Abstract
Cross-sectional areas (CSA) of skeletal muscles observed in the CT image at the E12 level of Erdheim's grid (the level on the upper margin of pubic symphysis) were measured as part of a series of studies to elucidate the development of skeletal muscle in situ. The subjects included 99 healthy adults (50 males, 49 females), grouped into five age groups and three body types. The shape of each muscle on the CT image was traced, and the CSAs were measured. The results were analyzed against sex, age and body type, and functional differences were considered. Results : 1) The CSA of m. gluteus maximus, which was largest, occupied about 47.8 % of the whole CSA (7349.2 mm2) of the skeletal muscles. The CSAs of iliopsoas, obturatorius internus, gemellus and gluteus medius followed gluteus maximus and occupied about 9.0 %. Those of pectineus and tensor fasciae latae occupied approximately 4.0 %, and rectus femoris and sartorius occupied approxi-mately 3.0 %. The CSA of pyramidalis was smallest, about 1.2 %. 2) In general, the CSAs of male skeletal muscle were larger than those of females and this tendency was remarkable for muscles of the gluteal region. The gluteus maximus and obturatorius internus were relatively superior in females compared to males. 3) The whole CSA of the skeletal muscles decreased from ages in the forties in males and fifties in females and was smallest in the seventies in both sexes. CSAs of the muscles of the iliac and the gluteal region, and extensor in femoris decreased with age in males, and this tendency was remarkable in obturatorius internus. In females, CSAs of obturatorius internus and gluteus maximus decreased with age. 4) Remarkable differences among body types were observed in the muscles of the gluteal region. In body type D, gluteus medius in males and gluteus maximus in females and obturatorius internus in body type C in males were larger than other muscles.
