2006 ISEK Congress Basmajian Student Award Paper Control of head stability during gait initiation in young and older women L. Laudani a,b , A. Casabona b , V. Perciavalle b , A. Macaluso a, * a Department of Applied Physiology, University of Strathclyde, Glasgow, UK b Dipartimento di Scienze Fisiologiche, Universita ` degli Studi di Catania, Catania, Italy Abstract Transition tasks between static and dynamic situations may challenge head stabilization and balance in older individuals. The study was designed to investigate differences between young and older women in the upper body motion during the voluntary task of gait ini- tiation. Seven young (25 ± 2.3 years) and seven older healthy women (78 ± 3.4 years) were required to stand on a force platform and initiate walking at their self-selected preferred speed. Angles of head, neck and trunk were measured by motion analysis in the sagittal plane and a cross-correlation analysis was performed on segments pairs. Variability of head and neck angular displacements, as indicated by average standard deviation, was significantly greater in the older than in the young participants. The young women maintained dynamic stability of the upper body, as forward flexion of the trunk was consistently counteracted by coordinated head–neck extension. Differently, movement patterns employed by the older women also included a rigid motion of all upper body segments leaning forward as a single unit. These results demonstrated that older women perform the transition from standing to walking with greater variability in the patterns of upper body motion compared to young women. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Motor variability; Elderly; Upper body kinematics; Cross-correlation; Walking initiation 1. Introduction Stabilization of the head with respect to the environ- ment is considered as fundamental in the control of whole body balance and co-ordination during the performance of several motor actions, such as daily-life locomotor tasks (Pozzo et al., 1990; Cromwell et al., 2001b; Muluvara et al., 2002). As an inertial guide platform, in fact, stability of the head helps maintain gaze and optimizes input from the visual, vestibular and somatosensory systems (Pozzo et al., 1990). During walking on a level surface, such a sta- bilization process is accomplished through coordinated movements of the head on the trunk, which compensate for trunk oscillations (Cromwell et al., 2001b). At self- selected preferred speeds of locomotion, previous investiga- tors have shown that accelerations are attenuated from the body lower districts to the head across the gait cycle (Cap- pozzo, 1981; Prince et al., 1994; Kavanagh et al., 2006). The upper body has therefore been characterized as a rela- tively stable system, which maintains a state of dynamic equilibrium and produces minimal oscillations about a mean position, in response to the motion of lower limbs (Cromwell et al., 2001a). Transitory motor tasks, such as gait initiation, involve complex interactions between neural and biomechanical factors that may challenge postural stability and head sta- bilization in older individuals. Declining balance is a very major factor facing the ageing population, as it is crucial in determining risk of injuries and loss of life due to falls (Winter, 1995). Many falls in older people are commonly reported when they walk only short distances (Ashley et al., 1977) and/or during some forms of locomotion, such 1050-6411/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jelekin.2006.08.001 * Corresponding author. Address: Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, 199 Cathedral Street, Glasgow G4 0QU, UK. Tel.:+44 141 548 5773; fax: +44 141 548 5792. E-mail address: andrea.macaluso@strath.ac.uk (A. Macaluso). Journal of Electromyography and Kinesiology 16 (2006) 603–610 www.elsevier.com/locate/jelekin