My first objective was to understand and quantify the energy cost and muscular activity required for forward propulsion and leg swing during level walking. To accomplish this goal, I applied various combinations of external horizontal force at the waist and pulling forces at the feet. Concurrently, I measured the corresponding changes in metabolic rate and electromyographic activity. I reasoned that the reduction in net energy cost and muscle activity when a device performs a task reflects the energy cost and muscular activity of normally performing the task. The data indicate that forward propulsion consumes about 42%, and leg swing consumes approximately 10% of the net metabolic cost. Additionally, it appears that the primary muscles for forward propulsion and leg swing are the medial gastrocnemius and rectus femoris, respectively.

My second objective was to understand and quantify the forces and mechanical energy saving mechanisms during hill walking and running. To accomplish this goal, I constructed aluminum wedges that decline and incline our force treadmill. I measured ground reaction forces during walking and rurming on the level, down, and up at 3, 6 and 9 degrees. My rationale was that downhill and uphill locomotion must fundamentally change the fluctuation patterns of gravitational potential and kinetic energy of the body center of mass. During downhill walking, energy must be dissipated to resist gravity, yet fluctuations in total energy decreased compared to the level. During uphill walking, energy must be generated to overcome gravity and fluctuations in total energy increased compared to the level. For downhill running, the possibility for elastic energy storage exists but almost all of this energy must be dissipated. For uphill running, the possibility of elastic energy storage is greatly reduced and therefore little energy can be recovered.