***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 In spite of ongoing prevention developments , anterior cruciate ligament injury rates and the associated sex-disparity have remained , suggesting an incomplete underst and ing of the injury mechanism . While both fatigue and decision making are known in isolation to directly impact anterior cruciate ligament injury risk , their combined manifestations remain unknown . We thus examined the combined effects of fatigue and decision making on lower limb kinematics during sports relevant l and ings . METHODS Twenty five female National College Athletic Association athletes had initial contact and peak stance phase 3D lower limb joint kinematics quantified during anticipated and unanticipated single ( left and right ) leg l and ings , both before and during the accumulation of fatigue . Jump direction was governed by light stimuli activated prior to and during the pre-l and phase of respective anticipated and unanticipated trials . To induce fatigue , subjects performed repetitive squat ( n=5 ) and r and omly ordered jump sequences , until squats were no longer possible . Subject-based measures of each dependent factor were then calculated across pre-fatigue trials , and for those denoting 100 % and 50 % fatigue , and su bmi tted to a 3-way mixed design analysis of covariance to test for the main effects of fatigue time , decision and leg . FINDINGS Fatigue caused significant increases in initial contact hip extension and internal rotation , and in peak stance knee abduction and internal rotation and ankle supination angles . Fatigue-induced increases in initial contact hip rotations and in peak knee abduction angle were also significantly more pronounced during unanticipated compared to anticipated l and ings . INTERPRETATION The integrative effects of fatigue and decision making may represent a worst case scenario in terms of anterior cruciate ligament injury risk during dynamic single leg l and ings , by perpetuating substantial degradation and overload of central control mechanisms UNLABELLED Fatigue has been shown to alter the biomechanics of lower extremity during l and ing tasks . To date , no study has examined the effects of two types of fatigue on kinetics and kinematics . OBJECTIVES This study was conducted to assess biomechanical differences between two fatigue protocol s [ Slow Linear Oxidative Fatigue Protocol ( SLO-FP ) and Functional Agility Short-Term Fatigue Protocol ( FAST-FP ) ] . DESIGN Single-group repeated measures design . METHODS Fifteen female collegiate soccer players had to perform five successful trials of  unanticipated sidestep cutting ( SS ) pre- and post-fatigue protocol s. The SLO-FP consisted of an initial VO(2peak ) test followed by 5-min rest , and a 30-min interval run . The FAST-FP consisted of 4 sets of a functional circuit . Biomechanical measures of the hip and knee were obtained at different instants while performing SS pre- and post-fatigue . Repeated 2 × 2 ANOVAs were conducted to examine task and fatigue differences . Alpha level set a priori at 0.05 . RESULTS During the FAST-FP , participants had increased knee internal rotation at initial contact ( IC ) ( 12.5 ± 5.9 ° ) when compared to the SLO-FP ( 7.9 ± 5.4 ° , p<0.001 ) . For hip flexion at IC , pre-fatigue had increased angles ( 36.4 ± 8.4 ° ) compared to post-fatigue ( 30.4 ± 9.3 ° , p=0.003 ) , also greater knee flexion during pre-fatigue ( 25.6 ± 6.8 ° ) than post-fatigue ( 22.4 ± 8.4 ° , p=0.022 ) . CONCLUSION The results of this study showed that hip and knee mechanics were substantially altered during both fatigue conditions OBJECTIVE : To compare the effects of an isokinetic fatigue protocol and a functional fatigue protocol on time to stabilization ( TTS ) , ground reaction force ( GRF ) , and joint kinematics during a jump l and ing . DESIGN AND SETTING : Subjects were assessed on 2 occasions for TTS , GRF , and joint kinematics immediately before and after completing a fatigue protocol . One week separated the 2 sessions , and the order of fatigue protocol s was r and omly assigned and counterbalanced . SUBJECTS : Twenty healthy male ( n = 8 , age = 21.8 + /- 1.4 years , height = 180.6 + /- 7.6 cm , and mass = 74.1 + /- 13.0 kg ) and female ( n = 12 , age = 22.2 + /- 2.1 years , height = 169.3 + /- 9.8 cm , and mass = 62.5 + /- 10.1 kg ) subjects volunteered to participate . MEASUREMENTS : Subjects performed 2-legged jumps equivalent to 50 % of maximum jump height , followed by a single-leg l and ing onto the center of a forceplate 70 cm from the starting position . Peak vertical GRF and vertical , medial-lateral , and anterior-posterior TTS were obtained