title: Knee flexor muscle responses under fatigue after harvesting the hamstrings for anterior cruciate ligament reconstruction. [corrected].
abstract: OBJECTIVE
  To investigate if harvesting of semitendinosus (ST) and gracilis for anterior cruciate ligament (ACL) reconstruction will have an effect in coordinative firing pattern of the hamstrings under fatigue. We hypothesized that fatigue will increase the electromechanical delay (EMD) of the hamstrings on the harvested site and impair the synchronization between the medial and lateral hamstrings, in terms of muscle activity onsets.
  
  
  METHODS
  Prospective nonrandomized study.
  
  
  METHODS
  Institutional.
  
  
  METHODS
  Twelve ACL reconstructed patients with hamstrings, 2 years postoperatively.
  
  
  METHODS
  The patients performed a fatigue protocol with 25 continuous maximal isometric voluntary contractions of 8-second duration with 2-second intervals.
  
  
  METHODS
  The electromyography activity of biceps femoris (BF) and ST was recorded bilaterally and simultaneously with the torque measurements. The dependent variable examined was the EMD difference between BF and ST (muscle activation pattern).
  
  
  RESULTS
  The fatigue protocol caused significant differences for the EMD values for both the intact and the reconstructed leg, demonstrating the influence of fatigue in EMD. However, the synchronization pattern between the medial and lateral hamstrings did not change significantly throughout the fatiguing protocol, revealing a balanced effect of fatigue.
  
  
  CONCLUSIONS
  Although the EMD of ST and BF was significantly increased due to fatigue, as expected, their synchronization pattern as identified by the difference in their EMDs remained the same. Thus, the reconstructed knee responded in a balanced manner and the hamstrings firing pattern remained the same, despite the intervention to the ST tendon.
authors.affiliation: Orthopaedic Sports Medicine Center of Ioannina, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.
authors.forename: Stavros
authors.initials: S
authors.lastname: Ristanis
authors.forename: Elias
authors.initials: E
authors.lastname: Tsepis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Giotis
authors.forename: Franceska
authors.initials: F
authors.lastname: Zampeli
authors.forename: Nicholas
authors.initials: N
authors.lastname: Stergiou
authors.forename: Anastasios D
authors.initials: AD
authors.lastname: Georgoulis
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007718:Knee Injuries / Q000534:rehabilitation / Q000601:surgery*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D019637:Orthopedic Procedures / Q000379:methods*; D016059:Range of Motion, Articular / Q000502:physiology; D020858:Tissue and Organ Harvesting; D055815:Young Adult