4 . شماره16 . دوره1394 زمستان 324 * Corresponding Author: Hamideh Khodaveisi, PhD Address: Department of Physical Educaion & Sport Sciences, Faculty of Humani ies, Islamic Azad University, Hamedan Branch, Hamedan, Iran. Tel: +98 (918) 8156787 E-Mail: khodaveisi_h@yahoo.com Research Paper: Comparison of Electromyographic Acivity Patern of Knee Two-Joint Muscles between Youngs and Olders in Gait Diferent Speeds 1. Department of Physical Educaion & Sport Sciences, Faculty of Humaniies, Islamic Azad University, Hamedan Branch, Hamedan, Iran. 2. Department of Sport Biomechanics, Faculty of Physical Educaion and Sport Sciences, Bu-Ali Sina University, Hamedan, Iran. * Hamideh Khodaveisi 1 , Mehrdad Anbarian 2 , Maryam Khodaveisi 1 Objecive In recent years, it has been focused much atenion on gait analysis. Factors such as speed, age and gender afect gait parameters. The purpose of the present study was to compare the electromyo- graphic acivity patern of knee two-joint muscles between younger and older subjects in diferent gait speeds. Materials & Methods The method of current study was analyical cross-secional method in which 15 healthy young men and 15 old men, were selected conveniently. Electromyographic acivity of rectus femoris, biceps femoris, semitendinus and gastrocenemius were recorded during walking with preferred (100%), slow (80%) and fast (120%) speeds in a 10 meter walkway. Normalized RMSs of muscles were compared using RM-ANOVA and Tokey’s tests by SPSS 18 sotware. Results According to results, RMSs of rectus femoris in midstance (P<0.01) and gastrocenemius in loading response (P=0.02) phases in all walking speeds were higher in older subjects than in younger ones, and it increased with speed in both age groups (P<0.01). Biceps femoris RMS in terminal stance at 80% speed, was lower in older subjects than in younger ones (P=0.01) and it increased with walking speed (P=0.01). Semitendinus acivity in loading and midstance phases at 120% speed was higher in older subjects than in younger ones (P<0.01), and it increased with speed in both age groups in swing phase (P<0.05). Conclusion According to the results, older subjects have more muscle co-contracion around knee at high speed in midstance phase than younger subjects. These age-related changes in muscle acivity, leads to increase in joint sifness and stability during single support, and probably play a role in reducing push of power at faster speeds. A B S T R A C T Keywords: Electromyography acivity, Gait, Lower extremity, Elderly, Young Received: 20 May 2015 Accepted: 9 Aug. 2015