• Monroe Santos posted an update 1 week, 5 days ago

    Bates Schachner (2012: p.1342) inferred that, mainly because their model’s outputs matched experimental data, “predicted abduction/adduction and long-axis rotation moments are good estimates.” We come across some important differences amongst our outcomes and these of either or both studies that somewhat weaken this inference (Figs. 125). Having said that, we reiterate and celebrate that all 3 research discussed right here receive broadly related outcomes for many muscles, in specific emphasizing that moment arms aren’t continuous for most muscle tissues. Furthermore, Smith et al. (2007) and Bates Schachner (2012) noted limitations similar to those pointed out above. Some comparative data exist from studies of other ratites or a lot more restricted datasets for ostriches. Hutchinson (2004) offered estimates weighted by physiological cross-sectional area (Aphys ) of “antigravity” (extensor) muscle moment arms to get a 2D model of an ostrich, making use of the same specimen and therefore congruent with our benefits. Alexander et al. (1979) made a very simple 2D geometric model of an Iagnosis– unit at Ashworth to save its life (my words namely ostrich whose limb dimensions have been similarHutchinson et al. (2015), PeerJ, DOI ten.7717/peerj.33/to ours (cf. their Table I and our Table 1), acquiring comparable muscle moment arm measurements: femorotibialis five.1 cm concerning the knee (ours five cm), gastrocnemius three.eight cm in regards to the ankle (ours four cm), and digital flexors three.2 cm regarding the MTP joint (ours 2 cm). This ostrich was 64 of the physique mass of ours but had muscle masses about 85 of ours, assisting to explain its 30 higher Aphys and Fmax values (also, surely, to shorter muscle fascicles; Eqs. (1) and (2)), that are variations probably attributable to its wild-caught status as opposed to our specimen’s farm provenance. Goetz et al. (2008) developed a musculoskeletal model of an emu using a procedure grossly comparable to ours, and obtained related results–e.g., ILFB muscle possessing the biggest hip extensor moment arm (but see Appendix ). Troy, Brown Conzemius (2009) assumed that only the IFE, ITM, ITCR and PIFML muscle tissues (homologous to ours) would resist hip adduction in their simplified emu model, but our evaluation reveals that a number of additional hip abductors exist, namely the IL, ILFB, FCM/L and CFP muscle groups (Table four; Figs. 14 and 15). See Lamas, Most important Hutchinson (2014) for much more consideration of emu pelvic limb muscle functions. There are anatomical and methodological causes to recommend that musculoskeletal modelling approaches (this study and Bates Schachner (2012)) can at times be much more dependable than tendon-travel-based empirical data (e.g., Smith et al., 2007; also possibly Carr et al., 2011). 1st, the typical experimental approach, as applied to date with birds, removes surrounding muscles and replaces entire 3D muscle bellies with quasi-2D strings (normally lacking essential “via points” or wrapping surfaces) that need to alter the lines of action and therefore moment arms of the in situ muscles. The possible for such alteration is experimentally testable, but current studies of moment arms in various species (particularly humans) already give strong precedent for this inference: analogous comparisons of “straight-line” 2D measurements (e.g., Jensen Davy, 1975) vs. 3D medical imaging or in situ measurements (e.g., Young, Scott Loeb, 1993; Arnold Delp,.