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Hamstring to quadriceps strength ratio and noncontact leg injuries: A prospective study during one season

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Previous studies have proposed that thigh muscle imbalance is a critical risk factor for the athletic non-contact knee injuries. However, there is a little consensus among prospective studies with regard to the correlation between isokinetic hamstring to quadriceps strength ratio (HQR) and the non-contact knee injury rates. Most of athletic movements at risk are closed kinetic chain movements, and compensatory effect among ankle, knee, and hip joints during the closed kinetic chain movement was observed in the previous literatures. Therefore, it is assumed that hamstrings and quadriceps (H:Q) imbalance can cause non-contact lower extremity injuries without necessarily causing knee injuries. The purpose of this study was to prospectively investigate the relationship between H:Q strength imbalance and overall non-contact lower extremity injuries. A prospective cohort study was conducted on NCAA division III basketball and soccer players during one season. A total of eighty two NCAA Division III athletes (41 female [19.56 ± 1.34 yrs, 68.2 ± 10.84 kg, 166.3 ± 6.78 cm] and 40 male [19.97 ± 1.43 yrs, 75.45 ± 8.23 kg, 173.21 ± 7.65 cm]) volunteered to participate in this study which tested Q and H strength at 60 • /s. A trend (p < 0.05) indicating that lower than 60% of HQR was associated with non-contact leg injuries was apparent. This suggests that the H:Q imbalance may be of significance in athletic non-contact leg injuries.
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Isokinetics and Exercise Science 19 (2011) 1–6 1
DOI 10.3233/IES-2011-0406
IOS Press
Hamstring to quadriceps strength ratio and
noncontact leg injuries: A prospective study
during one season
Daehan Kimaand Junggi Hongb,
aDepartment of Kinesiology, University of Saskatchewan, Saskatchewan, Canada
bDepartment of Exercise Science, Willamette University, Salem, OR, USA
Abstract. Previous studies have proposed that thigh muscle imbalance is a critical risk factor for the athletic non-contact knee
injuries. However, there is a little consensus among prospective studies with regard to the correlation between isokinetic
hamstring to quadriceps strength ratio (HQR) and the non-contact knee injury rates. Most of athletic movements at risk are closed
kinetic chain movements, and compensatory effect among ankle, knee, and hip joints during the closed kinetic chain movement
was observed in the previous literatures. Therefore, it is assumed that hamstrings and quadriceps (H:Q) imbalance can cause
non-contact lower extremity injuries without necessarily causing knee injuries. The purpose of this study was to prospectively
investigate the relationship between H:Q strength imbalance and overall non-contact lower extremity injuries. A prospective
cohort study was conducted on NCAA division III basketball and soccer players during one season. A total of eighty two NCAA
Division III athletes (41 female [19.56 ±1.34 yrs, 68.2 ±10.84 kg, 166.3 ±6.78 cm] and 40 male [19.97 ±1.43 yrs, 75.45 ±
8.23 kg, 173.21 ±7.65 cm]) volunteered to participate in this study which tested Q and H strength at 60/s. A trend (p < 0.05)
indicating that lower than 60% of HQR was associated with non-contact leg injuries was apparent. This suggests that the H:Q
imbalance may be of significance in athletic non-contact leg injuries.
Keywords: Kineticintegration, isokinetic strength, neuromuscular, co-contraction, plyometrics, prophylactic
1. Introduction
Co-contraction of agonist and antagonist muscles
is important for joint stabilization during the dynam-
ic movement [8,15,24]. Researchers have consistent-
ly proposed that balance of these opposing muscles is
imperative in maintaining ideal joint position, there-
fore it is a critical factor for avoiding injuries during
the athletic movements such as jumping, pivoting, and
cross-cutting [5,8,28].
The National Collegiate Athletic Association
(NCAA) Injury Surveillance System (ISS) has collect-
ed injury data from various sport activities over a 16-
year time period (1988 through 2004). According to
Address for correspondence: J. Hong, Department of Exercise
Science, Willamette University, 900 State Street, Salem, OR97301,
USA. E-mail: jhong@willamette.edu.
its report, more than 50% of all injuries were to the
lower extremity and most of them were non-contact
injuries [17]. Researchers in clinical and exercise
sciences field have focused on developing prevention
strategies of these injuries in an effort to reduce injury
rates and related medical costs over time [10,12,13,22].
One of the most important goals of currently used
prophylactic training programs is to enhance neuro-
muscular balance of hamstring and quadriceps mus-
cles [14,16,23]. While researchers have reported that
preventative conditioning program such as plyomet-
rics and balance exercises not only decreased knee in-
jury rates but also improved balance of hamstring and
quadriceps [12–14], surprisingly, there is little consen-
sus with regard to whether strength ratio of hamstring
to quadriceps (H:Q) can be used as a predictor of non-
contact knee or surrounding tissue injuries [2,9,22].
