Meeting Abstract
Many ectotherms exhibit a thermal plateau, over which whole animal performance is largely constant. One example is the western fence lizard, Sceloporus occidentalis, which maintains nearly constant running performance between 25° and 40° C. This performance plateau is apparent despite changes in muscle kinetics that would predict a performance decrease at low temperatures. Here, we test the hypothesis that fence lizards can use stored elastic energy to enhance muscle power and minimize the deleterious effects of low temperature on locomotor performance. We use 3D kinematics of lizard accelerations along with ground reaction force data collected from a six-axis force transducer under the left hind foot of the lizards to run an inverse dynamics analysis. We then use the mass of the limb extensors and their insertions to estimate muscle power during acceleration. From our preliminary data, we find that at 35° C, lizards may have just enough muscle to power the fastest accelerations we measured. However, at 25° C, we find that the muscle power needed to elicit the fastest accelerations is higher than the lizards can produce. We also find unexpected similarities in the ground reaction forces, timing of movement, and kinematics of lizards accelerating at 25° and 35° C. We believe these similarities provide additional evidence for elastic energy storage and power amplification during acceleration in lizards. These results add to the growing body of evidence that suggests elastic mechanisms allow ectothermic organisms to maintain performance across a broad thermal plateau.
