title: Long-term deficits in quadriceps strength and activation following anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  Even some time after a ruptured ACL has been reconstructed thigh musculature atrophy, voluntary activation, and knee-extensor strength deficits may be encountered. The purpose of this study was to evaluate bilateral knee-extension strength, voluntary activation of the quadriceps, and thigh circumference in males and females with ACL reconstruction (ACLR).
  
  
  METHODS
  Within-subject and between-subject designs were used to evaluate 24 unilateral ACLR individuals and 23 controls.
  
  
  METHODS
  Isokinetic knee-extension strength was assessed in ACLR participants while central activation ratio (CAR) and thigh circumference measures were obtained from both groups.
  
  
  RESULTS
  Knee-extensor strength deficits (p < .039) and lower CAR of the quadriceps were found in the ACLR limb compared to the uninvolved limb (p = .047). Extensor strength was greater in males (p < .001), however, CAR was not different between sexes (p = .086). No difference in voluntary activation was revealed among the ACLR limb, uninvolved limb, and control limb when compared as independent groups (p = .460). The strength deficits found in the ACLR limb are partly attributable to lower voluntary activation compared to the uninvolved leg, given that no difference was found in thigh circumference between legs.
  
  
  CONCLUSIONS
  Clinicians should consider the deficits in muscle function when returning patients to pre-injury activity levels.
authors.affiliation: Study Conducted at Biomechanics Laboratory, University of Florida, 151 Florida Gym, Gainesville, FL 32611, USA; Geriatric Research Education and Clinical Centers, Malcom Randall VA Medical Center, 1601 SW Archer Rd, Gainesville, FL 32608, USA. Electronic address: Dana.Otzel@va.gov.
authors.forename: Dana M
authors.initials: DM
authors.lastname: Otzel
authors.affiliation: Study Conducted at Biomechanics Laboratory, University of Florida, 151 Florida Gym, Gainesville, FL 32611, USA; Motion Analysis & Human Performance, Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation Center, 1350 East Woodrow Wilson, Jackson, MS 39216, USA. Electronic address: jchow@mmrcrehab.org.
authors.forename: John W
authors.initials: JW
authors.lastname: Chow
authors.affiliation: Study Conducted at Biomechanics Laboratory, University of Florida, 151 Florida Gym, Gainesville, FL 32611, USA; Kinesiology and Health Promotion, Troy University, 112 Wright Hall, Troy, AL 36082, USA. Electronic address: mdtillman@troy.edu.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Tillman
mesh_terms: D059549:Anterior Cruciate Ligament Reconstruction / Q000534:rehabilitation*; D056352:Athletes; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D017063:Outcome Assessment, Health Care; D052097:Quadriceps Muscle / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology; D055815:Young Adult
keywords: Anterior cruciate ligament; Central activation ratio; Quadriceps inhibition; Return to sport