPC), and burst duration (10 ms for
is administered as a 2500 Hz sinusoidal alternating Russian, 1.7 ms for BMPC). The greater force
current burst modulated at 50 bursts per second, observed with BMPC in this study is consistent
with 200 µs phase durations, 10 ms burst and inter- with previous literature suggesting lesser carrier fre-
burst intervals, and 50% burst duty cycle. PC for quency, burst duration, and burst duty cycle (Bankov,
NMES is commonly administered at pulse frequen- 1980; Liebano, Waszczuk, and Corrêa, 2013; McLoda
cies of 20–100 Hz and pulse durations from 100 to and Carmack, 2000; Moreno-Aranda and Seireg,
600 µs and has shown effectiveness for eliciting mus- 1981; Ward, Robertson, and Ioannou, 2004).
cle force consistent with the purpose of NMES While the findings of our study suggest greater
(Snyder-Mackler, Garrett, and Roberts, 1989). efficiency with BMPC, this was only assessed over a
BMPC, only recently reported in the literature by single session, up to a VAS tolerance rating of 5/10,
Bellew, Sanders, Schuman, and Barton (2014) and and in a sample size of 15. What effect repeated
Bellew et al. (2012), is a burst-modulated form of administration of the three test waveforms over mul-
PC with three consecutive biphasic pulses with fixed tiple sessions, or at VAS tolerance levels greater than
100 µs interphase and interpulse intervals. With our 5/10, or in a larger population would have is a matter
self-selected phase duration of 200 µs and burst fre- of conjecture and beyond the scope of this singular
quency of 50 Hz, our burst duration was 1.7ms, burst investigation. While the individuality of subject
duty cycle was 8.5%, and carrier frequency was response to discomfort is well described (Delitto,
1667 Hz. Strube, Shulman, and Minor, 1992), scales such as
Some researchers have suggested that the 2500 Hz VAS rating systems are of clinical use. Previous
carrier frequency of Russian current may be subopti- authors have suggested that the considerable interin-
mal for purposes of NMES (Ward, 2009; Ward, dividual variation in response to NMES may be more
Robertson, and Ioannou, 2004). In contrast, lesser closely related to subject characteristics than to the
kilohertz frequency carrier currents of 1000 and parameters of the electrical currents (Delitto, Strube,
2000 Hz have shown significantly greater muscle Shulman, and Minor, 1992; Lyons, Robb, Irrgang,
torque, with 1000 Hz showing the greatest torque and Fitzgerald, 2005).
(Bankov, 1980; Ward and Robertson, 1998; Ward, Nevertheless, the findings of our study have
Robertson, and Ioannou, 2004). Previous research important clinical implications. Although Russian,
has also shown that lesser burst duration and duty PC, and BMPC are capable of eliciting muscle forces
cycles (10% and 20%) are optimal for eliciting muscle capable of increasing strength, tolerance to NMES-
 PHYSIOTHERAPY THEORY AND PRACTICE 7

induced discomfort remains a limiting factor in the Adams GR, Harris RT, Woodard D, Dudley GA 1993
administration, continued use, and efficacy of NMES. Mapping of electrical muscle stimulation using MRI.
BMPC has been previously shown to elicit superior Journal of Applied Physiology 74: 532–537.
Aldayel A, Jubeau M, McGuigan M, Nosaka K 2010
muscle force when compared to Russian and PC Comparison between alternating and pulsed electrical
(Bellew et al., 2012) but not until this study has the muscle stimulation for muscle and systematic responses.
concept of NMES efficiency been presented. That Journal of Applied Physiology 109: 735–744.
significantly greater force was achieved at the same Bankov S 1980 Medium frequency modulated impulse cur-
magnitude of self-reported discomfort with BMPC rent for electric stimulation of non-denervated muscles.
Acta Medica Bulgarica 7: 12–17.
versus Russian offers significant new findings to the
Bellew JW, Beiswanger Z, Freeman E, Gaerte C, Trafton J
literature. Future studies should be undertaken to 2012 Interferential and burst modulated biphasic pulsed
extend the findings of this study and examine currents yield greater muscular force than Russian current.
NMES efficiency over a greater spectrum of the Physiotherapy Theory and Practice 28: 384–390.
0–10 VAS scale. Although our findings were over- Bellew JW, Sanders K, Schuman K, Barton M 2014 Muscle
served with healthy uninjured subjects, future studies force production with medium and low-frequency bust
modulated biphasic pulsed currents. Physiotherapy
should also consider vetting these findings on sub- Theory and Practice 30: 105–109.
jects with neuromuscular impairment. Finally, this Bennie SD, Petrofsky JS, Nisperos J, Tsurudome M, Laymon M
study used Russian current as the BMAC. Future 2002 Toward the optimal waveform for electrical stimulation.
studies may consider examining NMES efficiency of European Journal of Applied Physiology 88: 13–19.