One explanation of the unclear correlation between
H:Q strength ratio (HQR) and injuries is that imbalance
ISSN 0959-3020/11/$27.50 2011 – IOS Press and the authors. All rights reserved
2D. Kim and J. Hong / Hamstring to quadriceps strength ratio and noncontact leg injuries
of strength between hamstrings and quadriceps have
been retrospectively associated with the injuriesin most
of the previous literatures [6,30]. These retrospective
studies compared HQR of normal and deficient legs [6,
19,20], however, it is unclear if any of the strength im-
balance were present before the injury. Therefore, it
was suggested that thoroughly designed prospective in-
vestigations could clarify the association between HQR
and injuries in knee and surrounding tissues [30].
Currently, few prospective studies are available, but
these studies also reported contradicting results [2,9,
27]. While the role of HQR playing in knee and sur-
rounding tissue injuries remain asan enigma,we cannot
ignore the current emphasis of prophylactic approach
on improving H:Q strength balance. Previous studies
on HQR and susceptibility to injuries have focused on
examining only the knee related injuries. However,
trying to find the direct relationship between a risk fac-
tor and the injuries at corresponding anatomical region
may not be the feasible method because non-contact
athletic leg injuries are multi-factorial. Although ham-
string and quadriceps muscles are directly related to
knee joint stabilization, H:Q strength imbalance may
not necessarily cause knee injuries. Most of the non-
contact athletic lower extremity injuries happen during
the closed kinetic movement such as running, landing
from jumping, pivoting, or cross-cutting. It is well
known that forces acting upon one joint inevitably af-
fect forces exerting on other linked joints during the
closed kinetic movement [31]. Van Ryssegem dis-
cussed that instability at the knee joint can cause dys-
function at ankle, hip, and eventually upper body joints
through the kinetic chain because the person would use
compensatory movement strategies in order to avoid
pain and injuries [29].
In this context, it is inferred that even if an athlete
with low HQR can successfully avoid knee injury, the
strength imbalance still has a considerable potential to
impose undesirable stress on ankle or hip joint, which
can cause non-contact lower extremity injuries. There-
fore, the purpose of this study was to investigate the re-
lationship between H:Q strength imbalance with over-
all non-contact lower extremity injuries. It was our hy-
pothesis that lower HQR would have an effect on lower
leg injuries of Division III male and female basketball
and soccer players.
2. Method
2.1. Participants
Men and women intercollegiate basketball and soc-
cer players were recruited as the participants of the
Table 1
Subject’s demographics
Male Female
Number of participants 40 42
Age (yrs) 19.97 ±1.55 19.56 ±1.34
Height (cm) 178.21 ±8.42 169.3 ±6.78
Weight (kg) 75.45 ±8.2 68.2 ±10.84
study because lower extremity injuries accounted for
approximately one quarter of all injuries in these
sports [17]. In addition, basketball and soccer mainly
involves movements which are at risk of non-contact
leginjuries such as jumping,pivoting and cross-cutting.
A total of eighty two NCAA Division III intercolle-
giate basketball and soccer players volunteered to par-
ticipate in this study (Table 1). Before the commence-
ment of the testing, all participants read and signed an
informed consent form. This study was approved by
the Institutional Review Board.
2.2. Procedure
A Biodex isokinetic dynamometer (Biodex System
3, Biodex Medical Systems, Shirley, NY) was used
to assess Q and H strength. Tests were carried out
at 60/s [11] and along a range of motion of at 90,
using a knee common protocol (sitting, axes alignment,
stabilization). Gravity correction was performed for
each limb before testing. Once the participants seated
and secured, they performed 3 repetitions of extension
and flexion as a warm-up. A single set of 3 maximal
exertions was performed bilaterally.
In this study, an injury was defined as such providing
1) it occurred as a result of participation in an organized
practice and competition; 2) it prevented the injured
athletes from participating in practices and competition
at least for two weeks; and 3) it required the injured ath-
letes seek medical attention from either athletic trainers
or team doctors [26]. Among the total lower extremity
injuries, we validated only the injuries which were non-
contact in nature. Strain, sprain, and overuse injuries
were included, and contusions were excluded for data
analysis. We also collected the history of ligamentous
injuries.
2.3. Statistical analysis
A statistical analysis was performed using SPSS 17
software (SPSS, Inc., Chicago, IL). The chi-square test
was used to examine the likelihood ratio that legs with
H:Q strength imbalance get injured. An HQR of 0.60
and above was defined as “balance”, while an HQR
D. Kim and J. Hong / Hamstring to quadriceps strength ratio and noncontact leg injuries 3
Table 2
Pre-season hamstring: Quadriceps (H: Q) ratio, in-season lower extremity injuries, and
the pearson chi-square value
HQR Lower extremity injuries Asymp. Sig.
