Does lower limb preference influence gait initiation? Yoann Dessery a,b,c,d, *, Franck Barbier a,b,c , Christophe Gillet a,b,c , Philippe Corbeil d,e, ** a Univ Lille Nord de France, F-59000 Lille, France b UVHC, LAMIH, F-59313 Valenciennes, France c CNRS, UMR 8530, F-59313 Valenciennes, France d Universite ´ Laval, Division de Kine ´siologie, Faculte ´ de Me ´decine, 2300, rue de la Terrasse, Quebec, Qc, Canada G1V 0A6 e Unite ´ de recherche sur le vieillissement, Centre de recherche FRSQ du CHA universitaire de Que ´bec, Que ´bec, Canada 1. Introduction Gait initiation (GI) is the transient period from a static upright position to a steady-state gait. This transition consists of an anticipatory postural adjustment (APA) followed by an execution of the first step [1,2]. Several studies have shown differences between the lower limbs regarding their mechanisms of action. Propulsive forces are generated by the swing limb during APA and by the stance limb during the execution phase [3,4]. Moreover, the swing limb is responsible for bodyweight displacement to the stance limb before Heel-Off (HO) of the swing limb [5]. These differing functions of the lower limbs question the influence of lower limb preference on GI. To date, a number of studies have been interested in the general characteristics of GI [1,2,5–7], however, authors tended to focus on GI with the preferential limb and generalized results to the other limb. Laterality and limb preference are used to express the preferential use of one limb in voluntary motor acts [8]. The influence of limb preference on human movements has been heavily studied, particularly in the upper limbs. The upper limbs are used to grasp, manipulate objects and write, permitting easier determination of preference. With the lower limbs, preference is more ambiguous as they are often involved in bilateral tasks such as locomotion and kicking. Nevertheless, a definition to distinguish both limbs in a bilateral context is given by Peters [9] and is used in gait study [8,10–12]: the mobilizing limb (swing limb) is the preferred limb whereas the support limb is the non-preferred limb. Although, no single study focuses on limb preference in GI, one study has looked at the symmetry of GI. Symmetry implies that both limbs behave identically [8] without taking into account limb preference. Hesse et al. [13] studied differences between lower limbs in GI but failed to demonstrate any difference between start with either limb. Some studies have shown differences between lower limbs at kinematic, kinetic and electromyographic (EMG) parameters during steady state gait [8]. As in GI, each lower limb has a different functions in gait (control or propulsion) and according to Sadeghi et al. [8], these different roles may be the cause of Gait & Posture 33 (2011) 550–555 ARTICLE INFO Article history: Received 28 June 2010 Received in revised form 8 January 2011 Accepted 15 January 2011 Keywords: Postural adjustment Frontal plane body motion Center of mass Step width Impulse ABSTRACT Gait initiation (GI) has been the focus of many investigations in order to determine the kinematic and kinetic parameters associated with this process. In these studies, the parameters are observed during GI with the preferential lower limb. However, none of these studies have looked at the impact on GI parameters when the start is achieved with the non-preferential limb. This investigation focused on the effects of lower limb preference on the kinematic and kinetic parameters of GI. Upon display of a visual cue, subjects stepped with preferential limb or non-preferential limb at natural speed. The duration of GI phases, the medio-lateral component of the center of mass (CM) displacement, the medio-lateral distance between the center of pressure and the CM, the step width as well as the medio-lateral impulse, were observed. When subjects started with the non-preferential limb, the bodyweight transfer was facilitated by a greater impulse during the anticipatory postural adjustment (APA) phase. Conversely, a more lateral CM displacement during the execution phase and a more lateral step in preferential start were observed. Asymmetry in frontal plane body motion was observed during weight transfer following APA, as well as during assistive control of ballistic body motion during the execution phase of the first step. In both conditions, the non-preferential limb provided the greater lateral impulse on the ground. This may have clinical relevance especially in individuals with unilateral limb dyscontrol and postural asymmetry that may require rehabilitation. ß 2011 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 418 656 2131x14784. ** Corresponding author. Tel.: +1 418 656 5604; fax: +1 418 656 2441. E-mail addresses: yoann.dessery.1@ulaval.ca (Y. Dessery), pco@kin.msp.ulaval.ca (P. Corbeil). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2011.01.008