A novel method of studying fascicle architecture in relaxed and contracted muscles

Computational methods for quantifying in vivo muscle fascicle curvature from ultrasound images

“…8) this pattern would suggest that the curvature varies along each fascicle and indeed that the fascicles take on an S-shape profile. Stark and Schilling (2010) predicted that curvature coefficients may change along the fascicle and amongst the fascicles, which is consistent with these initial results. S-shaped fascicles have been previously predicted or modelled (van Leeuwen and Spoor, 1992;van Leeuwen and Spoor, 1993;Otten, 1988) but have never before been experimentally quantified.…”

“…The methods in this study differ from previous studies in that they calculate local curvatures across the whole region of imaged muscle, rather than a more general curvature value for a more limited selection of discrete fascicles (Kawakami et al, 1998;Muramatsu et al, 2002;Stark and Schilling, 2010;Wang et al, 2009). We found greatest curvatures near the superficial aponeurosis and these contribute to high RMS curvatures.…”

“…These fascicle coordinates were then parameterized to create a parametric pixel coordinate function, r(p), pertaining to the fascicle curve. The curvature k for the pixel in the middle of these three neighbourhoods was calculated using Frenet-Serret formulas (Stark and Schilling, 2010):…”

“…To date, only a few studies have predicted (van Leeuwen and Spoor, 1992;Sejersted et al, 1984) or quantified curvatures of the muscle fascicles (Kawakami et al, 1998;Muramatsu et al, 2002;Stark and Schilling, 2010;Wang et al, 2009). Previous ultrasoundbased studies have used manual digitisation to quantify the path of select fascicles in ultrasound images of muscle.…”

Force reduction induced by unidirectional transversal muscle loading is independent of local pressure

“…Therefore, it seems important to examine the intermuscular pressure in muscle groups and threedimensional muscle deformations during contraction (Böl et al, 2015Röhrle et al, 2012;Rupp et al, 2015) in more detail. With such studies, questions related to evolution of sometimescomplex muscle architecture (e.g., distributions of varying fiber lengths and pennation angles or inner tendon sheets (Gorb and Fischer, 2000;Hiepe et al, 2014;Schenk et al, 2013;Siebert et al, 2015;Stark and Schilling, 2010)) could be addressed. However, it is also possible that transversal pressure is not a bad thing per se.…”