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The present study investigated the influence of a 5-week electrostimulation (EMS) training program on muscular strength, kicking velocity, sprint, and vertical jump performance in soccer players. Twenty amateur soccer players participated in the study, 10 in the electrostimulated group and the remaining 10 in a control group. Electrostimulation was applied on the quadriceps muscles over 5 weeks. Subjects were tested before, during (wk-3), and after (wk-5) the EMS training program. Maximal voluntary contraction using different contraction mode (i.e., eccentric, concentric, and isometric), vertical jump height, sprint running for 10 m, and ball speed were examined. We observed an increase in isometric and eccentric maximal knee extension torques and also a gain in ball speed performance without run up at wk-3. After 5 weeks of EMS training, eccentric, isometric, and concentric torques and ball speed had significantly improved. It appeared appropriate to conduct EMS training during at least 3 weeks to observe beneficial effects in specific soccer skills such as ball speed.
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EFFECTS OF AN ELECTROSTIMULATION TRAINING
PROGRAM ON STRENGTH,JUMPING,AND KICKING
CAPACITIES IN SOCCER PLAYERS
MAXIME BILLOT,
1
ALAIN MARTIN,
1
CHRISTOS PAIZIS,
1,2
CAROLE COMETTI,
2
AND NICOLAS BABAULT
2
1
Laboratory INSERM U887 Motricity-Plasticity, Faculty of Sport Science, University of Burgundy, Dijon, France; and
2
Performance Expertise Center, Faculty of Sport Science, University of Burgundy, Dijon, France
ABSTRACT
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(5): 1407–1413, 2010—The present study investi-
gated the influence of a 5-week electrostimulation (EMS) train-
ing program on muscular strength, kicking velocity, sprint, and
vertical jump performance in soccer players. Twenty amateur
soccer players participated in the study, 10 in the electro-
stimulated group and the remaining 10 in a control group.
Electrostimulation was applied on the quadriceps muscles over
5 weeks. Subjects were tested before, during (wk-3), and after
(wk-5) the EMS training program. Maximal voluntary contraction
using different contraction mode (i.e., eccentric, concentric,
and isometric), vertical jump height, sprint running for 10 m, and
ball speed were examined. We observed an increase in
isometric and eccentric maximal knee extension torques and
also a gain in ball speed performance without run up at wk-3.
After 5 weeks of EMS training, eccentric, isometric, and
concentric torques and ball speed had significantly improved. It
appeared appropriate to conduct EMS training during at least 3
weeks to observe beneficial effects in specific soccer skills
such as ball speed.
KEY WORDS ball speed, knee extensors, isokinetic dynamometer,
isometric and eccentric strength
INTRODUCTION
Soccer necessitates explosive-type efforts such as
tackling, jumping, kicking, and sprinting (32). It has
previously been demonstrated that 10-m sprint
performance was higher in elite than in amateur
soccer players (4,9), and it is generally accepted that muscles
of the thigh play an important role in running (35), jumping,
and ball kicking (2,14,30). Some studies, such as that of Narici
et al. (27), demonstrated a positive correlation between
quadriceps maximal voluntary contraction (MVC) and maxi-
mal ball velocity. Furthermore, Wisloff et al. (35) reported
a positive correlation between maximal squat strength,
sprinting, and jumping in elite soccer players. A correlation
has also been observed between sprinting and jumping abilities
and torque at concentric velocities normalized to subjects’
body mass (10). Quadriceps muscles seem important for
soccer players. Training of these specific muscles could
therefore induce positive modifications in soccer performance.
It has been reported that a 12-week (4 days a week)
voluntary isometric training program induced a significant
increase in squat jump (SJ)–height performance in young
adults (20). In the specific case of soccer, previous studies
have found that voluntary strength training improved
performance in a specific kicking ball task in soccer (8,11).
Therefore, voluntary strength training induces benefits in
specific soccer abilities. Among the different training
methods, the electrostimulation (EMS) method could
improve muscle strength production (5,12,13,21). Indeed,
enhancement in strength production was evident in many
muscular groups after EMS training ranging from 10 to 41%
for quadriceps muscles (3,7,15,16,23,25). Some authors have
tested the effects of EMS training on sport performance.
After 4 weeks of EMS training on quadriceps and triceps
surae muscles, Malatesta et al. (23) reported the positive
effects on vertical jump performance in volleyball players.
Furthermore, Maffiuletti et al. (23) found that SJ performance
in basketball players was improved by 14% after 4 weeks of
EMS training on quadriceps muscles. Similarly, it was
reported that 3 weeks of EMS on latissimus dorsi and
quadriceps muscles decreased stroke and sliding sprint time
in swimming and ice hockey, respectively (7,31). On the
other hand, Babault et al. (3) measured an increment in squat
performance after 6 and 12 weeks of quadriceps EMS
training, but observed no significant change on specific
scrumming tasks in rugby players.
It thus appeared that EMS training may enhance specific
sports movements such as stroke and sliding sprint (3,7,23–25,31),
Address correspondence to Maxime Billot, maxime.billot@u-bourgogne.fr.
24(5)/1407–1413
Journal of Strength and Conditioning Research
Ó2010 National Strength and Conditioning Association
VOLUME 24 | NUMBER 5 | MAY 2010 | 1407
whereas improvements in others, such as jump height and
sprint time, remain unclear in the literature. To date, no study
has investigated the evolution of specific performance in
soccer after an EMS training program. Indeed, analysis of the
physiological profile of soccer players reveals the importance
of anaerobic power in most decisive skills such as jump,
sprint, and ball-kicking ability (4). It was also reported that
quadriceps femoris muscles are important for specific soccer
abilities. Thus, the aim of this study was to test the effects of
a 5-week EMS training program on the quadriceps femoris of
soccer players. With this intention, strength was measured in
different contractile conditions (i.e., isometric, concentric,
and eccentric). Moreover, special interest was given to the
evaluation of specific soccer tasks such as vertical jump,
sprint, and ball speed during kicking. We hypothesized
that a 5-week EMS training program on the quadriceps
femoris improved muscle strength and sport performance in
soccer players.
