Meeting Abstract
Rabbits have hindlimb extensor muscles that allow them to accelerate rapidly during locomotion, and our previous analyses indicate that juveniles have certain performance advantages that could increase their survival to reproductive maturity. Specifically, we found that extension at the lumbosacral joint provides the most work of acceleration, thus emphasizing the importance of the vertebral extensor muscles to the mechanics of their half-bound gait. To further investigate the ontogeny of force and power capacity in these muscles, muscle architectural properties and myosin heavy chain (MHC) isoform content are being quantified in both juvenile and adult cottontail rabbits (Sylvilagus floridanus). Muscle architectural properties including muscle moment arm, mass, belly length, fascicle length, pennation angle, and physiological cross-sectional area (PSCA) were measured and used to provide functional estimates of maximum isometric force, joint torque, and power. MHC isoform distribution will be determined by SDS-PAGE and densitometry techniques. Preliminary results from dissection and measurement indicate the m. longissimus dorsi and m. sacrospinalis of juveniles are massive, and together they are capable of higher force and power than any of their hindlimb extensor muscles. The results will be used to test the hypothesis that the hindlimb and vertebral column extensor muscles of juveniles are capable of performing similar amounts of mechanical work and power to those of adult rabbits. Supported by NSF IOS-1146916.
