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Effects of Electromyostimulation Training on Muscle Strength and Power of Elite Rugby Players

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The present study investigated the influence of a 12-week electromyostimulation (EMS) training program performed by elite rugby players. Twenty-five rugby players participated in the study, 15 in an electrostimulated group and the remaining 10 in a control group. EMS was conducted on the knee extensor, plantar flexor, and gluteus muscles. During the first 6 weeks, training sessions were carried out 3 times a week and during the last 6 weeks, once a week. Isokinetic torque of the knee extensors was determined at different eccentric and concentric angular velocities ranging from -120 to 360 degrees .s(-1). Scrummaging and full squat strength, vertical jump height and sprint-running times were also evaluated. After the first 6 weeks of EMS, only the squat strength was significantly improved (+8.3 +/- 6.5%; p < 0.01). After the 12th week, the -120 degrees .s(-1) maximal eccentric, 120 and 240 degrees .s(-1) maximal concentric torque (p < 0.05), squat strength (+15.0 +/- 8.0%; p < 0.001), squat jump (+10.0 +/- 9.5%; p < 0.01), and drop jump from a 40-cm height (+6.6 +/- 6.1%; p < 0.05) were significantly improved. No significant change was observed for the control group. A 12-week EMS training program demonstrated beneficial effects on muscle strength and power in elite rugby players on particular tests. However, rugby skills such as scrummaging and sprinting were not enhanced.
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431
Journal of Strength and Conditioning Research, 2007, 21(2), 431–437
2007 National Strength & Conditioning Association
E
FFECTS OF
E
LECTROMYOSTIMULATION
T
RAINING ON
M
USCLE
S
TRENGTH AND
P
OWER OF
E
LITE
R
UGBY
P
LAYERS
N
ICOLAS
B
ABAULT
,
1
G
ILLES
C
OMETTI
,
2
M
ICHEL
B
ERNARDIN
,
3
M
ICHEL
P
OUSSON
,
4
AND
J
EAN
-C
LAUDE
C
HATARD
5
1
Faculty of Sport Science, Marc Bloch University, Strasbourg, France;
2
Performance Expertise Center, Faculty of
Sport Science, University of Burgundy, Dijon, France;
3
French Rugby Federation, Paris, France;
4
INSERM/ERM
207 Motricity-Plasticity, Faculty of Sport Science, University of Burgundy, Dijon, France;
5
Laboratory of
Physiology, St-Etienne, France.
A
BSTRACT
.Babault, N., G. Cometti, M. Bernardin, M. Pousson,
and J.-C. Chatard. Effects of electromyostimulation training on
muscle strength and power of elite rugby players. J. Strength
Cond. Res. 21(2):431–437. 2007.—The present study investigat-
ed the influence of a 12-week electromyostimulation (EMS)
training program performed by elite rugby players. Twenty-five
rugby players participated in the study, 15 in an electrostimu-
lated group and the remaining 10 in a control group. EMS was
conducted on the knee extensor, plantar flexor, and gluteus mus-
cles. During the first 6 weeks, training sessions were carried out
3 times a week and during the last 6 weeks, once a week. Iso-
kinetic torque of the knee extensors was determined at different
eccentric and concentric angular velocities ranging from 120
to 360·s
1
. Scrummaging and full squat strength, vertical jump
height and sprint-running times were also evaluated. After the
first 6 weeks of EMS, only the squat strength was significantly
improved (8.3 6.5%; p0.01). After the 12th week, the
120·s
1
maximal eccentric, 120 and 240·s
1
maximal concen-
tric torque (p0.05), squat strength (15.0 8.0%; p0.001),
squat jump (10.0 9.5%; p0.01), and drop jump from a 40-
cm height (6.6 6.1%; p0.05) were significantly improved.
No significant change was observed for the control group. A 12-
week EMS training program demonstrated beneficial effects on
muscle strength and power in elite rugby players on particular
tests. However, rugby skills such as scrummaging and sprinting
were not enhanced.
K
EY
W
ORDS
. isokinetic torque, scrum, sprint, vertical jump
I
NTRODUCTION
Rugby competition is typically characterized by
high-intensity activities (15% of the game
time) interspersed with low-intensity activities
(11). On average, 70% of the high-intensity ac-
tions last from 4 to 10 seconds with the major-
ity of rest periods being shorter than 40 seconds (26).
Therefore, in addition to equally essential technical skills
and aerobic endurance (required for low-intensity activi-
ties), rugby players must have sufficient anaerobic capac-
ities to produce high levels of muscular strength, power,
and speed (4, 8) required for heavy physical body contacts
and sprints with or without the ball. As a matter of fact,
professionals appear stronger and more powerful than
younger players for both the upper and lower body (3).
Consequently, before and during the rugby season, play-
ers participate in resistance training programs designed
to improve and maintain their anaerobic parameters at
high levels during the entire competition season (2).
Various training modalities can be used for improving
muscular strength. More particularly, electromyostimu-
lation (EMS) has been previously employed as a means
of strength training in healthy humans (18, 31, 33). Many
authors have reported increases in maximal voluntary
torque during isometric actions for joint angles close to
the training angle (20) and during isokinetic solicitations
for a wide range of concentric and eccentric angular ve-
locities (10, 20). Nevertheless, while monoarticular per-
formance enhancements are well established, the EMS
training effects during complex and specific polyarticular
abilities remain unclear. Indeed, immediate significant
improvements of the vertical jump height have been re-
corded (21, 38) but remain debated (9, 24). For example,
Malatesta et al. (24) only registered vertical jump im-
provements 10 days after the end of the EMS training.
Performance improvements, induced by EMS, may origi-
nate from neural factors (10, 13, 22) as well as changes
in the muscle itself (15, 32) but seem to be closely related
to training durations. Neural adaptations, revealed by
both muscular activation and electromyographic activity
increases, are mainly obtained after short EMS training
periods (4 weeks) (15, 22), whereas longer training du-
rations (e.g., 8 weeks) are accompanied by significant
muscular hypertrophy (15, 32).
Recently, some studies have examined the training-
induced adaptations following short-term EMS programs
on specific athlete performance of various team sports (9,
20, 21). However, no study has attempted to investigate
EMS training effects in rugby players. Therefore, the
main purpose of the present investigation was to deter-
mine the influence of an EMS training program on mus-
cle strength and power of elite rugby players. Studies re-
lated with EMS predominantly considered short periods
(4 weeks). Therefore, long-term effects were investigat-
ed here while performing 12 weeks of EMS training. Be-
cause highly skilled rugby players were considered, this
12-week training duration seems more appropriate for
neuromuscular adaptations and for neuromuscular per-
formance improvements during complex and specific abil-
ities. The training program was divided into two 6-week
intervals to simulate a taper period. We, therefore, hy-
pothesized that 12 weeks of EMS training was beneficial
for elite rugby players and that reducing training sessions
during the last 6 weeks was associated with additional
physical performance improvements.
M
ETHODS
Experimental Approach to the Problem
This study was designed to determine whether a long-
term EMS training program (12 weeks) has beneficial ef-
432 B
ABAULT
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OMETTI
,B
ERNARDIN ET AL
.
F
IGURE
1. Illustration of the training procedure for both elec-
trostimulated (ES) and control groups (C). During the experi-
mental procedure, both groups performed rugby trainings with
the same coach (5 sessions a week). In addition, the ES group
underwent a 12-week electromyostimulation (EMS) training.