METHODS
Experimental Approach to the Problem
This study was designed to determine the beneficial effects of
a 5- weeks EMS training program in soccer players. Strength
adaptations were investigated by measuring the isokinetic
torque during maximal voluntary eccentric, isometric, and
concentric knee extensions. Sport performance adaptations
were investigated using ball speed after kicking, vertical
jumps, and sprinting. These variables were tested before, 3
weeks (wk-3) and 5 weeks (wk-5) after the beginning of
training. Two groups of soccer players were considered.
During the 5-week period, the first group (control, C) only
followed soccer trainings. The second group (electrostimu-
lated, EMS), in addition to the same soccer training,
underwent a 5-week EMS training on the knee extensors.
During the 5 weeks, the EMS training program consisted of 3
sessions a week. Statistical analyses allowed us to evaluate the
effect of EMS training on physical performances of soccer
players. Independent variables
were time (before, wk-3, and
wk-5) and groups (EMS and C).
Values obtained for the different
tests were used as dependent
variables.
Subjects
Twenty male soccer players
from the faculty of sport science
competing at least in the re-
gional division of the French
Football Federation voluntarily
participated in this study. They
were randomly assigned to an
electrostimulated group (EMS,
n= 10; age 20.1 62.1 years;
height 1.76 60.06 m; mass
69.5 67.4 kg) or control group
(C, n= 10; age 21.7 63.4 years;
height 1.80 60.05 m; mass
70.7 611.0 kg). All players
technically trained twice a week
(without physical training) and
competed once a week for a
total of practical soccer averag-
ing 5 hours a week. They were
asked to maintain their usual
training, food intake, and hy-
dration. The experiment was
conducted during March, cor-
responding to the last part of
the championship. None of
them had previously engaged
in systematic strength or EMS
training. Written informed con-
sent was obtained. All
Figure 1. Torque-angular velocity of knee extensors in electrostimulation group and control group. Values
measured before and after wk-3 and wk-5 are means 6SD. *,**, and ***Significant differences at p,0.05,
p,0.01, and p,0.001, respectively.
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Electrostimulation in Soccer Players
experimental procedures conformed to the standards set by
the Declaration of Helsinki and were approved by the local
Committee on Human Research.
Procedures
The EMS group participated in a 5-week training program
that consisted of 12-minute EMS sessions, at a rate of 3
sessions per week. Electrostimulation was performed on both
quadriceps femoris muscles. During the stimulation, subjects
were seated on a machine used for strength quadriceps
strength training (Multi-form, La Roque D’anthe
´ron, France)
with the knee fixed at a 60°angle (0°corresponding to the full
extension of the leg). A portable battery-powered stimulator
(Compex-Energy, Medicompex SA, Ecublens, Switzerland)
was used. Three 2-mm-thick self-adhesive electrodes were
placed over each thigh. The positive electrodes, measuring 25
cm
2
(5 cm 35 cm), which had membrane-depolarizing
properties, were placed as close as possible to motor points of
vastus medialis and vastus lateralis muscles. Negative
electrodes, measuring 50 cm
2
(10 cm 35 cm), were placed
near the proximal insertion of rectus femoris muscle.
Rectangular wave pulsed currents (100 Hz) lasting 400 ms
were used. Electrical stimulation was 3-second long and was
followed by a rest period of 17-second (duty cycle 15%). This
program was adapted from Compex commercially strength
programs. During the training sessions, 36 contractions were
performed. Stimulation intensity was determined by the pain
tolerance of the subject. The maximally tolerated intensity
varied between 60 and 120 mA. The level of force produced
by EMS was measured with a myostatic type dynamometer
(Allegro, Sallanches, France),
and it was verified by the
examiner to produce a force
higher than 60% of MVC
during each training session.
For both EMS and C groups,
similar soccer training was
conducted twice a week.
Testing
Strength Tests. Tests were per-
formed before and after
a 3-week (wk-3) and 5-week
(wk-5) period. We used an
isokinetic dynamometer (Bio-
dex Corporation, Shirley, NY,
USA) to test the strength of the
dominant leg (i.e., kicking leg)
of each subject. The reliability
of strength measurements of
the isokinetic dynamometer
was previously validated (34).
Before the test, a warm-up was
carried out by means of 2 series
of 10 concentric actions
(30°s
21
) with increasing inten-
sities. Subjects were seated with
the hip at a 90°angle. To
minimize hip and thigh motion
during the contractions, straps
were applied across the chest
and pelvis and at midthigh.
Another strap secured the leg
to the Biodex lever arm, and
the alignment between the
center of rotation of the dyna-
mometer shaft and the axis of
the knee joint was checked at
the beginning of each trial. The
arms were positioned across
Figure 2. Ball speed during soccer kicking in electrostimulation group and control group. Measured values before
and after a wk-3 and a wk-5 period are means 6SD. *,**, and ***Significant difference between before, wk-3, and
wk-5 at p,0.05, p,0.01, and p,0.001, respectively.
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the chest with each hand clasping the opposite shoulder.
