title: Changes in lower extremity biomechanics due to a short-term fatigue protocol.
abstract: BACKGROUND
  Noncontact anterior cruciate ligament injury has been reported to occur during the later stages of a game when fatigue is most likely present. Few researchers have focused on progressive changes in lower extremity biomechanics that occur throughout fatiguing.
  
  
  OBJECTIVE
  To evaluate the effects of a sequential fatigue protocol on lower extremity biomechanics during a sidestep-cutting task (SS).
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Eighteen uninjured female collegiate soccer players (age = 19.2 ± 0.9 years, height = 1.66 ± 0.5 m, mass = 61.6 ± 5.1 kg) volunteered.
  
  
  METHODS
  The independent variable was fatigue level, with 3 levels (prefatigue, 50% fatigue, and 100% fatigue). Using 3-dimensional motion capture, we assessed lower extremity biomechanics during the SS. Participants alternated between a fatigue protocol that solicited different muscle groups and mimicked actual sport situations and unanticipated SS trials. The process was repeated until fatigue was attained.
  
  
  METHODS
  Dependent variables were hip- and knee-flexion and abduction angles and internal moments measured at initial contact and peak stance and defined as measures obtained between 0% and 50% of stance phase.
  
  
  RESULTS
  Knee-flexion angle decreased from prefatigue (-17° ± 5°) to 50% fatigue (-16° ± 6°) and to 100% fatigue (-14° ± 4°) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (-52.9° ± 5.6°) to 50% fatigue (-56.1° ± 7.2°) but decreased from 50% to 100% fatigue (-50.5° ± 7.1°) (F2,34 = 8.282, P = 001). Knee-adduction moment at peak stance increased from prefatigue (0.49 ± 0.23 Nm/kgm) to 50% fatigue (0.55 ± 0.25 Nm/kgm) but decreased from 50% to 100% fatigue (0.37 ± 0.24) (F2,34 = 3.755, P = 03). Hip-flexion angle increased from prefatigue (45.4° ± 10.9°) to 50% fatigue (46.2° ± 11.2°) but decreased from 50% to 100% fatigue (40.9° ± 11.3°) (F2,34 = 6.542, P = .004). Hip flexion at peak stance increased from prefatigue (49.8° ± 9.9°) to 50% fatigue (52.9° ± 12.1°) but decreased from 50% to 100% fatigue (46.3° ± 12.9°) (F2,34 = 8.639, P = 001). Hip-abduction angle at initial contact decreased from prefatigue (-13.8° ± 6.6°) to 50% fatigue (-9.1° ± 6.5°) and to 100% fatigue (-7.8° ± 6.5°) (F2,34 = 11.228, P < .001). Hip-adduction moment decreased from prefatigue (0.14 ± 0.13 Nm/kgm) to 50% fatigue (0.08 ± 0.13 Nm/kgm) and to 100% fatigue (0.06 ± 0.05 Nm/kg) (F2,34 = 5.767, P = .007).
  
  
  CONCLUSIONS
  The detrimental effects of fatigue on sagittal and frontal mechanics of the hip and knee were visible at 50% of the participants' maximal fatigue and became more marked at 100% fatigue. Anterior cruciate ligament injury-prevention programs should emphasize feedback on proper mechanics throughout an entire practice and not only at the beginning of practice.
authors.affiliation: Sports Medicine Assessment, Research & Testing (SMART) Laboratory, George Mason University, Manassas, VA 20110, USA.ncortes@gmu.edu
authors.forename: Nelson
authors.initials: N
authors.lastname: Cortes
authors.forename: Eric
authors.initials: E
authors.lastname: Greska
authors.forename: Roger
authors.initials: R
authors.lastname: Kollock
authors.forename: Jatin
authors.initials: J
authors.lastname: Ambegaonkar
authors.forename: James A
authors.initials: JA
authors.lastname: Onate
mesh_terms: D001696:Biomechanical Phenomena; D005221:Fatigue / Q000503:physiopathology*; D005260:Female; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D007869:Leg Injuries / Q000503:physiopathology; D035002:Lower Extremity / Q000502:physiology*; D012916:Soccer / Q000293:injuries / Q000502:physiology*; D055815:Young Adult