Meeting Abstract
For the last several decades the field of comparative locomotion mechanics has been dominated by analyses directed at documenting and assessing mechanisms of energy exchange (transduction) that occur within a stride. It has been thought logical that legged animals will benefit from reusing energy available from one portion of the stride in another portion of the stride. Increases and decreases of energy corresponding to patterns expected for pendulum-like and spring-like exchange do indeed occur. However, demonstration of such patterns does not indicate their value to the dynamics of legged locomotion. In order to evaluate the potential role of pendular and spring exchange in bipedal locomotion we use a dynamic optimization model to predict movement strategies that require the least energetic investment. Predictions of the model operating under specified circumstances are then compared with the spontaneous movement patterns of humans in the same circumstances. Successful prediction by the optimization strategy then allows detailed analysis of the model and the identification of the factors that determine cost optimization. It is found that spring-like leg motion is energetically favorable even if no energy exchange takes place (where cost of the motion has to be actively provided by positive and negative work). It is also found that the inverted pendulum is a favorable motion pattern for slower (walking) speeds, but the value of this strategy is dependent on limiting the energetic loss at transition between support limbs, rather than transferring energy from one portion of the stride to another. Identification of the factors involved in effective legged locomotion will allow the interpretation of the morphological and behavioral strategies implemented by legged organisms.
