Morpho-functional relationship between muscular architecture and proportion of myofiber types in ovine antebrachial musculature

Abstract

The antebrachium of domestic animals supports the trunk against gravity and generates propulsive force. The antigravity action of antebrachium is attributed to the contraction of flexor muscles of the carpal and digital joints. Mammalian skeletal muscles consist of myofibers, which are histochemically classified into type I, type IIA, and type IIB myofibers, of which composition reflects the proportional involvement of the muscle in varying function, such as posture maintenance and locomotion. The physiological cross-sectional area (PCSA), which are calculated from muscle volume, myofiber length, and pennation angle, reflects the maximum force of muscle. In the present study, we evaluated the PCSA of myofiber types in the antebrachial musculature and determined the magnitude of contribution from individual muscles toward varying actions of carpal and digital joints. The extensor carpi ulnaris and flexor digitorum superficialis muscles possessed a large proportional PCSA of type I myofibers, indicating the role for these muscles in maintaining a standing posture. The additional force required for walking/running was primarily provided by the flexor digitorum profundus caput humerale and extensor carpi radialis muscles. The proportional PCSA of myofiber types reflected the force generated for varying muscular function and provided insights into the dynamics of carpal and digital joints.