Improving the physical conditions and following some simple rules can help preventing back ache: it is important to do aerobic physical activity periodically (i.e. swimming or walking).
In fact, training helps to strengthen the back and its resistance. Moreover it is important to hold in check the body weight, losing weight if necessary and doing reinforcement and stretching exercises focused on the abdomen, buttocks and back muscles.
Here are some suggestions that can turn useful in daily life.