Strength measurements consisted of 2 series of 4 consecutive
maximal knee extensions and flexions from 90°of flexion
to full extension (0°). Contractions were performed at 3 ran-
domized angular velocities (concentric: +60 and +240°s
21
;
and eccentric: 260°s
21
), then 3 MVCs were performed in
isometric conditions at 60°. A 3-minute rest period was
allowed between series to eliminate the effects of fatigue. The
peak torque was directly measured by the Biodex software.
For each condition, only the best trial was included in the
analysis. Torques were gravity corrected at each joint angle,
using the resistive torque of the weight of the limb obtained
at the joint angle where the gravity effect was greatest.
Kicking Tests. Kicking performance was determined from
maximal ball speed during shots. The speed, was measured
with 44 Check Speed Radars (Tibar Industries, Downview,
Ontario, Canada). Check Speed Radars operate with
10.25-GHz frequency, and the frame of the signal is
approximately 60°vertical by 40°horizontal. Radars were
positioned in both upper and lower corners, behind the goal.
This goal was materialized on a net by means of an adhesive
strip (3 m wide and 2 m high). The soccer ball was placed at
a distance of 9 m. For speed values, we retained speed from the
radar nearest the ball impact. The ball characteristics were in
accordance with Fe
´de
´ration Internationale de Football
Association approval (size: 5, weight: 440 g, circumference:
69 cm, and pressure: 1,000 gcm
22
), and the pressure was
verified before each testing session. Shots were effectuated
using the dominant leg without run-up (one step before
kicking) and with run-up (3 steps before kicking). The best of
3 trials was analyzed for each subject.
Vertical Jump Tests. Each subject performed vertical jumps on
an Optojump system (Optojump, Microgate, Bolzano, Italy).
A digital timer was connected to the system to measure the
flight times of the jumps. The SJ was measured starting from
a static semisquatting position (knee angle 90°) and without
any preliminary movement. The countermovement jump
(CMJ) was performed starting from a standing position, then
squatting down to a knee angle of 90 65°and then extending
the knee in one continuous movement. During these tests,
the arms were kept close to the hips to minimize their
contribution. The third jump was a CMJ in which the
movement of the arms was free (CMJf ). The position of the
upper body was also controlled so as to minimize trunk
flexion and extension. Subjects were asked to jump as high as
they could 3 times, and the best performance was reported.
Sprint Test. Subjects performed 3 10-m sprints, separated by
3-minute recovery periods. Speed was measured with infrared
photoelectric cells positioned at 1 m from the floor and 10 m
from the start line and controlled by TAC (Test Atletici
Computerizzati, TEL.SI. s.r.l. Vignola, Italy) software. After
a visual signal, the players started from a standing position and
ran the 10-m distance as fast as possible. Performances did not
include reaction time. The fastest of 3 trials was used for
subsequent analysis.
Statistical Analyses
Standard statistical techniques were used to calculate means
and SDs. A 2-way analysis of variance (group 3time) with
repeated measures was used to compare MVC, jump height,
sprint, and ball speed. When significant effects occurred,
Tukey post hoc analyses were used to test significant
differences among values. Statistical power values were
calculated for various significant differences. The level of
significance was set at p#0.05 for all procedures. All
statistical tests were performed with Statistica software
(version 6.1, StatSoft, Tulsa, OK, USA).
RESULTS
Reliability of measurement showed that the statistical power
values for various significant differences ranged from 0.64
to 0.99.
Before training, EMS and C groups were similar in physical
characteristics, knee extensor strength, ball speed, vertical
jump, or sprint performance (p.0.05). No significant time
effect was observed for the C group in all tests (p.0.05).
Concerning the EMS group, eccentric torque increased
significantly at wk-3 (+11.5 610.4%, p,0.01) and wk-5
(+22.1 616.4%, p,0.001) as compared with before. A
further increase was observed from wk-3 to wk-5 (+9.6 6
8.1%, p,0.01) (Figure 1). A similar significant increase was
obtained in isometric conditions from before to wk-3 and wk-
5 (+16.3 621.3, p,0.01 and +27.1 622.6%, p,0.001,
respectively) and from wk-3 to wk-5 (+9.2 67.4%, p,0.05).
We observed no significant increment between before and
wk-3 for both concentric conditions. However, we observed
a significant increment between before and wk-5 (+14.0 6
9.9% at 60°s
21
and +23.2 618.9% at 240°s
21
,p,0.001)
TABLE 1. Vertical jump performance during SJ, CMJ,
and CMJf in EMS and C groups, mean values 6SD.*
SJ (cm) CMJ (cm) CMJf (cm)
EMS group
Before 32.0 66.4 35.1 66.5 40.9 66.1
wk-3 31.7 65.9 33.7 66.3 39.7 66.1
wk-5 33.1 66.2 35.9 65.941.6 65.1
C group
Before 29.7 64.4 34.4 64.7 40.5 65.8
wk-5 29.3 64.1 33.9 64.8 40.8 65.8
*SJ = squat jump; CMJ= countermovement jump;
CMJf = countermovement jump free; C = control; EMS =
electrostimulation.
Significant difference between wk-3 and wk-5
(p,0.05).
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Electrostimulation in Soccer Players
and from wk-3 to wk-5 (+10.0 69.6% at 60°s
21
and +14.2 6
16.5% at 240°s
21
,p,0.01). Our measurements showed that
ball speed without run-up improved significantly at wk-3
(+6.6 68.7%, p,0.05) and wk-5 (+9.6 610.6%, p,0.001)
compared with measurements taken before the program. Ball
speed with run-up improved significantly at wk-5 (+5.6 6
4.0%, p,0.05) (Figure 2).
