title: Quadriceps muscle function after exercise in men and women with a history of anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Sex differences in lower extremity neuromuscular function have been reported after anterior cruciate ligament reconstruction (ACLR). Research evidence supports different levels of fatigability in men and women and between patients with ACLR and healthy controls. The influence of sex on the response to continuous exercise in patients with ACLR is not clear.
  
  
  OBJECTIVE
  To compare quadriceps neuromuscular function after exercise between men and women with ACLR.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Twenty-six active volunteers (13 men [50%]: age = 24.1 ± 4.4 years, height = 179.1 ± 9.8 cm, mass = 80.1 ± 9.4 kg, months since surgery = 43.5 ± 37.0; 13 women [50%]: age = 24.2 ± 5.6 years, height = 163.0 ± 5.9 cm, mass = 62.3 ± 8.3 kg, months since surgery = 45.8 ± 42.7) with a history of unilateral primary ACLR at least 6 months earlier.
  
  
  METHODS
  Thirty minutes of continuous exercise comprising 5 separate 6-minute cycles, including 5 minutes of uphill walking and 1 minute of body-weight squatting and step-ups.
  
  
  METHODS
  Normalized knee-extension maximal voluntary isometric contraction torque, quadriceps superimposed-burst torque, and quadriceps central activation ratio before and after exercise. We performed separate 2 (sex: men, women) × 2 (time: preexercise, postexercise) repeated-measures analyses of variance for the 3 variables. Separate, independent-samples t tests were calculated to compare preexercise with postexercise change in all dependent variables between sexes.
  
  
  RESULTS
  A significant group-by-time interaction was present for knee-extension torque (P = .04). The percentage reduction in knee-extension maximal voluntary isometric contraction torque (men = 1.94%, women = -10.32%; P = .02) and quadriceps central activation ratio (men = -1.45%, women = -8.69%; P = .03) experienced by men was less than that observed in women.
  
  
  CONCLUSIONS
  In the presence of quadriceps dysfunction, female participants experienced greater-magnitude reductions in quadriceps function after 30 minutes of exercise than male participants. This indicates a reduced ability to absorb knee-joint loads, which may have significant implications for reinjury and joint osteoarthritis in women after ACLR.
authors.affiliation: Department of Kinesiology and Sport Sciences, University of Miami, Coral Gables, FL;
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kuenze
authors.forename: Jay
authors.initials: J
authors.lastname: Hertel
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects* / Q000379:methods; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000503:physiopathology; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D011183:Postoperative Complications / Q000175:diagnosis / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012737:Sex Factors; D019415:Torque
keywords: fatigue; knee injury; quadriceps activation