***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: OBJECTIVE To compare differences in kinematic and kinetic parameters of knee , hip and ankle joints between male and female college volleyball players . DESIGN Cross-sectional study . BACKGROUND L and ing injuries , which usually involve anterior cruciate ligament injuries , are common in volleyball with a higher incidence in females . L and ing preferences of both male and female players may provide additional background about the mechanisms contributing to the anterior cruciate ligament injuries . METHODS Eight female and eight male college volleyball players performed spike and block l and ings from 40 and 60 cm height platforms .  Lower extremity joint kinetics and kinematics , and leg muscle strengths were recorded . RESULTS Females demonstrated significantly lower knee and hip flexion angles compared to their male counterparts in knee flexion at 40 cm spike and hip flexion at 40 cm block l and ings . Group comparison also revealed that male players ' peak knee extensor moment at 60 cm block l and ing was significantly different than female players . Additionally , female players applied significantly higher normalized ground reaction forces and males knee flexion angles and thigh muscle strength results positive and highly correlated but relation could not found in females . It is likely that females may not use their thigh muscles as effective as males in l and ing . CONCLUSION Female volleyball players initiate different lower extremity mechanics during l and ings than that of males . RELEVANCE Identifying the l and ing strategy differences between female and male college volleyball players may provide detailed perspective about the load distribution in lower extremity joints for determining major factors affecting the increased incidence of anterior cruciate ligament injuries in females The aim of the present work was to verify that skilled volleyball players present specific adaptations in both neuromuscular control and movement biomechanics , showing an improved neuromuscular control around the knee joint than in non-jumper athletes . Seven male volleyball players and seven male non-jumper athletes were recruited for this study . The following tests were performed in a r and om order : single countermovement jump ( CMJ ) , single squat jump . At the end of the series , subjects performed a repetitive CMJ test . Electromyographic signals  were recorded from vastus lateralis and biceps femoris muscles on both sides . Ground reaction forces and moments were measured with a force plate . Volleyball athletes performed better in all tests and were more resistant to fatigue than non-jumper athletes . Furthermore , volleyball athletes showed a reduced co-activation of knee flexor/extensor muscles . The present results seem to st and for a neural adaptation of the motor control scheme to training When humans hop in place or run forward , leg stiffness is increased to offset reductions in surface stiffness , allowing the global kinematics and mechanics to remain the same on all surfaces . The purpose of the present study was to determine the mechanism for adjusting leg stiffness .  Seven subjects hopped in place on surfaces of different stiffnesses ( 23 - 35,000 kN/m ) while force platform , kinematic , and electromyographic data were collected . Leg stiffness approximately doubled between the most stiff surface and the least stiff surface . Over the same range of surfaces , ankle torsional stiffness increased 1.75-fold , and the knee became more extended at the time of touchdown ( 2.81 vs. 2.65 rad ) . We used a computer simulation to examine the sensitivity of leg stiffness to the observed changes in ankle stiffness and touchdown knee angle . Our model consisted of four segments ( foot , shank , thigh , head-arms-trunk ) interconnected by three torsional springs ( ankle , knee , hip ) . In the model , an increase in ankle stiffness 1.75-fold caused leg stiffness to increase 1.7-fold . A change in touchdown knee angle as observed in the subjects caused leg stiffness to increase 1.3-fold . Thus both joint stiffness and limb geometry adjustments are important in adjusting leg stiffness to allow similar hopping on different surfaces OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity We investigated gender differences in motor performance in 9- , 12- , and 17-year-olds . The tasks included simple thumb tapping ( sTT ) , h and writing ( HW ) and finger-to-thumb opposition sequence ( FOS ) learning . In sTT there was a significant advantage for the 17-year-old males . In HW , 12-year-old females were faster , initially , than the males , but this gap was closed by a single training session ; in the 17-year-olds although no significant difference was found initially , the males became faster than the age-matched females post-training . In the FOS , there were no initial gender differences ( speed or accuracy ) . However , males benefited more from training , with the 17-year-old males attaining a significant post-training speed advantage . Moreover , males , of all three age-groups , evolved significantly larger delayed ( " off-line " ) performance gains in the FOS task compared to females ; gains which were retained 6-weeks post-training . There may be a male advantage in motor learning rather than in motor performance per-se ; this advantage is enhanced during adolescence This study investigated the modulation of  prel and ing muscle activity with normal or perturbed vision under conditions where jump height was known or unknown .  