DYNAMIC ANALYSIS OF STABILITY IN HUMAN LOADED WALKING AT DIFFERENT VELOCITIES AND HEIGHTS OF THE CENTER OF MASS, AND POSSIBLE OPTIMAL AREAS IN DIFFERENT MODES OF WALKING
Keywords: Stability, dynamic analysis, optimum, the center of mass (COM), height and velocity
AbstractINTRODUCTION: Loaded walking plays an important role in man’s many activities, including sport, such as leisure travel and hill walking. It is known that in loaded walking velocity and height of the body center of mass (COM) are two important factors for the stability of the whole body. This paper investigates which heights and velocities of COM lead to stable loaded and unloaded walking. METHODS: The method was as follows: 1) We considered the whole body as a simple three-segment model, made of two lower limbs (leg-foot) and one upper body (head-trunk-arm, HTA); 2) We recorded motion and ground reaction forces from real subjects walking at self-determined 'slow', 'comfortable', 'fast' speeds and loaded in one of three different ways and different carried ways; 3) We applied dynamic equations to the models; 4) We input the motion and ground reaction forces acquired into the models, and obtained their dynamic response at the body center of mass; 5) From these experiments and simulation, we can analyze possible optimum areas at different velocities and heights of COM. RESULTS: Results confirm that there are different dynamic responses for different modes of walking. In general, taking the stability of the center of mass as our criterion, stability in loaded walking decreases with an increase in the height and velocity of COM. However, a lower height of COM does not always satisfy the criterion of stability. Neither does a greater height of COM always lead to reduced stability. Rather, it is apparent that different modes of loaded walking each have a characteristic height/velocity area, beyond which stability decreases. So it is discovered that a special stability area may exist for a relative walking way. CONCLUSIONS: In fact, for different carried walking ways, there are some suitable areas where optimum stability may be obtained and beyond which the stability of human walking may decrease. For a different height of COM, this paper recommends some relative walking velocity which may be referenced in human leisure, sport and transport activities.
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