Tests at week 6 and 12 were the same as those performed be-
fore training. MVC maximal voluntary contraction; 1RM
1 repetition maximum; SJ squat jump; CMJ counter
movement jump; DJ drop jump; 15J 15 consecutive CMJ.
fects in elite rugby players. Muscular adaptations were
investigated by measuring the isokinetic torque during
maximal voluntary eccentric and concentric knee exten-
sions, scrummaging, and full squat strength, vertical
jump performance, and sprint-running times. These var-
iables were tested on 3 occasions: pretraining (week 0,
beginning of the EMS training), mid-training (week 6),
and posttraining (week 12). Two groups of elite rugby
players were considered. During the 12-week period, the
first group (control, C) only followed rugby trainings. The
second group (electrostimulated, ES), in addition to the
same rugby training, underwent a 12-week EMS training
on the knee extensor, plantar flexor, and gluteus muscles.
During the first 6 weeks, the EMS training program con-
sisted of 3 sessions a week. Only 1 session per week was
applied during the remaining 6 weeks to simulate a taper
period (Figure 1). Statistical analyses of pretraining, mid-
training, and posttraining values allowed us to evaluate
the effect of 12-week EMS training on physical perfor-
mances of elite rugby players. Independent variables
were time (pretraining, midtraining, and posttraining)
and group (ES and C). Values obtained for the different
tests were used as dependent variables.
Subjects
A group of 25 highly skilled rugby players competing in
the first or second division of the French Rugby league
(with 3 players also competing in the national French
team) participated in this study. All were members of the
national French military team and were trained by the
same coach. They were randomly divided into 2 groups.
Fifteen subjects were assigned to the electrostimulation
group (ES) and the remaining 10 served as controls (C).
Mean age, height, and mass were 22 1 year, 187.0
8.5 cm, 93.2 13.0 kg and 22 1 year, 180.5 3.2 cm,
85.9 10.6 kg, respectively, for ES and C groups. After
being informed about the nature of the experiment, sub-
jects agreed to take part in the study on a voluntary basis
and provided their written informed consent for partici-
pation. The experimental procedure was performed in ac-
cordance with the declaration of Helsinki and was ap-
proved by the local committee of human research.
Procedures
Training. The present experiment started about 2 weeks
after the end of the midwinter break. During this period,
all athletes (i.e., ES and C group) took part in specific
rugby workouts supervised by the national French mili-
tary team coach (5 sessions a week including, e.g., defen-
sive and attacking fundamentals). Special attention was
given to reduce any training difference depending on
player positions, and none of the subjects completed ad-
ditional weight training. In addition to this rugby train-
ing, the ES group performed an EMS training program
lasting 12 weeks. The EMS program was divided into 2
periods. The first 6 weeks consisted of 18 EMS sessions
(12 minutes for each muscle group) with 3 sessions a
week. During the remaining 6-week period, EMS training
was composed of only 1 EMS session per week (Figure 1).
EMS sessions were performed at the same time of the day
and same days of the week.
EMS was delivered bilaterally on knee extensor, then
plantar-flexor, and finally gluteus muscles using a por-
table battery-powered stimulator (Compex Medical SA,
Ecublens, Switzerland). Rectangular-wave pulsed cur-
rents (100 Hz) lasting 400 s were used as previously
recommended (16, 36). Indeed, rectangular waves asso-
ciated with long pulse durations (300 to 400 s) appear
to produce the most powerful contraction of the quadri-
ceps muscle group (7); 100 Hz stimulation frequencies
were used because 50 to 120 Hz frequencies have been
shown to be the most efficient for strength training (16).
During the 12-minute EMS sessions, contractions, lasting
5 seconds, were followed by 15 seconds of rest. During
each session and for each muscle group, 36 contractions
were completed. These stimulation characteristics were
selected among the Compex commercially available
strength programs. Because elite athletes were consid-
ered, the most difficult strength program was chosen and
E
LECTROSTIMULATION IN
R
UGBY
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433
slightly modified (i.e., contraction number, rest time) to
reduce EMS sessions durations. The stimulation intensity
(range 0–100 mA) was monitored on-line and determined
by the subject at the start of each EMS session according
to his pain threshold and so as to produce a force corre-
sponding to at least 60% of the pretest maximal voluntary
contraction (MVC) score. This level was measured and
verified by the examiner on the knee extensor muscles
with a myostatic type dynamometer (Allegro, Sallanches,
France). No subject reported serious discomfort from this
current. Each session was preceded by a standardized
warm-up, consisting of 5 minutes of submaximal EMS (5
Hz pulses; pulses lasting 200 s).
The EMS was delivered using 2-mm thick self-adhe-
sive electrodes. Pairs of positive electrodes (each measur-
ing 25 cm
2
;5cm5 cm), which have the property of
depolarizing the membrane, were placed as close as pos-
sible to the motor point of the vastus lateralis, vastus me-
dialis, medial and lateral gastrocnemius, and gluteus
maximus muscles. Rectangular negative electrodes, each
measuring 50 cm
2
(10 cm 5 cm), were placed over the
femoral triangle of each leg (1–3 cm below the inguinal
ligament), over the proximal aspect of the gastrocnemii
and gluteus, i.e., close to the proximal insertion of the
respective muscle. During EMS of the knee extensor mus-
cles, subjects were seated on a leg extension machine
(Multiform, La Roque D’Anthe´ ron, France) with the knee
flexed and fixed at a 60joint angle (0corresponding to
complete knee extension). For plantar flexor muscles
EMS, subjects were seated on a calf machine (Multiform)
with joint angles at the hip, knee and ankle maintained
at 90. The subjects lay in the prone position during
EMS of the gluteus muscles.
Testing
Tests were carried out in both groups before (week 0), in
the middle (week 6), and immediately after the end of the
training period (week 12) (Figure 1). Tests, conducted in
a single session, consisted in the evaluation of (a) mus-
cular strength by measuring the maximal voluntary iso-
kinetic eccentric and concentric torque production capac-
ity, scrimmaging, and squat strength and (b) power with
the determination of vertical jump heights and power and
sprint-running times.
Isokinetic Tests. The maximal voluntary torque of the
right knee extensor muscles was measured using a Biod-
ex isokinetic dynamometer (Biodex, Shirley, NY) validat-
ed by Taylor et al. (35). Subjects were seated upright on
the dynamometer chair with a 95hip angle. Velcro
straps were applied tightly across the thorax and pelvis;
the leg being fixed to the dynamometer lever-arm. The
axis of rotation of the dynamometer was aligned to the
lateral femoral condyle, indicating the anatomical joint
axis of the knee. Arms were positioned across the chest
with each hand clasping the opposite shoulder. After a
standardized warm-up session including submaximal
concentric and eccentric knee extensions with progres-
sively increasing intensity until the MVC, subjects per-
formed maximal voluntary leg extensions at 8 different
angular velocities. Two eccentric (60 and 120·s
1
) and
6 concentric (60, 120, 180, 240, 300 and 360·s
1
) angular
velocities were considered. Three consecutive contrac-
tions were achieved for each angular velocity and only the
best peak voluntary torque was retained for analysis. An-
gular velocities were randomly presented and a 4-minute
rest period was allowed between each velocity to avoid
fatigue effects. Leg extensions were conducted within a
90range of motion (from 90 to 0;0corresponding to the
complete knee extension). Appropriate corrections were
made for the gravitational effect of the leg for all torque
measurements. Whatever the contraction, subjects were
strongly encouraged by the same investigator to push as
hard as possible to perform all actions maximally, i.e.,
throughout the whole range of motion for concentric and
eccentric contractions.
Scrum Test. Specific rugby strength was measured us-
ing a scrum machine (Multiform). The isometric scrum-
maging force was assessed by means of strain gauge force
transducers (Captels, St. Mathieu de Tre´ viers, France).
