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Low back pain

Danny O'Dell explains the physiology and anatomy of the spine and some of the reasons for low back pain.

The primary purpose of the spine is to support the upright position and allow the body to move about during everyday activities, including sports performances. The bony structure of the spinal column protects the spinal cord and its branching out nervous system. The individual vertebrae synergistically act as built-in shock absorbers for the trunk. The vertebrae give structural support to the spine.

Spine structure

The four curves of the spine allow for flexibility and shock absorption. Included in the anatomy of the spine are the facet joints where each vertebra meets. These control direction and the amount of spinal movement. The ligaments that connect the vertebrae and the non-vertebral discs are the final pieces of the spinal picture.

The non-vertebral discs can rupture, causing in some cases, instant pain. They are sometimes considered the shock absorbers of the spine and allow for a great deal of flexibility inherent in the spine. Recent research by Stuart McGill and associates has disputed the shock-absorbing characteristics of the spinal column.

The spinal column is broken into five major areas:

  • The cervical, beginning at the base of the skull, consists of seven vertebrae
  • The Thoracic (mid-back) portion incorporates twelve vertebrae
  • The Lumbar region begins at the end of the thoracic and ends with the lowest vertebrae attaching to the sacrum/pelvis. This is the area where most injuries occur. The L-5, S-1 segment is the most likely to be damaged of all the vertebrae in the back structure because it is the recipient of the greatest load-bearing in comparison to the rest of the spinal column
  • Sacral-pelvis is the triangular bone that is inside the pelvis
  • The Coccyx, known as the tailbone, is the final part of the spine.

The lumbar region is the source of most of the lower back problems worldwide. 8 out of 10 adults will experience lower back pain at some point in their lives. According to the National Strength and Conditioning Association, about 5 million Americans suffer from acute or chronic back pain. This condition accounts for over 90 million lost production days a year in the United States alone.

The vertebrae of the lumbar region are larger than those of the cervical and thoracic areas. These vertebrae are responsible for supporting the body's weight. Extremely powerful lumbar muscles attach to this part of the spine.

The facet joints connect the vertebrae above and below one another, and their shape restricts the rotational movement of the lumbar spine. Flexion to the side and extension and flexion of the lower back are all controlled by the lumbar facet joints. Amazingly, enough they are non-weight bearing and act passively unless the spine is extended or arched backward. The shape of these vertebrae produces a slight curve of the lower back, and this curve is different for each individual.

It should not be a surprise to learn that different postures alter the pressure on the intervertebral discs. Review the following chart and notice the tremendous differences in the load supported by the back in the various body positions. Especially note the last entry 269% of body weight by not using good body position to lift an object of only 44 pounds.

Chart of pressures on the discs, expressed as a percentage of body weight, for various activities (NSCA, n.d.)[1]

Position/activity Disc pressure expressed as a % of body weight
Supine with both knees flexed 5%
Supine lying face up 25%
Side-lying 75%
Seated in a flexed position 85%
Standing 100%
Coughing or sneezing 105 to 135%
Walking 115%
Rotation 120%
Side Bending 125%
Small Jumps 140%
Laughing 140 to 150%
Standing and bending forward 150%
Lifting 44 pounds with the back straight and the knees bent (good body mechanics) 173%
Lifting 44 pounds with the back bent and the knees straight (poor body mechanics) 269%

Looking at the chart should be an important reminder to always use proper body mechanics whenever lifting objects. The 5th lumbar-1st sacral vertebral area (L5-S1) is the site that causes most of the problems because this joint area carries more weight than any other vertebral joint in the spinal complex! Most people, when they 'hurt' their back, hold onto this area when they stand up again, that is if they can even stand up after being injured. In retrospect, it is easy to see why there are so many lower back injuries each year. It does not take a great deal of weight to cause grief, just poor positioning during a lift.