For jump performance, we observed a significant increase
from wk-3 and wk-5 in CMJ condition for the EMS group
(+6.7 66.3%, p,0.05) (Table 1). However, no significant
difference was observed in SJ, CMJ, and CMJf conditions at
wk-3 or wk-5 compared with before. Moreover, no signifi-
cant time effect was observed either in sprint time or velocity
after the wk-3 and wk-5 period in either group (Table 2).
DISCUSSION
The main finding of this study was that in addition to the well-
known strength increase, EMS training could lead to benefits
in more specific attributes such as kicking speed, with and
without run-up. However, strength gains were not directly
transferable to jumping ability or sprint performance in our
soccer players.
The results of the present study showed smaller strength
increases than those previously observed in elite ice hockey
players in eccentric conditions (12 vs. 24% in soccer players
and ice hockey players, respectively) after 3 weeks of EMS
training (7). However, these authors also found a significant
increase in the C group and explained gains in eccentric
conditions by noting the fact that subjects were more
accustomed to performing isokinetic contractions at pretests.
Furthermore, it was suggested that fast-twitch fibers might be
preferentially recruited during eccentric submaximal con-
tractions (22,33) and that total recruitment may take place
during eccentric maximal contractions (19). In addition,
Jubeau et al. (19) reported that EMS contractions may result
in neither motor unit recruitment according to Henneman’s
size principle nor in a reversal in this voluntary recruitment
order. Thus, a random recruitment of motor units during
EMS training may activate easily fast fibers in comparison
with voluntary contraction during submaximal level of force.
In our study, we suggested that eccentric adaptations may be
because of the result of motor unit recruitment. In fact,
Nardone et Schieppati (26) reported a greater fast MUs
recruitment during eccentric contraction.
The enhancements we observed in isometric conditions
corroborated the existing literature. For example, Gondin
et al. (16) observed an increment of 15% in the isometric
MVC of quadriceps muscles after 4 weeks of EMS training.
Early progress in strength production after wk-3 in isometric
but not in concentric conditions may be explained by the fact
that the angular position during EMS sessions was the same
as the isometric test position (i.e., 60°) (16). We also observed
that 2 additional weeks of EMS training induced significant
enhancements in MVCs in eccentric, isometric, and
concentric conditions. We would suggest that benefits
observed after 3 and 5 weeks of EMS training were mainly
because of neural adaptation. Indeed, it has been previously
reported that adaptations observed after 4 weeks of EMS
training on quadriceps muscles were mainly because of
neural adaptations, whereas changes in muscle mass and
architecture became significant between the fourth and the
eighth weeks (16). However, our measurements could not
confirm these previous adaptive mechanisms.
Research dealing with EMS training and kicking has until
now not been undertaken. This study reported an increase in
kicking performance without run-up after 3 weeks of EMS
training on the quadriceps muscle. Increments were higher
and significant after 5 weeks of EMS training in both
conditions (with and without run-up). We can thus suggest
that strength improvements are transferable to a specific
movement such as kicking in soccer players. This finding
confirms that quadriceps muscles play an important role
during kicking movements (2,28–30). Other studies have
found that EMS training could improve specific movements
in sports. Indeed, a beneficial effect in swimming sprint and
skating performance has previously been reported after 3
weeks of EMS training on latissimus dorsi and quadriceps
muscles, respectively (7,31). Conversely, Babault et al. (3)
found no improvement in a scrumming task after 6 weeks of
EMS training in elite rugby players. These authors explained
that the lack of gains in the scrum test may be partly
attributed to technical and motivational factors. Technical
considerations cannot, therefore, be excluded from criteria of
specific performance. Our results, therefore, suggest that
EMS training appears to be a viable approach for developing
specific attributes used in soccer.
We observed no significant increase in vertical jump
performance after 3 or 5 weeks of our EMS training program.
These results were in contradiction with Maffiuletti et al. (23)
who observed an increment of 14% in SJ after 4 weeks of
TABLE 2. Sprint time and velocity at 10 m in EMS and
C groups before, after wk-3, and after wk-5.*
10-m Sprint
time (s)
Velocity at
10 m (ms
21
)
EMS group
Before 1.91 60.06 6.83 60.37
wk-3 1.91 60.07 6.95 60.56
wk-5 1.90 60.05 6.83 60.29
C group
Before 1.91 60.06 7.24 60.70
wk-5 1.93 60.07 7.37 60.61
*EMS = electrostimulation; C = control.
Values are means 6SD.
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EMS training on quadriceps femoris. These different results
could be explained by the fact that fewer contractions were
performed in our study for each training session. However,
some previous studies were in accordance with our results
and reported no significant increase in vertical jump
performance. In fact, Malatesta et al. (25) and Herrero
et al. (17) reported no significant increase in SJ and CMJ after
4 weeks of EMS training on knee extensors. In addition,
a decrease in jumping ability after 3 weeks of EMS training in
ice hockey players has been reported (7). The lack of
increment or even decline in vertical jump performance
might be explained by fatigue or overtraining induced by
short EMS training programs. Some studies have reported
that a recovery period after EMS or resistance training is
necessary to allow an enhancement in jumping performance
(1,23–25). Furthermore, it has been previously demonstrated
that SJ and CMJ involve not only knee extensor muscles but
also plantar flexors (6,18). In this way, Malatesta et al. (25)
found a significant increase in mean height during consec-
utive CMJs after 4 weeks of EMS training of the quadriceps
femoris and triceps surae muscles. An increment in jump
performance may therefore necessitate training of more than
just the quadriceps femoris muscles. It has also been
previously reported that EMS training coupled with specific
training such as plyometric training induced gains in jump
ability (17). Indeed, plyometric training solicits quadriceps
muscles in the same way as jumping. Thus, an increase in
strength production of quadriceps muscles by EMS and the
specificity of plyometric training could induce an enhance-
ment in jumping ability.
