title: Voluntary activation of quadriceps femoris in patients with unilateral anterior cruciate ligament rupture within 6 months of injury: A cross-sectional observational study.
abstract: BACKGROUND
  Deficits in quadriceps femoris strength and voluntary activation have been well documented in chronic anterior cruciate ligament (ACL) injuries, but less is known about the acute or early phase after injury.
  
  
  OBJECTIVE
  The aim of this study was to evaluate and compare the levels of quadriceps voluntary activation (VA) and strength in both limbs of participants with unilateral ACL ruptures (complete tears) within 6 months of injury.
  
  
  METHODS
  Cross-sectional observational study.
  
  
  METHODS
  Seventeen participants, 12 male, mean age 30 (17-45) years, performed maximal voluntary isometric contractions with the interpolated twitch technique.
  
  
  RESULTS
  Mean (SD) peak VA was significantly lower in the injured limb 76.5 (15.0) % than the uninjured limb 85.9 (6.7) % (p = 0.02). Mean (SD) peak torque in the injured limb was significantly lower 162.7 (74.1) Nm than the uninjured limb 240.5 (81.0) Nm (p < 0.01).
  
  
  CONCLUSIONS
  This between-limb difference in VA has not previously been observed in patients within 6 months of ACL rupture. Our findings suggest that early rehabilitation programs for adults with ACL rupture should focus on reducing VA deficits to facilitate improvement of the quadriceps femoris muscle strength in the injured limb to comparable values of the uninjured limb.
authors.affiliation: Health & Social Care Institute, School of Health and Social Care, Teesside University, Middlesbrough, UK. Electronic address: Amanda.Trees@stees.nhs.uk.
authors.forename: Amanda
authors.initials: A
authors.lastname: Trees
authors.affiliation: Health & Social Care Institute, School of Health and Social Care, Teesside University, Middlesbrough, UK. Electronic address: John.Dixon@tees.ac.uk.
authors.forename: John
authors.initials: J
authors.lastname: Dixon
authors.affiliation: School of Health & Life Sciences, Glasgow Caledonian University & Glasgow City of Science, Glasgow, UK. Electronic address: Tracey.Howe@gcu.ac.uk.
authors.forename: Tracey E
authors.initials: TE
authors.lastname: Howe
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D006113:United Kingdom; D055815:Young Adult
keywords: Anterior cruciate ligament; Quadriceps strength; Voluntary muscle activation