A few of the causes of low back pain are:

  • Poor overall posture
  • Slumped over, flexion of the lower back
  • Poor back posture
  • Stress and daily work habits
  • Riding in a vehicle for hours on end without a break, especially in a vibrating vehicle is very hard on the lower back
  • Lack of flexibility
  • Lack of flexibility in the hip joint causes the back to compensate by flexing/bending forward
  • Deterioration of general physical fitness
  • Overweight
  • Lack of endurance in the extensor muscles of the lower back
  • If fit then incorrect lifting techniques are being utilized
  • Rounded back when lifting
  • Bending forward during a lift
  • Failure to flex at the hip and substituting the lower back to make up for the lack of flexibility in the hip joint

Types of pain

Low back pain comes in two variations, neither of which is good. The more intense of the two will be the acute episodes. These come on suddenly and are very intense in the pain aspect. They will occur from doing something unusual, something that is not part of your regular activity, or if it is normal, then you are doing it the wrong way and become injured. Pain that arises lasts but a short time and then disappears.

Acute strains (muscle injury) and sprains (injury to the ligaments) are often caused by lifting improperly, twisting while lifting, or even just twisting and falling accidents. These injuries cause tearing, bleeding, and irritation of the lower back muscles or the ligaments of the vertebral tissues in the lumbar region. A specific incident can be identified as the culprit causing the pain.

The second type of back pain is more insidious as it may result from any movement for unknown reasons or by overdoing a normal activity. It also periodically reoccurs throughout a lifetime with no apparent reason. McGill and associates believe the tissues have reached the end of their tolerance for abuse, and there is no more leeway, so they become injured.

Chronic strains and sprains result from hours, days, or even years of undue stress placed upon the joints and muscles of the lumbar region. Poor posture stress in one's daily life or some common mechanical back problem, such as scoliosis, can predispose a person to a chronic back injury and the associated pain.

Do the muscles and ligaments become not only injured but also so can the discs themselves Degeneration tears or cracks may disrupt the normal state of these vertebrae discs. Sudden movements in a twisting manner can cause almost immediate pain. Once the discs crack open, the material inside them may begin to bulge outward onto the nerves of the lower body. Often this causes numbness or weakness in the lower extremity.

Two common causes of bulges are sitting or standing in a forward slumped position or twisting the torso while lifting an object. Which incidentally everyone does every single day! Can you grab the groceries from the back seat or trunk and lift them out without twisting? Hardly! So this is an area that needs attention. Hint: turn with the hips, midsection, and shoulders as a unit to avoid damage to the back.

In most cases, injuries are preventable if proper attention is paid to the attending causes. Education and maintenance of a strong musculature in the back and surrounding areas are the two crucial elements in the prevention of back injuries. Educate yourself about the causes of and the prevention of back injuries. During this process, learn the correct body mechanics of posture while standing, sitting, and laying down or lifting objects. Learn correct back-saving motor movements.

Exercise to maintain and increase the strength of your back and all the supporting musculature surrounding it. Specifically increase the strength of the core of your body, i.e. the area from the knees to the shoulders.

Always be aware of your posture and body mechanics as you lift or move. Exercise appropriately and consistently each day to improve your physical fitness level. Follow the solid principles of exercise prescription of load, duration, and frequency and warming up and cooling down for each session. Feed your body good food and liquids each day by following a solid nutrition plan.

Article Reference

This article first appeared in:

  • O'DELL, D. (2004) Low back pain. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 18 / December), p. 1-3


  1. NSCA (n.d) Training and rehabilitation for the lower back. Quick series guide to:

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • O'DELL, D. (2004) Low back pain [WWW] Available from: [Accessed

About the Author

Danny O`Dell is an NSCA Certified Strength and Conditioning coach from the USA. He is the author of several training manuals including The Ultimate Bench Press Manual, Wilderness Basics, Strength training Secrets, Composite training, and Power up your Driving Muscles. Danny has published articles in national and international magazines describing the benefits of living a healthy fitness lifestyle.