Right Left Right Left Right Left
55.65 ±9.57 54.02 ±8.79 35 32 0.058 0.046
Indicates significant dependence (Asymp. Sig. <0.05).
Table 2 represents the pre-season mean values ±standard deviation (SD) for the ham-
strings to quadriceps (H:Q) ratios, the number of lower extremity injuries occurred
during the season, and the pearson chi-square value.
Table 3
HQR and injury cross tabulation
Criteria Number of legs Number of injuries % within total
IP1injuries
Right Left Right Left Right Left
HQR <60% 52 55 29 28 63.4% 67.1%
HQR >60% 30 27 6 4 36.6% 32.9%
1IP =Ipsilateral.
Table 3 shows the distribution of H:Q strength ratio among total legs and injured legs.
below 0.60 was defined as “imbalance”. Pearson chi-
square value below 0.05 indicates H:Q strength ratio
and rate of lower extremity injuries are dependent.
3. Results
The mean (SD) of the HQ ratio of total 82 athletes
were 0.55 ±0.09 for the right leg and 0.54 ±0.08 for
the left leg. During season, there were a total of 35
non-contact lower extremity injuries on right legs and
32 on left leg (Table 2).
Outof 35 rightleginjuries,12 weregame-related and
23 were practice-related. For the left leg, out of 32 in-
juries, the respective injuries were 8 and 24. The mean
number of practices per season for men and women’s
basketball team was 75.5, and the number of games
played for both teams was 19. For the soccer players,
the average number of practices was 47.5 and the aver-
age number of games played per season was 19.5. In
recording the number of injury, if athletes had a history
of injury on the same body parts, the injury was not in-
cluded. The results of the analysis showed that 63.4%
of the injured right legs and 67.1% of the injured left
legs had an HQR of less than 0.6 (Table 3, Fig. 1). The
difference in the number of left leg injuries between the
athletes with an HQR <0.6 and those with a ratio >
0.6 was statistically significant (p=0.046). Although
there was a notable difference in the number of right leg
injuries between the athletes with less or more than 0.6,
the pvalue didn’t reveal a significant difference (p=
0.058). However, the chi-square test demonstrated sig-
nificant likelihood ratio in the relationship between the
number of right leg injuries and the right HQR (p=
0.041).
4. Discussion
The question addressed by the present study was
whether the quadriceps and hamstrings isokinetic
strength imbalance was associated with susceptibility
to lower leg injuries. The main finding of the study
is a trend according to which injured athletes had pre-
season HQ ratio of less than 0.6 (p < 0.05). For the left
leg injuries, the result revealed the statistically signifi-
cant relationship between the lower pre-season HQ ra-
tio(<0.6) and the number of the lower leg injuries. For
the right leg injuries, the result showed no statistically
significant relationship but revealed statistically signif-
icant likelihood through the Chi Square test (p=0.03).
This noticeable difference between muscle imbalance
andinjuries is consistentwith previous reports [2,9,11].
Considering that most of the injuries from the study
were the knee joint injuries, a possible explanation for
this demonstrable relationship may arise from the knee
joint mechanism. It has been suggested that the role of
the hamstring muscles during leg extension is to assist
the anterior musculotendinous structures in preventing
anterior tibial force, by pulling the knee joint poste-
riorly, increasing joint stiffness and reducing anterior
laxity force during quadriceps loading [2].
In previous studies, the effects of muscle imbalance
have been reported specifically regarding the suscep-
4D. Kim and J. Hong / Hamstring to quadriceps strength ratio and noncontact leg injuries
Fig. 1. Distribution of HQR within legs (preseason).
tibility of the knee injury; however, in this study, we
included other lower limb injuries to elucidate possible
connections between the thigh muscle imbalance and
other common lower leg injuries among basketball and
soccerplayers. The relationshipbetween low HQR and
overall lower leg injuries shown in our study may as-
cribe to bi-articulate nature of leg muscles and neuro-
muscular compensation among lower extremity joints
in joint stabilization. Dontigny [3] suggested that the
opposing force of hamstring muscles and psoas mus-
cles act as a force couple in stabilizing a pelvis during
thenormal gait. Previousliterature revealedthat a com-
bination of weak hamstring and strong anterior muscles
could cause anterior pelvic tilt, which would demand
muscles and soft tissues around hip and trunk to work
harder in order to stabilize the lumbopelvic complex.
This may explain the result of our study that more than
a quarter of the total leg injuries were to the muscle and
tendons around the hip and knee joints (Table 4). Stabi-
lization of knee and protection of ligaments throughout
the whole flexion angle require simultaneous contrac-
tion of quadriceps, hamstring, and gastrocnemius [25].
