An inactive lifestyle or poor physical condition. Weak muscles leave one susceptible to strains and sprains of the muscles, tendons, and ligaments. Heavy labor frequently contributes to back injury as it can put undue stress on the muscles, ligaments and discs. Obesity increases the load on the lower back, especially when a person is more that 50 pounds over their ideal body weight. Improper diet can contribute to weakness of the spine.
Psychological stress can increase tightness and inflexibility of the back.
Improper ergonomics such as chairs, tables, mattresses etc. Carbon monoxide from cigarette smoke decreases the ability of blood to supply oxygen which weakens the back. It is also believed that nicotine breaks down collagen, the protein that holds connective tissue together. Back pain is the leading cause of missed work, with more lost work days than the common cold. Back pain is most common in people between the ages of 30 and 50.