Effect of two loading rates on the elasticity of the human anterior rectus sheath.

Tensile properties of connective tissues of the abdominal wall are necessary to better analyze the mechanical response of the human abdominal wall. Some tensile properties of these tissues have been reported in the past but data are still missing regarding the dependence of the elasticity on the loading rate, especially for the rectus sheath. Thus the aim of this study was to assess for the variation of human anterior rectus sheath elasticity using two loading rates. Seventeen samples of the rectus sheath were taken from three human post-mortem subjects and tested under tension at two different loading rates (0.01s(-1) and 50s(-1)). The mean value (standard deviation) of the quasi-static elasticity is 5.6 (3.2)MPa for the rectus sheath. The values at the high loading rate are 14 (8.3)MPa. The failure strength and the elasticity (at 50s(-1)) are significantly correlated (r²=0.79, p<0.01). Such a relationship opens the way to the estimation of the failure strength by a unique measurement of the elasticity. The loading rate influence was statistically significant with a linear elasticity 2.5 times greater at 50s(-1) than 0.01s(-1). Thus the loading rate influence on the mechanical properties would have to be taken into account in models considering transitory loading such as coughing and sneezing.