Content uploaded by Kayvan Seyri
Author content
All content in this area was uploaded by Kayvan Seyri on Jul 03, 2019
Content may be subject to copyright.
Effect of
Electromyostimulation
Training on Muscle
Strength and Sports
Performance
Kayvan M. Seyri, MSc, NSCA-CPT*D, CSCS
1
and Nicola A. Maffiuletti, PhD
2
1
A.T. Still University, Kirksville, Missouri; and
2
Neuromuscular Research Laboratory, Schulthess Clinic,
Zurich, Switzerland
SUMMARY
ELECTROMYOSTIMULATION (EMS)
IS A WIDELY USED METHODOLOGY
IN APPLIED SPORTS SCIENCE. IN
CONTRAST TO A TYPICAL VOLUN-
TARY CONTRACTION INITIATED BY
THE CENTRAL NERVOUS SYSTEM
(E.G., IN RESISTANCE TRAINING),
EMSINVOLVESINVOLUNTARY
CONTRACTIONS ELICITED BY
ELECTRICAL CURRENT APPLIED TO
THE MUSCLE. THE EFFECTIVENESS
OF THIS TECHNIQUE HAS BEEN
EVALUATED IN NUMEROUS STUDIES
EXAMINING STRENGTH AND PHYS-
ICAL PERFORMANCE. OTHER RE-
PORTS COMPARING SHORT-TERM
(I.E., #3WEEKS)ANDLONG-TERM
(I.E., $12 WEEKS) EMS APPLICATION
HAVE ALSO REPORTED DIFFEREN-
TIAL RESULTS. THIS ARTICLE WILL
REVIEW RESEARCH EXAMINING
THEEFFECTOFEMSONINCREAS-
ING STRENGTH AND POWER, ES-
PECIALLY IN SPORTS
PERFORMANCE.
QUICK DEFINITION AND
COMMON USE
Electromyostimulation (EMS)—
electrical muscle stimulation
or neuromuscular electrical
stimulation—involves artificially acti-
vating the muscle with a protocol
designed to minimize the discomfort
associated with the stimulus. EMS has
long been used to either supplement or
substitute voluntary muscle activation
in many rehabilitation settings, for
example, for re-education of muscle
action, facilitation of muscle contrac-
tion, muscle strengthening, and main-
tenance of muscle mass and strength
during prolonged periods of immobi-
lization (14,18,28). EMS training pro-
grams have further been used to
improve muscle strength of healthy
individuals (6,7), and more recently,
EMS has been implemented in com-
petitive athletes (21,33).
Typical settings of EMS exercise in-
volve the application of electrical
stimuli delivered in intermittent trains
through surface electrodes positioned
in proximity of the muscle motor point
and preprogrammed stimulation units
(Figure 1). Owing to recent advances in
EMS technology, portable and rela-
tively low-cost stimulators (300–500
U.S. dollars) can be purchased, thus are
being used by a growing number of
individuals. It is important to know the
stimulus parameters, how contractions
are triggered by EMS, and the effect of
EMS on neuromuscular function to
optimize its use and minimize the
possible risks. After a brief overview
of the methodological and physiolog-
ical aspects of EMS, this article will try
to answer these important questions on
appropriate use of EMS in sports
training:
Does EMS improve muscle
strength?
Could EMS improve sport
performance?
Recommendations and practical exam-
ples of EMS use will also be provided.
METHODOLOGICAL ASPECTS OF
EMS: THE MAIN PARAMETERS
The main stimulus parameters for
EMS, dictated by the physiological
characteristics of nerves and muscles,
include
Frequency (number of pulses per
second);
Intensity, or current amplitude
(probably the most important
parameter);
KEY WORDS:
maximal strength; jump ability; sprint
ability; strength training; sport
performance; neuromuscular electrical
stimulation
VOLUME 33 | NUMBER 1 | FEBRUARY 2011 Copyright ÓNational Strength and Conditioning Association
70
Pulse characteristics (shape and
duration);
On/off cycle or duty cycle (to
minimize the occurrence of fatigue);
Ramping (to reduce contraction
abruptness and to improve comfort);
Electrode material, size, and
placement.
At present, there is no general consen-
sus on the optimal stimulus parame-
ters, so that considerable heterogeneity
exists between the different EMS
studies. There is nevertheless an in-
formal agreement on some current
characteristics. For example, EMS
strength training is commonly realized
using biphasic symmetrical rectangular
pulses lasting 100–500 microseconds
and being delivered at a pulse rate of
50–100 Hz (35) to maximize the level
of evoked force (muscle tension). For
the same reason, current amplitude
should be at the maximum level
tolerated by the participants (18).
