title: Selective strength loss and decreased muscle activity in hamstring injury.
abstract: METHODS
  Cross-sectional, controlled laboratory study.
  
  
  OBJECTIVE
  To determine whether thigh muscle isokinetic torque patterns and activity, measured by electromyography (EMG), of individuals with hamstring injury differ from control individuals.
  
  
  BACKGROUND
  Neuromuscular control during thigh muscle strength assessment following hamstring injuries has not been reported.
  
  
  METHODS
  Fifteen athletes with prior hamstring injury (hamstring-injured group [HG]) were compared to 15 uninjured athletes (control group [CG]). The injuries were incurred 6 weeks to 12 months prior to participation, and all injured athletes had returned to at least partial training. Participants performed 5 isokinetic concentric extensor, concentric flexor, and eccentric flexor torque tests at 60°/s in the seated position. Peak torque was determined for each contraction type, as well as average torque for each of 4 time-based movement quartiles. EMG root-mean-squares were calculated in these movement quartiles for the biceps femoris and medial hamstrings.
  
  
  RESULTS
  No significant differences were found for peak torque for all contractions, when comparing HG injured and uninjured sides to CG bilateral averages. The HG injured limb eccentric flexor torque was significantly lower in the fourth quartile (approximately 25° to 5° knee flexion, hamstring lengthened range) compared to the CG bilateral average (P = .025). Eccentric flexor biceps femoris and hamstrings EMG root-mean-squares of the HG injured and the uninjured sides were significantly lower in the second to fourth quartiles (towards the lengthened range), compared to the CG bilateral averages (P<.05).
  
  
  CONCLUSIONS
  Decreased strength and EMG activation in a lengthened hamstrings range for the athletes with prior hamstring injury suggested a change in neuromuscular control. Lengthened range assessment of isokinetic eccentric flexor torque may be useful for the assessment of athletes with a prior injury; however, results should be confirmed with prospective studies.
authors.affiliation: Centre for Physiotherapy Research, University of Otago, Box 56, Dunedin, 9054, New Zealand. gisela.sole@otago.ac.nz
authors.forename: Gisela
authors.initials: G
authors.lastname: Sole
authors.forename: Stephan
authors.initials: S
authors.lastname: Milosavljevic
authors.forename: Helen D
authors.initials: HD
authors.lastname: Nicholson
authors.forename: S John
authors.initials: SJ
authors.lastname: Sullivan
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000175:diagnosis* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D004576:Electromyography; D006801:Humans; D007551:Isotonic Contraction / Q000502:physiology; D007719:Knee Joint / Q000503:physiopathology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology; D013708:Tendon Injuries / Q000175:diagnosis* / Q000503:physiopathology; D055815:Young Adult