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Avian downstroke during flight is primarily powered using a single muscle, the pectoralis. The large power requirement for flight has spurred the adaptation of birds such that their pectoralis muscles make up 15-25% body weight and their chest bone, the keel, has been enlarged in order to form a broad attachment site for this now massive muscle. Dial even found that when the nerves to the wing of a pigeon were severed, preventing active muscle control, the birds were still able to fly (1). Due to this, the pectoralis has been a major muscle of interest for avian flight research and its work production during the wingbeat cycle has been characterized in vivo (2,3,4). While the strain and activation data is fairly reliable from these studies, acquisition of the in vivo force production has yet to be confidently estimated. The small size of most birds prevents direct measurement of the muscle force and instead a strain gauge is typically adhered to the bone adjacent to the pectoralis tendon insertion and a manual pull calibration is performed post mortem. This method has consistently underestimated the force required to power flight. Simulation of the avian downstroke could potentially capture the force production of the pectoralis and help to estimate a more accurate work loop.
Research Questions
1. Can in vivo pectoralis muscle emg data produce reasonable wing kinematics during a forward dynamics simulation of downstroke when the distal wing joints are passively actuated?
2. How do the pectoralis muscle activation, force, and fiber length change compare to published work loop studies when experimentally collected kinematic and aerodynamic force data are used to drive a CMC simulation of downstroke?
Progress
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References
1. Dial KP. Avian Forelimb Muscles and Nonsteady Flight - Can Birds Fly Without Using the Muscles in Their Wings. Auk. 1992;109(4):874–85.
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