INTERNATIONAL JOURNAL OF ATHLETIC THERAPY & TRAINING NOVEMBER 2014 17
© 2014 Human Kinetics - IJATT 19(6), pp. 17-21
http://dx.doi.org/10.1123/ijatt.2014-0042
SYSTEMATIC REVIEW
Neuromuscular Training for Prevention
of Anterior Cruciate Ligament Injury
in Female Athletes
Anterior cruciate ligament (ACL) injury
occurs often in athletes. The ACL can become
twisted during rapid deceleration and sudden
cutting, leading to ACL tears or ruptures.
1
ACL injury is four to six times more common
among female athletes than among male
athletes.
2
These sex differences indicate
that female athletes are
more likely to experi-
ence ACL injury during
high-intensity exercise
than male athletes are.
3
In the United States,
95,000 people experi-
ence ACL injuries each
year. Among female ath-
letes with ACL injuries,
70% decide to undergo
surgery.
4
One year of
rehabilitation is nec-
essary following ACL
reconstruction surgery,
which requires a considerable amount of
money and time. In addition, only 30% to
50% of athletes are able to return to the field
successfully.
3
ACL injury often results in knee
osteoarthritis, causing knee inflammation
and pain that affect athletic performance and
shorten athletic careers.
5
Therefore, athletes
must focus on preventing ACL injury.
Anterior knee laxity and lower extremity
strength are easier to find in female athletes
than in male athletes. Thus, the unstable knee
structure that leads to ACL injury is more
likely to occur in female athletes during cer-
tain activities, particularly landing.
6,7
Strength
training for lower extremity muscles must
be included in physical training programs
for female athletes to improve knee instabil-
ity and prevent ACL injury.
8
Neuromuscular
training is often used in physical training
for athletes and in rehabilitation training for
athletes with sports injuries.
9
Neuromuscular
control emphasizes the conscious control
of the body and the coordination of various
special movements to maintain stability,
and is used in lower extremity training for
preventing ACL injury. Training the ham-
string muscles and quadriceps to generate
tension through antagonistic movement
reduces the risk of ACL injury.
10
Female
athletes lack muscle strength and stability
compared with that of male athletes. There-
fore, neuromuscular control is a common
type of physical training.
6,8
Studies have
often investigated the therapeutic effects of
The prevention of anterior cruciate lig-
ament injury in female athletes through
neuromuscular training is explored.
Neuromuscular training can increase ham
-
string muscle strength and improve knee
stability.
The program design and exercise intensity
of neuromuscular training must be revised
for female athletes.
Key Points
Key Points
Wen-Dien Chang, PhD • China Medical University; and Ping-Tung Lai, OT •
Da-Chien General Hospital
18 NOVEMBER 2014 INTERNATIONAL JOURNAL OF ATHLETIC THERAPY & TRAINING
neuromuscular training following ACL injury or ACL
reconstruction surgery, reporting that neuromuscular
training facilitates postoperative rehabilitation and
functional recovery.
9,11
However, relatively few studies
have examined the effect of neuromuscular training
in preventing ACL injury in female athletes. Therefore,
we performed a systematic review on the influence of
neuromuscular training on the incidence of ACL injury
in female athletes.
Search and Review of Previous Studies
In this study, we used the electronic journal databases
of MEDLINE, PubMed, and CINAHL to obtain the arti-
cles on ACL injury and neuromuscular training. We
used knee injury, anterior cruciate ligament injury, and
neuromuscular training as keywords for this search. The
studies were required to meet the following criteria:
female athletes were used as research participants,
neuromuscular training programs were used to pre-
vent ACL injury, control groups without training were
included, ACL injury incidence was used to assess the
results, and the study was published internationally
between 1995 and 2013. We excluded studies in which
sports training was applied after ACL reconstruction
surgery in the sample. Finally, two specialists in sports
medicine with more than 10 years of experience
selected the articles and compared the content of the
studies that met the criteria based on the published
year and authors of the article, number of participants,
neuromuscular intervention training program, com-
pliance, and results. The analyzed outcome was the
incidence of ACL injuries after the athletes received
neuromuscular training. We assessed the quality of
each study based on the Physiotherapy Evidence
Database (PEDro) scale.
12
Neuromuscular Training
for the Lower Extremities
The initial keyword search resulted in 132 articles.
After removing articles based on their abstracts and
the expert review, we retained five studies.
13–17
Table 1
shows that the PEDro scores of these five articles were
between 6 and 9. The five articles all involved the use
of various neuromuscular training programs. Hewett
et al used a jump training program that included 60
minutes to 90 minutes of flexibility training, plyomet-
rics, weight training, and stretching three times a week
for six weeks.