Electrostimulation training induced adaptations on explo-
sive type movements such as sprint performance. In this
study, sprint time and velocity at 10 m did not change
significantly after 3 and 5 weeks of EMS training. These
findings are contradictory to those of a previous study. Indeed,
Herrero et al.(17) reported a significant improvement in 20-m
sprint performance after 4 weeks of EMS training on
quadriceps muscles. The lack of gain in sprint performance in
our study could be explained by the complexity of the
running task in which many muscles are involved and by the
technical level of the amateur soccer players tested here. The
transfer of strength gains after EMS training appeared more
difficult for nonspecific sport performance (i.e., vertical jump
and sprint) than specific sport performance (i.e., kicking) in
soccer players.
PRACTICAL APPLICATIONS
In summary, soccer necessitates not only technical and
strategic training, but also physical conditioning. Three weeks
of EMS training programs seems appropriate to improve knee
extensors muscle strength in eccentric and isometric
conditions in soccer players. However, 2 additional weeks
appears necessary to observe increments in all contractile
conditions. Moreover, EMS training leads to an improvement
in specific soccer tasks such as ball speed performance after
kicking. Exclusive EMS training of the quadriceps femoris
muscles may be of limited value for improving jumping
performance in amateur soccer players. However, some of the
following might provide a significant training effect for
jumping including (a) the concurrent training of the triceps
surae, gluteus maximus, and hamstrings, (b) the inclusion of
an optimal recovery period, and (c) the coupling of EMS
training with plyometric training. Additionally to traditional
soccer training, an EMS training program of 3- or 5-week
period appears to represent a viable means for improving force
and specific soccer tasks at preseason and during the season.
In fact, this original method might be used to complement
traditional training for soccer. It would infuse variability into
the training program, which might enhance the motivation
of some players. Furthermore, EMS might also be used for
injured athletes to attenuate or eliminate detraining effects.
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VOLUME 24 | NUMBER 5 | MAY 2010 | 1413
Journal of Strength and Conditioning Research
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... 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). ...
... The longest single EMS, of approximately 80 minutes, appeared in the study of , while the shortest session lasted 12 minutes (Brocherie et al., 2004;Billot et al., 2010;Benito-Martinez et al., 2011;Martinez-Lopez et al., 2012). The lowest frequency was used in the study of Marqueste et al. (2010) and it was 4-75 Hz which lasted 400 ms, while the highest was 150 Hz and which lasted 350 ms (Martinez-Lopez et al., 2012). ...
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.
... Traditionally, the performance during the kicking ball has been assessed by measuring the maximal ball speed, as an increase in this parameter reduces the time for the goalkeeper or an opponent to intercept the ball successfully, therefore raising the probability of scoring [1,11,12]. For this reason, several studies on soccer players have focused on analyzing the kicking ball speed [8,13], its determinant factors [14][15][16], and the effect induced by different training programs [17,18]. Accordingly, due to the relevance of this variable, the use of accurate, valid, and reliable devices for measuring the kicking ball speed is warranted. ...
... Studies analyzing the kicking ball speed in soccer players have used different devices, including high-speed cameras [4,16,19,20], photocells [13], inertial sensors [21], and radar guns [2,5,14,17,18,22,23]. In this regard, radar guns are a common tool both in practical use and scientific research due to their high accuracy [24,25]. ...
Article
Full-text available
The aim was to analyze the reliability and validity of a low-cost instrument, based on a radar system, to quantify the kicking ball speed in soccer. A group of 153 male soccer players (under-13, n = 53; under-15, n = 54; under-18, n = 46) participated in this study. Each player performed three kicks on the goal in a standardized condition while the ball speed was measured with three different devices: one Radar Stalker ATS II® (reference criterion) and two Supido Radar® (Supido-front of the goal and Supido-back of the goal). The standard error of measurement (SEM) expressed as a coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were employed for assessing the reliability of each instrument. Stalker and Supido-back showed very high absolute (CV = 4.0–5.4%) and relative (ICC = 0.945–0.958) reliability, whereas Supido-front resulted in moderate to low reliability scores (CV = 7.4–15%, ICC = 0.134–0.693). In addition, Lin’s concordance correlation coefficient (CCC) values revealed an ‘almost perfect’ agreement between Stalker and Supido-back for the average (r = 0.99) and maximal (r = 0.98) ball speed, regardless of the ball speed range analyzed. However, Supido-front resulted in a poor degree of concordance (CCC = 0.688) and a high magnitude of error (17.0–37.5 km·h−1) with the reference Stalker radar gun. The Supido Radar® placed behind the goal could be considered a reliable and valid device for measuring ball speed in soccer.
... Electromyostimulation (EMS) training can be an effective and alternative method to traditional strength training, to improve muscle strength, speed strength, sprinting, jumping and athletic performance [1][2][3][4][5]. However, this technology can be applied only to specific muscles with single electrodes, and usually in a passive way. ...
Article
Full-text available
Whole-body electromyostimulation (WB-EMS) training is effective in improving training adaptation. However, WB-EMS may have side effects and contraindications that can lead to excessive muscle damage and physiological impairment. This randomized crossover study aimed to analyze the acute effects of WB-EMS on muscle damage, autonomic modulation and performance during a single maximal strength session in physically active participants. Twenty healthy and physically active participants randomly performed three maximal strength training sessions (90% 1RM) consisting of bench presses and squat exercises, with a continuous stimulus, a coordinated stimulus with concentric and eccentric phases, and without WB-EMS. Data showed no significant differences between the trials for muscle damage (blood creatine kinase levels), lactate blood levels and performance after exercise. Likewise, the heart rate, blood oxygen saturation and the rate of perceived exertion were similar during exercise between trials. The heart rate variability analysis also showed a similar autonomic response among the trials. Training with WB-EMS seemed to be safe at the observed time intervals while offering a stimulus similar to regular training in physically active participants, regardless of the delivery of the electrical stimuli. More studies are needed to assess the effectiveness of WB-EMS in improving exercise adaptations during training programs.
