CHANGES IN THE COORDINATION OF WALKING MOVEMENTS UNDER CONDITIONS OF CONSTANT AND VARIABLE SPEED

Abstract

INTRODUCTION: A great number of scientific studies on the biomechanics of walking are available. In addition to the analysis of the time course of kinematic and dynamic quantities, increased efforts were made for the estimation of the muscle activities. It is common to use an average of the muscle activity patterns of several steps (Zwick (1993); Konrad/Tyry (1996)). This procedure presupposes constant external constraints, similar biomechanical curves and equal muscle activity patterns. Here arises the problem: How stable or variable is the movement coordination of single steps if a) the walking speed is constant and b) the walking speed is changed? METHODS: The investigations were carried out with three male sports students on a treadmill. As an example, the results of one subject (SR) will be represented in this presentation. Three walking speeds were selected which the subjects could realize as comfortable and below the point where running begins. The speeds for SR were 1.0 m/s (SR1), 2.0 m/s (SR2) and 2.2 m/s (SR3). The subjects walked for four minutes at each speed level. The breaks between the speed levels were used for relaxation. Muscle fatigue was thus minimized. By means of the SIMI-Motion movement analysis system and EMG-Telemetry system of Noraxon-Neurodata, two dimensional video analysis (50 s-1 and 200 s- 1) of the left side was carried out and the EMG signals of five muscles (m. biceps femoris, m. vastus medialis, m. rectus femoris, m. gastrocnemius, m. tibialis) were recorded synchronously. The cycles were divided in two phases (support and swing) on the basis of characteristics of the time courses of relative ankle velocity in relation to the hip. Due to high-speed video limitations, five cycles for SR1 and eight cycles for SR2 and SR3 could be analyzed. We applied the adaptive estimation of the momentary power of the EMG-signals for timedependent analysis of muscle activities (Grießbach, Schack et al., 1994).