Aussie current (with lesser burst duty cycles of Binder-Macleod SA, Halden EE, Jungles KA 1995 Effects
of stimulation intensity on the physiological responses
10–20% as compared to the 50% burst duty cycle of
of human motor units. Medicine and Science in Sports
Russian), a lesser known but available form of and Exercise 27: 556–565.
BMAC. Botter A, Oprandi G, Lanfranco F, Allasia S, Maffiuletti N,
Minetto M 2011 Atlas of the muscle motor points for
the lower limb; implications for the electrical stimulation
Conclusion procedures and electrode positioning. European Journal
of Applied Physiology 111: 2461–2471.
NMES is predicated on the elicitation of muscle force Butikofer R, Lawrence P 1979 Electrocutaneous nerve stimu-
to increase strength. However, tolerance to NMES- lation- II: Stimulus waveform selection. IEEE Transact on
induced discomfort is a primary limiting factor to its Biomedical Engineering 2: 69–75.
Cohen J 1992 A power primer. Psychological Bulletin 112:
repeated clinical use. This study showed that for the 155–159.
same level of self-reported tolerance, BMPC yielded da Silva VZ, Durigan JL, Arena R, de Noronha M, Burney B,
33% greater muscle force than Russian and at a lesser Cipriano G 2015 Current evidence demonstrates similar
current amplitude. These data evidence a greater effects of kilohertz frequency and low frequency current on
efficiency for BMPC when compared to the more quadriceps evoked torque and discomfort in healthy indi-
viduals: A systematic review with meta-analysis.
commonly used Russian current (BMAC). Due to
Physiotherapy Theory and Practice 31: 533–539.
the small sample size of 15, these results should be Dantas LO, Vieira A, Siqueira S, Durigan JLQ 2015
considered preliminary. Nevertheless, the findings of Comparison between the effects of 4 different electrical
this study offer novel and evidence-based informa- stimulation current waveforms on isometric knee exten-
tion to guide clinical decision-making when selecting sion torque and perceived discomfort in healthy women.
an NMES waveform. NMES efficiency should be Muscle and Nerve 51: 76–82.
Delitto A, Rose SJ 1986 Comparative comfort of thee wave-
considered when NMES is administered as part of forms used in electrically eliciting quadriceps femoris mus-
the rehabilitation plan. By optimizing elicited force, cle contractions. Physical Therapy 74: 901–907.
efficacy of NMES is increased. Delitto A, Strube MJ, Shulman AD, Minor SD 1992 A study
of discomfort with electrical stimulation. Physical Therapy
72: 410–421.
Declaration of Interest Doheny EP, Caulfield BM, Minogue CM, Lowery MM 2010
Effect of subcutaneous fat thickness and surface electrode
The authors report none. configuration during neuromuscular electrical stimulation.
Medical Engineering and Physics 32: 468–474.
Downie WW, Leatham PA, Rhind VM 1978 Studies with
References pain rating scales. Annals of the Rheumatic Diseases 37:
378–381.
Abram SE, Asiddao CB, Reynolds AC 1980 Increased skin Forrester B, Petrofsky JS 2004 Effect of electrode size and
temperature during transcutaneous nerve stimulation. shape on electrical stimulation. European Journal of
Anesthesia and Analgesia 59: 22–25. Applied Physiology 4: 346–354.
8 J. W. BELLEW ET AL.

Fukuda TY, Marcondes FB, Rabelo N, Vasconcelos A, thresholds between men and women. Annals of
Junior CC 2013 Comparison of peak torque, intensity Neurology 63: 507–512.
and discomfort generated by neuromuscular electrical Maffiuletti NA, Minetto MA, Farina D, Bottinelli R 2011
stimulation of low and medium frequency. Isokinetics Electrical stimulation for neuromuscular testing and train-
and Exercise Science 21: 167–173. ing: State of the art and unresolved issues. European
Gibson JN, Smith K, Rennie MJ 1988 Prevention of disuse Journal of Applied Physiology 111: 2391–2397.
muscle atrophy by means of electrical stimulation: McLoda TA, Carmack JA 2000 Optimal burst duration dur-
Maintenance of protein synthesis. Lancet 2: 767–770. ing a facilitated quadriceps femoris contraction. Journal of
Gorgey AS, Black C, Elder C, Dudley G 2009 Effects of Athletic Training 35: 145–150.
electrical stimulation parameters on fatigue in skeletal Moreno-Aranda J, Seireg A 1981 Investigation of over-the-skin
muscle. Journal of Orthopedic Sports Physical Therapy electrical stimulation parameters for different normal muscles
39: 684–692. and subjects. Journal of Biomechanics 14: 587–593.
