title: Dynamic restraint capacity of the hamstring muscles has important functional implications after anterior cruciate ligament injury and anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  The purpose of this study was to investigate the relation between knee functionality of anterior cruciate ligament deficient (ACLD) and anterior cruciate ligament reconstruction (ACLR) patients and hamstring antagonist torque generated during resisted knee extension.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  Laboratory based.
  
  
  METHODS
  Male ACLD subjects (n=10) (18-35 y) and 27 matched males who had undergone ACLR (14 patella tendon [PT] grafts and 13 combined semitendinosus/gracilis tendon grafts).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Knee functionality was rated (0- to 100-point scale) by using the Cincinnati Knee Rating System. Using electromyography data from the semitendinosus (ST) and biceps femoris muscles, we created a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10 degrees intervals from 80 degrees to 10 degrees knee flexion.
  
  
  RESULTS
  Pearson product-moment correlations revealed that more functional ACLD subjects generated significantly (P<.05) higher hamstring antagonist torque throughout knee extension. In contrast, more functional PT subjects produced significantly lower hamstring antagonist torque at 80 degrees to 70 degrees knee flexion, whereas no significant associations were found between hamstring antagonist torque and knee functionality for the ST/gracilis tendon subjects.
  
  
  CONCLUSIONS
  An increased hamstring antagonist torque generated by the more functional ACLD subjects, reflective of increased hamstring contractile force, is thought to represent a protective mechanism to compensate for mechanical instability. The restoration of anterior knee stability through ACLR negates the need for augmented hamstring antagonist torque.
authors.affiliation: Centre for Health, Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Melbourne, Australia. albryant@unimelb.edu.au
authors.forename: Adam L
authors.initials: AL
authors.lastname: Bryant
authors.forename: Mark W
authors.initials: MW
authors.lastname: Creaby
authors.forename: Robert U
authors.initials: RU
authors.lastname: Newton
authors.forename: Julie R
authors.initials: JR
authors.lastname: Steele
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004576:Electromyography; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000534:rehabilitation*; D008297:Male; D016555:Matched-Pair Analysis; D008954:Models, Biological; D009119:Muscle Contraction; D019637:Orthopedic Procedures / Q000534:rehabilitation; D020127:Recovery of Function; D013710:Tendons / Q000637:transplantation; D019415:Torque