Similar Kinematics Between Flat and Curved Treadmills Confirm That Reduced Body Center of Mass Leads to Increased Energy Expenditure

Human gait is an advanced process with many variables affecting efficiency. One controversial aspect is the displacement of the body’s center of mass (COM). Initially, the clinicians suggested that by decreasing the body’s vertical COM fluctuation, the energy expenditure would decrease also. Previously, we expanded on other research that contradicted this theory. Specifically, we introduced a curved treadmill with an arc shaped walking platform similar to the path of motion of the COM when walking overground, but inverted. Thus, this design counters the arc of the COM, movement of the COM. This made possible achievement of reduced vertical COM movement while maintaining a more natural walking motion, as opposed to subjects’ purposefully altering gait. Our previous study did not examine subjects’ gait beyond an anecdotal report. Therefore, the purpose of this study was to examine the kinematics of the ankle, knee, and hip between the two treadmill conditions. Our results did not directly confirm our theory, as subjects differed in hip and knee joint range of motion. However, the results do further confirm our first hypothesis. In our initial study, we found that at the slowest speed had the least amount of variation in energy expenditure between the two treadmills but increased with speed. However, in this study the slowest speed had the largest difference in range of motion. This suggests that because range of motion and energy expenditure do not show the same pattern, change in energy expenditure was not a secondary effect of treadmill type