Unfortunately, a detailed and complete
description of the EMS procedures
(including stimulus parameters) is fre-
quently lacking. Even if EMS param-
eters may facilitate the effectiveness of
EMS, the practitioners agree that there
is considerable subject variation in
response to EMS, and optimization
may relate more to the subject than to
the stimulus parameters themselves
(20). Similarly, Lieber and Kelly (19)
suggest that the effectiveness of EMS
would not depend on external control-
lable factors (such as electrode size or
stimulation current) but rather on
some intrinsic anatomical/neuromus-
cular characteristics.
PHYSIOLOGICAL ASPECTS OF
EMS: MOTOR UNIT RECRUITMENT
During voluntary contractions, motor
units are activated according to their
size and threshold of recruitment, that
is, small low-threshold motor units are
recruited before large high-threshold
ones. On the other hand, when skeletal
muscles are artificially activated by
EMS, the involvement of motor units
is different from that underlying vol-
untary activation. The main argument
supporting this difference is that large
diameter axons are more easily excited
by electrical stimuli, which would alter
the activation order during EMS
compared with voluntary contractions
(9). However, human experiments
yielded contradictory findings with
some studies suggesting preferential/
selective activation of fast motor units
with EMS and others demonstrating
minimal or no difference between the
2 contraction modalities (for an over-
view of these studies, see (12)).
In a recent review article, Gregory and
Bickel (12) suggested that EMS-
induced motor unit recruitment is
nonselective/random (also see (15)),
that is, muscle fibers are recruited
without obvious sequencing related
to their types; thus, EMS can be used
to activate fast motor units (in addition
to the slow ones) at relatively low force
levels. The principal differences in
motor unit recruitment between vol-
untary and stimulated contractions are
summarized in Table 1.
The main consequence of such unique
motor unit recruitment patterns is the
exaggerated metabolic cost of an EMS
contraction (36), which—compared
with a voluntary action of the same
intensity—provokes greater and earlier
muscle fatigue (16,34). According to
Vanderthommen and Duchateau (35),
these differences in motor unit re-
cruitment and thus in metabolic de-
mand between electrically evoked and
voluntary contractions constitute an
argument in favor of the combination
of these 2 modalities of activation in
the context of sports training.
EFFECT OF EMS TRAINING ON
MUSCLE STRENGTH
For unimpaired muscles, EMS train-
ing–induced strength gains are similar
Figure 1. Typical settings of isometric EMS exercise for the quadriceps muscle. MVC = maximal voluntary contraction.
Strength and Conditioning Journal | www.nsca-lift.org 71
(and complementary) to, but not
greater than, those that can be achieved
with traditional voluntary training. In
a recent systematic review of EMS
studies, Bax et al. (2) concluded that
for impaired quadriceps (postinjury or
postoperative subjects), EMS training
could be more effective than voluntary
training, whereas for unimpaired quad-
riceps (healthy subjects), the effective-
ness of EMS training is generally lower
compared with those of voluntary
modalities. Training studies performed
in the past 20 years have also demon-
strated that it is possible to obtain
significant improvements of muscle
strength—particularly for the lower
extremity muscles—in amateur and com-
petitive athletes of all levels (Table 2).
EMS training–induced increases in
muscle strength are largely mediated
by neural adaptations, for example,
increased muscle activation (26), par-
ticularly in the case of short-term
training programs. On the other hand,
EMS regimens of longer duration can
elicit morphological changes in the
muscle (11). In their study, Gondin
et al. (11) demonstrated the time
course of neuromuscular adaptations
to EMS strength training. After 4
weeks of training, strength increases
were accompanied by increased
muscle activation, whereas the cross-
sectional area of the muscle was not
significantly modified. Interestingly,
both neural and muscular adaptations
mediated the strength improvements
observed after 8 weeks of EMS, similar
to the classical model proposed by Sale
(30) for neuromuscular adaptations to
voluntary strength training.
In summary, does EMS improve
muscle strength? Yes, but results differ
according to the muscle status:
For unimpaired muscles, EMS is
effective but not more than volun-
tary training;
For impaired muscles, EMS can be
more effective than voluntary training;
For athletes, EMS is effective for
increasing general not necessarily
specific strength.
These studies are examples of the
potential complementary role EMS
could play in conventional strength
training. The next avenue to explore is
how EMS could be practically applied
to various sports.