... 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) interventions on performance parameters in 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 CI]), 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 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 patterns appeared to positively influence adaptations in athletes. • HIGHLIGHTS • Key performance parameters such as maximal strength, jump height and sprint time can be increased by adequate EMS intervention programs in already well-trained athletes. • The effectiveness of EMS training in athletes is highly dependent on the selected EMS method. Volume, intensity, exercise and movement specificity play a crucial role for the efficiency of the training. • The most effective option for athletes appears to be a combination of superimposed EMS with relatively low EMS volume, high intensity, and movement-specific exercise pattern.
... Concerning young athletes, it has shown RT to be important in preadolescence, highlighting neural plasticity associated with prepubertal players that support muscular strength development in these years through gains in neuromuscular adaptations as intra-and intermuscular coordination (Peña-González et al., 2019). Although different RT methodologies have been used to improve physical performance in soccer, such as programs bases on traditional exercises (Spineti et al., 2016), eccentric-overload training (Suárez-Arrones et al., 2019), plyometric training (Haghighi et al., 2012;Falces-Prieto et al., 2021), ballistic exercises (Loturco et al., 2020), Olympic exercises (Hori et al., 2008), electrostimulation training (Billot et al., 2010), and a combination of different methods (Raya-González and Sánchez-Sánchez, 2018). Most of these methods need expensive materials and equipment that preclude its applicability for most athletes and thus its implementation in most soccer training facilities; so strength and conditioning coaches are advised to find valid, simple, and economic resources for this purpose (Raya-González et al., 2020). ...
Article
The incidence and recurrence of hamstrings injuries are very high in sports, posing elevated performance and financial-related costs. Attempts to identify the risk factors involved in predicting vulnerability to hamstrings injury is important for designing exercise-based programs that aim to mitigate the rate and severity of hamstrings injuries and improve rehabilitation strategies. However, research has shown that non-modifiable risk factors may play a greater role than modifiable risk factors. Recognizing nonmodifiable risk factors and understanding their implications will afford the prescription of better suited exercise programs, i.e., that are more respectful of the individual characteristics. In a nutshell, non-modifiable risk factors can still be acted upon, even if indirectly. In this context, an underexplored topic is how intra and inter- individual anatomic and physiologic variations in hamstrings (e.g., muscle bellies, fiber types, tendon length, aponeurosis width, attachment sites, sex- and age-related differences) concur to alter hamstrings injuries risk. Some anatomic and physiologic variations may be modifiable through exercise interventions (e.g., cross-sectional area), while others may not (e.g., supernumerary muscle bellies). This apparent dichotomy may hide a greater complexity, i.e., there may be risk factors that are partially modifiable. Therefore, we explored the available information on the anatomic variations of the hamstrings, providing a deeper insight into the individual risk factors for hamstrings injuries and contributing with better knowledge and potential applications toward a more individualized exercise prescription.
... Concerning young athletes, it has shown RT to be important in preadolescence, highlighting neural plasticity associated with prepubertal players that support muscular strength development in these years through gains in neuromuscular adaptations as intra-and intermuscular coordination (Peña-González et al., 2019). Although different RT methodologies have been used to improve physical performance in soccer, such as programs bases on traditional exercises (Spineti et al., 2016), eccentric-overload training (Suárez-Arrones et al., 2019), plyometric training (Haghighi et al., 2012;Falces-Prieto et al., 2021), ballistic exercises (Loturco et al., 2020), Olympic exercises (Hori et al., 2008), electrostimulation training (Billot et al., 2010), and a combination of different methods (Raya-González and Sánchez-Sánchez, 2018). Most of these methods need expensive materials and equipment that preclude its applicability for most athletes and thus its implementation in most soccer training facilities; so strength and conditioning coaches are advised to find valid, simple, and economic resources for this purpose (Raya-González et al., 2020). ...
Article
Background: Post-exercise (i.e., cool-down) stretching is commonly prescribed for improving recovery of strength and range of motion (ROM) and diminishing delayed onset muscular soreness (DOMS) after physical exertion. However, the question remains if post-exercise stretching is better for recovery than other post-exercise modalities. Objective: To provide a systematic review and meta-analysis of supervised randomized-controlled trials (RCTs) on the effects of post-exercise stretching on short-term (≤1 h after exercise) and delayed (e.g., ≥24 h) recovery makers (i.e., DOMS, strength, ROM) in comparison with passive recovery or alternative recovery methods (e.g., low-intensity cycling). Methods: This systematic review followed PRISMA guidelines (PROSPERO CRD42020222091). RCTs published in any language or date were eligible, according to P.I.C.O.S. criteria. Searches were performed in eight databases. Risk of bias was assessed using Cochrane RoB 2. Meta-analyses used the inverse variance random-effects model. GRADE was used to assess the methodological quality of the studies. Results: From 17,050 records retrieved, 11 RCTs were included for qualitative analyses and 10 for meta-analysis (n = 229 participants; 17–38 years, mostly males). The exercise protocols varied between studies (e.g., cycling, strength training). Post-exercise stretching included static stretching, passive stretching, and proprioceptive neuromuscular facilitation. Passive recovery (i.e., rest) was used as comparator in eight studies, with additional recovery protocols including low intensity cycling or running, massage, and cold-water immersion. Risk of bias was high in ∼70% of the studies. Between-group comparisons showed no effect of post-exercise stretching on strength recovery (ES = −0.08; 95% CI = −0.54–0.39; p = 0.750; I2 = 0.0%; Egger’s test p = 0.531) when compared to passive recovery. In addition, no effect of post-exercise stretching on 24, 48, or 72-h post-exercise DOMS was noted when compared to passive recovery (ES = −0.09 to −0.24; 95% CI = −0.70–0.28; p = 0.187–629; I2 = 0.0%; Egger’s test p = 0.165–0.880). Conclusion: There wasn’t sufficient statistical evidence to reject the null hypothesis that stretching and passive recovery have equivalent influence on recovery. Data is scarce, heterogeneous, and confidence in cumulative evidence is very low. Future research should address the limitations highlighted in our review, to allow for more informed recommendations. For now, evidence-based recommendations on whether post-exercise stretching should be applied for the purposes of recovery should be avoided, as the (insufficient) data that is available does not support related claims. Systematic Review Registration: PROSPERO, identifier: CRD42020222091.