Gorgey AS, Dudley G 2008 The role of pulse duration and Petrofsky J 2008 The effect of the subcutaneous fat on the
stimulation duration in maximizing the normalized torque transfer of current through skin and into muscle. Medical
during neuromuscular electrical stimulation. Journal of Engineering and Physics 30: 1169–1176.
Orthopedic Sports Physical Therapy 38: 508–516. Scott WB, Causey JB, Marshall TL 2009 Comparison of
Grimby G, Wigerstad-Lossing I 1989 Comparison of high maximum tolerated muscle torques produced by 2 pulse
and low-frequency muscle stimulators. Archives of durations. Physical Therapy 89: 851–857.
Physical Medicine and Rehabilitation 70: 835–838. Scott WB, Flora K, Kitchin BJ, Sitarski AM, Vance JB 2014
Holcomb WR, Golestani S, Hill SA 2000 Comparison of Neuromuscular electrical stimulation pulse duration and
knee-extension torque production with biphasic versus maximum tolerated muscle torque. Physiotherapy Theory
Russian current. Journal of Sports Rehabilitation 9: 229– and Practice 30: 276–281.
239. Selkowitz D 1985 Improvement in isometric strength of the
Laufer Y 2013 A brief interphase interval interposed within quadriceps femoris muscle after training with electrical
biphasic pulses enhances the contraction force of the quad- stimulation. Physical Therapy 65: 186–196.
riceps femoris muscle. Physiotherapy Theory and Practice Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL 1994 Use of
29: 461–468. electrical stimulation to enhance recovery of quadriceps
Laufer Y, Elboim M 2008 Effect of burst frequency and femoris muscle force production in patients following anterior
duration of kilohertz frequency alternating current and of cruciate ligament reconstruction. Physical Therapy 74: 901–
low frequency pulsed currents on strength of contraction, 907.
muscle fatigue, and perceived discomfort. Physical Snyder-Mackler L, Garrett M, Roberts M 1989 A comparison
Therapy 88: 1167–1176. of torque generating capabilities of three electrical stimu-
Laufer Y, Ries JD, Leininger PM, Alon G 2001 Quadriceps lating currents. Journal of Orthopedic and Sports Physical
femoris muscle torques and fatigue generated by neuro- Therapy 11: 297–301.
muscular electrical stimulation with three different wave- Stefanovska A, Vodovnik V 1985 Change in muscle force
forms. Physical Therapy 81: 1307–1316. following electrical stimulation. Dependence on stimula-
Liebano RE, Alves LM 2009 Comparison of the sensory tion waveform and frequency. Scandinavian Journal of
discomfort index during neuromuscular electrical stimula- Rehabilitation Medicine 17: 141–146.
tion with low and medium excitomotor frequencies in Vaz MA, Aragao FA, Boschi ES, Fortuna R, De Oliveira Melo M
healthy women. Revista Brasileira de Medicina do 2012 Effects of Russian current and low frequency pulsed
Esporte 15: 50–53. current on discomfort level and current amplitude at 10%
Liebano RE, Waszczuk S Jr, Corrêa JB 2013 The effect of maximal extensor torque. Physiotherapy Theory and Practice
burst-duty-cycle parameters of medium-frequency 28: 617–623.
alternating current on maximum electrically induced Ward AR, Robertson VJ, Archives Of Physical Medicine And
torque of the quadriceps femoris, discomfort, and tol- Rehabilitation [Arch Phys Med Rehabil], ISSN: 0003-9993,
erated current amplitude in professional soccer players. 1998 Nov; Vol. 79(11), pp. 1399–404
Journal of Orthopedic and Sports Physical Therapy 43: Ward A 2009 Electrical stimulation using kilohertz frequency
920–926. alternating current. Physical Therapy 89: 181–190.
Lyons CL, Robb JB, Irrgang JJ, Fitzgerald GK 2005 Ward A, Oliver W, Buccella D 2006 Wrist extensor torque
Differences in quadriceps femoris muscle torque when production and discomfort associated with low frequency
using a clinical electrical stimulator versus a portable and burst modulated kilohertz-frequency currents.
electrical stimulator. Physical Therapy 85: 44–51. Physical Therapy 86: 1360–1367.
Maffiuletti NA 2010 Physiological and methodolgical consid- Ward AR, Robertson VJ, Ioannou H 2004 The effect of duty
erations for the use of neuromuscular electrical stimula- cycle and frequency on muscle torque production using
tion. European Journal of Applied Physiology 110: 223– kilohertz frequency range alternating current. Medical
234. Engineering and Physics 26: 569–579.
Maffiuletti NA, Herrero AJ, Jubeau M, Impellizzeri FM, Ward AR, Shkuratova N 2002 Russian electrical stimulation:
Bizzini M 2008 Differences in electrical stimulation The early experiments. Physical Therapy 82: 1019–1030.