Title

MUSCLE MORPHOLOGY AND LOCATION AS AN INDICATOR OF FUNCTION IN THE PIGEON

Presenter Information

Vik Weston

Presentation Type

Presentation

Abstract

We undertook this study to test a current hypothesis that, during locomotion, proximal, parallel-fibered muscles maximize work whereas distal, pennate muscles maximize isometric force. Using pigeons (N = 2) in different modes of flight (ascending, level, descending), we test two muscles for comparison against the pectoralis (PECT). The PECT is a large, proximally-located parallel-fibered muscle, known from previous work to be the primary source of work and power during downstroke. The scapulohumeralis caudalis (SHC) is a parallel-fibered muscle, proximal muscle that retracts and elevates the humerus. The extensor metacarpi radialis (EMR) is a small, pennate, distal forelimb muscle of the pigeon forelimb that functions in extending the wrist. We measured timing of motor-unit recruitment using electromyography and instantaneous length using sonomicrometry. Our results support the hypothesis that location and morphology of a muscle is indicative of its function. The proximal, parallel-fibered SHC underwent strains (relative length change) of 26% -30%, similar to those of the PECT (30% -38%). The distal, pinnate EMR underwent considerably less strain (11% -16%) in all modes of flight. Strain in the EMR was larger than what has been considered isometric in studies of terrestrial locomotion, which may indicate that the function of muscle is constrained in part by the substrate (air versus ground). Supported by NSF IOS-0923606 and IOS-0919799.

Category

Life Sciences

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MUSCLE MORPHOLOGY AND LOCATION AS AN INDICATOR OF FUNCTION IN THE PIGEON

UC 331

We undertook this study to test a current hypothesis that, during locomotion, proximal, parallel-fibered muscles maximize work whereas distal, pennate muscles maximize isometric force. Using pigeons (N = 2) in different modes of flight (ascending, level, descending), we test two muscles for comparison against the pectoralis (PECT). The PECT is a large, proximally-located parallel-fibered muscle, known from previous work to be the primary source of work and power during downstroke. The scapulohumeralis caudalis (SHC) is a parallel-fibered muscle, proximal muscle that retracts and elevates the humerus. The extensor metacarpi radialis (EMR) is a small, pennate, distal forelimb muscle of the pigeon forelimb that functions in extending the wrist. We measured timing of motor-unit recruitment using electromyography and instantaneous length using sonomicrometry. Our results support the hypothesis that location and morphology of a muscle is indicative of its function. The proximal, parallel-fibered SHC underwent strains (relative length change) of 26% -30%, similar to those of the PECT (30% -38%). The distal, pinnate EMR underwent considerably less strain (11% -16%) in all modes of flight. Strain in the EMR was larger than what has been considered isometric in studies of terrestrial locomotion, which may indicate that the function of muscle is constrained in part by the substrate (air versus ground). Supported by NSF IOS-0923606 and IOS-0919799.