The scrum machine was fixed in a horizontal position
with height adjusted according to each subject’s position.
Subjects were free to choose their scrummaging position.
Knee flexion angles and feet positions were determined
individually and fixed using wedges. Positions were re-
corded so as to be identical for all test sessions. Each play-
er was allowed to perform three 5-second trials, in which
he attempted to push as hard as possible against the 2
central pads of the machine. Four-minute rest periods
were allowed between trials. Force, measured at stabili-
zation after impact, was evaluated for all trials and only
the best performance was retained for analysis.
Squat Test. Subjects were evaluated during concentric
strength tests while performing full squats (starting po-
sition complete knee flexion). Players were tested for 1
repetition maximum (1RM) using standard Olympic style
bar and weights. Players were familiar with squats since
all have previously performed such movements during
their training program. Each subject performed submax-
imal repetitions at low weights for warm-up before grad-
ually increasing the load (10-kg increments, then 5-kg in-
crements near maximum) until the maximum. Four-
minute rest periods were allowed between trials.
Vertical Jump Tests. Jumping ability was evaluated
with a contact mat (Ergo tests, Globus, Codogne, Italy)
measuring the flight time of the jumps. Squat jumps (SJ),
counter movement jumps (CMJ), drop jumps (DJ), and 15
repetitive CMJ (15J) were randomly performed. For each
test, subjects were asked to jump as high as possible with
their hands kept on the hips to minimize the contribution
of the upper body. The SJ started from a static semis-
quatting position (90knee flexion), maintained 1 sec-
ond; subjects were instructed to jump without any prelim-
inary movement. The CMJ started from a standing posi-
tion. Subjects were instructed to squat down until a 90
knee flexion angle and to extend the knee in 1 continuous
movement. The DJ started from a standing position at a
40-cm height above the floor. Subjects then dropped on
the contact mat, squatted down until 90knee flexion and
extended the knee in 1 continuous movement. Three tri-
als were performed for SJ, CMJ, and DJ, with a 2-minute
rest period between trials, and the best performance was
recorded. For 15J, 15 consecutive CMJ were performed
without any rest between jumps. Only 1 trial was
achieved for this jump test. The average height and power
were then calculated according to single jump flight and
contact time.
Sprint Test. Because, high-intensity rugby actions are
shorter than 10 seconds (21), running times were evalu-
ated during 20- and 50-m maximal running tracks using
infrared photoelectric cells (TT Sport, Dogana, San Ma-
rino). Cells, positioned at a 1.15-m height, were placed 20
and 50 m from the start line. Subjects started in a stand-
ing position and ran the 50-m distance as fast as possible.
During this maximal run, both the 20- and 50-m times
434 B
ABAULT
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.
F
IGURE
2. Torque-angular velocity relationships of the knee
extensors for electrostimulated (ES, upper graph) and control
groups (C, lower graph) before and after a 6-week and 12-week
period. Values are mean (SE). * Differences between values
obtained before and after the 12-week training period (p
0.05).
F
IGURE
3. Squat performance (kg) for electrostimulated and
control groups before and after a 6-week and 12-week period.
Values are mean (SE). Differences between before, week 6,
and week 12 are shown (* p0.05, ** p0.01, and *** p
0.001).
F
IGURE
4. Scrummaging performance (kg) for electrostimu-
lated and control groups before and after a 6-week and 12-
week period. Values are mean (SE). The electrostimulated
(ES) group showed significantly higher values than the control
(C) group. Whatever the group, no difference was obtained
with time (before vs. week 6 vs. week 12).
were measured. These performances did not include the
reaction time. Three trials were performed with a 4-min-
ute rest period, and the best performance was retained
for subsequent statistical analysis.
Statistical Analyses
Mean values SD were calculated for all dependent var-
iables (i.e., knee extension torque, scrum and squat
strength, vertical jump height or power, and running
times). Figures are presented as mean value SE for
more clarity. Values were analyzed using a 2-way anal-
ysis of variance to test differences between groups (ES or
C) and time (before, after week 6, or after week 12). Time
factor was analyzed as repeated measures. Fratio was
considered significant at a plevel less than 0.05. A New-
man-Keuls post hoc test was conducted if significant main
effects or interactions were present. Statistical analyses
were undertaken using Statistica software for Windows
(StatSoft, Version 5, Tulsa, OK).
R
ESULTS
At midtraining, the ES group did not exhibit any modi-
fication of the torque-angular velocity relationship (Fig-
ure 2). After 12 weeks of training, the ES group exhibited
significant voluntary torque improvements (p0.05) un-
der eccentric (18.0 26.3% at 120·s
1
) and concentric
conditions (19.4 28.9% at 120·s
1
and 10.0 21.5%
at 240·s
1
) compared with pretraining. In the same way,
the squat strength enhancement was 8.3 6.5% and
15.0 8.0%, respectively after a 6- (p0.01) and 12-
week (p0.01) EMS training period (Figure 3). A sig-
nificant squat improvement was also recorded between
mid- and posttraining (6.2 4.9%; p0.05). The
scrummaging strength did not demonstrate any time ef-
fect (Figure 4).
A significant improvement in vertical jump height (p
0.05) was obtained after 12 weeks of EMS training for
SJ and DJ (Table 1). For these 2 tests (SJ and DJ), no
difference was recorded when comparing values regis-
tered before and after 6 weeks of EMS training. After the
12th week, the performance enhancement was 10.0
9.5% (p0.01) and 11.8 9.9% (p0.001) for SJ and
6.6 6.1% (p0.05) and 7.6 5.7% (p0.05) for
DJ when respectively compared with pre- and midtrain-
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435
T
ABLE
1. Vertical jump performances (mean value SD)on
electrostimulated (ES) and control (C) groups before and after a
6-week and 12-week training period.*
Group Before Week 6 Week 12
SJ (cm) ES 33.5 3.5 33.0 4.0 36.7 3.6 ‡
C 37.9 4.8 36.8 3.7 38.1 4.1
CMJ (cm) ES 39.0 3.9 37.2 3.6 40.1 4.3
C 42.8 5.0 42.3 4.7 43.3 4.3
DJ (cm) ES 34.6 2.5 34.3 2.9 36.7 2.2 †§
C 41.6 4.3 40.5 6.3 43.8 3.1
15J height (cm) ES 30.7 3.1 29.8 2.9 30.8 3.3
C 35.7 2.9 33.2 3.6 34.6 3.6
15J power (W) ES 37.3 6.2 38.1 5.8 40.0 6.8
C 42.3 5.7 41.0 8.3 42.7 7.1
*SJ squat jump; CMJ counter movement jump; DJ
drop jump; 15J 15 repetitive CMJ. Differences between before
and week 12 training are shown († p0.05 and p0.01).
Differences between week 6 and 12 are also shown (§ p0.05
and p0.001). Except for 15J power and SJ after week 12,
group C exhibited significantly higher values than group ES.
T
ABLE
2. Running times for electrostimulated (ES) and con-
trol (C) groups over 20 and 50 m before and after a 6-week and
12-week training period. Values are mean SD.*
Group Before Week 6 Week 12
20 m (s) ES 3.17 0.11 3.24 0.14 3.18 0.11
C 3.01 0.10 3.14 0.19 3.05 0.11
50 m (s) ES 6.82 0.29 6.92 0.33 6.82 0.26
C 6.31 0.19 6.46 0.19 6.38 0.17
* Group C exhibited significantly lower values than ES. What-
ever the group, no difference was obtained with time (before vs.
week 6 vs. week 12).
ing tests. No difference was obtained with time for ES
when considering the 2 other jump tests (i.e., CMJ and
15J) and running times (Table 2).
