An Index of Gait Instability Based on Electromyographic Findings during the Development of Gait

To develop an index of gait instability from electromyographic information, we made observations on infants from the time they first began to walk independently at about one year of age until around three years of age. From our findings we obtained the following criteria. (1) Very unstable gait: As seen in a child within the first month of learning to walk the vastus medialis is active in the latter half of swing phase, the tibialis anterior and rectus femoris are active during stance phase, and activity of the vastus medialis is continuous. These electromyographic characteristics are not usually seen in subsequent childhood gait or in adult gait, and they serve as markers of very unstable gait. (2) Unstable gait: Activity of the gastrocnemius in the latter half of swing phase is generally noted only within the first three months after a child learns to walk, and that activity is interpreted as a sign of unstable gait. (3) Slightly unstable gait: Activity of the gastrocnemius in the first half of stance phase and continuous activities of the biceps femoris and gluteus maximus from initial contact with the floor until push off are found in children until three years of age. These activities are considered electromyographic markers of slightly unstable gait.