The Effect of Quadriceps Fatigue on Co-Activation of Knee Muscles during Walking

Localized muscle fatigue in lower extremity can result in disturbance muscular co-activation during walking. The purpose of this study was to examine the effect of quadriceps fatigue on muscle co-activation of the knee during stance phase of walking. Subjects and Twenty-four university male students participated in this study. Leg extension machine was used to induce quadriceps fatigue with 50% of one-repetition maximum load. Surface electromyographic signals from rectus femoris، vastus medialis، vastus lateralis، biceps femoris، semitendinosus، lateral gastrocnemius، medial gastrocnemius and tibialis anterior muscles were recorded during walking before and after fatigue protocol. Paired t-test was used to analyze the data (P<0. 05). General co-contraction during contact phase (P=0. 001) and propulsion phase (P=0. 009) decreased significantly. Directed co-contraction during propulsion phase increased significantly (P=0. 017). Flexor directed co-contraction during propulsion phase increased significantly (P=0. 013). Hamstring to Quadriceps activity ratio during contact phase decreased significantly (P=0. 036) and propulsion phase increased significantly (P=0. 013). According to the results of this study، it can be concluded that localized quadriceps muscle fatigue alters the quadriceps to hamstring activity ratio consequently، the body attempts to compensate risk factors for related-fatigue with co-activation pattern of the knee muscles.