title: Extensibility of the hamstrings is best explained by mechanical components of muscle contraction, not behavioral measures in individuals with chronic low back pain.
abstract: OBJECTIVE
  To examine the relationship between hamstring extensibility by use of the instrumented straight leg raise; mechanical components of muscle contraction, including muscle recruitment, passive torque measures of tissue stiffness, and eccentric strength; and self-reported measures of pain and disability.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  Twenty-one individuals with chronic nonspecific axial lower back pain and 15 healthy control subjects.
  
  
  RESULTS
  Instrumented straight leg raise, concentric and eccentric hamstring strength, self-reported measures of pain, disability, fear avoidance, general health and well-being
  
  
  METHODS
  Objective measures included hamstring extensibility, hamstring muscle stiffness, absolute and relative concentric/eccentric strength, concentric/eccentric strength ratios. Self-reported measures included Oswestry disability index, visual analog pain scale, fear avoidance beliefs, and general health and well being.
  
  
  RESULTS
  Patients with lower back pain had lower range of motion, greater changes in muscle stiffness, and impaired concentric-to-eccentric strength levels. Stepwise regression identified measures of stiffness as significantly predicting hamstring extensibility (adjusted r(2) = 0.58, F = 23.76, P < .001). Self-reported measures were not associated with extensibility. Gender differences were noted for passive stiffness and absolute strength. For women, later onset of the medial hamstrings also was associated with greater hamstring extensibility.
  
  
  CONCLUSIONS
  Decreased extensibility of the hamstrings was associated with increased passive stiffness during the common range of motion (20 to 50 degrees ). Impaired stretch tolerance is associated with actual mechanical restriction, not behavioral measures indicating increased pain or fear-avoidant behavior. With no relationship to actual disability and contradictory findings in the literature for the relationship of the hamstrings to the mechanics of the low back, it is unclear whether decreased hamstring extensibility should be targeted in rehabilitation programs for axial lower back pain.
authors.affiliation: Department of Sport and Exercise Science, University of Auckland, Tamaki Campus Private Bag 92019, Auckland, New Zealand. p.marshall@auckland.ac.nz
authors.forename: Paul W M
authors.initials: PW
authors.lastname: Marshall
authors.forename: Jamie
authors.initials: J
authors.lastname: Mannion
authors.forename: Bernadette A
authors.initials: BA
authors.lastname: Murphy
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005239:Fear / Q000502:physiology; D005260:Female; D006801:Humans; D007866:Leg; D017116:Low Back Pain / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D009129:Muscle Tonus / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013710:Tendons / Q000503:physiopathology*