Women have only two-thirds the muscle mass of men who are otherwise the same size, so women are more susceptible to muscle pulls. Most people suffer from lower-back pain, which is generally caused by straining muscles and tissues that connect bones and cartilage. A sudden action in which you use muscles that are tired or out of condition is particularly likely to cause pain. Childbearing and child rearing also put a heavy load on women's backs. During the last two trimesters of pregnancy, the fetus literally can shift the centre of gravity of your back, increasing the curve of your spine, so that your back may really hurt.
Poor posture increases back strain that can aggravate arthritis and lead to disk problems.
Get an exercise plan. Support your back. Use a footrest. Do an early morning stretch. Walking and other aerobic exercises such as swimming, biking and running keep your back healthy by conditioning your whole body.