At baseline, the ES group exhibited significantly high-
er scrummaging values and lower vertical jump and
sprint performances than the C group. No difference was
obtained for the torque-angular velocity relationship and
squat strength. After the 6-week and 12-week periods, the
C group did not demonstrate any significant changes for
all tests.
D
ISCUSSION
EMS is largely employed for strength training but no
study has established its effect in rugby players. The
present study demonstrated that a 12-week EMS training
program has positive effects on muscle strength and pow-
er of highly skilled rugby players. Moreover, reduction of
the training session number from 3 to once a week during
the last 6 weeks, like in a taper period, was beneficial for
physical performance improvements.
After a 12-week training period, EMS produced im-
provements in (a) muscle strength as revealed by maxi-
mal voluntary torque and squat strength measurements
and (b) power (i.e., SJ and DJ height). Although per-
formed isometrically, gains were primarily registered
during dynamic and more particularly concentric actions.
Moreover, the stimulation of the main extensor muscles
of the lower limb yield to improvements in both single-
joint and multi-joint performances.
Posttraining, rugby players exhibited increases in
squat strength and maximal voluntary torque during iso-
kinetic tests performed under eccentric (120·s
1
) and
concentric conditions (120 and 240·s
1
). Magnitudes of
the relative strength increases (on average 16%) were
consistent with previous EMS studies (9, 20, 29) but ap-
peared larger than reported by others (10, 25). Gains
were obtained after the 12th week, whereas the previous
experiments consisted in shorter training programs (e.g.,
3 weeks for ref. 29). For example, after a 4-week EMS
training period, Maffiuletti et al. (20) registered a 29%
torque increase under eccentric condition at 120·s
1
.
Using slightly longer training duration (7 weeks) Colson
et al. (10) registered only 10% torque increases at a
120·s
1
eccentric angular velocity. Differences between
the present experiment and these studies could be partly
attributed to differing stimulation modes (e.g., stimula-
tion frequencies), muscle group (knee extensors vs. elbow
flexors), and training status of the subjects considered.
Indeed, in the present study, subjects were all highly
skilled rugby players. It is generally accepted that
strength gains, consecutive to training, are usually lower
for highly skilled than for sedentary subjects (1). There-
fore, long-term EMS seems to be more appropriate for
elite rugby players to improve muscle strength.
Paradoxically, the present study showed performance
improvements for squat strength and not for scrummag-
ing. High muscle strength of the whole lower body
(trained here with EMS) is needed to obtain elevated per-
formances for these 2 tests. The lack of gain in the scrum
test could be partly explained by factors such as tech-
nique or motivation. Quarrie and Wilson (30) demonstrat-
ed that the scrum force was primarily related to anthro-
pometric characteristics and physical factors such as an-
aerobic power attained on a cycle ergometer and to a less-
er extent to isokinetic knee extension torque. Therefore,
it may be postulated that isokinetic torque increases, ob-
served in the present study, were not sufficient to induce
enhancements of scrummaging performance. Further-
more, both forward and back players participated in this
experiment. Backs, uninvolved and unfamiliar with
scrummaging, were technically less skilled for strength
transfer for this type of exercise. Quarrie and Wilson (30)
noted that technique and coordination may be the most
important parameters for maximal scrum force. There-
fore, association of technique and EMS training might
lead to performance improvements and might also mini-
mize the risk of potential injury during the rugby union
scrum (27).
Muscular strength, enhanced with EMS, is an essen-
tial anaerobic characteristic for rugby players. Power, as
well as important for rugby players, was also improved
as revealed by SJ and DJ height increases. However, both
repetitive jumps (15J) and running times remained un-
changed after the 12-week training period. The lack of
change, in disagreement with previous investigations (9,
24), was unexpected since EMS was performed on the
main lower limb extensor muscles. According to Wisloff
et al. (37), gains of maximal quadriceps femoris isokinetic
torque and squat strength should have been associated
with decreased sprint times. However, Wisloff et al. (37)
suggested emphasizing concentric movements during
strength training for a better sprint improvement. Her-
rero et al. (17) also concluded that EMS training alone
did not result in any improvement in jumping height or
even interfered in sprint run. Likewise, as suggested by
Bobbert and Van Soest (5), strength-training programs
should be associated with specific exercises to improve
jumping ability by an optimization of the control of neu-
romuscular properties. Therefore, EMS training, con-
436 B
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.
ducted under isometric conditions, should be accompa-
nied with specific dynamic exercises (e.g., jumping and
sprinting) for a better power improvement.
Like in a taper period, EMS training consisted of 3
sessions a week during the first 6 weeks and only 1 ses-
sion from the sixth to the 12th week. Midtraining, our
results revealed only squat strength increases (8.3%).
Despite the reduction in the number of EMS sessions, a
squat strength improvement was also obtained between
the sixth and 12th week (6.2%). Besides, most increases
in muscle strength and power were obtained during the
second part of the training program. Indeed, voluntary
isokinetic torque and vertical jump height predominantly
increased after week 6. These results demonstrated that
reducing EMS volume (sessions per week) was beneficial
for physical performance enhancements. Quite similarly,
the reduction of heavy-resistance training session num-
ber previously exhibited strength increases but for elderly
subjects (19). With EMS, no study demonstrated the pos-
itive effects of training volume reduction. Nevertheless,
stopping EMS trainings produced persisting results (25)
or delayed positive effects (20, 24). Indeed, Malatesta et
al. (24) obtained SJ and CMJ increases 10 days after the
end of EMS training while no gain was obtained imme-
diately after the 4 weeks of training.
Except for squat strength, the absence of performance
improvements at midtraining was surprising. Indeed,
studies dealing with EMS generally registered voluntary
torque (9, 20, 29) and vertical jump height (21, 24) gains
for short training durations (4 weeks). As stated above,
this result could partly be explained by the elite training
status of our subjects. Moreover, the lack of significant
vertical jump gain at week 6 could be attributed to the
fact that subjects tested in the present study were not
specifically trained for vertical jumps. Combination of
EMS with specific exercises such as scrummaging or ver-
tical jumps might favor physical performance improve-
ments. Indeed, no gain was observed midtraining for ver-
tical jumps, whereas Maffiuletti et al. (21) registered 7
cm increases for SJ after only 4 weeks EMS combined
with plyometric exercises. More recently, Brocherie et al.
(9) suggested that EMS training programs should be of
longer duration when performed alone to achieve benefi-
cial effects in vertical jump height. Present results sup-
port this hypothesis since vertical jump improvements
(3 cm for SJ) were obtained with training duration 4
times longer than the last cited study (12 vs. 3 weeks).
Therefore, it can be concluded that long-term EMS pro-
grams (6 weeks) conducted alone or short-term pro-
grams accompanied by jump exercises are required to ob-
tain significant improvements in vertical jump height.
Mechanisms, related with muscle strength and power
increases after EMS training, may originate from central
neural drive adaptations (13, 22) and/or from peripheral
modifications, i.e., hypertrophy (12). Most authors favor
the neural drive hypothesis because EMS training is gen-
erally not long enough (5 weeks) to induce modifications
at the muscle level (15). The observed increased EMG ac-
tivity (10) and higher activation level (22) corroborate this
enhanced volitional drive originating from spinal as well
as supraspinal centers. However, the absence of reflex
modification after 4 weeks of EMS training suggests that
neural adaptations were primarily supraspinal (23). This
suggestion is reinforced by Smith et al. (34). Despite the
fairly long training period used in the present study (12
weeks), we think that performance improvements more
likely resulted from neural processes than peripheral
muscular adaptations. Peripheral adaptations would ef-
fectively produce uniform torque gains among velocities
while gains were obtained for only 3 angular velocities
and in particular under eccentric conditions (120·s
1
).
