Effects of gravitational and inertial forces on human locomotion .

摘要

Walking and running are fundamental forms of human locomotion. Humans may walk or run to enhance fitness, and/or compete, where performance is the primary goal. A biomechanical and metabolic analysis of human locomotion is therefore important to better understand how humans move and their metabolic power demand. On a broader scale, we may extend this basic knowledge to the design and development of assistive devices.; In chapter one, I used simulated reduced gravity and added loading to determine the independent metabolic power required for generating force to support body weight and performing work to redirect/accelerate body mass during walking. In chapter two, I repeated this protocol for running. Force generated to support body weight comprises ~28%, and work done to redirect/accelerate body mass comprises ~45% of the overall net metabolic power required for normal walking. In running, force generated to support body weight comprises ~74%, and work done to redirect/accelerate body mass comprises an insignificant percentage of the overall net metabolic power.; Generating force for horizontal braking and propulsion demands a substantial percentage of metabolic power during running. Previous studies have measured this metabolic power by using applied horizontal pulling forces (towing). Towing is also used in adventure racing to enhance team performance by improving overall running speed. In chapter three, I modeled the effects of towing on running performance. Then, I empirically validated the predictions of my model. I found that performance times were accurately predicted while runners utilized optimal towing, and that towing greatly improves overall running performance.; Previous studies have either determined the metabolic and biomechanical effects of varied running speed at normal body weight or have determined the effects of body weight support at constant speeds. In chapter four, I used a novel device to support body weight, and quantified the effects of speed and weight support on metabolic power demand and GRF production during running. I found that speed and weight individually and interactively effect metabolic power and GRF production during running. I also found that weight supported running at fast speeds could decrease the potential risk of over-use injury while providing cardiovascular benefits.