RENEW OR SUBSCRIBE TO PPM
Subscription is FREE for qualified healthcare professionals in the US.
5 Articles in Volume 5, Issue #4
Chronic Pain and Cannabinoids
Lumbar Back Belts in the Workplace
Pain from Muscular Dysfunction
Spinal Cord Stimulation
Ziconotide for Chronic Severe Pain

Lumbar Back Belts in the Workplace

A review of the efficacy of lumbar back belts in the workplace in reducing back injuries and pain.

Editor’s note: the subject of efficacy of back belt use in the workplace remains a controversial subject more than a decade after the results from the National Institute for Occupational Safety and Health’s Back Belt Working Group, which found, in 1994, “that the effectiveness of using back belts to lessen the risk of back injury among uninjured workers remains unproven; there are insufficient evidence indicating that typical industrial back belts significantly reduce the biomechanical loading of the trunk during manual lifting; there is insufficient scientific evidence to conclude that wearing back belts reduces risk of injury to the back based on changes in intra-abdominal pressure (IAP) and trunk muscle electromyography (EMG); the use of back belts may produce temporary strain on the cardiovascular system; there are insufficient data to demonstrate a relationship between the prevalence of back injury in healthy workers and the discontinuation of back belt use.” The Working Group specifically concluded: “The Working Group does not recommend the use of back belts to prevent injuries among uninjured workers, and does not consider back belts to be personal protective equipment. The Working Group further emphasizes that back belts do not mitigate the hazards to workers posed by repeated lifting, pushing, pulling, twisting, or bending.” Finally, their overall conclusion was that “The Working Group recommends that the most effective means of minimizing the likelihood of back injury is to develop and implement a comprehensive ergonomics program.”*

In the following article, Dr. Marovino reviews the current status of lumbar belts in the workplace and presents the latest thinking regarding their use.

*Source:http://aepo-xdv-www.epo.cdc.gov/wonder/prevguid/ p0000421/p0000421.asp. Last visited 5/4/2005.

There are few topics in occupational medicine that can stimulate more controversy and debate than the utility of lumbar belt use in the workplace. Over the years researchers have attempted to study the putative benefits of these lumbar supports since affirmatory evidence of positive results could have far reaching implications in employer policy making. Back injuries have been the leading cause of disability in the United States for people younger than 45 years of age, and have been the most expensive health care problem for the 30-50 year old age group.1

In Canada, back injuries account for over 25% of all lost time claims, the largest single claims category in most workers compensation jurisdictions.2 A similar prevalence is seen in the US with back injuries accounting for approximately 23% of all workers compensation payments ($13 billion) in 2002. The Bureau of Labor Statistics indicates that in 1998 there were 279,507 back injuries caused by overexertion that resulted in lost work days, 89% being in materials handling type jobs.1 In response to the enormous social and economic losses involved with back injury, many employers have attempted to adopt preventive measures, specifically, the widespread use of industrial back belts.3

How clinicians, researchers and policymakers feel about back supports have partly to do with their individual perspective on the nature of back pain and how it interacts with a particular employees work setting, job satisfaction level (psycho-social factors) and underlying conditioning level. Over the years, several postulated mechanisms of action for back belts have been popularized, most of these relating to a belt’s ability to affect a positive biomechanical alteration in the worker. This report will examine the research support for these common beliefs along with some of the epidemiological data that examines the effectiveness of these back supports in industry to date.

Do Belts Increase Intra-abdominal Pressure?

There have been numerous mechanisms of action for back belts that have been studied and made popular over the years. Barron and Feuerstein list 5 mechanisms which have been studied and debated including; a back belt’s ability to redistribute spinal forces during a lift action so that there is an increased intra-abdominal pressure (IAP).4 The potential effect of increasing IAP resulting in a decreased intradiscal pressure (IDP) has been studied and supported by some investigators, while challenged by others. Two studies suggested that by wearing a back belt, a person could reduce their risk of injury. Both studies (Harmon et al 1989 and Lander et al 1992) reported ground reaction forces and measured intra-abdominal pressures while subjects repeatedly lifted a weight. Both reports identified an increase in IAP in persons wearing the belt. These research groups made the assumption that IAP is a good indicator of spinal forces, and that an increase in IAP is indicative of increased low back support thereby justifying the use of a back belt.5-6 The underlying rationale for their conclusions however had been tested by other groups in the past, and remained contentious at best. McGill and Norman had questioned the hypothesized link between elevated IAP and a reduction in low back load. In 1987 they used an analytical model and data collected on several subjects lifting varying load magnitudes. They found that an increase in IAP required additional activation of abdominal musculature with a resultant increase in spinal compressive load.7 This was consistent with some work done the year before by Nachemson et al where they found that performing a Valsalva maneuver increased, not decreased, the spinal disc compression loads. In this study, four subjects without a history of back pain were tested during three sitting and two standing conditions, with and without using a Valsalva maneuver. These were isometric tasks while intradiscal (IDP).

