***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Women have higher rates of knee ligament injury than men . Co-contraction of knee muscles is proposed to be an important mechanism to protect the joint from injuries . HYPOTHESIS Females have lower co-contraction levels when compared to males . STUDY DESIGN Exploratory , cross-sectional design . METHODS Thirty-six men and women equally divided into four groups according to gender and activity level ( sedentary and athletic ) were compared in relation to vastus lateralis and biceps femoris co-contraction before heel strike during level walking and before floor contact during l and ing from a jump . Muscular co-contraction was assessed by surface electromyography .  Correlations between co-contraction and ligament laxity , extensor and flexor work , and flexion/extension torque ratio were also analyzed . RESULTS No differences between genders were found in the studied situations ( p0.381 ) . During walking , co-contraction was greater in sedentary women compared to athletic women ( p=0.002 ) . A moderate inverse correlation was found between co-contraction during walking and women extensor ( r=-0.613 ; p=0.007 ) and flexor ( r=-0.575 ; p=0.012 ) work . During l and ing from a jump , no variables correlated to co-contraction in any of the groups tested ( r0.477 ; p0.061 ) . CONCLUSION Co-contraction levels were not different between genders . Results suggest that women compensate strength deficits by means of increasing activation levels , possibly to generate adequate joint stiffness to meet stabilization dem and s. However , this is not evident in a more stressful activity like l and ing from a jump . CLINICAL RELEVANCE This study contributes to a better underst and ing of the factors related to joint protection in females , who are at a greater risk of ligament injuries BACKGROUND Despite recent evidence supporting the use of neuromuscular training to reduce anterior cruciate ligament injury risk , female athletes continue to show an increased anterior cruciate ligament injury rate in collegiate basketball and soccer when compared to males . The purpose of the current study was to identify gender and task differences in measures that may increase the risk of anterior cruciate ligament injury in female basketball and soccer athletes . METHODS Eleven female and 11 male collegiate basketball and soccer athletes were height ( female mean 176 ( SD 8 cm ) , male mean 176 ( SD 8 cm ) ) and weight ( female mean 73 ( SD 7 kg ) , male mean 74 ( SD 6 kg ) ) matched .  Three-dimensional motion analysis was used to calculate differences in total coronal plane angular joint excursion ( maximum-minimum ) between male and female athletes when performing a series of medially and laterally directed drop l and ings . FINDINGS Female athletes demonstrated increased total coronal plane excursion for the hip , knee and ankle ( P < 0.05 ) during the medial drop l and ing . During the lateral drop l and ing females displayed increased excursion at the hip and knee . When comparing tasks , the lateral drop l and ing result ed in greater coronal plane excursion at the hip ( P < 0.05 ) while the knee showed no differences between movements . In contrast , females demonstrated increased ankle excursion during the medial drop task ( P < 0.05 ) . INTERPRETATION Female athletes demonstrate increased lower extremity coronal plane excursion when performing single leg drop l and ing in both the medial and lateral direction when compared to height/weight matched male athletes . This increased coronal plane oscillation of lower extremity joints may be related to the increased risk of anterior cruciate ligament injury for female basketball and soccer athletes BACKGROUND It is thought that female athletes with limited experience in a sport perform athletic maneuvers differently than their more experienced counterparts , and that they do so in a manner that places them at greater risk for injury . The purpose of this study was to evaluate the influence of athletic experience on knee mechanics during the execution of a side-step cutting maneuver in young female athletes . METHODS Three-dimensional kinematics , ground reaction forces and electromyographic activity ( surface electrodes ) were recorded during the early deceleration phase of side-step cutting in 30 high school females ( 15 experienced , 15 novice ) . Group differences in knee joint kinematics , peak moments , net joint moment impulse and average muscle activation were evaluated . FINDINGS No significant group differences were found in knee kinematics . When compared to experienced females , novice females demonstrated significantly smaller flexor , adductor , and internal rotator peak moments and smaller net joint moment impulse in all three planes at the knee . No group differences were