title: Effect of natural trunk inclination on variability in soleus inhibition and tibialis anterior activation during gait initiation in young adults.
abstract: BACKGROUND
  Anticipatory postural adjustments (APAs) of gait initiation (GI) permit first step execution. APAs are characterized by a structured pattern of soleus (SOL) inhibition followed by tibialis anterior (TA) activation. This pattern shows variability among young adults where SOL is not always inhibited before TA activation. Initial posture preceding GI could explain a part of this variability. The aim of the study was to investigate the effect of natural trunk inclination on APAs during GI.
  
  
  METHODS
  Two groups of twelve subjects divided by natural trunk inclination angle performed five gait initiation trials. A regression model was computed to predict SOL inhibition and TA activation.
  
  
  RESULTS
  Backward leaners showed less SOL inhibition in stance leg (25.8% of trials) compared to forward leaners (55.6% of trials). Regression model revealed that high tonic EMG activity in SOL in the stance leg is the variable that best explains SOL inhibition variation within trials but not TA activation.
  
  
  CONCLUSIONS
  Slight variations in APAs are due to natural trunk inclination but more contribution in APAs is due to initial posture, future step speed and initial tonic soleus activity. Absence of SOL inhibition could be in part explained by natural trunk inclination, where the backward inclination leads to lower tonic SOL activity in quiet standing. These effects could be due to inherent and functional variability, which depend on postural variation, muscular coordination and limb roles.
authors.affiliation: Université Laval, Département de Kinésiologie, Faculté de Médecine, 2300, rue de la Terrasse, Québec, QC, Canada G1V 0A6. Electronic address: annie-pier.fortin.2@ulaval.ca.
authors.forename: Annie-Pier
authors.initials: AP
authors.lastname: Fortin
authors.affiliation: Université Laval, Département de Kinésiologie, Faculté de Médecine, 2300, rue de la Terrasse, Québec, QC, Canada G1V 0A6. Electronic address: yoann.dessery.1@ulaval.ca.
authors.forename: Yoann
authors.initials: Y
authors.lastname: Dessery
authors.affiliation: Université Lille Nord de France, Lille, France; UVHC, LAMIH, Valenciennes, France; CNRS, UMR CNRS 8201, Valenciennes, France; Centre de Rééducation Fonctionnelle La Rougeville, Saint-Saulve, France. Electronic address: sebastien.leteneur@univ-valenciennes.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Leteneur
authors.affiliation: Université Lille Nord de France, Lille, France; UVHC, LAMIH, Valenciennes, France; CNRS, UMR CNRS 8201, Valenciennes, France. Electronic address: franck.barbier@univ-valenciennes.fr.
authors.forename: Frank
authors.initials: F
authors.lastname: Barbier
authors.affiliation: Université Laval, Département de Kinésiologie, Faculté de Médecine, 2300, rue de la Terrasse, Québec, QC, Canada G1V 0A6. Electronic address: philippe.corbeil@kin.ulaval.ca.
authors.forename: Philippe
authors.initials: P
authors.lastname: Corbeil
mesh_terms: D000328:Adult; D004576:Electromyography; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D060726:Torso / Q000502:physiology*; D055815:Young Adult
keywords: Anticipatory postural adjustment; EMG; Gait initiation variability; Initial posture; Motor program