from forceplate recordings . Maximum ankle dorsiflexion , knee-flexion , and knee-valgum angles were determined using 3-dimensional motion analysis . RESULTS : A 2-way analysis of variance with repeated measures revealed no significant differences when comparing TTS , GRF , and joint kinematics after isokinetic and functional fatigue protocol s. CONCLUSIONS : No difference was noted between isokinetic and functional fatigue protocol s relative to dynamic stability when l and ing from a jump Background Altered motor control strategies in l and ing and jumping maneuvers are a potential mechanism of noncontact anterior cruciate ligament injury . There are biomechanical differences between male and female athletes in the l and ing phase of stop-jump tasks . Fatigue is a risk factor in musculoskeletal injuries . Hypothesis Lower extremity muscle fatigue alters the knee kinetics and kinematics during the l and ing phase of 3 stop-jump tasks and increases an athlete 's risk of anterior cruciate ligament injury . Study Design Controlled laboratory study . Methods Three-dimensional videography and force plate data were collected for 20 recreational athletes ( 10 male and 10 female athletes ) performing 3 stop-jump tasks before and after completing a fatigue exercise .  Knee joint angles and result ant forces and moments were calculated . Results Both male and female subjects had significantly increased peak proximal tibial anterior shear forces ( P = . 01 ) , increased valgus moments ( P = . 03 ) , and decreased knee flexion angles ( P = . 03 ) during l and ings of all 3 stop-jump tasks when fatigued . Fatigue did not significantly affect the peak knee extension moment for male or female athletes . Conclusion Fatigued recreational athletes demonstrate altered motor control strategies , which may increase anterior tibial shear force , strain on the anterior cruciate ligament , and risk of injury for both female and male subjects . Clinic Relevance Fatigued athletes may have an increased risk of noncontact anterior cruciate ligament injury PURPOSE Anterior cruciate ligament injuries and patellofemoral pain syndrome are both common and significant injuries to the knee that have been associated with hip weakness . Prospect i ve studies have linked the risk of experiencing either injury to alterations in the frontal plane knee angle and moment during activity . These components of knee mechanics are theorized to be affected by hip abductor weakness . The purpose of this study was to identify the effects of isolated hip abductor fatigue-induced weakness on lower extremity kinematics and kinetics in recreationally active women . METHODS Twenty participants performed cut  ,  jump  , and run tasks off a raised platform while three-dimensional motion analysis data were collected . Participants then performed an isolated hip abductor fatigue protocol in side lying against isokinetic resistance , followed immediately by repeated biomechanical data collection . Separate repeated- measures ANOVA ( P G 0.05 ) were used for each dependent variable . RESULTS After the hip fatigue protocol , regardless of task , the knee angle at initial ground contact was more adducted ( pre = 0.7 degrees + /- 3.4 degrees , post = 1.2 degrees + /- 3.9 degrees , F(1,19 ) = 5.3 , P = 0.032 ) , the knee underwent greater range of motion into abduction ( pre = 0.7 degrees + /- 1.5 degrees , post = 2.1 degrees + /- 1.6 degrees , F(1,19 ) = 73.2 , P < 0.001 ) , and there was a greater internal knee adductor moment ( pre = -2.6 + /- 13.3 N x m , post = 4.7 + /- 14.1 N x m , F(1,19 ) = 41.0 , P < 0.001 ) during the weight acceptance phase of stance . CONCLUSIONS This study demonstrates that simulated hip abductor weakness causes small alterations of frontal plane knee mechanics . Although some of these alterations occurred in directions associated with increased risk of knee injury , changes were small in magnitude , and the effect of these small changes on knee injury risk is unknown PURPOSE Fatigue contributes directly to anterior cruciate ligament ( ACL ) injury via promotion of high risk biomechanics . The potential for central fatigue to dominate this process , however , remains unclear . With central ly mediated movement behaviors being trainable , establishing this link seems critical for improved injury prevention . We thus determined whether fatigue-induced l and ing biomechanics were governed by a central ly fatiguing mechanism . METHODS Twenty female NCAA athletes had initial contact ( IC ) and peak stance ( PS ) three-dimensional hip and knee biomechanics quantified during anticipated and unanticipated single-leg l and ings , before and during unilateral