Part of this increase in eccentric torque may originate
from preferential adaptations of fast twitch fibers (22).
Indeed, EMS (14) and eccentric actions (28) have been
shown to preferentially recruit fast twitch fibers. Al-
though peripheral adaptations cannot be excluded, the in-
creased neural drive or preferential activation of fast
muscle fibers, may additionally explain the improvement
in explosive-type actions (e.g., vertical jumps) (6) by an
optimization of neuromuscular properties control during
complex dynamic tasks (24).
P
RACTICAL
A
PPLICATIONS
Muscle strength and power appear to be important pa-
rameters for rugby players’ careers. On the basis of the
present investigation, it appears that EMS can be used
on rugby players, even with highly skilled athletes, for
strength and jumping ability improvements. However,
specific rugby skills such as scrummaging and sprint-run-
ning were not improved with EMS. In the practical set-
ting, it is suggested to combine technical and more spe-
cific rugby exercises with EMS so as to optimize strength
gains. Furthermore, reducing EMS sessions during the
second half of our training program (from week 6 to week
12) demonstrated persistent physical performance en-
hancements. This result is of interest for the rugby play-
ers’ conditioning periodization. Indeed, EMS could be con-
ducted during the preseason conditioning and prolonged
during the in-season conditioning with a lower volume.
The in-season EMS volume reduction could, therefore, be
helpful for performance maintenance across the whole
season (essential for successful rugby competition). EMS
training volume should, therefore, be carefully periodized
and sequenced with complementary exercises for optimal
gains and performance preservation in elite rugby play-
ers.
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Acknowledgments
The authors gratefully acknowledge Dr. Nicola A. Maffiuletti
and Dr. Gerald G. Pope for carefully reviewing the manuscript
and English corrections.
Address correspondence to Nicolas Babault, nicolas.
babault@u-bourgogne.fr.
... The total sample size was 445 respondents, of which 158 females and 287 males. Nine studies were based on examining only the male gender (Maffiuletti et al., 2000;Brocherie et al., 2004;Herrero et al., 2005;Babault et al., 2007;Billot et al., 2010;Amaro-Gahete et al., 2016;Filipović et al., 2016;Wirtz et al., 2016), four studies included female respondents (Willoughby et al., 1998;Marqueste et al., 2010;Deley et al., 2011;Dörmann et al., 2019), while two studies included respondents of both genders (Benito-Martinez et al., 2011;Martinez-Lopez et al., 2012). The age of the respondents ranged on average from 16.16±1.72 ...
... to 27.0±7.5 years of age. One study examined the impact of EMS on physical performance of basketball players (Maffiuletti et al., 2000), hockey players (Brocherie et al. 2004), rugby players (Babault et al., 2007) and female gymnasts (Deley et al., 2011), while two studies examined this impact on football players (Billot et al., 2010;Filipović et al., 2013) and volleyball players Marqueste et al., 2010). Four studies used athletes of different orientations as a sample of respondents (Herrero et al., 2005;Amaro-Gahete et al., 2016;Wirtz et al., 2016;Dörmann et al., 2019). ...
... p<0.01 and p<0.001) of the influence of local and global EMS on the vertical jumping performance of athletes, with the help of, in total four monitored variables: SJ, CMJ, DJ and AJ. The number of monitored variables, by study, ranged from one (Willoughby & Simpson 1998;Benito-Martinez et al., 2011) to three Brocherie et al., 2004;Babault et al., 2007;Martinez-Lopez et al., 2012;Filipović et al., 2016;Dörmann et al., 2019). ...
Conference Paper
Full-text available
Electromyostimulation (EMS) represents an artificial muscle stimulation with a well-defined protocol that is precisely designed to reduce discomfort during unnatural muscle activation. The main goal was to find new information on the basis of systematic review of many studies which examined the impact of EMS on athletes vertical jumping performance, as well as to expand the already known conclusions. Electronic databases (Google Scholar, Pub Med, Web of Science and ResearchGate) were searched for the original scientific research projects on the topic of the impact of EMS on athletes' vertical jumping performance. The last search was conducted in June 2020 with a limitation to study published in English. As many as 415 scientific studies were indentified and only 15 of them were selected and then systematically reviewed and analyzed. The results of the research projects with the total sample size of 445 athletes showed that the treatment of global and local EMS, in combination with another types of training, is an effective method for the development of explosive strength, such as vertical jumping. It has been proven that the EMS represents an effective strategy for improving vertical jumping performance, as well as for improving physical performance of athletes in general.
... 6 Several studies have examined prolonged periods of no resistance training, while continuing to complete skills sessions, reporting a disparity in results. 10,11 Football players exhibited significant decreases in jump height following 16 weeks of competition and field only practices. 11 Whereas, rugby league players maintained jump height performance following 6 to 12 weeks of field only practice. ...
... 11 Whereas, rugby league players maintained jump height performance following 6 to 12 weeks of field only practice. 10 Following a typical rugby league competitive season, players have previously demonstrated trivial decreases in upper and lower body power. 12 The lack of consensus between detraining studies provides limited insight into answering the question of the effect of a cessation in training that is observed during extended periods away. ...
... 7 The paucity of research on the effects of detraining on muscular power in professional rugby league warrants further study. 6,10,11 Given the differing findings of jump performance, the varying lengths and degrees of training cessation, and the majority of the findings reporting jump heights (an indirect measure of muscular power), it is necessary to further investigate the effects of periods of no structured team-based training on muscular power in professional rugby league. 5 Of interest is the change in muscular power variables during periods away from structured team-based training, as this information may allow for more effective periodization strategies prior to, and following, no or minimal training with the aim of limiting the rate of possible muscular power decay. ...
Article
Purpose: Periods away from training and competition are necessary for physical and mental restoration in sport. There is limited research investigating changes to physical qualities in rugby league following prolonged breaks. This study aimed to evaluate the effects of the off-season on muscular power in rugby league. In addition, this study aimed to determine whether the type and volume of training players chose to complete had any relationship to feelings of restoration and/or readiness to return to training. Methods: Twenty professional rugby league players participated in this study. Lower-body muscular power was evaluated using a countermovement jump prior to the off-season and at the recommencement of training. Players completed a questionnaire to identify training and activities completed during the break and to assess feelings of restoration and readiness to commence training. Linear regression was used to estimate the effects of the number of days off on muscular power. One-way repeated-measures analysis of variance was conducted to examine differences in lower-body power throughout the study. Spearman rank order correlation was calculated to determine the relationship between off-season activities and feelings of restoration and readiness. Results: Peak velocity and peak force significantly increased following the off-season break. There were significant relationships between mental restoration and upper-body resistance training, as well as physical restoration and full-body resistance training. Conclusions: The off-season has a positive effect on a player's ability to generate muscular power. Coaches may want to encourage players to complete resistance training sessions with the aim simply to maintain training load and potentially help players to feel rested.
... [4,6,[25][26][27] For example, 12 weeks of NMES training using PC (100 Hz) in rugby players resulted in a significant improvement in squat jump (SJ) (11.8%) and drop jump (DJ) (7.6%) performance. [28] However, no study has investigated the effect of NMES training alone on jump performance. Furthermore, studies that have used AC NMES to examine its effect on jump performance are still rare and debatable. ...
... Participants were instructed to squat down until a 90 knee flexion angle and to extend the knee in 1 continuous movement. [28] All jumps were performed by both legs (bilateral jump) followed by each leg (unilateral jump) in a random order. The subjects were instructed to keep both hands on their hips during the entire test. ...