EFFECT OF EMS TRAINING ON
SPORT PERFORMANCE
Several studies involving individual and
team sport athletes have reported a
significant improvement in maximal
strength (as assessed using isokinetic or
isometric dynamometers), and in some
cases, even in anaerobic power pro-
duction (vertical jump and sprint
ability, as assessed using contact mats
and photoelectric cells) after EMS
training (Table 2). These improve-
ments are likely to affect the field
performance. However, because the
stress is applied during nonspecific
contractions (i.e., isometric in general),
excessive use of EMS could impair
motor coordination (13). Therefore,
performance of complex movements
requiring high levels of neuromuscular
coordination can only be obtained if
EMS is used in conjunction with
voluntary ‘‘technical’’ exercise, for ex-
ample, plyometrics (25).
In the study of Maffiuletti et al. (25),
subelite volleyball players completed
5 sets of 10 consecutive vertical jumps
immediately after EMS of the thigh and
calf muscles. Jumps were completed
starting from a standing position, squat-
ting down, and then extending the knee
in one continuous movement, so that
the first jump of a set was a counter-
movement jump and the 9 others were
a type of drop jump. To ensure maximal
intensity, hurdles and benches (approx-
imately 40 cm) were used.
As a practical recommendation for both
individual and team sports, it is sug-
gested that EMS training could be used
to enhance muscle strength and anaer-
obic performance without interfering
excessively with sport-specific training
(4,25,27). Therefore, EMS training
would be best used early in the
training season (i.e., at the beginning
of the preparatory training season), with
10–15 minutes of treatments, 2–3
sessions per week for 3–4 weeks
(21,24,27). Electrical current intensity
(in milliampere) and evoked force (as
a percentage of the maximum voluntary
contraction), which are strongly corre-
lated (21), should be strictly and
consistently controlled to allow EMS
training intensity to be carefully quan-
tified (22,32). It is recommended that
EMS should be administered, at least for
the first few training sessions (first week
of a training program), by athletic train-
ers or strength and conditioning coaches
who are familiar with the methodolog-
ical and physiological aspects of EMS
exercise.
The main interest of using EMS in high
level sport is that this modality could be
considered as a new stimulus to favor
plasticity; that is, a new form of stress
from a neuromuscular and metabolic
point of view. EMS could be particu-
larly useful for athletes whose perfor-
mance has plateaued after several years
of training and competition, but it
would be supplementary to, rather than
Table 1
Comparison of motor unit recruitment between voluntary and EMS
contractions
Voluntary contraction EMS contraction
Selective (slow to fast) Nonselective/random (both slow and fast)
Asynchronous Synchronous
Rather dispersed Spatially fixed
Rotation is possible Superficial (close to electrodes)
Complete (at maximal level) Incomplete (even at maximal level)
VOLUME 33 | NUMBER 1 | FEBRUARY 2011
72
Strength Training by Electrical Stimulation
a substitute for, more traditional forms
of training (21). Another interest of
EMS for elite sportsmen is that a single
EMS bout is usually less time consum-
ing (12–18 minutes) than traditional
volitional exercise sessions. This is
extremely appealing for athletes who
have a limited amount of time for
conditioning (e.g., tennis players). It is
not tempting to suggest that EMS
could replace traditional strength
training methods, but rather, EMS has
to be considered as an important
complement/supplement to conven-
tional (voluntary) training programs (21).
As shown in Table 2, research in this
area has examined the effect of EMS
on performance enhancement of elite
and subelite (noninjured) athletes in
individual and team sports, such as ice
hockey, basketball, volleyball, soccer,
track and field, swimming, tennis,
weightlifting and rugby.
As an example, Willoughby and
Simpson (39) examined the effect of
EMS and dynamic contractions supple-
mented with EMS applied during
weightlifting exercises on knee extensor
strength and vertical jump performance.
Based on a pre- to posttraining compar-
ison among 3 experimental groups
(weight training only, EMS only, and
weight training plus EMS), they sug-
gested that supplementing dynamic
contractions with EMS could be more
effective than either EMS or weight
training in isolation for increasing knee
extensor strength and vertical jump
performance. These results are compat-
ible with previous findings by the same
authors (38) who examined EMS
training–induced strength gains in
college basketball players.
From all the EMS studies conducted in
competitive athletes, only one concen-
trated on long-term (12 weeks) training
effects in professional rugby players (1).