fatigue accumulation . To induce fatigue , subjects performed repetitive ( n = 3 ) single-leg squats and r and omly ordered l and ings , until squats were no longer possible . Subject-based dependent factors were calculated across prefatigue trials and for those denoting 100 % , 75 % , 50 % , and 25 % fatigue and were su bmi tted to three-way mixed- design analyses of covariance to test for decision , fatigue time , and limb effects . RESULTS Fatigue produced significant ( P < 0.01 ) decreases in IC knee flexion angle and PS knee flexion moment and increases in PS hip internal rotation and knee abduction angles and moments , with differences maintained from 50 % fatigue through to maximum . Fatigue-induced increases in PS hip internal rotation angles and PS knee abduction angles and loads were also significantly ( P < 0.01 ) greater during unanticipated l and ings . Apart from PS hip moments , significant limb differences in fatigued l and ing biomechanics were not observed . CONCLUSIONS Unilateral fatigue induces a fatigue crossover to the contralateral limb during single-leg l and ings . Central fatigue thus seems to be a critical component of fatigue-induced sports l and ing strategies . Hence , targeted training of central control processes may be necessary to counter successfully the debilitative impact of fatigue on ACL injury risk BACKGROUND Lower extremity kinematics may change as a result of impaired hip muscle function , thereby placing athletes at increased risk of injury . The purpose of this study was to examine whether experimentally-induced hip extensor fatigue alters lower extremity kinematics during a jump-l and ing task in women . METHODS Forty healthy women were r and omly assigned to an experimental group in which participants performed modified Biering-Sørenson tests to fatigue the hip extensors or to a sham control group in which participants performed repeated push-ups to exhaustion . Three-dimensional hip and knee kinematics and gluteus maximus electromyography ( EMG ) signals were measured during jump-l and ing tests to examine the effects of hip extensor fatigue . FINDINGS Hip extension strength decreased in the experimental group by 25 % following the intervention , thereby confirming effects of the fatigue intervention . No group × time interactions in hip and knee motions were statistically significant , indicating that hip and knee kinematics did not change following the fatigue-inducing intervention . Gluteus maximus recruitment during the post-fatigue test , however , increased by 55 % in the experimental group . INTERPRETATION A 25 % reduction in hip extensor strength did not lead to changes in hip or knee kinematics . Rather , participants accommo date d for the loss of strength by recruiting more Gmax activation to complete the task . Gmax recruitment may compensate when hip extensor strength is impaired , suggesting that improved neuromuscular control can influence motor performance when strength is diminished Abstract The main aim of this study was to assess neuromuscular fatigue during a typical high-load , low-repetition loading protocol . Muscle stimulations were used to assess maximum voluntary contraction , resting single- and double-pulse twitch characteristics , and superimposed double-pulse twitch force ( used to calculate voluntary activation ) before and after an acute knee extension loading protocol . In our participants , who had previous resistance training experience , the mean voluntary activation level was 96.2 % in an unfatigued state . Maximum voluntary contraction ( −11.8 % ) , resting double-pulse twitch force ( −10.6 % ) , and voluntary activation ( −2.1 % ) were markedly decreased as a consequence of loading ( P < 0.05 ) . In addition , although potentiated twitch characteristics were observed during the loading protocol , this was short-lived , as fatigue surpassed the potentiation mechanisms . Our results show that both central and peripheral mechanisms contributed to neuromuscular fatigue during the present loading protocol 
    Output:
    
There was no consistency among investigations regarding the effects of fatigue on hip , knee , or ankle joint angles and moments or surface electromyography muscle activation patterns .
The fatigue protocol s typically did not produce statistically significant changes in ground-reaction forces .
Conclusion : Published fatigue protocol s did not uniformly produce alterations in lower limb neuromuscular factors that heighten the risk of noncontact ACL injuries .
Therefore , justification does not currently exist for major changes in ACL injury prevention training programs to account for potential fatigue effects .