13
This program emphasized increasing
hamstring muscle strength to reduce landing force
and increasing lower extremity stability upon landing.
Table 1. Description and Intervention of Reviewed Articles
Author (years) Groups (subjects; season) Intervention PEDro
Hewett et al (1999)
13
Intervention group (n = 366; NA)
Control group (n = 897; NA)
Jump training program 7
Myklebust et al (2003)
14
Intervention group
(n = 855; 1999–2000)
Intervention group
(n = 850; 2000–2001)
Control group
(n = 942; 1998–1999)
Circuit of floor, wobble board, bal-
ance mat exercises
8
Mandelbaum et al
(2005)
15
Intervention group
(n = 1,041; 2000)
Control group (n = 1,905; 2000)
Intervention group (n = 844; 2001)
Control group (n = 1,913; 2001)
Warm-up, stretches, strengthen-
ing, plyometric exercise, and soc-
cer-specific agility drills
8
Petersen et al (2005)
16
Intervention group
(n = 134; 2003)
Control group (n = 142; 2003)
Balance board and jump exercise
program
6
Gilchrist et al (2008)
17
Intervention group
(n = 583; 2002)
Control group (n = 852; 2002)
Warm-up, stretching, strengthen-
ing, plyometrics, and sport-specific
agility exercises
9
NA = not applicable.
INTERNATIONAL JOURNAL OF ATHLETIC THERAPY & TRAINING NOVEMBER 2014 19
Myklebust et al used a program comprising 15 minutes
of three balance exercises performed three times a
week for eight weeks. The athletes switched exercises
every five minutes. The first seven weeks of training
were conducted before the competition season and
the eighth week of training was during the competition
season.
14
This program emphasized changing land-
ing techniques to increase proprioception, changing
landing style through neuromuscular training, and
reducing the effects of ground reaction force on the
knees. Mandelbaum et al used 20 minutes of warm-up
before training. The training comprised stretches,
strength training, plyometrics, and special soccer skills
training.
15
Petersen et al created a six-stage training
program that included balance-board exercises and
jump exercises. The athletes performed this program
three times a week for eight weeks before the com-
petition season.
16
Gilchrist et al combined stretching,
strengthening, plyometrics, and sport-specific agility
exercises to form a training module called Prevent
Injury and Enhance Performance. The athletes used
this module for 12 weeks.
17
Incidences of ACL Injury
After Neuromuscular Training
The results of these five articles indicated that 4,673
athletes received neuromuscular training and 6,651
athletes who comprised the control groups did not.
Table 2 shows that compliance for the five programs of
neuromuscular training was between 42% and 100%.
The groups that received neuromuscular training
exhibited a lower incidence of ACL injury than did the
control groups in all five articles.
13–17
Figure 1 shows
that the incidences of ACL injury for the groups that
received neuromuscular training was between 0.04
ACL injuries per 1,000 athlete-exposures and 0.13 ACL
injuries per 1,000 athlete-exposures. The incidence
in the control groups was between 0.14 ACL injuries
per 1,000 athlete-exposures and 0.51 ACL injuries per
1,000 athlete-exposures.
13–17
The incidence of ACL
injury was statistically significantly lower in the groups
that received neuromuscular training compared with
that in the control groups in both the Hewett et al and
Mandelbaum et al studies (P < .05).
13,15
Mandelbaum
et al analyzed athletes over two seasons and indicated
that the incidence of ACL injury during both seasons
was statistically significantly lower in the group that
received neuromuscular training compared with that
in the control groups (P < .05).
15
Myklebust et al
divided amateur athletes and elite athletes into sepa-
rate groups when analyzing the incidence of ACL injury
and reported that the incidence of ACL injuries was
statistically significantly lower in the group of profes-
sional athletes who received neuromuscular training
compared with that in the control group (P < .05).
14
Discussion
Effects of Neuromuscular Training
Previous studies have indicated that neuromuscular
training can improve joint position sense, stability,
and protective reflexes, thereby preventing ACL injury.
9
Noyes and Barber-Westin stated that neuromuscular
training can prevent ACL injury in female athletes
effectively. This is consistent with our results.
11
The five
articles we examined involved the use of plyometric
exercises, jump training, agility exercises, and board
exercises for neuromuscular training.