... 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. ...
Article
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.
... Concerning young athletes, it has shown RT to be important in preadolescence, highlighting neural plasticity associated with prepubertal players that support muscular strength development in these years through gains in neuromuscular adaptations as intra-and intermuscular coordination (Peña-González et al., 2019). Although different RT methodologies have been used to improve physical performance in soccer, such as programs bases on traditional exercises (Spineti et al., 2016), eccentric-overload training (Suárez-Arrones et al., 2019), plyometric training (Haghighi et al., 2012;Falces-Prieto et al., 2021), ballistic exercises (Loturco et al., 2020), Olympic exercises (Hori et al., 2008), electrostimulation training (Billot et al., 2010), and a combination of different methods (Raya-González and Sánchez-Sánchez, 2018). Most of these methods need expensive materials and equipment that preclude its applicability for most athletes and thus its implementation in most soccer training facilities; so strength and conditioning coaches are advised to find valid, simple, and economic resources for this purpose (Raya-González et al., 2020). ...
Article
Full-text available
Purpose: The purpose of this study was to examine the effects of 15 weeks (2/week) of two different resistance training (RT) programs [the self-load group (SG) vs. the overload group (OG)] on selected measures of physical performance in young male soccer players. Methods: The countermovement jump (CMJ), aerobic endurance (VO 2 max), and body composition [body mass (BM), height (H), body fat percentage (% BF), and lean mass (LM)] were measured before and after the 15-week RT interventions. Subjects were randomized to treatments: 1. SG [age = 15.34 ± 1.34 years]; 2. OG [age = 16.28 ± 1.21 years]. Results: The level of significance set for the study ( p ≤ 0.05). Within-group analysis did report significant differences in all variables for the SG ( p = 0.008 to 0.001; ES = −0.33 to 1.41, small to large) as in the OG ( p = 0.001; ES = 0.82 to 1.30, large). Between-groups analysis reported differences in CMJ ( F = 4.32; p = 0.004) for the OG. Conclusion: The main findings of this study indicated that RT with and without external load was effective in improving the measures of physical performance in young soccer players, with special attention to jumping ability, where the OG group was more effective. Furthermore, there is no interference to aerobic endurance. It is recommended that soccer coaches implement RT without external load in the early stages of training or in players with late maturation development and in those soccer clubs with limited material resources.
Article
Strength and conditioning coaches frequently use traditional resistance training (TRT) to build strength. However, in recent years, whole-body electromyostimulation (WB-EMS) was used in elite athletes to increase muscle strength. This study aimed to assess the effect of two different types of training on muscular strength. Sixty female collegiate players (Age = 23.52±1.89 years, Height = 156.20±1.71cm; Mass = 53.21±3.17kg) participated in this study and were randomly assigned to three training groups. All groups trained as usual for eight weeks, except for the first group, which received additional TRT. The second group received additional electrical stimulation training, and the third group did not receive any additional training following the regular softball bat swing training. Muscular strength (upper and lower body) was assessed by a 3RM bench press and a 3RM squat test before and after the eight-week programme. The primary findings indicate that after eight weeks of training, upper body and lower body strength increased significantly in both the TRT and WB-EMS groups (p = 0.000 and p = 0.000, respectively) in comparison to the control group. However, the t value indicated that the TRT group improved both upper body strength (20.18) and lower body strength (29.18) more than the WB-EMS group (upper body = 6.18; lower body = 6.47). The findings demonstrate the efficacy of both training modalities for increasing muscular strength and suggest that TRT be prioritised over whole-body electrical stimulation training for increasing muscular strength in collegiate softball players.
Article
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.
Article
Full-text available
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.
Article
The most common injuries in soccer involve the ankle and knee joints, and the muscles and ligaments of the thigh and calf. Rehabilitation to restore strength and endurance after healing is extremely important to prevent a recurrence of the injury, which is much more severe and disabling than the initial injury. Sprains and strains of the hamstring and quadriceps, and injuries to the external and internal structures of the knee joints are frequent and relatively more disabling. Recent progress in the technical aspect of investigative medicine, such as magnetic resonance (MRI) imaging/quantitative only computer tomography (CT) scanning, ultrasonic imaging of soft tissues and isokinetic measurement of muscle characteristics, lead to better diagnosis and management of soccer injuries. Appropriate nutritional and physiological preparation, maintaining fluid and electrolytes during the game and restoration of the reserves following completion of exhaustive activities will help to minimise injuries.
