***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: The purpose of the present study was to investigate whether different  walking patterns in healthy subjects and in coper and non-coper subjects with deficient anterior cruciate ligaments could be quantified . An inverse dynamics approach was used to calculate joint kinematics and kinetics for flexion and extension . EMG signals of the hamstrings and quadriceps muscles were recorded . The results showed that the peak knee flexion angle was greater in the copers than in the controls . There was a positive correlation between the peak knee extensor moment and peak knee flexion angle . Furthermore , at a given peak knee flexion angle , the peak knee extensor moment was significantly larger in the controls than in the non-copers . The hip extensor moment in the copers was significantly larger than that of the non-copers and the controls . In conclusion , the three groups walked according to different patterns . It is suggested that the copers stabilized their knee joint by co-contraction of the hamstrings and quadriceps muscles , while the non-copers lacked this ability . Instead , the non-copers reduced the knee extensor moment in order to decrease anterior displacement of the tibia . The walking pattern differences observed between the copers and non-copers may explain their different post-injury activity levels Abstract The aim of this study is to analyse the changes in select gait parameters following  anterior cruciate ligament ( ACL ) reconstruction .  The study was performed on 15 subjects who underwent ACL reconstruction by the bone-patellar tendon-bone technique .  Gait analysis was performed using the Elite three-dimensional ( 3D ) optoelectronic system ( BTS ) , a Kistler force platform and the Telemg telemetric electromyograph ( BTS ) .  Kinematic data were recorded for the principal lower limb joints ( hip , knee and ankle ) . The examined muscles include vastus lateralis , rectus femoris , biceps femoris and semitendinosus . The results obtained from the operated subjects were compared with those of 10 untreated subjects and 5 subjects without ACL damage .  In the operated subjects the knee joint angular values regained a normal flexion pattern for the injured limb during the stance phase . The analysis of joint moments shows : ( a ) sagittal plane : recovery of the knee flexion moment at loading response and during preswing ; ( b ) frontal plane : recovery of the normal patterns for both hip and knee adduction-abduction moments during the entire stance phase . The examination of ground reaction forces reveals the recovery of frontal component features . The EMG traces show the normal biphasic pattern for the operated subjects as compared to the untreated subjects . The results suggest that the gait parameters shift towards normal value patterns PURPOSE The purpose of this study was to describe the sagittal tibial translation and EMG activity of muscles v. medialis and lateralis , gastrocnemius , and hamstrings , during common locomotion , in patients with an anterior cruciate ligament deficiency ( ACL-def ) and uninjured controls . METHODS In 12 ACL-def patients and 17 controls , sagittal tibial translation was registered with the CA-4000 electrogoniometer during level walking , cutting , and stair walking . Tibial position at each flexion angle was expressed relative to the femuro-tibial position at passive knee extension .  EMG activity , measured with ME-4000 , was normalized to the individual maximum isometric voluntary contraction for each muscle . RESULTS During the weight-bearing phase of motion , the tibia was anteriorly positioned in all legs . In the injured leg , the tibia translated more rapidly to an anterior position that was maintained for a longer time during the gait cycle . In the noninjured knees , motions with increased load lead to an increased anterior tibial translation in contrast to the injured knees , where the maximum displacement was already reached during level walking . The quadriceps and gastrocnemius muscles were simultaneously active during stance phase . Hamstrings were mainly active when the knee was close to extension and translation increased in spite of this activity . CONCLUSIONS The mechanism of the anterior positioning of tibia is qualitatively similar in the normal and the injured knee , but that position is obtained much further forward in the ACL deficient knee . Quadriceps and gastrocnemius muscles seem to work synergistically to stabilize the knee by maintaining the anterior position of tibia during weight-bearing motion . The role of hamstrings to restrict anterior translation is question ed The objective of this study is to determine how kinematical parameters and electromyography data of selected muscles may change as a result of anterior cruciate ligament ( ACL ) deficiency and following ACL reconstruction .  The study was conducted on 25 anterior cruciate ligament deficient subjects prior to and 6 weeks , 4 months , 8 months and 12 months following ACL reconstructive surgery using the bone-patellar tendon-bone technique .  Gait analysis was performed by applying the zebris three-dimensional ultrasound-based system with surface electromyograph ( zebris ) .  Kinematic data were recorded for the lower limb . The muscles surveyed include vastus lateralis and medialis , biceps femoris and adductor longus . The results obtained from the injured subjects were compared with those of 51 individuals without any ACL damage whatsoever . Acute ACL deficient patients exhibited a quadriceps avoidance pattern prior to and 6 weeks following surgery . No quadriceps avoidance phenomenon develops in chronic ACL deficient patients . In operated individuals , tempo-spatial parameters and the knee angle regained a normal pattern for the ACL-deficient limb during gait as early as 4 months following surgery . However , the relative ACL movement parameter , which describes the tibial translation into the direction of ACL , and the EMG traces show no significant statistical difference compared with the same values of the healthy control group just 8 months following surgery . The analysis of spatial-temporal parameters and EMG traces show that the development of a quadriceps avoidance pattern is less common than previously reported . These data suggest that anterior cruciate ligament deficiency and reconstruction produce considerable changes in the lower extremity gait pattern . The results suggest that gait parameters tend to shift towards a normal value pattern ; and the re-establishment of pre-injury gait patterns-including the normal biphase of muscles-takes at least 8 months to occur 
    Output:
    
Conclusion This review highlighted that the results of the studies are in favour of increased hamstring muscular activity .