Biomechanical Considerations in the Use of Backbelts
By: Ken Zans
A comprehensive study of the effectiveness of the use of Musculoskeletal Support Devices in the workplace.
To date, the use of back belt type supports in the workplace has been a source of heated debate among both end users and manufacturers. The growing tendency to utilize these devices by employers has allowed interested parties the opportunity to study the effectiveness of these devices. Consequently, there is a "gap" between the information distributed by manufacturers and the results of studies done by NIOSH (National Institute for Occupational Safety and Health), ACOEM (American Committee on Occupational Medical Practice), and other interested parties.
The following statements were taken directly from advertisements for back support products in popular journals or in product literature:
"Engineered to give needed back support and freedom of movement."
"Acts as a preventative and rehabilitative device for muscular low back discomfort. Maintenance of proper alignment of the back is the key to accident prevention."
"Effective support for the types of lifting, twisting, standing, and sitting movements made on the job."
"At present, there is no legal requirement for those selling back support belts to conduct any type of controlled clinical trial similar to that currently required with drugs and medical devices. Specification of criteria for selection and wearing back belts as well as identification of problems of use, is essential to the success of the program. However, until more studies provide clear direction and answer key questions, the old adage 'caveat emptor' is still good advice." ACOEM,1992
In 1992, "buyer beware" was the rallying cry among medical professionals, ergonomists and end users. Since that time, there have been considerable studies made in this arena with quantitative results pointing to the ineffectiveness of these devices. NIOSH published findings and concluded the most significant benefit of a back belt program in the workplace is the benefits the employees gain from any "training" they may receive in proper lifting techniques.
Studies performed to determine the effectiveness of these devices have been based primarily on the following rationale made by manufacturers:
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Rationale Number One: Back belts increase abdominal pressures during lifting, which lowers lumbar disc compression forces.
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Rationale Number Two: Back belts directly reduce torso muscle activity by stiffening torso support.
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Rationale Number Three: Back belts reduce mobility and keep torso erect, thus reducing low-back stress.
Generally, there are two products available on the market today. The "traditional" back belt used by weightlifters and the more prevalent belt in the workplace commonly called the "soft belt". The weightlifter's belt is usually made of a stiff leather and is much wider (taller) and has a greater capability to "cinch" down at the abdomen. While there are many "soft belt" products on the market, they share many of the same characteristics, i.e.: they are lightweight, narrow, and do not have a great amount of "cinching" capabilities. Most of the latter are made primarily for comfort of use. It is important to recognize these basic differences in belts as we explore the manufacturers' rationale listed above.
Rationale Number One
Back belts increase abdominal pressures during lifting, which lowers lumbar disc compression forces. Studies performed at the University of Michigan measured the abdominal forces on the discs at L5/S1 in four common postures. Using a 15 lb. load in the hands, measurements were taken with the torso flexed at 0, 30, 60, and 90 degrees from vertical. Abdominal pressure readings were taken with the subject wearing a "stiff belt", "soft belt" and without. Under the best conditions (use of stiff weightlifter's belt), the intra-abdominal pressure may be able to reduce lumbar disc compression by about 10%.
Conclusion - Light load lifting resulted in no statistically significant increase in lAP with soft belts. Pressure increases with stiff, wide and tight belts is very small in normal lifting, and not present with soft belts.
Rationale Number Two
Back belts directly reduce torso muscle activity by stiffening torso support. Tests were performed using a "soft belt" cinched around the waist using three hand load weights of 10, 30, and 50 pounds stoop lifting from the floor. In addition, measurements were taken with the belts cinched at different tensions: no belt, loose belt (2 lbs. tension), moderate belt (10 lbs. tension), and tight belt (20 lbs. tension).
Conclusion - Even very tight, stiff, wide belts cannot support the torso sufficiently to reduce torso muscle activity during high risk lifting. The use of a lumbar belt does not enhance isometric lumbar muscle strength or dynamic lifting capacity. Soft belts do not reduce muscle activity.
Rationale Number Three
Back belts reduce mobility and keep torso erect, thus reducing low-back stress. Tests were performed measuring pelvic rotation during lifting tasks ranging from an erect lift (180 degrees) to a deep squat (45 degrees), using both a "stiff," tight fitting corset and a traditional soft lumbar belt.
These tests addressed two key questions: (1) does the use of back belts significantly reduce torso range of motion? And, (2) is reduced torso range of motion desirable?
Conclusion
Question one: With full form-fitted, tight corset, torso flexion from vertical was restricted 20%, and almost 50% in extension, lateral bending and twisting. Narrower, stiff belt had much less effect. With a soft "ergonomic" belt, no restricted range of motion was documented.
Question two: Such a restriction in torso mobility would force a person to lift with legs when lifting from the floor. When lifting compact objects, erect torso-squat lifting can reduce spinal compression forces if a person lifts the object between the legs. However, if an object lifted is too large to pass between the legs, the lifting task (while using a restrictive device) will result in larger low back stresses than without the use of a back belt. This is a result of having to hold the "bulkier" object further away from the body.
A wide, very stiff, custom fitted belt (corset type) will restrict mobility, and may reduce spinal forces a small amount if a person can hold objects close to the torso. Such restricted mobility along with training on how to lift and ergonomic changes can reduce low back stresses. Back belt programs using wide, stiff, form fitting belts without training and ergonomic workplace changes are not biomechanically justified for primary prevention of low back pain or rehabilitation purposes. Soft, narrow belts are not biomechanically justified for any purpose.
The best preventive measures for low back pain, strain, and injury are through the use of proper body mechanics while lifting and ergonomic changes in the workplace. Employee training programs in safe lifting techniques provide a much greater advantage in the control of these injuries than the use of mechanical devices whether they are the very restrictive "weight lifter corset" type or the more traditional "soft, narrow, ergonomic" devices.
"The Back Belt Working Group concludes that the effectiveness of using back belts to lessen the risk of back injury among uninjured workers remains unproven." NIOSH/CDC Conclusion (1994)
By: Ken Zans
© 2015 Alliance Training and Consulting, Inc.