Nyland et al. suggested that increased ankle dorsiflex-
ion and eversion moment is due to the compensatory
movement of the ankle joint in order to decelerate the
anterior translation and internal rotation of tibia during
the closed kinetic flexion at the knee joint [24].
The trend describing the dependency between
strengthimbalance and thenon-contact injury observed
in our study suggests that intervention strategies of cor-
recting strength imbalance are urgently required for the
athleteswho haveparticipated in this study,because ap-
proximately 63% of the group demonstrated muscular
imbalance. Previous literatures hinted that quadriceps-
related strength imbalance was likely caused by ha-
bitual quadriceps dominant movement strategies [16,
18,21]. Van Ryssegem emphasized that athletes must
unlearn compensatory movement pattern and learn the
proper movement technique as they train for strength
of the musculature [29]. Therefore, correct movement
training plays an important role in correcting strength
imbalance and preventing athletic non-contact injuries.
For example, traditional jump training suggested for
preventing non-contact injuries should focus more on
proper landing techniques than jumping height in or-
der to unlearn quadriceps dominant movement strate-
gies and learn to properly use hamstrings for knee joint
stabilization during the landing.
4.1. Limitation and suggestion
The speed chosen for the isokinetic strength testing
in the study was 60/s. One limitation is not using
other speeds for the isokinetic test. Another limitation
relates to the strength ratio used in the present study.
HQR in the study was only expressed in a conven-
tional manner, which compares concentric quadriceps
muscle actions to concentric hamstring muscle actions.
Recently more functionally relevant protocol (known
as Dynamic Control Ratio or Functional Ratio of HQ)
been suggested as more common parameter in examin-
ing HQ imbalance [1,4,7]. Evaluation of this Dynamic
Control Ratio, which eccentric hamstring muscle ac-
tions are compared to concentric quadriceps actions
(Hecc:Qcon) could have provided more functionally
relevant insights.
5. Clinical implication
To our knowledge, this is the first prospective study
to demonstrate the relationship between H:Q strength
D. Kim and J. Hong / Hamstring to quadriceps strength ratio and noncontact leg injuries 5
imbalance and overall non-contact lower extremity in-
jury rates. The result of our study indicates that an
HQR <0.6 may be a risk factor for non-contact lower
extremity injuries. In Division III setting, athletes re-
ly on unsupervised self-conditioning until the official
practice season begins. Considering the importance
of HQR in preventing lower leg injuries the feasibility
of correcting H:Q strength imbalance through unsuper-
vised training is low. Therefore, thoroughly planned
and supervised conditioning is necessary for division
III athletes. NCAA division III athletes are occupying
more than 40% of the total NCAA athletes [32]. Even
though the rationale of limiting practice seasons in di-
vision III athletes is to protect their academic activi-
ties from excessive practices, it should not be ignored
that radical limitation of supervised conditioning may
lead to engagement in intense athletic activities with
“untrained legs” which may cause more injuries.
Acknowledgments
We would like to sincerely thank the participants,
Guido Van Ryssegem, Stasinos Stavrianeas, Peter
Harmer,Judy Gordon,andGianni Maddalozzo for their
constructive advice and support.
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... Proper balance of agonist and antagonist muscles is important for joint stabilization during the dynamic movement (Hewett, Myer, & Zazulak, 2008;Kim & Hong, 2011;Knapik et al., 2004). To our knowledge, there are no relevant stu- imperative in maintaining ideal joint position, therefore it is a critical factor for avoiding injuries during the athletic movements such as jumping, pivoting, and crosscutting (Dontigny, 2005;Solomonow & Krogsgaard, 2001). ...
... One of the most important goals of prophylactic training programs is to enhance neuromuscular balance of hamstring and quadriceps muscles (Hewett, Myer, & Ford, 2001;Myer, Ford, & Hewett, 2004). The instability at the knee joint can cause dysfunction at ankle, hip, and eventually upper body joints through the kinetic chain because the person would use compensatory movement strategies in order to avoid pain and injuries (Kim & Hong, 2011). ...
... When the hamstring strength is within expected values in relation to quadriceps, the result is reduced stress exerted on anterior cruciate ligament (ACL). The anterior cruciate liga- (Kim & Hong, 2011). The stronger the hamstring the better protection for knee during sudden changes in direction and sliding. ...
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... Moreover, it has been reported that greater strength asymmetries have a negative effect on skill performance in elite soccer [23]. Kim et al. [24] stated that isokinetic testing with a low angular speed (60 • ·s −1 ) is a strong predictor for a non-contact leg injuries in National College American Association athletes. Additionally, Sugiura et al. [25] reported significant relationships between hamstring injuries in elite sprinters and hamstring muscle weakness only at lower speeds of testing. ...
