Meeting Abstract
Lizards are exceptionally adept at moving through highly complex environments, and this extreme performance requires that their muscles function effectively under widely disparate conditions. Among the properties that can impact muscle function, the force-length relationship is of considerable importance in determining how force can be generated over a range of limb positions, as different joint angles may result in different muscle lengths. Unfortunately, due to the small size of most lizard muscles, it is difficult to use surgical techniques to directly measure muscle lengths and forces in vivo and in ecologically relevant contexts. We employed an integrative approach to explore the impact of substrate on muscle function in the arboreal lizard, Anolis equestris. We assessed muscle and tendon architecture to determine the potential for tendon strain to decouple muscle length from limb kinematics. Assuming 100% of muscle recruitment, maximum tendon stretch would be equal to less than 1% of muscle-tendon length for all hindlimb muscles. As this clearly precludes decoupling of kinematics and muscle strain, we quantified the relationship between muscle length and joint angle using high-speed video. We then used this relationship to link in situ force-length curves to kinematic and muscle activity data obtained from lizards running on perches of different diameter and incline. Thus, we have not only established that tendons are unlikely to deform and thus primarily function to connect muscle to structures rather than to store elastic energy in small lizards, but we have demonstrated the utility of using a combination of techniques to determine the impact of ecological factors such as substrate incline and diameter on muscle function in small animals. Supported by NSERC PGSD 405019-2011 and NSF IOS-1147043.
