title: Neuromuscular fatigue alters postural control and sagittal plane hip biomechanics in active females with anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Females with history of anterior cruciate ligament (ACL) injury and subsequent ligament reconstruction are at high risk for future ACL injury. Fatigue may influence the increased risk of future injury in females by altering lower extremity biomechanics and postural control.
  
  
  OBJECTIVE
  Fatigue will promote lower extremity biomechanics and postural control deficits associated with ACL injury.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Fourteen physically active females with ACL reconstruction (mean age, 19.64 ± 1.5 years; mean height, 163.52 ± 6.18 cm; mean mass, 62.6 ± 13.97 kg) volunteered for this study. Postural control and lower extremity biomechanics were assessed in the surgical limb during single-leg balance and jump-landing tasks before and after a fatigue protocol. Main outcome measures were 3-dimensional hip and knee joint angles at initial contact, peak angles, joint angular displacements and peak net joint moments, anterior tibial shear force, and vertical ground reaction force during the first 50% of the loading phase of the jump-landing task. During the single-leg stance task, the main outcome measure was center of pressure sway speed.
  
  
  RESULTS
  Initial contact hip flexion angle decreased (t = -2.82, P = 0.01; prefatigue, 40.98° ± 9.79°; postfatigue, 36.75° ± 8.61°) from pre- to postfatigue. Hip flexion displacement (t = 2.23, P = 0.04; prefatigue, 45.19° ± 14.1°; postfatigue, 47.48° ± 14.21°) and center of pressure sway speed (t = 3.95, P < 0.05; prefatigue, 5.18 ± 0.96 cm/s; postfatigue, 6.20 ± 1.72 cm/s) increased from pre- to postfatigue. There was a trending increase in hip flexion moment (t = 2.14, P = 0.05; prefatigue, 1.66 ± 0.68 Nm/kg/m; postfatigue, 1.91 ± 0.62 Nm/kg/m) from pre- to postfatigue.
  
  
  CONCLUSIONS
  Fatigue may induce lower extremity biomechanics and postural control deficits that may be associated with ACL injury in physically active females with ACL reconstruction.
  
  
  CONCLUSIONS
  Rehabilitation and maintenance programs should incorporate activities that aim to improve muscular endurance and improve the neuromuscular system's tolerance to fatiguing exercise in efforts to maintain stability and safe landing technique during subsequent physical activity.
authors: Department of Exercise & Sport Science, Human Movement Science Curriculum, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors: Barnett S
authors: BS
authors: Frank
authors: Athlete's Performance Center, Raleigh Orthopaedic Clinic, Raleigh, North Carolina.
authors: Christine M
authors: CM
authors: Gilsdorf
authors: Department of Kinesiology and Health, Georgia State University, Atlanta, Georgia.
authors: Benjamin M
authors: BM
authors: Goerger
authors: Department of Exercise & Sport Science, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors: William E
authors: WE
authors: Prentice
authors: Department of Exercise & Sport Science, Human Movement Science Curriculum, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors: Darin A
authors: DA
authors: Padua
keywords: anterior cruciate ligament; fatigue; injury; postural control; rehabilitation