Passive mechanics of canine internal abdominal muscles

Abstract

The internal abdominal muscles are biaxially loaded in vivo, and therefore length-tension relations along and transverse to the directions of the muscle fibers are important in understanding their mechanical properties. We hypothesized that 1) internal oblique and transversus abdominis form an internal abdominal composite muscle with altered compliance than that of either muscle individually, and 2) anisotropy, different compliances in orthogonal directions, of internal abdominal composite muscle is less pronounced than that of its individual muscles. To test these hypotheses, in vitro mechanical testing was performed on 5 x 5 cm squares of transversus abdominis, internal oblique, and the two muscles together as a composite. These tissues were harvested from the left lateral side of abdominal muscles of eleven mongrel dogs (15-23 kg) and placed in a bath of oxygenated Krebs solution. Each tissue strip was attached to a biaxial mechanical testing device. Each muscle was passively lengthened and shortened along muscle fibers, transverse to fibers, or simultaneously along and transverse to muscle fibers. Both transversus abdominis and internal oblique muscles demonstrated less extensibility in the direction transverse to muscle fibers than along fibers. Biaxial loading caused a stiffening effect that was greater in the direction along the fibers than transverse to the fibers. Furthermore, the abdominal muscle composite was less compliant than either muscle alone in the direction of the muscle fibers. Taken together, our data suggested that the internal abdominal composite tissue has complex mechanical properties that are dependent on the mechanical properties of internal oblique and transversus abdominis muscles.

Passive nonlinear elastic behaviour of skeletal muscle: Experimental results and model formulation

“…The in vitro stress-strain relationships obtained in this study showed similar nonlinear patterns to those previously published for soft tissues in general, also undergoing large deformations (Quapp and Weiss, 1998;Davis et al, 2003;Hwang et al, 2005;Lopez et al, 2008;Calvo et al, 2009). The results of the in vitro experiments showed that the strain level at which the muscle stress began to increase rapidly for increased strain levels was around 20%, while for the tendon it was around 5%, coinciding with Hawkins and Bey (1997).…”

“…Very few studies have tested muscle samples from different animals; for instance, canine (Hwang et al, 2005) and porcine muscle (Van Loocke et al, 2006) specimens were tested passively while Lopez et al (2008) tested mice specimens both passively and actively. To the authors' knowledge, there is no study including all the steps described above carried out upon the same specimen.…”

Mechanical response of human abdominal walls ex vivo: Effect of an incisional hernia and a mesh repair

“…Indeed, many studies only focused on the response of some components of the abdominal wall using an ex vivo sample testing approach. For example, Hwang et al (2005) and Hernández et al (2011) studied the behaviour of the abdominal muscles on animals. Some authors conducted tensile tests on the human linea alba and rectus sheath (Rath et al 1997;Hollinsky and Sandberg, 2007;Förstemann et al, 2011;Martins et al, 2012;Ben Abdelounis et al, 2013).…”

Contribution of the skin, rectus abdominis and their sheaths to the structural response of the abdominal wall ex vivo

“…Studies on the abdominal muscles seem less frequent and did not include human samples. Nilsson (1982) and Hernández et al (2011) characterized rabbit abdominal muscles while Hwang et al (2005) tested dog lateral abdominal muscles (obliquus externus abdominis, obliquus internus abdominis and transversus abdominis). The results reported in the literature were found to be different from one component to another and show high variations and standard deviations.…”