... Isokinetic strength evaluation with 90 • knee flexion and extension of the knee extensors (KE) and flexors (KF) during concentric muscle contraction at a 60 • ·s −1 angular velocity [24,25] was performed using a Cybex Humac Norm dynamometer (Cybex NORM ® , Humac, CA, USA). Limb dominance was defined by determining which leg each participant preferred to kick with (i.e., the kicking leg) [29]. ...
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... Liporaci et al. [4] showed that BA (> 10%) between knee extensors (KEs) increased musculoskeletal injuries up to 16-fold and ligament/meniscus injuries up to 28-fold. BA evaluation at a low angular velocity (60 • ·s −1 ) was presented as a predictor of non-contact leg injury [7], while a combination of pre-season isokinetic strength tests using bilateral, ipsilateral, and mixed ratios can detect up to 79% of all hamstring injuries [3]. Most soccer players prefer using one particular lower limb to kick the ball and center, which requires asymmetric motor patterns that lead to the development of asymmetric adaptations of musculoskeletal lower limb function [8]. ...
... This advantage has been noted for direction control in juggling and dribbling, movement timing to trap an approaching ball, and power and accuracy to kick a static or moving ball [14]. Although strength BA as a negative factor for health and performance is well researched in professional soccer [3,4,7,12,15], we observed a paucity of literature on BA in various stages of childhood and adolescence in elite youth players. Some authors have attempted to clarify the effect of maturation [10,16] and chronological or professional training age [8,17,18] on the BA level; however, the conclusions vary. ...
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The strength asymmetry of athletes as a negative health and performance factor is increasingly being researched in sports with a high load on the dominant limb when some specific unilateral movements, such as passing, jumping, and tackling, are required. This study aimed to determine the level of isokinetic strength bilateral asymmetry (BA) among knee extensors (KEs) and knee flexors (KFs) of elite youth soccer players. The sample (n = 87) consisted of three age categories of under 13 (U13), under 15 (U15), and under 17 (U17) years old. Isokinetic dynamometry was used to obtain the maximum peak torque of the KEs and KFs in the dominant and non-dominant lower limbs during concentric muscle contraction. The analysis revealed significantly lower values (p < 0.05) of BA in KEs in U17 than in younger categories, U13 and U15, and higher values (p < 0.05) of BA in KFs in the U15 category than in the U17category. The majority of the players in the U15 category (68%) reached KFs BA higher than 10% in comparison with U13 players (50%) and U17 players (28% of players) (p < 0.05). Our results showed a significant effect of age category on BA levels in young soccer players. High incidences of increased BA in the lower limbs occurred in the younger categories (U13, U15) and subsequently decreased in the later adolescent stages.
... The commonly used "conventional" hamstringto-quadriceps ratio (H/Q ratio) represents the ratio of concentric peak torque during knee flexion (mainly generated by the hamstring muscles) to concentric peak torque during knee extension (mainly generated by the quadriceps muscles) [28]. A low H/Q ratio (i.e., below the generally accepted threshold value of 60%) may lead to hamstring strain and/or anterior cruciate ligament (ACL) injury [19,[29][30][31]. However, the relationships between the H/Q ratio and sports performance (e.g., sprinting and jumping) have not been sufficiently investigated [32,33]. ...
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The correct torque ratio between the knee joint extensor and flexor muscle groups can effectively prevent injuries to the anterior cruciate ligament and hamstring strain. However, it is unclear whether a high torque ratio of the knee joint flexor muscles to the extensor muscles is beneficial for sport performance. Therefore, the aim of the study was to investigate the relationshipbetween the hamstring-to-quadriceps (H/Q) ratio and sprint times (10- and 30-m) and jump heights (CMJ and SJ) in soccer players. The study examined 26 young elite soccer players (age: 18.1 ± 0.7 years; body height: 1.77 ± 0.05 m; body mass: 72.7 ± 5.7 kg). Knee joint flexor and extensor peak torques were assessed using the Cybex dynamometer (at 60◦/s, 120◦/s and 180◦/s). Additionally, each participant performed the CMJ, SJ, and 30 m sprint. A significant relationship was obtained between the H/Q ratio (60◦/s) and 30 m sprint time (r = 0.47). The positive direction of this relationship may indicate an important role of knee joint extensors in sprinting performance. Moreover, the H/Q ratio was not significantly associated with the CMJ, SJ or 10 m sprint performance. The H/Q ratio should be considered together with the peak torque values in terms of the assessment of sprinting and jumping performance.
... While muscle weakness may cause muscle injuries, stronger muscles can supply protection from injuries (Garrett et al., 1987). In the knee joint, dominant-nondominant strength and hamstring/quadriceps ratio are used to determine muscular imbalance (Kong and Burns, 2010;Kim and Hong 2011;Croisier et al., 2002;Myer et al., 2009). Hamstring and quadriceps muscles surrounding the knee joint provide joint stability and athletic performance during running, stopping, and jumping. ...
