Women are very vulnerable to back pain. Childbearing and child rearing put a heavy load on women's backs. During the last two trimesters of pregnancy, the fetus can shift the center of gravity of women's back. This alters the curve of their spine, resulting in back pain. Soon after pregnancy and when children are toddlers, women experience back pain from bending and lifting.
Women have two-thirds the muscle mass as compared to men of same size.
This means that women need more muscle power to do the same work. We generally do not think about the implication of what we routinely do. Most of us are careful when we lift weights or heavy objects. But we won't think of much when we pick up a toddler and a 10-pound bag of groceries while still carrying a briefcase crammed with books and papers. This puts severe strain on the back-muscles.