Lower leg electromyography ( EMG )  was monitored while subjects jumped from a constant ( 0.45 m ) or variable ( 0.35 - 0.55 m ) heights when vision was unaltered or perturbed by a strobe light , blackened goggles or a visual conflict dome . Results indicated that visual perturbations had a global effect on muscle onsets only when height was r and omized . R and omization rather than jump height also affected the onset patterns observed for normal vision jumps . It is suggested that strategies for triggering prel and ing EMG are mutable and may depend on availability of sensory modalities and impact force estimation as well as on vision Objectives : In this study , the effects of temporal changes in unanticipated ( UN ) prel and ing stimuli on lower limb biomechanics and the impact of sex and limb dominance on these variables during single-leg l and ings were determined . It was hypothesised that reductions in the time of prel and ing UN stimuli , female sex , and the non-dominant limb would significantly increase high-risk l and ing biomechanics during UN jump l and ings . Methods : 26 ( 13 men and 13 women ) had initial contact ( IC ) and peak stance ( 0–50 % ) phase ( PS ) lower limb joint kinematics and kinetics quantified during anticipated ( AN ) and UN single-leg ( left and right ) l and ings . Postl and ing jump direction was governed via one of two r and omly ordered light stimuli , presented either before initiation of the jump ( AN ) , or 600 ms ( UN1 ) , 500 ms ( UN2 ) or 400 ms ( UN3 ) immediately before ground contact . Results : Statistically significant ( p<0.05 ) differences in IC hip posture and PS hip and knee internal rotation moments occurred in UN compared with AN l and ings . Differences were not observed , however , among UN conditions for any biomechanical comparisons . Significant ( p<0.05 ) differences in specific IC and PS hip and knee postures and loads occurred between sexes and limbs . Neither of these factors , however , influenced movement condition effects . Conclusion : UN l and ings induce modifications in l and ing biomechanics that may increase anterior cruciate ligament injury risk in both men and women . These modifications , however , do not appear overly sensitive to the timing of the UN stimulus , at least within a temporal range affording a successful movement response . Exp and ing UN training to include even shorter stimulus-response times may promote the additional central control adaptations necessary to manoeuvre safely within the r and om sports setting 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 Background Female athletes are at significantly greater risk of anterior cruciate ligament ( ACL ) injury than male athletes in the same high-risk sports . Decreased trunk ( core ) neuromuscular control may compromise dynamic knee stability . Hypotheses ( 1 ) Increased trunk displacement after sudden force release would be associated with increased knee injury risk ; ( 2 ) coronal ( lateral ) , not sagittal , plane displacement would be the strongest predictor of knee ligament injury ; ( 3 ) logistic regression of factors related to core stability would accurately predict knee , ligament , and ACL injury risk ; and ( 4 ) the predictive value of these models would differ between genders . Study Design Cohort study ( prognosis ) ; Level of evidence , 2 . Methods In this study , 277 collegiate athletes ( 140 female and 137 male ) were prospect ively tested for trunk displacement after a sudden force release . Analysis of variance and multivariate logistic regression identified predictors of risk in athletes who sustained knee injury . Results Twenty-five athletes ( 11 female and 14 male ) sustained knee injuries over a 3-year period . Trunk displacement was greater in athletes with knee , ligament , and ACL injuries than in uninjured athletes ( P < .05 ) . Lateral displacement was the strongest predictor of ligament injury ( P = .009 ) . A logistic regression model , consisting of trunk displacements , proprioception , and history of low back pain , predicted knee ligament injury with 91 % sensitivity and 68 % specificity ( P = .001 ) . This model predicted knee , ligament , and ACL injury risk in female athletes with 84 % , 89 % , and 91 % accuracy , but only history of low back pain was a significant predictor of knee ligament injury risk in male athletes . Conclusions Factors related to core stability predicted risk of athletic knee , ligament , and ACL injuries with high sensitivity and moderate specificity in female , but not male , athletes M ultiple risk factors , both modifiable and nonmodifiable , are known to 
    Output:
    
The wider literature indicates that a combination of biological , environmental and sociocultural constraints may shape movement patterns differently in females and males .
Sociocultural factors differentially affect accumulated motor experience , practice opportunities and focus of attention in females , leading to differences in motor skill that confound the comparison of female and male movements .
The findings of the review support the hypothesis that such sex differences in athletic performance are likely to diminish or disappear with increasing skill .
In everyday movement tasks , however , where level of skill is a less meaningful dimension than in sport , differences in movement patterns observed between females and males point instead to the influence of subtle societal expectations on movement patterns