112.3 Saturday, Jan. 7 Analysis of rat hindlimb muscle and tendon mechanics using x-ray videoradiography HORNER, Angela M*; ASTLEY, Henry C; ROBERTS, Thomas J; Brown University; Brown University; Brown University email@example.com
Biomechanical scaling principles have shaped our understanding of mammal locomotion for decades, but our understanding of tissue level function is biased toward taxa 1 kg or larger. For example, although rats are commonly used in muscle physiology research, few studies have measured muscle and tendon function in vivo. This bias in data is due in part to the technical challenges imposed by instrumentation of small mammal tissue in vivo. In this study we apply a novel methodology for the study of small mammal muscle and tendon function utilizing high speed, biplanar videoradiography (as used in X-Ray Reconstruction of Moving Morphology, or XROMM). In this system, movements of bone and markers can be tracked accurately (± 0.1mm) with minimal invasiveness. We surgically implanted rats with small (< 1.0mm) radio-opaque beads; two beads were implanted into the medial gastrocnemius muscle fascicles and one into the shared tendon of the triceps surae. In vivo muscle and tendon length changes were recorded with videoradiography during locomotion on level, inclined and declined trackways, as well as during short jumps. Following locomotor measurements, animals were anesthetized and the length-tension (LT) and force-velocity (FV) properties of the muscle were measured in situ via videoradiography. The measurements revealed typical LT and FV behavior, confirming that radio-opaque markers can accurately track muscle length. These data demonstrate the wider applicability of videoradiography to soft tissue mechanics and hold promise for further study of muscle and tendon mechanics in smaller animals.