The Changes of Leg Musclus Activities Following Increase of Gait Velocity

Purpose: Motor control evaluation and analysis of it"s specifications for diagnosis of neuromuscular diseases is new approach in clinical electroneurophysiology, that is based on the changes of electromyography responses and classic reflexes in this field. In this study quantitative power spectrum frequency used for changes of motor control strategies. Materials and Methods: Twenty five healthy subjects (15 women and 10 men) between 20 to 30 years old participated in this study. After attachment of surface electrodes on tibialis anterior and gastrocnemius muscles, subjects walked without foot wears on treadmill with three speeds, comfortable (80 m/min), slow (40 m/win) and fast (120 m/min). Results: Results indicated with increase of gait velocity, mean and median frequency of gastrocnemius muscle were reduced, whereas it, mean and median frequency of motor units recruitment were increased significantly (P<0.05). Tibialis anterior muscle activities evaluated in three gait speed and two types of contraction, concentric in initial swing, mid swing, and eccentric in late stance stage. Following increase of gait velocity, median frequency of concentric contraction was reduced, whereas in eccentric contraction, increase of median frequency was observed (P<0.05).In concentric contraction, the firing rate of motor unit recruitment was increased by increment of gait velocity (P<0.05), but in eccentric contraction, there was no significant changes. At the same time, with increment of gait velocity in fast speed, values of RMS, ARV and IAV were increased (P<0.05).In comparison to maximal isometric contraction, muscle force estimation in fast speed was increased, and also muscle force was increased at slow speed walking in comparison with comfortable speed (P<0.05). Conclusion: Motor control mechanism will follow specific patterns at individual changes level in constant environment and task, and on the basis of time and biomechanical factors show changes of behavioral movement. Therefore, increase of firing rate for high force is not parallel to increase of frequencies values of muscle contraction and cognition of subject from movement and type of task demand determine motor units recruitment.