... Numerous studies have reported the effects of NMES such as PC in combination with resistance training on vertical jump performance. [4,6,[25][26][27]47] Babault et al. [28] have examined the effect of electromyostimulation (EMS) training (PC, 100 Hz) along with resistance training on the knee extensor, plantar flexor, and gluteus muscles in rugby players. Their methods of EMS training lasted for 12 weeks (three times per week in the first 6 weeks and once a week in the last 6 weeks). ...
... 7,9 Moreover, EMS has been widely used for a long time to improve muscle strength in sports medicine and physical therapy. 10 The EMS mainly affects type II muscle fibers. 11 Therefore, when applied to the muscles that are important in joint stability (such as PL), it does not only increase strength but may also improve balance, by increasing proprioceptive acuity. ...
... 19 In addition to traditional strength training, EMS was also used to improve muscle strength in athletes. 10 However, it was observed that athletes focus on large and multiple muscle groups, such as quadriceps femoris and biceps femoris in both traditional strength training and EMS applications. 20 This may lead to neglect of muscles, such as the PL and brevis, despite PL playing a key role in maintaining ankle stability. ...
Article
Purpose: The aim of this study was to evaluate the effect of 5 weeks of electromyostimulation (EMS) of the peroneus longus muscle on balance and muscle strength in American Football (AmF) players. Methods: Thirty-two healthy male athletes (4 American Football team training sessions per week, college level) were randomly divided into the EMS and control groups. The EMS applications were conducted on the dominant peroneus longus muscle 3 times per week for 5 weeks, with each application lasting 25 minutes. Before and after the interventions, the strength of ankle dorsiflexion-plantar flexion and foot eversion-inversion was measured with isometric dynamometer and anterior-posterior sway, mediolateral sway, perimeter, and ellipse area were measured with the Technobody Balance System in unilateral stance positions, while eyes were open. Results: Changes between initial and final tests for dorsiflexion and eversion strength, and mediolateral sway for dynamic balance in the groups were significantly different (P = .039, P = .027, P = .030, respectively). Conclusion: The EMS application had positive effects on muscle strength and dynamic balance of AmF players. The EMS can be used to improve isometric strength and dynamic balance in AmF players.
... It has been known for many years that muscles can be stimulated by passing an electric current through the muscle or the peripheral nerves. Many studies examining the chronic effects of EMS applications have shown an increase in strength or power [9][10][11]. However, the number of studies investigating the acute effects of EMS is scarce. ...
... This may explain the mechanism underlying the PAP effect that occurs with EMS. In this regard, using only EMS can be considered as an alternative method to reduce the risk of injury that may occur in resistance exercises using large external loads [9]. The use of EMS to create the PAP effect during the pre-competition warm-up phase can be used to reduce this risk, especially by athletes with a history of injury and at risk of injury. ...
Article
Full-text available
Post-activation potentiation (PAP) is a phenomenon which can improve force performance executed after a previous conditioning activity. PAP is usually evoked through heavy resistance, but many new methods are being suggested that acutely improve performance in post-activation potentiation protocols. The purpose of this study was to examine the effect of simultaneous application of Smith machine back squats (BS) with electromyostimulation (EMS) on sprint performance. Sixteen male (age = 22.9 ± 2.3 years, body mass = 79.9 ± 13.8 kg, BS one-repetition maximum (1 RM) = 120.5 ± 17.3) amateur football and rugby players volunteered for this study. Participants randomly performed PAP protocols (CON = no load, BS = 3 × 85% of 1 RM BS, EMS = 3 × weightless squat with electric current and BS + EMS = 3 × 85% 1 RM BS with electric current) on four different days with at least 48 h intervals. Participants rested passively for 7 min after preloads and performed the 30 m sprint test. Sprint times for 10 and 30 m were recorded for each condition. As a result, no significant difference was found in the 10 m (p = 0.13) and 30 m (p = 0.10) sprint performance between the preload protocols. The effect size was found to be trivial (ηp2: 0.13 for 10 m; ηp2: 0.11 for 30 m). In individual results, the 10 m sprint performance of five participants and 30 m sprint performance of two participants decreased in BS, EMS, or BS + EMS conditions compared with CON. No PAP effect in other participants was observed. In conclusion, preloads did not affect 10 m and 30 m sprint performance of football and rugby players. It can be said that the applied PAP protocols or physical exertion alone may cause fatigue in some individuals.
... 23 trials used a two-armed design (Amaro-Gahete et al., 2018;Avila et al., 2008;Babault et al., 2007;Billot et al., 2010;Brocherie et al., 2005;da Cunha et al., 2020;Dörmann et al., 2019;Filipovic et al., 2015Filipovic et al., , 2016Kale & Gurol, 2019;Ludwig et al., 2020;Maffiuletti et al., 2000Maffiuletti et al., , 2002Martin et al., 1994;Mathes et al., 2017;Micke et al., 2018;Miller & Thépaut-Mathieu, 1993;Oliveira et al., 2018;Pantović et al., 2015;Pichon et al., 1995;Schuhbeck et al., 2019;Wirtz et al., 2016;Zory et al., 2010), 9 studies a three-armed design (Benito-Martínez et al., 2013;Dervisevic et al., 2002;Filipovic et al., 2019;Girold et al., 2012;Gulick et al., 2011;A. J. Herrero et al., 2010aA. ...
Article
This systematic review and network meta-analysis aimed to evaluate the effectiveness of different electromyostimulation (EMS) training interventions on performance parameters in trained athletes. The research was conducted until may 2021 using the online databases PubMed, Web of Science, Cochrane and SPORTDiscus for studies with the following inclusion criteria: (a) controlled trials, (b) EMS trials with at least one exercise and/or control group, (c) strength and/or jump and/or sprint and/or aerobic capacity parameter as outcome (d) sportive/trained subjects. Standardized mean differences (SMD) with 95% confidence interval (CI) and random effects models were calculated. Thirty-six studies with 1.092 participants were selected and 4 different networks (strength, jump, sprint, aerobic capacity) were built. A ranking of different exercise methods was achieved. The highest effects for pairwise comparisons against the reference control "active control" were found for a combination of resistance training with superimposed EMS and additional jump training (outcome strength: 4.43 SMD [2.15; 6.70 CI]; outcome jump: 3.14 SMD [1.80;4.49]), jump training with superimposed whole-body electromyostimulation (WB-EMS) (outcome sprint: 1.65 SMD [0.67; 2.63 CI] and high intensity bodyweight resistance training with superimposed WB-EMS (outcome aerobic capacity: 0.83 SMD [-0.49; 2.16 CI]. These findings indicate that the choice of EMS-specific factors such as the EMS application mode, the combination with voluntary activation, and the selection of stimulation protocols has an impact on the magnitude of the effects and should therefore be carefully considered, especially in athletes. Superimposed EMS with relatively low volume, high intensity and outcome-specific movement pattern appeared to positively influence adaptations in athletes.
... Electrostimulation consists of electrical currents applied in muscles or peripheral nerves in order to provoke involuntary muscle contractions [12]. Its main advantage for athletes is an increase in the maximum strength and power during voluntary contractions [13,14]. ...
