World Journal of Sport Sciences 5 (3): 205-215, 2011 ISSN 2078-4724 © IDOSI Publications, 2011 Corresponding Author: Heydar Sadeghi, Department of Kinesiology, Tarbiat Moallem University, Theran, Mirdamad, Razan e Jonobi Shahid Keshvari Complex, Iran. Tel: +21-22228001, Fax: +21-22269547. 205 Dynamic Stability and Propulsion During Gait of the Healthy Elderly and Young Subjects Using Three Dimensional Kinetic Data Heydar Sadeghi Department of Kinesiology, Tarbiat Moallem University, Tehran, Iran Abstract: Using 3D kinetic data, this study was undertaken to determine whether similar joint muscle power activities or mechanical energies are developed for dynamic stability and propulsion during the gait of healthy elderly and young individuals’ dynamic stability. Eighteen elderly (71±6.8 years) and 18 young (25±4.1 years) able-bodied male subjects walked along a 10 m walkway at a freely-chosen speed. Data acquisition was performed with a Motion Analysis system and with a three Optotrak position sensors while one AMTI force platform recorded ground reaction forces. Spatio-temporal parameters as well as 22 peak joint muscle powers and their corresponding mechanical energies were calculated for each gait cycle. T-tests for independent samples was applied to determine statistical differences between the two groups (p<0.05). Though similar power patterns were observed for both groups, significant differences were noted for the peak joint muscle powers and their associated energies developed in most of the phases. In both groups, the greatest total work (positive and negative) was done at the hip, followed by the ankle and the knee, while the smallest and greatest differences between total energy in the elderly and young subjects were noted at the knee (58%) and ankle (36%), respectively. The hip extensors compensated for the hip abductors to maintain balance in elderly gait. For the younger subjects, propulsion from the hip extensors was initiated shortly after heel-strike, maintained throughout midstance and completed at push-off by the ankle and the hip for pull-off. In elderly gait, propulsion was limited to the ankle push-off and hip pull-off in the sagittal plane. Key words: Biomechanics %Gait %Young %Elderly %Spatio-temporal parameters %Joint muscle power INTRODUCTION tasks of propulsion and dynamic stability [11]. Changes in stereotypic movements such as walking between net joint powers (muscle activities) in all three patterns have been reported as early as 60 years old [1-9]. different planes could reflect propulsion [18] and the Hence, attempts have been made to better understand the consequence or outcome of higher hierarchy dynamic mechanism of these changes in the geriatric population, stability [19] actions during walking. This study was particularly for body support against gravity (dynamic undertaken to provide information about lower limb stability) and forward propulsion (propulsion) [10-15]. To muscle dynamics during elderly gait with the focus on our knowledge, while the lack of dynamic stability has understanding how lower limb muscle activities are been recognized as a major potential cause of falls and associated with body support against gravity and significant risk for injury [16], or destabilize lateral motion propulsion functions. [17], less attention has been paid to providing insight into To explore this avenue, spatio-temporal parameters propulsion or understanding how both dynamic stability were used as a conventional approach for characterizing and propulsion are modified in the gait of the elderly the gait of elderly and young subjects. Joint muscle population. moments [20] and joint muscle powers [18, 19] were used The aim of locomotion is to support the body against as more convenience gait indicators to understand control gravity while generating movements to propel the body and forward propulsion tasks [21]. The time integral of the forward. It requires precise coordination between the power bursts (i.e. mechanical energy) was also calculated Furthermore, it has been documented that interaction