Meeting Abstract
Although muscle architecture and musculoskeletal scaling patterns have been examined, there has been little study of ontogenetic scaling patterns of muscle architecture. How muscles with different anatomical features and muscles that produce different types of movement within the limb change in architecture during growth and what these patterns suggest for changes in limb function have received little attention. Because muscles have different mechanical roles within the limb that may be dependent on location and anatomy, we hypothesize that muscles may grow at different rates and exhibit varying architectural scaling patterns determined by their function and evolutionary constraints. To test this hypothesis, we examine the ontogenetic scaling patterns of proximal and distal muscles of the guineafowl (N. meleagris) hindlimb: iliotibialis lateralis pars postacetabularis (ILPO), iliofibularis (IF), iliotibialis cranialis (IC), lateral and medial gastrocnemius (LG & MG), superficial digital flexor IV (SDF-IV), tibialis cranialis (TC) and fibularis longus (FL). Muscle mass, fiber length, pennation angle, and tendon length were measured. Preliminary results demonstrate that the physiological cross-sectional area of several of the muscles studied demonstrate positive allometry as a function of body mass (exponent ranges vs Mb0.67), with the exception of the FL (0.23 Mb0.67), the IF (0.11Mb0.56) and IC (-0.08 Mb0.54). In addition the CSA of the FL and IF tendon are isometric, the LG tendon is negatively allometric (-0.87 Mb0.46) and MG and SDF-IV are positively allometric (-1.8Mb0.75 & -2.6Mb0.90) relative to body mass. Tendon scaling patterns relative to muscle scaling patterns suggest increased strain and energy storage in the LG and IC tendons and decreased strain and energy storage in MG and SDF-IV tendons with growth and age.
