title: Females exhibit shorter paraspinal reflex latencies than males in response to sudden trunk flexion perturbations.
abstract: BACKGROUND
  Females have a higher risk of experiencing low back pain or injury than males. One possible reason for this might be altered reflexes since longer paraspinal reflex latencies exist in injured patients versus healthy controls. Gender differences have been reported in paraspinal reflex latency, yet findings are inconsistent. The goal here was to investigate gender differences in paraspinal reflex latency, avoiding and accounting for potentially gender-confounding experimental factors.
  
  
  METHODS
  Ten males and ten females underwent repeated trunk flexion perturbations. Paraspinal muscle activity and trunk kinematics were recorded to calculate reflex latency and maximum trunk flexion velocity. Two-way mixed model analyses of variance were used to determine the effects of gender on reflex latency and maximum trunk flexion velocity.
  
  
  RESULTS
  Reflex latency was 18.7% shorter in females than in males (P=0.02) when exposed to identical trunk perturbations, and did not vary by impulse (P=0.38). However, maximum trunk flexion velocity was 35.3% faster in females than males (P=0.01) when exposed to identical trunk perturbations, and increased with impulse (P<0.01). While controlling for differences in maximum trunk flexion velocity, reflex latency was 16.4% shorter in females than males (P=0.04).
  
  
  CONCLUSIONS
  The higher prevalence of low back pain and injury among females does not appear to result from slower paraspinal reflexes.
authors.affiliation: Virginia Polytechnic Institute and State University, School of Biomedical Engineering and Sciences, USA.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Miller
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Slota
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Agnew
authors.forename: Michael L
authors.initials: ML
authors.lastname: Madigan
mesh_terms: D000328:Adult; D019567:Back Injuries / Q000175:diagnosis*; D001696:Biomechanical Phenomena; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis*; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D011187:Posture; D012018:Reflex; D012737:Sex Factors; D013131:Spine / Q000473:pathology