In this study, EMS was delivered to the
knee extensor, plantar flexor, and gluteus
maximus muscles of 15 experimental
subjects with 10 other individuals serving
as controls. After 12 weeks of carefully
monitored procedures, the EMS group
showed a significant increase in maximal
concentric/eccentric torque, squat
strength, and squat and drop jump
height, compared with the controls.
Based on these findings, 12 weeks of
EMS training had a significant effect on
muscle strength and power of elite rugby
players, although their specific skills like
scrummagingandsprintingwerenot
affected by EMS.
In summary, does EMS could improve
sport performance? If it is adequately
combined with technical training (e.g.,
plyometric) and logically integrated into
yearly training season, improvements
could be achieved in the following
capabilities:
Jumping ability (both general and
specific jumps)
Sprinting ability (including shuttle
sprints)
Other sport performances (swim-
ming, weightlifting, and shooting)
PROBLEM STATEMENT AND
CONCLUSIONS
Numerous studies have shown the
effectiveness of EMS on healthy un-
trained and trained individuals includ-
ing athletes. However, the significance
of the observed improvements is
partially compromised by factors such
Table 2
EMS strength training in competitive sport
Year 1st author Sport Muscle Weeks (x/wk) Type of EMS (settings;
frequency [Hz]) Main findings
1989 Delitto (8) Weightlifting Q 6 (3) I-LE; 2500 [weightlifting
1989 Wolf (40) Tennis Q 3 (4) C-S; 75 [strength, sprint, jump
1995 Pichon (29) Swimming LD 3 (3) I-OC; 80 [strength, swimming
1996 Willoughby (38) Basketball BB 6 (3) I-PC; 2500 [strength
1998 Willoughby (39) Track and field Q 6 (3) C/E-LE; 2500 [strength, jump
2000 Maffiuletti (24) Basketball Q 4 (3) I-LE; 100 [strength, jump
2002 Malatesta (27) Volleyball Q + TS 4 (3) I-S; 105–120 [strength, jump
2002 Maffiuletti (25) Volleyball Q + TS 4 (3) I-LE/SC; 120 [strength, jump
2005 Brocherie (4) Ice hockey Q 3 (3) I-LE; 85 [strength, sprint
2007 Babault (1) Rugby Q + TS + G 6 (1–3) I-LE/CM; 100 [strength, jump
2009 Maffiuletti (23) Tennis Q 3 (3) I-LE; 85 [strength, sprint, jump
2010 Billot (3) Soccer Q 5 (3) I-LE; 100 [strength, shoot
[= increased; BB = biceps brachii; C = concentric; CM = calf machine; G = gluteus; E = eccentric; I = isometric; LD = latissimus dorsi; LE = leg
extension; MT = motor threshold; OC = open chain; PC = preacher curl; Q = quadriceps; S = squat; SC = standing calf; TS = triceps surae; x/wk =
training sessions per week.
Strength and Conditioning Journal | www.nsca-lift.org 73
as the pretraining status of the subjects,
lack of standardization of methods, or
testing protocols (31). For example,
while the study by Venable et al. (37)
on short-term EMS training found no
effect on muscular strength, vertical
jump performance, or power, a recent
study by Babault et al. (1) on long-term
EMS training reported significant in-
creases in muscle strength and vertical
jump ability of elite athletes.
Some studies support EMS methodol-
ogy and its training modalities in
enhancing the contractile quality of
muscle under isometric conditions
(12), whereas others support EMS in
combination with dynamic contrac-
tions to increase muscle strength (38).
Hence, any standardization methods
or testing protocol must take such
factors into consideration. Such dis-
parities in the findings warrant further
systematic research that considers the
possible impact of those factors on
EMS effectiveness.
In conclusion, EMS has been con-
firmed to be an important complement
to conventional strength training pro-
grams for the enhancement of athletic
performance. EMS can also be applied
in conjunction with sport-specific
training in annual periodic training
schedules (Figure 2). However, as is
apparent in this brief literature review,
there is heterogeneity in the magnitude
of improvements between studies,
depending on factors such as EMS
intensity, the modality of EMS appli-
cation, frequency, time course, recov-
ery between EMS protocols, and
implementation of EMS into annual
periodic sports conditioning. Future
research should focus on reaching
a solid conclusion to ascertain its
effectiveness on athletic performance.
Kayvan Seyri is
the athletic perfor-
mance trainer for
the U18 England
women’s National
Basketball Team
and the owner of
Kayvan Seyri’s
Personal Training
in London, United Kingdom.