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The literature has revealed that knee injuries are the most common injury among basketball players. The strength ratios dominant/non-dominant and posterior-anterior around the knee joint are used to evaluate strength balances. But there has been far less research published about strength evaluation in professional-level basketball. The objectives of the present study were: (i) to compare hamstring and quadriceps muscles' strength values during concentric knee extension and flexion at different angular velocities at professional level basketballers, (ii) to determine dominant and non-dominant strength values during these contractions. 13 professional male basketball athletes voluntarily participated in the study. The leg strength was evaluated with an isokinetic dynamometer at 240-180-120-60 0 /s angular velocities. The hamstring and quadriceps unilateral peak torque ratio (H/Q) and dominant non-dominant strength ratio were calculated.
... Additionally, a high CON PT of Q and a low CON PT of H results in a low HQR ratio (L 0.54; R 0.63), which puts the knee joint at risk. It was reported that lower than 60% of HQR is associated with non-contact leg injuries [57]. This could be explained by all judokas being right-hand dominant, which usually reflects in the judo bout to be right stance dominant. ...
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Background: This study was designed to perform isokinetic knee testing of male judokas competing in the under 73 kg category. The main aims were: to establish the concentric (CON) and eccentric (ECC) strength profile of hamstrings (H) and CON profile of quadriceps (Q) muscles; to evaluate the differences in CON and ECC peak torques (PT) with various strength ratios and their bilateral asymmetries; the calculation of the dynamic control ratio (DCR) and H ECC to CON ratio (HEC); Methods: 12 judokas competing on a national and international levels with a mean age of 19 ± 4 years, a weight of 75 ± 2 kg and with a height of 176 ± 5 cm were tested. All the subjects were right-hand dominant. Isokinetic testing was performed on iMOMENT, SMM isokinetic machine (SMM, Maribor, Slovenia). The paired t-test was used to determine the difference between paired variables. The level of significance was set at p ≤ 0.05; Results: Statistical differences between left (L) and right (R) Q PT (L 266; R 241 Nm), H ECC PT (L 145; R 169 Nm), HQR (L 0.54; R 0.63), DCR (L 0.55; R 0.70), HEC (L 1.02; R 1.14) and PTQ/BW (L 3.57; R 3.23 Nm/kg) were shown. Bilateral strength asymmetries in CON contraction of 13.52% ± 10.04 % for Q, 10.86% ± 7.67 % for H and 22.04% ± 12.13% for H ECC contraction were shown. Conclusions: This study reports the isokinetic strength values of judokas in the under 73 kg category, emphasising eccentric hamstring strength and eccentric derived strength ratios DCR and HEC. It was shown that asymmetries are better detected using eccentric testing and that the dominant leg in judokas had stronger eccentric hamstring strength resulting in higher DCR and HEC.
... Although the eccentrically co-acting hamstrings have a dynamic role in maintaining the stability of the knee during forceful knee extension (Coombs and Garbutt, 2002), there are conflicting results whether strength imbalances between the hamstrings and the quadriceps (H:Q ratios) are effective in the identification of risk factors in different populations (Soderman et al., 2001;Kim and Hong, 2011;Freckleton and Pizzari, 2012;Van Dyk et al., 2016;Lee et al., 2018). The frequency distribution of players that have been classified as injured or non-injured by the Decision Tree is displayed against the frequency distribution of players that did or did not suffer an injury. ...
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Introduction: Elite youth soccer players suffer increasing numbers of injuries owing to constantly increasing physical demands. Deficits in neuromuscular performance may increase the risk of injury. Injury risk factors need to be identified and practical cut-off scores defined. Therefore, the purpose of the study was to assess neuromuscular performance parameters within a laboratory-based injury risk screening, to investigate their association with the risk of non-contact lower extremity injuries in elite youth soccer players, and to provide practice-relevant cut-off scores. Methods: Sixty-two elite youth soccer players (age: 17.2 ± 1.1 years) performed unilateral postural control exercises in different conditions, isokinetic tests of concentric and eccentric knee extension and knee flexion (60°/s), isometric tests of hip adduction and abduction, and isometric tests of trunk flexion, extension, lateral flexion and transversal rotation during the preseason period. Non-contact lower extremities injuries were documented throughout 10 months. Risk profiling was assessed using a multivariate approach utilizing a Decision Tree model (Classification and Regression Tree (CART) method). Results: Twenty-five non-contact injuries were registered. The Decision Tree model selected the COP sway, the peak torque for knee flexion concentric, the functional knee ratio and the path of the platform in that hierarchical order as important neuromuscular performance parameters to discriminate between injured and non-injured players. The classification showed a sensitivity of 0.73 and a specificity of 0.91. The relative risk was calculated at 4.2, meaning that the risk of suffering an injury is four times greater for a player, who has been classified as injured by the Decision Tree model. Conclusion: Measuring static postural control, postural control under unstable condition and the strength of the thigh seem to enable a good indication of injury risk in elite youth soccer players. However, this finding has to be taken with caution due to a small number of injury cases. Nonetheless, these preliminary results may have practical implications for future directions in injury risk screening and in planning and developing customized training programs to counteract intrinsic injury risk factors in elite youth soccer players.