13–17
Athletes
must perform dynamic and static response actions
Table 2. Compliance and Results of Reviewed Articles
Author (years) Compliance (season) Results
a
Hewett et al (1999)
13
70% (NA) Intervention group > control group
Myklebust et al (2003)
14
42% (1999–2000)
50% (2000–2001)
Intervention group > control group*
Mandelbaum et al (2005)
15
96% (2000)
100% (2001)
Intervention group > control group*
Petersen et al (2005)
16
99% (2003) Intervention group > control group
Gilchrist et al (2008)
17
96% (2002) Intervention group > control group
NA = not applicable.
a
Athletes with ACL injuries in the intervention group compared with the control group.
*P < .05; intervention group vs. control group.
20 NOVEMBER 2014 INTERNATIONAL JOURNAL OF ATHLETIC THERAPY & TRAINING
when landing after jumps and decelerating to maintain
knee stability.
18
The programs used for neuromuscular
training in each of the five articles satisfied athlete
requirements for training in the use of dynamic and
static response actions. Our analysis indicates that
three factors may influence the effectiveness of neu-
romuscular training in preventing ACL injury. First,
strengthening the hamstring muscle groups facilitates
knee stability and reduces the incidence of ACL injury.
Second, because female quadriceps and hamstring
muscles are unbalanced and antagonistic, training
in the use of static response actions can improve the
antagonistic contraction capability of muscles. Third,
training in the use of dynamic response actions can
reduce knee varus and valgus upon landing and
increase joint stability against landing stress.
Compliance and Injury Prevention in Neuromuscular
Training
Medina et al examined electromyography changes in
the thigh muscles of athletes when landing after jumps.
They determined that the hamstring muscle activation
in females requires specific neuromuscular training to
prevent ACL injury.
19
In this study, we discovered that
the five neuromuscular training programs were all
capable of reducing the incidence of ACL injuries in
female athletes.
13–17
The reviewed literature indicates
that neuromuscular training can reduce force peaks
upon landing in female athletes.
13,15,16
In addition,
the quadriceps and hamstring muscles of female ath-
letes were imbalanced before training. The training
improved the strength and explosive power of the
hamstring muscles, thereby lending more support to
the ACL.
13,15,16
In addition, we compared athlete com-
pliance among the articles. Hewett et al, Petersen et
al, and Gilchrist et al indicated that 70% to 99% of the
athletes completed their training.
13,16,17
Mandelbaum
et al conducted analyses over two years.
15
In the first
year, 96.15% of the participants completed the pro-
gram (2000 season). In the second year, 100% of the
participants completed the program (2001 season).
15
Myklebust et al indicated that only 26% of the amateur
athletes completed the program in the first year (1999
to 2000 season), whereas 42% of the elite athletes
completed the program. In the second year (2000
to 2001 season), 29% of the amateur athletes and
50% of the elite athletes completed the program.
14
Athletes require time to adapt to neuromuscular train-
ing. Therefore, when athletes are accustomed to and
familiar with the workouts, compliance will increase
the following year. Dynamic and static response action
training included in neuromuscular training involves
particular training exercises and intensities.
20,21
Ama-
teur athletes struggle to adapt to workouts. Revisions
to neuromuscular training workouts for the general
female population and amateur athletes must be con-
sidered in the future.
We analyzed the prevention of ACL injury and
determined that the incidence of ACL injury was lower
in the groups that received neuromuscular training
Figure 1
The incidence of ACL injury of reviewed articles.
INTERNATIONAL JOURNAL OF ATHLETIC THERAPY & TRAINING NOVEMBER 2014 21
than that in the control groups. This indicates that
neuromuscular training facilitates the prevention of
ACL injury in female athletes.
13–17
Myklebust et al
reported an incidence of 0.13 ACL injuries per 1,000
athlete-exposures in the first year and 0.09 ACL injuries
per 1,000 athlete-exposures in the second year.
14
This
indicates that neuromuscular training was effective
in preventing ACL injury despite low compliance. The
incidence of ACL injury decreased further as compli-
ance increased.
22
Conclusion
Neuromuscular training is effective in preventing ACL
injury in female athletes. We recommend conduct-
ing specific training in the use of dynamic and static
actions. Furthermore, the training program design
should consider the involvement of the hamstring mus-
cles. The training program design must be revised, or
the exercise intensity must be reduced, for the general
female population and amateur athletes to increase
compliance and improve the prevention of ACL injuries.
Acknowledgments
The authors are grateful for financial support from
China Medical University under the contract No.
CMU102-N-12.
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Wen-Dien Chang is with the Department of Sports Medicine at China
Medical University, Taichung, Taiwan.
Ping-Tung Lai is with the Department of Physical Therapy and Reha-
bilitation at Da-Chien General Hospital, Miaoli, Taiwan.
Tricia Turner, PhD, ATC, University of North Carolina at Charlotte, is
the report editor for this article.
