Meeting Abstract
P1.156 Monday, Jan. 4 Modeling the consequences of non-steady speed locomotion on walking mechanics BIKNEVICIUS, A.R.**; REILLY, S.M.; KLJUNO, E.; Ohio Univ. ; Ohio Univ. ; Ohio Univ. biknevic@ohio.edu
Studies of walking mechanics are traditionally constrained to steady-speed locomotion even though the ecological relevance of steady locomotion is questionable for most terrestrial vertebrates. Yet intermittent locomotion (brief but frequent locomotor bouts) is common across vertebrates. In this study, we developed a computer-based model to assess the effect of acceleration (positive or negative) on the pendulum-like recovery of external mechanical energy during walking (recovery ratios). The model was based on a spring-mass inverted pendulum with a point mass (center of mass), a spring of specified stiffness, and a dashpot (damper). It also included a torque at the foot as the active element in the model, representing the source of energy needed to accelerate/decelerate the walking cycle. A separate model was developed for hypothetical small and large vertebrates (0.5 kg versus 30 kg). At steady locomotion (acceleration = 0 m/s), both models displayed a progressive decline in recovery ratios with speed but the decrease was more pronounced in the small model. Both models also displayed reductions in recovery ratios for non-steady locomotion compared with steady events, however, there were substantial differences between the small and large models based on initial speed. In the large model, accelerating from a slow initial velocity had a smaller degradative effect on recovery ratios than did accelerating from a faster initial velocity. In other words, the large vertebrate model was somewhat forgiving of non-steady locomotion when moving at slow to moderate speeds. By comparison, the small model showed the opposite pattern, namely, steeper declines in recovery ratios at the slower initial speed than at faster speeds. These results will be interpreted with an eye towards differences in the metabolic cost of walking in small versus large vertebrates.
