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Modeling musculoskeletal systems as mechanical linkages

The owl cranial bones modeled as a 3D linkage (modified from Olsen and Westneat 2016)
Mechanical linkages, interconnected chains of rigid links, provide a useful model for the motion and force transmission of musculoskeletal systems, particularly for those systems in which the skeletal elements interconnect to form closed chains (or loops). Mechanical linkages have been used as models for a diversity of musculoskeletal systems, including the skulls of fishes (Westneat 1990) , some lizards (Metzger 2002), and birds (Van Gennip and Berkhoudt 1992), the rib cages of birds (Claessens 2009), and the striking appendages of mantis shrimps (Patek et al. 2007). However, previous applications of linkage modeling have predominately focused on 2D models and linkages in which all the links interconnect as a single chain, excluding a number of diverse musculoskeletal characterized by 3D motions and elements that interconnect to form multiple, nested chains (referred to in engineering as multiloop or parallel linkages).

The salmon cranial bones modeled as a 3D linkage (modified from Olsen and Westneat 2016)
Working with Mark Westneat (University of Chicago), I have developed new 3D, parallel linkage models for cranial kinesis in the skulls of birds and fishes (Olsen and Westneat 2016). To perform linkage model simulations I have developed a new software package for the R language, linkR. Together with StereoMorph and svgViewR, this provides an entirely free and open-source workflow for 3D shape data collection, general kinematic simulation of 2D and 3D linkages, and 3D animated visualizations. I am currently working with Beth Brainerd (Brown University) and Ariel Camp (Brown University) to test 2D and 3D 4-bar linkage models against the in vivo kinematics of the lower jaw-opercular mechanism in largemouth bass. And as a part of my postdoctoral research I will be testing 3D, parallel linkage models against in vivo cranial kinematics in several species of primarily suction-feeding fishes. I will then apply these models to a diverse sampling of shape data from natural history collections to examine how cranial mobility and suction performance differ across different orders of fishes.

Publications resulting from this project

  • Olsen AM*, Camp AL* & Brainerd EL (2017). The opercular mouth-opening mechanism of largemouth bass functions as a 3D four-bar linkage with three degrees of freedom. Journal of Experimental Biology. 220:4612-4623. DOI: 10.1242/jeb.159079. Get via JEB, via ResearchGate.*Equal author contributions

  • Olsen AM, Westneat MW (2016). Linkage mechanisms in the vertebrate skull: Structure and function of three-dimensional, parallel transmission systems. Journal of Morphology. Early View. DOI: 10.1002/jmor.20596. Get via Wiley; Get via ResearchGate.

  • Olsen AM, Westneat MW (2015). StereoMorph: an R package for the collection of 3D landmarks and curves using a stereo camera setup. Methods in Ecology and Evolution. 6:351-356. DOI: 10.1111/2041-210X.12326. Get via Wiley (open access).

Software related to this project