title: The effect of selective muscle fatigue on sagittal lower limb kinematics and muscle activity during level running.
abstract: METHODS
  Controlled laboratory study.
  
  
  OBJECTIVE
  To compare the changes in lower limb sagittal kinematics in running after a knee fatigue protocol with those observed after an ankle fatigue protocol.
  
  
  BACKGROUND
  Impaired force-generating ability of specific muscles may affect running mechanics, with negative implications for injury occurrence and performance. Identifying the strategies used to compensate for fatigue of selected muscles may assist in the design of more effective exercise programs for injury prevention and performance enhancement in running.
  
  
  METHODS
  Sagittal plane kinematic data and the electromyographic (EMG) signal of the vastus medialis (VM), gastrocnemius (GAS), and biceps femoris (BF) muscles were collected from 15 females running at 3.61 m/s on a treadmill prior to, and following, an isokinetic knee extension/flexion and, on a separate day, an ankle plantar flexion/dorsiflexion fatigue protocol performed at 120 degrees/s.
  
  
  RESULTS
  Ankle muscle fatigue caused decreased ankle dorsiflexion, while knee fatigue caused increased knee flexion at initial contact (P<.05). Both protocols increased knee flexion angle at toe-off, as well as the amplitude of GAS and VM EMG signal, with the hip more extended after knee fatigue and the ankle more plantar flexed after ankle muscle fatigue. Ankle muscle fatigue caused a significant increase in hip extensionand ankle plantar flexion angular velocity, and a decline of BF EMG signal during the swing phase (P<.05). Knee muscle fatigue decreased hip and knee flexion angular velocity and increased BF EMG signal during the swing phase (P<.05).
  
  
  CONCLUSIONS
  Localized muscle fatigue effects on sagittal kinematics differed between the 2 protocols. However, the strategy used to compensate for fatigue was similar for both protocols: to protect the joints at initial impact and to prevent impairments in performance during toeoff and swing phase.
authors.affiliation: Department of Physical Education and Sports Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece. ekellis@phed-sr.auth.gr
authors.forename: Eleftherios
authors.initials: E
authors.lastname: Kellis
authors.forename: Christina
authors.initials: C
authors.lastname: Liassou
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012420:Running / Q000502:physiology*