The source of back pain can often be difficult to determine. However, it is assumed that a high percentage of back pain is due to sprains or strains. Factors that may cause sprains and strains include:

• Injury. Various injuries can sprain, strain or cause spasms in muscles or ligaments of the abdomen and back. Sources of such trauma pain include sports mishaps, extremes in activity, or sudden movements or accidents. Repeated injuries can result in the formation of scar tissue that is not as strong or flexible as the tissue it replaced. This can leave the back vulnerable to additional injuries in the future.
  
  
• Poor posture. Failure to sit or stand properly shifts the body out of balance, forcing just a few muscles and joints to support the entire body. This increases the vulnerability of these muscles to the types of stresses that cause back pain.
  
  
• Poor body mechanics. Bending the back rather than the knees when lifting objects is a common source of back sprains and strains. For more information, see Posture & Ergonomics.
  
  
• Emotional stress. People who are under stress experience a tightening of the back muscles that can worsen back problems.
  
  
• Excessive weight, obesity and pregnancy. Too much weight, especially around the abdomen, places strain on the back and stomach muscles, causing them to weaken and stretch.
  
  
• Poor muscle tone in the back and abdomen. Weakened muscles cannot properly support the back, leaving the back vulnerable to stresses and injuries.
  
  
• Age. As people age, bone strength and muscle elasticity and tone tend to decrease. As a result, back injuries are more likely after age 30.
  
  
• Use of heavy bags. Back pain is typically uncommon in children. However, backpacks overloaded with schoolbooks and supplies can strain the back and cause muscle fatigue, resulting in injuries to the back. Oversize purses, heavy briefcases or luggage can strain adults’ backs.
  
  
• Diseases of muscles. Conditions such as fibromyalgia can cause muscle spasms in the back.