... Co-contraction of the hamstring and quadriceps muscles has been found to stabilize the knee 24 and an imbalance in hamstring to quadriceps strength may be of significance in non-contact leg injuries. 25 The current study shows a significant increase in the ratio of hamstringto-quadriceps strength, normalized to body weight, from the school to high school age of male and female athletes but no difference between sex. This demonstrates that while the hamstrings and quadriceps of both sexes increased with age, hamstring strength increased to a greater extent. ...
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Background: The identification of risk factors for injury is a key step for musculoskeletal injury prevention in youth sports. Not identifying and correcting for injury risk factors may result in lost opportunity for athletic development. Physical maturation and sex affect these characteristics, which may indicate the need for both age and sex-based injury prevention programs. Hypothesis/purpose: This study examined age and sex differences in knee strength, static balance, jump height, and lower extremity landing biomechanics in school- and high school-age athletes. Study design: Cross-sectional. Methods: Forty healthy school aged (10.8±0.8 yrs) and forty high school (16.8±0.8 yrs) athletes completed isokinetic knee flexion and extension strength tests, single-leg static balance and single-leg vertical stop jump tasks. Results: High school athletes were significantly stronger (~67% and 35% stronger for males and females, respectively) and jumped higher (regardless of sex) compared to school age athletes. High school males had worse balance (~28%) compared to their younger counterparts. High school females had lower strength (~23%) compared to males but had better balance (~46%). Conclusion: Maturation had different effects on the variables analyzed and sex differences were mainly observed after maturation. These differences may be minimized through appropriate age and sex specific training programs. Levels of evidence: 3a. Clinical relevance: Neuromuscular and biomechanical differences between sex and age groups should be accounted for in injury prevention and rehabilitation. Inadequate training may be a primary factor contributing to injuries in a young athletic population. When designing training programs for long term athlete development, programs should be dependent on decrements seen at specific time points throughout maturation.What is known about the subject: Generally, both males and females get stronger and jump higher as they get older but the results comparing balance and biomechanics between genders or across age groups have been mixed.What this study adds to existing knowledge: The current study looks at multiple neuromuscular and biomechanical variables in male and female participants at different maturation statuses. The current data supports the significant changes observed in strength and jump height, as both genders age, but the data also demonstrates significant differences in balance between age groups in males and between genders in balance and knee flexion angles.
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The purpose of this paper is to describe the basic structure of the sacroiliac joint, the loading sequence of the primary ligaments, its function during normal gait and the supportive muscle functions. The goal of treatment of low back and pelvic pain should be the restoration of normal function and so it is important to understand just how the low back and the pelvis normally function.The sacroiliac joint has been assumed to be structurally so strong as to be immune to injury through minor trauma. Motion in the joint is minimal and its function has been obscure. There is essentially no motion in the sacroiliac joint on a transverse axis when the sacrum is loaded with the superincumbent weight and the pelvis is symmetrical as in relaxed standing. During normal gait, however, when the pelvis moves into asymmetry, the sacrum flexes laterally and rotates toward the side of loading to drive rotation and counter rotation of the trunk during normal gait to decrease the loading impulse. Primary loading o...
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Isokinetic moment ratios of the hamstrings (H) and quadriceps (Q) muscle groups, and their implication in muscle imbalance, have been investigated for more than three decades. The conventional concentric H/Q ratio with its normative value of 0.6 has been at the forefront of the discussion. This does not account for the joint angle at which moment occurs and the type of muscle action involved. Advances towards more functional analyses have occurred such that previous protocols are being re-examined raising questions about their ability to demonstrate a relationship between thigh muscle imbalance and increased incidence or risk of knee injury. This article addresses the function of the hamstring-quadriceps ratio in the interpretation of this relationship using the ratios Hecc/Qcon (ratio of eccentric hamstring strength to concentric quadriceps strength, representative of isolated knee extension) and Hcon/Qecc (ratio of concentric hamstring strength to eccentric quadriceps strength, representative of isolated knee flexion).
