title: Hip-abduction torque and muscle activation in people with low back pain.
abstract: Individuals with a history of low back pain (LBP) may present with decreased hip-abduction strength and increased trunk or gluteus maximus (GMax) fatigability. However, the effect of hip-abduction exercise on hip-muscle function has not been previously reported.
  
  
  
  To compare hip-abduction torque and muscle activation of the hip, thigh, and trunk between individuals with and without a history of LBP during repeated bouts of side-lying hip-abduction exercise.
  
  
  
  Repeated measures.
  
  
  
  Clinical laboratory.
  
  
  
  12 individuals with a history of LBP and 12 controls.
  
  
  
  Repeated 30-s hip-abduction contractions.
  
  
  
  Hip-abduction torque, normalized root-mean-squared (RMS) muscle activation, percent RMS muscle activation, and forward general linear regression.
  
  
  
  Hip-abduction torque reduced in all participants as a result of exercise (1.57 ± 0.36 Nm/kg, 1.12 ± 0.36 Nm/kg; P < .001), but there were no group differences (F = 0.129, P = .723) or group-by-time interactions (F = 1.098, P = .358). All participants had increased GMax activation during the first bout of exercise (0.96 ± 1.00, 1.18 ± 1.03; P = .038). Individuals with a history of LBP had significantly greater GMax activation at multiple points during repeated exercise (P < .05) and a significantly lower percent of muscle activation for the GMax (P = .050) at the start of the third bout of exercise and for the biceps femoris (P = .039) at the end of exercise. The gluteal muscles best predicted hip-abduction torque in controls, while no consistent muscles were identified for individuals with a history of LBP.
  
  
  
  Hip-abduction torque decreased in all individuals after hip-abduction exercise, although individuals with a history of LBP had increased GMax activation during exercise. Gluteal muscle activity explained hip-abduction torque in healthy individuals but not in those with a history of LBP. Alterations in hip-muscle function may exist in individuals with a history of LBP.
authors.affiliation: Dept of Kinesiology, University of Virginia, Charlottesville, VA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Sutherlin
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
mesh_terms: D000293:Adolescent; D000328:Adult; D004576:Electromyography; D005260:Female; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010147:Pain Measurement; D013848:Thigh / Q000502:physiology; D013909:Thorax / Q000502:physiology; D019415:Torque