Low Back Pain and Disorders

Low back pain (LBP) is among the most common health complaints in working-aged populations worldwide.  In the U.S., 70%-80% of adults will experience a significant episode of LBP at least once in their lives.  Episodes of LBP are characterized by varying levels of pain and symptoms in the low back (lumbar spine).  Low back disorders can even cause leg pain or numbness at times.

Work-Related Risk Factors

• Work-related lifting and forceful movements
• Whole body vibration
• Awkward postures (bending and twisting)
• Heavy physical work
• Poor job satisfaction, perception of intensified workload, lack of job control, and certain personality traits

Development and Progression

The low back may be injured due to either a sudden stressful event or the cumulative effect of stressful activities.  Strains of the muscle or sprains of the ligaments surrounding the spinal joints occur most commonly.  Injuries to the low back may also involve the intervertebral disc.

The intervertebral disc is composed of a ring of fibers surrounding a sac of fluid or gel-like material.  Discs may be damaged due to a sudden stress (e.g. a fall, slip, or catching an unexpected load), or due to cumulative problems when stressful activities stretch, tear, or unravel the protective fibers surrounding the sac of fluid.  When the fibers can no longer contain the fluid, small leaks or bulges can occur or the disc may flatten.  The most commonly injured low back discs are between the 4th and 5th lumbar vertebrae (L4-L5), and between the 5th lumbar vertebrae and the sacrum (L5-S1).  Disc problems may lead to a pinched nerve.

The causes of many episodes of LBP are unclear.  Even with clinical tests and imaging procedures, about 85% of patients cannot be given a precise diagnosis.  The pain in these cases is presumed to be related to muscle, ligament, or tendon injury or degenerative changes.

Common Symptoms

Individuals with low back problems typically experience pain in the low back (lumbar spine).  Leg pain or numbness may accompany low back pain.  Often, leg pain is localized to the side or back of the thigh, but sometimes the pain may go all the way to the foot.  This leg pain is called "sciatica."  Individuals may also have tenderness in the low back and a limited range of motion for bending forward, backward, sideways, or twisting.  Bending forward tends to increase pain levels.

Common Treatment

Initial treatment for most episodes of low back pain includes avoidance of stressful activities and occasionally one to two days of bed rest.  Nonsteroidal anti-inflammatory drugs (NSAIDs, e.g. ibuprofen or naproxen) are often helpful, and stronger drugs may be prescribed (muscle relaxants or narcotics) for more severe, acute pain.  Other treatment options may include application of heat and cold, physical therapy, spinal manipulation, or injections.  Some LBP cases may require surgery (ruptured disc or severe trauma cases).

Most workers with occupational LBP get better.  Half of workers improve in one week and 90% improve in 30 days, regardless of treatment.  Light duty work activities may be prescribed by the physician during the recovery period.  The remaining 10% of workers may have a chronic condition and may not be able to return to their previous jobs.  Many workers may suffer from residual pain that may affect work or activities of daily living.

Lifting or carrying heavy loads, frequent bending or twisting, and heavy physical work may cause low back disorders.  Lifting or carrying heavy loads has been linked to low back disorders in numerous publications.  Epidemiological research has identified that the risk of injury increases when lifting loads from low heights, holding the load away from the body, or lifting while the torso is twisted or flexed.  Biomechanical research supports these findings by demonstrating that loading of the spine increases in all of those conditions.  Intervention studies have determined that lift tables, lifting hoists, lightening loads, and other engineering interventions can lower the risk of developing back injuries among workers.

Lifting or carrying heavy loads, frequent bending or twisting, and heavy physical work are common in construction work.  In 2002, over 29% of lost work days in the construction industry were due to back injuries.  Epidemiologic studies also show that back injury prevalence among construction workers is high, with over 50% of workers reporting low back pain in a year.  In 1996, the University of Iowa surveyed 2,929 workers representing 13 different construction trades and found that 70% of workers experienced low back pain in the previous 12 months.

There has not been specific research on the relationship between manual material handling and the development of back disorders among construction workers.  However, the strong evidence cited above regarding lifting as a risk factor, and high rates of back disorders in the construction industry, show that the risk of back injury among carpenters from manual material handling is considerable.