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The purpose of this study was to examine the dynamic relationship between the quadriceps femoris and hamstrings in anterior cruciate ligament (ACL) insufficiency. Thirty-five young active patients with an untreated complete tear of the ACL took part in the study. Using a KINCOM isokinetic dynamometer, the dynamic capacity of each muscle group at 30° in concentric and eccentric exertion in both the deficient and sound knee was measured. Findings demonstrated a significant reduction (P<0.05) in the torque produced by the deficient-side quadriceps compared to the sound side but no significant variations in the hamstring torque. Discussion of the findings considers a possible involvement of neurophysiological inhibition of the quadriceps as a cause for the observed weakness.
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Background: Women have higher non-contact anterior cruciate ligament injury rate than men do in sport activities. Non-contact anterior cruciate ligament injuries frequently occur in sports requiring cutting tasks. Alternated motor control strategies have identified as a potential risk factor for the non-contact anterior cruciate ligament injuries. The purpose of this study was to compare the patterns of knee kinematics and electromyographic activities in running, side-cutting, and cross-cutting between men and women recreational athletes. Methods: Three-dimensional kinematic data of the knee and electromyographic data of selected muscles across the knee joint were collected for 11 men and 9 women recreational athletes in running, side-cutting, and cross-cutting. Regression analyses with dummy variables for comparison of knee motion patterns between men and women. Results: Women tend to have less knee flexion angles, more knee valgus angles, greater quadriceps activation, and lower hamstring activation in comparison to men during the stance phase of each of the three athletic tasks. Literatures suggest these alternated knee motion patterns of women tend to increase the load on the anterior cruciate ligament. Conclusion: Women on average may have certain motor control strategies that may alter their knee motion patterns. Women's altered knee motion patterns may tend to increase the load on the anterior cruciate ligament in the selected athletic tasks, which may contribute to the increased anterior cruciate ligament injury rate among women. Relevance: Non-contact anterior cruciate ligament injuries frequently occur in sports. Altered motor control strategies and lower extremity motion patterns are likely to play an important role in non-contact anterior cruciate ligament injuries. Non-contact anterior cruciate ligament injuries may be prevented by correcting altered motor control strategies and associated lower extremity motion patterns through certain training programs.
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Conventionally, the hamstring:quadriceps strength ratio is calculated by dividing the maximal knee flexor (hamstring) moment by the maximal knee extensor (quadriceps) moment measured at identical angular velocity and contraction mode. The agonist-antagonist strength relationship for knee extension and flexion may, however, be better described by the more functional ratios of eccentric hamstring to concentric quadriceps moments (extension), and concentric hamstring to eccentric quadriceps moments (flexion). We compared functional and conventional isokinetic hamstring: quadriceps strength ratios and examined their relation to knee joint angle and joint angular velocity. Peak and angle-specific (50 degrees, 40 degrees, and 30 degrees of knee flexion) moments were determined during maximal concentric and eccentric muscle contractions (10 degrees to 90 degrees of motion; 30 and 240 deg/sec). Across movement speeds and contraction modes the functional ratios for different moments varied between 0.3 and 1.0 (peak and 50 degrees), 0.4 and 1.1 (40 degrees), and 0.4 and 1.4 (30 degrees). In contrast, conventional hamstring:quadriceps ratios were 0.5 to 0.6 based on peak and 50 degrees moments, 0.6 to 0.7 based on 40 degrees moment, and 0.6 to 0.8 based on 30 degrees moment. The functional hamstring:quadriceps ratio for fast knee extension yielded a 1:1 relationship, which increased with extended knee joint position, indicating a significant capacity of the hamstring muscles to provide dynamic knee joint stability in these conditions. The evaluation of knee joint function by use of isokinetic dynamometry should comprise data on functional and conventional hamstring:quadriceps ratios as well as data on absolute muscle strength.
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Strain in the anteromedial fibers of the anterior cruciate ligament [ACL(am)] was studied in six cadaver knees. ACL(am) strain was measured in five knees during the application of isometric quadriceps forces alone and simultaneously applied isometric quadriceps and hamstrings forces at 10 degrees increments from 0 degrees to 90 degrees of knee flexion. ACL(am) strain during muscle loading was measured with respect to the ACL(am) strain measured with the knee in its resting position (neutral or near neutral position). A sixth knee was used to investigate the reproducibility of the resting position and quadriceps-induced ACL(am) strains. The strains induced in the ACL(am) by the quadriceps were significantly greater than 0 at knee flexion angles from 0 to 40 degrees and not significantly different from 0 for 50 to 90 degrees. The ACL(am) strains induced by simultaneously applied hamstrings and quadriceps forces were not significantly different from 0 at any of the knee flexion angles tested. Simultaneously applied hamstrings and quadriceps forces significantly reduced ACL(am) strain at 10, 20, and 90 degrees of knee flexion compared to the ACL(am) strain induced by quadriceps forces alone. The hamstrings are potentially capable of both significantly reducing and negating quadriceps-induced ACL(am) strain at 10 and 20 degrees of knee flexion.