found for average EMG ; however , novice athletes had significantly greater co-contraction at the knee . INTERPRETATION The finding of smaller knee moments and greater muscle co-contraction in the novice group suggests that these athletes may adopt a protective strategy in response to a relatively unfamiliar task . In addition , these results suggest that increased moments at the knee emerge with experience , indicating that more skilled athletes may be at greater risk for anterior cruciate ligament ( ACL ) injury BACKGROUND AND PURPOSE Dynamic knee stabilization strategies of people who successfully compensate for the absence of an anterior cruciate ligament ( ACL ) ( " copers " ) are different from those of people who do not compensate well for the injury ( " noncopers " ) . Early after injury , certain patients ( " potential copers " ) can increase the likelihood of successfully compensating for the injury by participating in 10 sessions of perturbation training . The purpose of this study was to determine how perturbation training alters muscle co-contraction and knee kinematics in potential copers . SUBJECTS Seventeen individuals with acute , unilateral ACL rupture who were categorized as potential copers and 17 subjects without injuries who were matched by age , sex , and activity level were recruited for this study . METHODS  Motion analysis and electromyographic data were collected as subjects walked across a stationary or moving platform ( horizontal translation ) before and after perturbation training . RESULTS Before training , potential copers had higher co-contraction indexes and lower peak knee flexion angles than subjects without injuries . After training , potential copers ' movement patterns more closely resembled those of subjects without injuries ( ie , they showed reduced co-contraction indexes and increased peak knee flexion angles during stance ) . DISCUSSION AND CONCLUSION Perturbation training reduced quadriceps femoris-hamstring muscle and quadriceps femoris-gastrocnemius muscle co-contractions and normalized knee kinematics in individuals with ACL rupture who were classified as potential copers . Findings from this study provide evidence for a mechanism by which perturbation training acts as an effective intervention for promoting coordinated muscle activity in a select population of people with ACL rupture Background Female athletes participating in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than do male athletes . Hypothesis Prescreened female athletes with subsequent anterior cruciate ligament injury will demonstrate decreased neuromuscular control and increased valgus joint loading , predicting anterior cruciate ligament injury risk . Study Design Cohort study ; Level of evidence , 2 . Methods There were 205 female athletes in the high-risk sports of soccer , basketball , and volleyball prospect ively measured for neuromuscular control using 3-dimensional kinematics ( joint angles ) and joint loads using kinetics ( joint moments ) during a jump-l and ing task . Analysis of variance as well as linear and logistic regression were used to isolate predictors of risk in athletes who subsequently ruptured the anterior cruciate ligament . Results Nine athletes had a confirmed anterior cruciate ligament rupture ; these 9 had significantly different knee posture and loading compared to the 196 who did not have anterior cruciate ligament rupture . Knee abduction angle ( P < . 05 ) at l and ing was 8 ° greater in anterior cruciate ligament-injured than in uninjured athletes . Anterior cruciate ligament-injured athletes had a 2.5 times greater knee abduction moment ( P < . 001 ) and 20 % higher ground reaction force ( P < . 05 ) , whereas stance time was 16 % shorter ; hence , increased motion , force , and moments occurred more quickly . Knee abduction moment predicted anterior cruciate ligament injury status with 73 % specificity and 78 % sensitivity ; dynamic valgus measures showed a predictive r2 of 0.88 . Conclusion Knee motion and knee loading during a l and ing task are predictors of anterior cruciate ligament injury risk in female athletes . Clinical Relevance Female athletes with increased dynamic valgus and high abduction loads are at increased risk of anterior cruciate ligament injury . The methods developed may be used to monitor neuromuscular control of the knee joint and may help develop simpler measures of neuromuscular control that can be used to direct female athletes to more effective , targeted interventions 
    Output:
    
The relationship between adequate dynamic joint stability and efficient movement patterns are complex .
Adequate antagonistic co-contraction of hamstring musculature seems to be a component of all functional movements , possibly maintain dynamic knee stability and protect against excessive joint loads .