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Introduction. The aim of the present study was to investigate the effects of a 6-week low intensity plyometric training (PT) + whole-body electrostimulation (WBES) combined program, compared with traditional PT, on vertical jump performance, 20 m sprint-time and handgrip strength. Material and methods. 10 male and 10 female Physical Education students were randomly allocated to a control (CON) or an experimental (EXP) group. Both groups performed a 6-week low intensity PT 3 days per week, and during the third day, PT was simultaneously combined with WBES in the EXP group. Countermovement jump (CMJ) height, CMJ peak power, 20 m sprint-time and handgrip strength were measured before (pre-test) and after (post-test) the training period. Repeated measures ANOVA was performed to identify differences after the training program. Effect sizes (ES) were assessed using Hedge’s g. Results. No significant differences between groups were observed at post-test. CMJ height and CMJ peak power significantly increased in both groups, with greater ES in the EXP group (p < 0.001, g = 0.68; p < 0.001, g = 0.70, respectively). 20 m sprint-time significantly improved in both groups, with greater ES in the CON group (p < 0.001, g = -1.68). Handgrip strength also increased in both groups, but ES were minimal. Conclusions. Both training methods demonstrated to be a good strategy to improve CMJ performance and 20 m sprint-time. The most effective training method for improving CMJ performance was PT + WBES combined program, and traditional PT obtained better results in 20 m sprint-time.
... Electromyostimulation training (EMS training) is a principle in which a current stimulates the muscle nerves to cause artificial muscle contraction and is used for muscle strength [12]. In the past, it was mainly used for the improvement and treatment of muscular nervous system dysfunction, the prevention of postoperative muscular atrophy, and pain relief [13], but in 1977, Kots in Russia showed positive effects after applying EMS training to elite athletes. ...
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Regular physical activity and exercise can improve your health and reduce your risk of developing various diseases including type 2 diabetes, cardiovascular disease, and cancer. Physical activity and exercise can have numerous immediate and chronic health benefits, such as managing weight, blood cholesterol level, blood pressure, and muscles [1]. Most importantly, regular physical activity and exercise can offer a better quality of life (e.g., more energy, a better mood, feeling more relaxed, and sleeping better). The American College of Sports Medicine (ACSM) provides recommendations and guidelines for physical activity and exercise that all healthy adults aged 18–65 years should participate in moderate-intensity aerobic activity for a minimum of 30 min five days per week or vigorous-intensity aerobic activity for a minimum of 20 min three days per week. In addition, adults should maintain or increase muscular strength and endurance for a minimum of two days per week (ACSM’s Guidelines for Exercise Testing and Prescription) [2]. Taken together, both aerobic and strength activities are important for optimal physical fitness. While practical concerns such as busy schedules and poor health can make exercise more challenging, for most of us, the biggest barriers are mental. Maybe it is a lack of confidence that keeps us from taking positive steps, or it is that the motivation easily burns out, or that we are too quickly discouraged and give up. Therefore, new exercise methods that enable exercise to be sustainable for managing health are essential. Among the many new exercise trends, we would like to briefly introduce some of the exercise modalities including blood flow restriction, electromyostimulation, hypoxic training, vibration, and interval training.
... The benefits of electrical stimulation are most noticeable in orthopaedics and sports medicine. in sports, electrical stimulation as a procedure supporting regular training to increase muscle strength and endurance is nothing innovative nowadays [1][2][3]. Current fitness facilities also offer training with the use of stimulation with low and medium frequency currents. in this kind of training, one can observe a comprehensive simultaneous effect on multiple muscles due to the application of several or over a dozen electrodes to the body at the same time. ...
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Electrical stimulation is a branch of physical therapy that applies low and medium frequency currents to stimulate the human body. The effects of electrical impulses on human beings have been observed since antiquity. The development of research in that scope commenced in the 18th century, the most important turning point, and is now continuing. The purpose of this narrative study is to present electrical stimulation in terms of its progressing development and to draw attention to its significant role in the therapeutic processes utilized in numerous medical specializations and comprehensive strength and endurance training of healthy people. The notions ‘electrical stimulation’ and ‘electrotherapy,’ as well as differences between electric current applications are explained. The most critical moments in the history of electrical stimulation development are highlighted. Recent research is presented, exhibiting the important role of electrical stimulation both in the therapeutic process and in strength and endurance training. This paper contains the most significant aspects of contemporary application of electrical stimulation, as well as recommendations and limitations for current usage in such areas as whole-body electrostimulation, urinary incontinence, pelvic floor muscle rehabilitation, rehabilitation after anterior cruciate ligament surgery, endurance training, and improvement of physical strength and appearance.
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Introduction Neuromuscular electrical stimulation (NMES) is used by athletes to improve muscle performance. However, evidence on the use of NMES in long distance runners is scarce. As such, this study aimed to evaluate the effects of NMES on the muscle torque and sports performance of long-distance recreational runners. Methods This was a blinded randomized controlled trial. Data from 30 volunteers were analyzed. Participants were randomly allocated to an experimental (n = 15) or control group (n = 15). The experimental group was submitted to running training (RT) and a strengthening protocol with NMES (1 kHz, modulated in 2ms bursts, 50Hz modulated burst frequency and 10% duty cycle, 15 minutes totaling 18 contractions per sessions) for 6 weeks, with 3 sessions per week, while controls were submitted to RT alone. The following variables were analyzed: peak isometric (ISO), concentric (CON), and eccentric (ECC) torque of the quadriceps muscle in voluntary contractions, ventilatory anaerobic thresholds (VATs), maximal oxygen uptake (VO2max), and oxygen cost of transport (OCT). Results The NMES group obtained higher values of ISO, 21.04% (p = 0.001), CON, 21.97% (p = 0.001) and ECC, 18.74% (p = 0.001) peak torque and VAT1, 9.56% (p = 0.001), as well as a statistically significant improvement in oxygen cost of transport at VAT1 when compared to controls (p = 0.001). Conclusion NMES was effective in improving peak isometric, concentric and eccentric quadriceps muscle torque, in addition to being an interesting resource for enhancing sports performance in long-distance recreational runners and future clinical trials should be performed to compare the use of NMES to different forms of training over longer training periods.
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Skeletal muscle undergoes substantial adaptation when it is subjected to a strength training regimen. At one extreme, these effects are manifested as profound morphological changes, such as those exemplified by bodybuilders. However, it is possible to increase strength without any change in muscle size. This dissociation underscores the notion that strength is not solely a property of muscle but rather it is a property of the motor system. The nervous system seems to be of paramount importance for the expression and development of strength. Indeed, it is probable that increases in strength can be achieved without morphological changes in muscle but not without neural adaptations. This review focuses on the role of the nervous system in the development of strength. In the strength literature, 3 topics exemplify the importance of the nervous system in strength development. These 3 topics are considered in detail in the review: electromyostimulation, cross-training effects, and EMG-force relationships. Evidence is presented from several different paradigms emphasising the significant contribution of neural mechanisms to the gains in strength with short term training. Although little is known about the specific neural mechanisms associated with strength training adaptations, the literature emphasises that the measure of human performance known as strength can be influenced by a variety of neurophysiological processes.
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To investigate the influence of skeletal muscle fiber composition on the mechanical performance of human skeletal muscle under dynamic conditions, 34 physical education students with differing muscle fiber composition (M. vastus lateralis) were used as subjects to perform maximal vertical jumps on the force-platform. Two kinds of jumps were performed: one from a static starting position (SJ), the other with a preliminary counter-movement (CMJ). The calculated mechanical parameters included height of rise of center of gravity (h), average force (F), net impulse (NI) and average mechanical power (W). It was observed that the percentage of fast twitch fibers was significantly related (p< 0.05-0.01) to these variables in SJ condition and also to h and NI of the positive work phase in CMJ. It is concluded that skeletal muscle fiber composition also determines performance in a multijoint movement. The result is explainable through the differences in the mechanical characteristics of the motor units and their respective muscle fibers.
