UC San Diego

It's estimated that up to 37% of women are affected by a pelvic floor (PF) disorder and that at least 11% of women will require a surgical PF repair in their lifetime (Lukacz et al., 2006). Despite the prevalence of PF dysfunction in women, there's limited knowledge on PF skeletal muscle architecture. To understand muscle design and functional performance, we need to have an accurate knowledge of its architecture which refers to the muscle's macroscopic arrangement of fibers (Gans, 1982; Sacks and Roy, 1982). Architectural parameters include sarcomere length (SL), fiber length (FL), and physiological cross- sectional area (PCSA). By studying architecture, we can gain insight on the muscles' functional properties. The purpose of this project was to quantify female PF muscle architecture and better understand their function within the human body. Muscle architecture was characterized according to the method previously described by Lieber et al., 1990. Pelvic floors were harvested from 5 formaldehyde-fixed human female cadavers without known PF dysfunction. PF muscles (coccygeus, iliococcygeus, and combined pubococcygeus and puborectalis).were bilaterally dissected (n=10) and used to determine architectural properties. SL was relatively short for all three muscles. FL was shortest in the coccygeus, intermediate in the iliococcygeus, and longest in the pubococcygeus/rectalis. PCSA was highest in the coccygeus, moderate in the iliococcygeus, and lowest in the pubococcygeus/rectalis. The coccygeus had the lowest FL coefficient of variation. Architectural data suggests that the coccygeus is designed for force production ([alpha] PCSA) while the pubococcygeus/rectalis is designed for excursion ([alpha] FL)