title: Pelvic step: the contribution of horizontal pelvis rotation to step length in young healthy adults walking on a treadmill.
abstract: Transverse plane pelvis rotations during walking may be regarded as the "first determinant of gait". This would assume that pelvis rotations increase step length, and thereby reduce the vertical movements of the centre of mass-"the pelvic step". We analysed the pelvic step using 20 healthy young male subjects, walking on a treadmill at 1-5 km/h, with normal or big steps. Step length, pelvis rotation amplitude, leg-pelvis relative phase, and the contribution of pelvis rotation to step length were calculated. When speed increased in normal walking, pelvis rotation changed from more out-of-phase to in-phase with the upper leg. Consequently, the contribution of pelvis rotation to step length was negative at lower speeds, switching to positive at 3 km/h. With big steps, leg and pelvis were more in-phase, and the contribution of pelvis rotation to step length was always positive, and relatively large. Still, the overall contribution of pelvis rotations to step length was small, less than 3%. Regression analysis revealed that leg-pelvis relative phase predicted about 60% of the variance of this contribution. The results of the present study suggest that, during normal slow walking, pelvis rotations increase, rather than decrease, the vertical movements of the centre of mass. With large steps, this does not happen, because leg and pelvis are in-phase at all speeds. Finally, it has been suggested that patients with hip flexion limitation may use larger pelvis rotations to increase step length. This, however, may only work as long as the pelvis rotates in-phase with the leg.
authors.affiliation: First Clinical College of Fujian Medical University, Fuzhou, Fujian, PR China; Department of Orthopaedic Surgery, Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian, PR China; Orthopaedic Biomechanics Laboratory, Fujian Medical University, Quanzhou, Fujian, PR China.
authors.forename: Bo Wei
authors.initials: BW
authors.lastname: Liang
authors.forename: Wen Hua
authors.initials: WH
authors.lastname: Wu
authors.forename: Onno G
authors.initials: OG
authors.lastname: Meijer
authors.forename: Jian Hua
authors.initials: JH
authors.lastname: Lin
authors.forename: Go Rong
authors.initials: GR
authors.lastname: Lv
authors.forename: Xiao Cong
authors.initials: XC
authors.lastname: Lin
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Prins
authors.forename: Hai
authors.initials: H
authors.lastname: Hu
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.forename: Sjoerd M
authors.initials: SM
authors.lastname: Bruijn
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005080:Exercise Test / Q000379:methods*; D005684:Gait / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D010388:Pelvis / Q000502:physiology*; D012399:Rotation; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Centre of mass; Leg-pelvis relative phase; Pelvic step; Pelvis rotation; Step length