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Neuromuscular electrical stimulation (NMES) has been in practice since the eighteenth century for the treatment of paralysed patients and the prevention and/or restoration of muscle function after injuries, before patients are capable of voluntary exercise training. More recently NMES has been used as a modality of strengthening in healthy subjects and highly trained athletes, but it is not clear whether NMES is a substitute for, or a complement to, voluntary exercise training. Moreover the discussion of the mechanisms which underly the specific effects of NMES appears rather complex at least in part because of the disparity in training protocols, electrical stimulation regimens and testing procedures that are used in the various studies. It appears from this review of the literature that in physical therapy, NMES effectively retards muscle wasting during denervation or immobilisation and optimises recovery of muscle strength during rehabilitation. It is also effective in athletes with injured, painful limbs, since NMES contributes to a shortened rehabilitation time and aids a safe return to competition. In healthy muscles, NMES appears to be a complement to voluntary training because it specifically induces the activity of large motor units which are more difficult to activate during voluntary contraction. However, there is a consensus that the force increases induced by NMES are similar to, but not greater than, those induced by voluntary training. The rationale for the complementarity between NMES and voluntary exercise is that in voluntary contractions motor units are recruited in order, from smaller fatigue resistant (type I) units to larger quickly fatiguable (type II) units, whereas in NMES the sequence appears to be reversed. As a training modality NMES is, in nonextreme situations such as muscle denervation, not a substitute for, but a complement of, voluntary exercise of disused and healthy muscles.
The validity and accuracy of the Biodex dynamometer was investigated under static and dynamic conditions. Static torque and angular position output correlated well with externally derived data (r = 0.998 and r greater than 0.999, respectively). Three subjects performed maximal voluntary knee extensions and flexions at angular velocities from 60 to 450 degrees.s-1. Using linear accelerometry, high speed filming and Biodex software, data were collected for lever arm angular velocity and linear accelerations, and subject generated torque. Analysis of synchronized angular position and velocity changes revealed the dynamometer controlled angular velocity of the lever arm to within 3.5% of the preset value. Small transient velocity overshoots were apparent on reaching the set velocity. High frequency torque artefacts were observed at all test velocities, but most noticeably at the faster speeds, and were associated with lever arm accelerations accompanying directional changes, application of resistive torques by the dynamometer, and limb instability. Isokinematic torques collected from ten subjects (240, 300 and 400 degrees.s-1) identified possible errors associated with reporting knee extension torques at 30 degrees of flexion. As a result of tissue and padding compliance, leg extension angular velocity exceeded lever arm angular velocity over most of the range of motion, while during flexion this compliance meant that knee and lever arm angles were not always identical, particularly at the start of motion. Nevertheless, the Biodex dynamometer was found to be both a valid and an accurate research tool; however, caution must be exercised when interpreting and ascribing torques and angular velocities to the limb producing motion.
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This paper compares the effects of 6 wk of sub-maximal training by electrostimulation (100 Hz) and voluntary contractions on the contractile properties of the adductor pollicis muscle in intact man. The daily training program consisted of ten series of twenty 1-s isotonic contractions (60 to 65% of maximum) separated by 1-s intervals. The observed increase in muscle force, tested in maximal voluntary and electrically evoked contractions, appears to be significantly smaller during electrostimulation than during a training session performed by voluntary contractions. The increase in force recorded during electrostimulation is not associated with changes in the tetanus rates of tension development and tension relaxation (dP0/dt). Conversely, the tetanus time course is found to be significantly accelerated in muscles trained by voluntary contractions. No change of the surface action potential total area was observed during both training procedures. Furthermore, electrostimulation does not improve muscle resistance to fatigue, which is observed to be significantly increased after training by voluntary contractions. This study indicates that electrostimulation augments the muscle force of contraction by changing peripheral processes associated with intra-cellular events, without modifying the nervous command of the contraction. The comparison of the peripheral changes recorded during sub-maximal training by electrostimulation and voluntary contractions suggests that electrostimulation is less efficient, but complementary to voluntary training because the number and the type of trained motor units are different in the two procedures.
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1. Raw or rectified and integrated electromyograms (integrated EMGs) of the leg muscles were recorded during (a) isotonic ramp shortening or lengthening contractions consisting of foot plantar flexions against a constant load, or dorsal flexions accomplished by braking the load and yielding to it, respectively, and (b) isometric increasing or decreasing plantar torques accomplished by graded contractions or relaxations of the triceps muscles. 2. During plantar flexions or increasing torques, the EMG of soleus, gastrocnemius lateralis, medialis, and peroneus increased in parallel. During decreasing torques, motor unit derecruitment took place gradually and simultaneously. The tibialis anterior was silent. During dorsal flexions, one of two characteristic patterns was observed in different subjects: (a) soleus was abruptly derecruited at the beginning of the task, while gastrocnemius lateralis (or medialis) exhibited a large recruitment lasting throughout the lengthening contraction; (b) soleus remained active during the task, showing large motor unit potentials, while the gastrocnemius lateralis recruitment was of a lesser extent than in (a). Peroneus derecruitment was gradual and tibialis anterior activity was absent in both cases. 3. The EMG patterns observed during plantar flexions or in increasing and decreasing torques, and the two patterns observed during shortening or lengthening contractions, were closely reproduced during sinusoidal oscillations of the foot or in isometric contractions and relaxations. 4. When recruitment of the gastrocnemius lateralis was present during dorsal flexion, the slope of its integrated EMG envelope was steeper, the higher the velocity of lengthening contraction. The most rapid and the slowest tasks, however, did not require its activation. Gastrocnemius lateralis integrated EMGs of an amplitude similar to those occurring during lengthening contractions were observed only during ballistic plantar flexions. 5. The two patterns of triceps activation occurring during lengthening contraction could be traced to different mechanical characteristics of the soleus muscles, the gastrocnemius lateralis being activated preferentially in subjects with long soleus half-relaxation times, and the soleus in subjects with short soleus half-relaxation times. 6. The soleus and gastrocnemius lateralis H reflexes were tested during shortening and lengthening contractions.(ABSTRACT TRUNCATED AT 400 WORDS)
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This study compared changes in movement velocity, force, and work from bilateral quadriceps muscle stimulation during resistive squatting exercise to identical exercise without stimulation. Both the group undergoing resistive training over 24 sessions (N = 9) and the group receiving the same treatment in conjunction with stimulation during the last 12 sessions (N = 9) showed significant improvements in measures of movement velocity, force, total work, power, sprint time, and vertical jump distance when compared to a control group receiving no treatment (N = 9). All subjects were baseline tested and tested at 3, 6, and 7 week intervals. Both experimental groups improved significantly for all measures, but the electrical stimulation group did not produce more significant changes overall than those with resistive training alone. However, when compared to control measures, the effect of electrical stimulation-augmented responses among some measures was more pronounced than the effect of resistive training alone.
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The purpose of this investigation was to determine if training isometrically with electrical stimulation (ES) alone would significantly increase isometric strength of the quadriceps femoris muscle. The relationships between the strength changes and the relative force and duration of training contractions were also studied. An experimental group (Group 1) and a control group (Group 2), 12 subjects in each, underwent pretesting and posttesting to obtain their maximum voluntary isometric contractions (MVICs). Group 1 trained with maximally tolerable isometric contractions induced by ES, three days a week for four weeks. Results showed that although both groups demonstrated increases in isometric strength of their quadriceps femoris muscles, training isometrically with ES produced a significantly greater increase (p less than .01) than not training with ES. The relative strength improvement in Group 1 was positively and significantly correlated with training-contraction intensity and duration. The relative increase in isometric strength, using only ES, may be determined by the ability of the subjects to tolerate longer and more forceful contractions. Suggestions for further research and implications for the clinical use of ES for strength-training are discussed.