Meeting Abstract
67.2 Monday, Jan. 6 08:15 Ontogeny of locomotor performance in Eastern cottontail rabbits: I. Hindlimb muscle architecture and fiber type. ROSE, JA*; RUSSO, GA; YOUNG, JW; SMITH, GA; BUTCHER, MT; Youngstown State University, Youngstown; NEOMED, Rootstown; NEOMED, Rootstown; University of Akron, Akron; Youngstown State University, Youngstown jarose@student.ysu.edu
Rabbits have powerful hindlimb muscles that allow them to accelerate rapidly during locomotion. Moreover, juveniles may have performance advantages relative to adults that could increase their survival to reproductive maturity. To investigate the ontogeny of power capacity in rabbit hindlimb extensors, muscle architectural properties and myosin heavy chain (MHC) isoform fiber type were quantified in six juvenile and four adult cottontail rabbits (Sylvilagus floridanus). It is hypothesized that musculoskeletal features of the hindlimb will be optimized in juveniles to promote increased locomotor performance. We measured architectural properties including muscle moment arm, mass, belly length, fascicle length, pennation angle, and physiological cross-sectional area (PSCA), known to provide functional estimates of maximum isometric force, joint torque, and power. MHC isoform distribution was determined by SDS-PAGE and immunohistochemistry techniques. Overall, the large proximal muscles of juvenile and adult rabbits have high fascicle length-to-muscle length ratios, suggesting similar muscle shortening abilities for high power generation. However, for each muscle studied, juveniles have larger PCSA-to-muscle mass ratios than the adults, suggesting higher force production capabilities, and this difference is most notable in the ankle extensors and digital flexors. Juvenile rabbits also have a relatively faster MHC isoform composition than the adults. These results support our hypothesis by indicating that the hindlimb muscles of juveniles are capable of performing greater amounts of mechanical work and power than those of adult rabbits. Supported by NSF IOS-1146916.
