Different changes of quantity due to aging in the psoas major and quadriceps femoris muscles in women.

Bone fractures cause disabilities that leave the elderly bedridden and strengthening the muscles of the lower limbs, especially the quadriceps femoris, is the main kinematical method of preventing falls. Recently, however, it has become clear that the psoas major is critical for walking ability. We examined changes due to aging in the size of the psoas major compared with changes in the quadriceps femoris. Bone fractures are more frequent in women than in men; our participants (n=210) were therefore exclusively women ranging in age from 20 to 79 and divided into 6 age groups (n=35 each) in 10-year increments. Cross-sectional areas of the two muscles were measured by an MR scanner for a comparative estimation of muscle size. The psoas major showed the greatest quantity in subjects in their 20s, after which it declined steadily until the 60s and dramatically in the 70s, while the area of the quadriceps femoris was preserved until the 40s and showed no dramatic later decline. Exercise beyond regular daily activities is recommended to prevent the psoas major from decreasing in volume. We also recommend the development of a method of maintaining its muscle volume which would target women younger than 40 and older than 60.