title: The effect of anterior cruciate ligament reconstruction on hamstring and quadriceps muscle function outcome ratios in male athletes.
abstract: BACKGROUND
  Maximal strength ratios such as the limb symmetry index (LSI) and hamstring-to-quadriceps ratio (HQ) may be considered the main outcome measures in the monitoring of recovery after anterior cruciate ligament (ACL) reconstruction. Although explosive strength is much more important than maximal strength, it is generally disregarded in the follow-up of muscle function recovery.
  
  
  OBJECTIVE
  The purpose of this study was to compare ratios between maximal (Fmax) and explosive strength (rate of force development--RFD) in individuals with ACL reconstruction.
  
  
  METHODS
  Fifteen male athletes were enrolled and had maximum voluntary isometric quadriceps and hamstring contractions tested (4.0 ± 0.1 months post reconstruction). In addition to Fmax RFD was estimated (RFDmax, as well as RFD at 50, 100, and 200 ms from onset of contraction) and LSI and HQ ratios were calculated.
  
  
  RESULTS
  The involved leg demonstrated significant hamstring and quadriceps deficits compared to uninvolved leg (p < 0.01). Deficits were particularly significant in the involved quadriceps, causing higher HQ ratios (average 0.63), compared to the uninvolved leg (0.44). LSI was significantly lower for RFD variables (average 55%) than for Fmax (66%).
  
  
  CONCLUSIONS
  The assessment of RFD may be considered an objective recovery parameter for one's readiness to return to sports and should be an integral part of standard follow-up protocol for athletes after ACL reconstruction. Moreover, the combination of indices derived from maximal and explosive strength may provide better insight in muscle strength balance, as well as a clear picture of functional implications.
authors.forename: Marko
authors.initials: M
authors.lastname: Kadija
authors.forename: Olivera M
authors.initials: OM
authors.lastname: Knezević
authors.forename: Darko
authors.initials: D
authors.lastname: Milovanović
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Nedeljković
authors.forename: Dragan M
authors.initials: DM
authors.lastname: Mirkov
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D056352:Athletes; D006801:Humans; D008297:Male; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D020127:Recovery of Function; D013848:Thigh; D016896:Treatment Outcome; D055815:Young Adult