Nicola A. Maf-
fiuletti is the
director of the
Neuromuscular
Research Labora-
tory at the
Schulthess Clinic
in Zurich (Swit-
zerland) and an
assistant professor at the University of
Burgundy in Dijon (France).
REFERENCES
1. Babault N, Cometti G, Bernardin M,
Pousson M, and Chatard JC. Effect of
electromyostimulation training on muscle
strength and power of elite rugby players.
J Strength Cond Res 21: 431–437, 2007.
2. Bax L, Staes F, and Verhagen A. Does
neuromuscular electrical stimulation
strengthen the quadriceps femoris? A
systematic review of randomised controlled
trials. Sports Med 35: 191–212, 2005.
3. Billot M, Martin A, Paizis C, Cometti C, and
Babault N. Effects of an electrostimulation
training program on strength, jumping, and
kicking capacities in soccer players.
J Strength Cond Res 24: 1407–1413,
2010.
4. Brocherie F, Babault N, Cometti G,
Maffiuletti N, and Chatard JC.
Electrostimulation training effects on the
physical performance of ice hockey players.
Med Sci Sports Exerc 37: 455–460, 2005.
5. Bompa TO. Annual training program. In:
Periodization: Theory and Methodology of
Training (4th ed). Champaign, IL: Human
Kinetics, 1999. pp. 215.
6. Currier DP, Lehman J, and Lightfoot P.
Electrical stimulation in exercise of the
quadriceps femoris muscle. Phys Ther
59: 1508–1512, 1979.
7. Currier DP and Mann R. Muscular strength
development by electrical stimulation in healthy
individuals. Phys Ther 63: 915–921, 1983.
Figure 2. Example of annual training plan, including EMS, for team sports (basketball). Inspired from Bompa (5).
VOLUME 33 | NUMBER 1 | FEBRUARY 2011
74
Strength Training by Electrical Stimulation
8. Delitto A, Brown M, Strube MJ, Rose SJ,
and Lehman RC. Electrical stimulation of
quadriceps femoris in an elite weight lifter:
a single subject experiment. Int J Sports
Med 10: 187–191, 1989.
9. Enoka RM. Activation order of motor axons
in electrically evoked contractions. Muscle
Nerve 25: 763–764, 2002.
10. Erickson E, Haggmark T, Kiessling L, and
Karlson J. Effect of electrical stimulation on
human skeletal muscle. Int J Sports Med
2: 18–22, 1981.
11. Gondin J, Guette M, Ballay Y, and Martin A.
Electromyostimulation training effects on
neural drive and muscle architecture. Med
Sci Sports Exerc 37: 1291–1299, 2005.
12. Gregory CM and Bickel CS. Recruitment
patterns in human skeletal muscle during
electrical stimulation. Phys Ther 85:
358–364, 2005.
13. Holcomb W. Is neuromuscular electrical
stimulation an effective alternative to
resistance training? Strength Cond J 27:
76–79, 2005.
14. Johnston D, Thurston P, and Ashcroft P.
The Russian technique of faradism in the
treatment of chondromalacia patellae.
Physiother Can 29: 1–4, 3, 1977.
15. Jubeau M, Gondin J, Martin A, Sartorio A,
and Maffiuletti NA. Random motor unit
activation by electrostimulation. Int J Sports
Med 28: 901–904, 2007.
16. Jubeau M, Sartorio A, Marinone PG, Agosti F,
Van Hoecke J, Nosaka K, and Maffiuletti NA.
Comparison between voluntary and
stimulated contractions of the quadriceps
femoris for growth hormone response and
muscle damage. J Appl Physiol 104:
75–81, 2008.
17. Kots YM. Electrostimulation. Paper
presented at: Symposium on
Electrostimulation of Skeletal Muscles,
Canadian-Soviet Exchange Symposium,
Concordia University; Montreal, Quebec,
Canada, December 6–15, 1977. Quoted
in: Kramer J, Mendryk SW. Electrical
stimulation as a strength improvement
technique. J Orthop Sports Phys Ther 4:
91–98, 1982.
18. Lake DA. Neuromuscular electrical
stimulation. An overview and its application
in the treatment of sports injuries. Sports
Med 13: 320–336, 1992.
19. Lieber RL and Kelly MJ. Factors influencing
quadriceps femoris muscle torque using
transcutaneous neuromuscular electrical
stimulation. Phys Ther 71: 715–721,
1991; discussion 722–713.