Article
Many acute muscle strain injuries are thought to occur during the eccentric phase of sudden, forceful muscle actions. Repeated eccentric muscle actions during exercise are also thought to contribute to microscopic muscle and tendon damage, leading to chronic muscle strains, muscle rupture and tendinopathy. Conversely, eccentric training has been demonstrated to have a positive effect in the prevention of muscle damage and injury. The properties of eccentric muscle actions which lead to this protective effect remain to be elucidated but are thought to include cellular, mechanical and neural adaptations. This clinical commentary is an attempt to analyze the potential role that eccentric training may have in both the contribution to and prevention of muscle injury by exploring the effect of various parameters on muscle structure and function. Guidelines as to the appropriate design of eccentric training programmes are also provided.
Article
Purpose – The aim of this study is to appreciate the relation between sprint, jump and knee isokinetic torque in high-level soccer players.Methods – Twenty soccer players (first french national division) were evaluated by sprint and jump tests. Extensors and flexors isokinetic torque was measured by a Cybex Norm dynamometer. Relations between sprints, jumps and isokinetic peak torque were appreciated after correlation analysis.Results – Jumps are correlated with the extensors concentric peak torque at the speed of 180°s−1 when values were corrected by weight (Squat Jump: r = 0.507; Countermovement Jump: r = 0.649; Vertical Jump: r = 0.496). Sprints are correlated with the extensors concentric peak torque at the speed of 180°s−1 when values were corrected by weight (10 and 20 m fixed departure sprint: r = −0.427 and −0.548; 10 and 20 m thrown departure sprint: r = −0.406 and −0.480). Furthermore, sprints with fixed departure are conversely correlated with the flexors eccentric peak torque at the speed of 60°s−1 (r = 0.546 and 0.478) doubtless because a mechanism of knees protection.Conclusions – According to these causal relations, knee extensors and flexors strengthening is recommended for high-level soccer players with the aim of improving sprints and jumps.
Article
The most common injuries in soccer involve the ankle and knee joints, and the muscles and ligaments of the thigh and calf. Rehabilitation to restore strength and endurance after healing is extremely important to prevent a recurrence of the injury, which is much more severe and disabling than the initial injury. Sprains and strains of the hamstring and quadriceps, and injuries to the external and internal structures of the knee joints are frequent and relatively more disabling. Recent progress in the technical aspect of investigative medicine, such as magnetic resonance (MRI) imaging/quantitative only computer tomography (CT) scanning, ultrasonic imaging of soft tissues and isokinetic measurement of muscle characteristics, lead to better diagnosis and management of soccer injuries. Appropriate nutritional and physiological preparation, maintaining fluid and electrolytes during the game and restoration of the reserves following completion of exhaustive activities will help to minimise injuries.
Article
In sports medicine, neuromuscular electrical stimulation (NMES) has been used for muscle strengthening, maintenance of muscle mass and strength during prolonged periods of immobilisation, selective muscle retraining, and the control of oedema. A wide variety of stimulators, including the burst-modulated alternating current ('Russian stimulator'), twin-spiked monophasic pulsed current and biphasic pulsed current stimulators, have been used to produce these effects. Several investigators have reported increased isometric muscle strength in both NMES-stimulated and exercise-trained healthy, young adults when compared to unexercised controls, and also no significant differences between the NMES and voluntary exercise groups. It appears that when NMES and voluntary exercise are combined there is no significant difference in muscle strength after training when compared to either NMES or voluntary exercise alone. There is also evidence that NMES can improve functional performance in a variety of strength tasks. Two mechanisms have been suggested to explain the training effects seen with NMES. The first mechanism proposes that augmentation of muscle strength with NMES occurs in a similar manner to augmentation of muscle strength with voluntary exercise. This mechanism would require NMES strengthening protocols to follow standard strengthening protocols which call for a low number of repetitions with high external loads and a high intensity of muscle contraction. The second mechanism proposes that the muscle strengthening seen following NMES training results from a reversal of voluntary recruitment order with a selective augmentation of type II muscle fibres. Because type II fibres have a higher specific force than type I fibres, selective augmentation of type II muscle fibres will increase the overall strength of the muscle. The use of neuromuscular electrical stimulation to prevent muscle atrophy associated with prolonged knee immobilisation following ligament reconstruction surgery or injury has been extensively studied. NMES has been shown to be effective in preventing the decreases in muscle strength, muscle mass and the oxidative capacity of thigh muscles following knee immobilisation. In all but one of the studies, NMES was shown to be superior in preventing the atrophic changes of knee immobilisation when compared to no exercise, isometric exercise of the quadriceps femoris muscle group, isometric co-contraction of both the hamstrings and quadriceps femoris muscle groups, and combined NMES-isometric exercise. It has also been reported that NMES applied to the thigh musculature during knee immobilisation improves the performance on functional tasks.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
In order to study the movement pattern of soccer players, 14 top-level players were filmed during several competitive matches. In addition, the relationship between the observed activity during match play and blood lactate values was examined. The mean distance covered during competitive matches was 10.80 km, and the average individual difference between matches was 0.92 km, with no difference in regard to high intensity activities. Midfielders covered a 10% longer (p less than 0.05) distance (11.4 km) than defenders and forwards, with no difference concerning high intensity running. There was a significant correlation (r = 0.61, p less than 0.05) between the amount of high intensity running during the match and lactate concentration in the blood. The results suggest that high intensity running can be used for making comparisons in soccer and that the interpretation of blood lactate in soccer is limited to giving an indication of the type of activity that has been carried out a few minutes before sampling.
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.
Article
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.