20. Lloyd T, De Domenico G, Strauss G, and
Singer K. A review of the use of electro-
motor stimulation in human muscles. Aust J
Physiother 32: 18–30, 1986.
21. Maffiuletti NA. The use of electrostimulation
exercise in competitive sport. Int J Sports
Physiol Perform 1: 406–407, 2006.
22. Maffiuletti NA. Physiological and
methodological considerations for the use
of neuromuscular electrical stimulation. Eur
J Appl Physiol. 110: 223–234, 2010.
23. Maffiuletti NA, Bramanti J, Jubeau M, Bizzini M,
Deley G, and Cometti G. Feasibility and
efficacy of progressive electrostimulation
strength training for competitive tennis
players. J Strength Cond Res 23: 677–
682, 2009.
24. Maffiuletti NA, Cometti G, Amiridis IG,
Martin A, Pousson M, and Chatard JC. The
effects of electromyostimulation training
and basketball practice on muscle strength
and jumping ability. Int J Sports Med 21:
437–443, 2000.
25. Maffiuletti NA, Dugnani S, Folz M, Di Pierno E,
and Mauro F. Effect of combined
electrostimulation and plyometric training on
vertical jump height. Med Sci Sports Exerc
34: 1638–1644, 2002.
26. Maffiuletti NA, Pensini M, and Martin A.
Activation of human plantar flexor muscles
increases after electromyostimulation
training. J Appl Physiol 92: 1383–1392,
2002.
27. Malatesta D, Cattaneo F, Dugnani S, and
Maffiuletti NA. Effects of
electromyostimulation training and
volleyball practice on jumping ability.
J Strength Cond Res 17: 573–579, 2003.
28. Nitz AJ and Dobner JJ. High-intensity
electrical stimulation effect on thigh
musculature during immobilisation for knee
sprain. J Phys Ther 67: 219–222, 1987.
29. Pichon F, Chatard JC, Martin A, and
Cometti G. Electrical stimulation and
swimming performance. Med Sci Sports
Exerc 27: 1671–1676, 1995.
30. Sale DG. Neural adaptation to resistance
training. Med Sci Sports Exerc 20(5 Suppl):
S135–S145, 1988.
31. Requena Sa
´nchez B, Padial Puche P,
Gonza
´lez-Badillo JJ. Percutaneous
electrical stimulation in strength training:
An update. J Strength Cond Res 19: 438–
448, 2005.
32. Stevens JE, Mizner RL, and Snyder-
Mackler L. Neuromuscular electrical
stimulation for quadriceps muscle
strengthening after bilateral total knee
arthroplasty: A case series. J Orthop
Sports Phys Ther 34: 21–29, 2004.
33. Siff M. Applications of electrostimulation in
physical conditioning: A review. J Appl
Sport Sci Res 4: 20–26, 1990.
34. Theurel J, Lepers R, Pardon L, and
Maffiuletti NA. Differences in
cardiorespiratory and neuromuscular
responses between voluntary and
stimulated contractions of the quadriceps
femoris muscle. Respir Physiol Neurobiol
157: 341–347, 2007.
35. Vanderthommen M and Duchateau J.
Electrical stimulation as a modality to
improve performance of the neuromuscular
system. Exerc Sport Sci Rev 35: 180–185,
2007.
36. Vanderthommen M, Duteil S, Wary C,
Raynaud JS, Leroy-Willig A, Crielaard JM,
et al. A comparison of voluntary and
electrically induced contractions by
interleaved 1H- and 31P-NMRS in humans.
J Appl Physiol 94: 1012–1024, 2003.
37. Venable MP, Collins MA, O’Bryant HS,
Denegar CR, Sedivec JM, and Alons G.
Effect of supplemental electrical
stimulation on the development of strength,
vertical jump performance and power.
J Strength Cond Res 5: 139–143, 1991.
38. Willoughby DS and Simpson S. The effects
of combined electromyostimulation and
dynamic muscular contractions on the
strength of college basketball players.
J Strength Cond Res 10: 40–44, 1996.
39. Willoughby DS and Simpson S.
Supplemental EMS and dynamic weight
training: Effects on knee extensor strength
and vertical jump of female college track
and field athletes. J Strength Cond Res
12: 131–137, 1998.
40. Wolf SL, Ariel GB, Saar D, Penny A, and
Railey P. The effect of muscle stimulation
during resistive training on performance
parameters. Am J Sports Med 14: 18–23,
1989.
Strength and Conditioning Journal | www.nsca-lift.org 75