IAP and Lumbar Muscle Activity

Another prevailing hypothesis regarding wearing a lumbar support while lifting is that the belt provides an increase in IAP and this leads to a reduced low back extensor muscle activation or strain level. A study by McGill et al investigated the effect of breathing on IAP and IDP, in the belted and unbelted condition, with and without a Valsalva maneuver. They used six males without low back pain as test subjects. When using the Valsalva maneuver during lifting, they observed peak IAPs being elevated, as opposed to peak IAPs during lifting without Valsalva maneuver. As well, EMG activity of the erector spinae muscles was decreased when lifting and using the Valsalva maneuver, as compared with EMG activity during lifting without the Valsalva maneuver. This finding may indicate that decreases in erector spinae muscle activity result primarily from the use of a Valsalva maneuver, and are not related to belted or unbelted conditions.8 The wearing of a belt was found to increase IAP by approximately 20%, so the authors further hypothesized that if belts indeed supported some of the low back extensor moment, they should expect to measure a reduction in extensor muscle activity. EMG readings showed no change in muscle activity for the back extensors or abdominal muscles.9 Lander et al examined lumbar muscle EMG activity in six male subjects without low back pain. They used two belted conditions and no belt condition. During lifting at 70% repetition maximum, they noted a reduction in erector spinae EMG activity in both belted conditions as compared to the no belt condition.10 In a separate study conducted two years later, Lander et al found that there were no reductions in lumbar muscle EMG activity in either belted or unbelted conditions.7

“There is mounting evidence that wearing a lumbar support can cause an increase in blood pressure...Both heart rate and blood pressure were increased by as much as 15 mmHg in subjects wearing belts.”

Ciriello and Snook examined 13 men over a four week period lifting several metric tons in four hours, twice a week — both with and without a belt. No differences in EMG median frequency signal in lumbar muscles were found between belted and non belted conditions. The findings did not support the idea that wearing a lumbar belt will significantly alleviate back extensor muscle loading.11 Woodhouse et al investigated the effects of two types of lumbar supports on lifting capability of nine male athletes without low back pain. The subjects performed isokinetic squat lifts at three different speeds in both belted and unbelted conditions. No differences were measured in maximum lift capacity by any of the three groups further strengthening the notion that wearing a lumbar belt may not impart any muscle unloading advantage.12

In 2004, the author’s research group designed a similar study to that of Woodhouse et al and selected 13 (seven male and six females) subjects who did not have a low back condition and tested maximum isometric strength capability in the belted and unbelted conditions. Using a static 39” lift task device (Hanoun Systems) that utilizes computer dynamometry to measure force, the subjects provided three consecutive maximal lift pulls in belted and unbelted conditions per session with adequate recovery time (five minutes) between the two sessions. The Hanoun device has been used as a measurement tool in various types of functional capacity evaluations which have demonstrated good reliability.13-14 The procedure was repeated on two separate occasions three days apart and reversed the testing order(belt/unbelted lift first or second) to account for a possible order effect. All subjects were instructed in a similar manner and had a practice session prior to formal testing to account for any learning effect. The results were similar to those already cited (Woodhouse et al) and finding no statistically significant differences in lift capability between belted and unbelted subjects, however there appeared to be a trend toward an increased lifting capability in the belted condition despite it not reaching statistical significance.15

Do Belts Limit Range of Motion?

In 1986 Lantz and Schultz measured spinal active range of motion alterations when wearing rigid spinal corsets and braces (not lumbar support belts) and did find restrictions in ROM with the least limited movement being spinal flexion.16 McGill et al observed a similar pattern to that of Lantz and Schultz when they measured torso stiffness in 35 subjects in the belted and unbelted condition using a four inch leather abdominal belt. Torso stiffness was significantly increased in the frontal (lateral bend) and transverse (trunk rotation) axis but not the sagittal axis (trunk flexion) such as would occur during industrial lifting.17 It is thought that stiffening the spine as it approaches end range flexion would provide prophylaxis from injury since there is evidence to show that compressive strength of the lumbar spine decreases as it approaches flexion end range.18 Although some ROM restrictions have been demonstrated in lateral bending and rotation, the more useful restriction would be in trunk flexion, where there is evidence that support belts restrict the least. However, the lumbar belts ability to moderate or control trunk rotational movements may be an important contribution to this discussion since rotational forces in the spine have been implicated as primary forces of injury in occupational low back injury.19

Lumbar Belts and Cardiovascular Factors

There is mounting evidence that wearing a lumbar support can cause an increase in blood pressure. Hunter et al examined the effects of performing dead lifts, bench presses and riding bicycles in six subjects while wearing and not wearing a weight belt. Subjects were required to hold in a lifting posture a load of 40% of their maximum weight in the dead lift position for two minutes. Subjects were monitored so as to avoid the Valsalva maneuver. Both heart rate and blood pressure were increased by as much as 15 mmHg in subjects wearing belts. These investigators concluded that persons undertaking exercise would be at less risk for a cardiovascular event if they did not wear a lumbar belt.20 Rafacz and McGill also monitored the pressor response of 20 males performing activities both with and without a belt. The subjects wore an industrial type belt made with an elastic and suspenders including Velcro tabs for cinching in the front. Subjects wearing this type of belt demonstrated an increased diastolic blood pressure while both sitting, standing and holding a hand weight during a trunk rotation action and during a squat lifting task.21 There have been other reports suggesting localized rises in tissue temperature, increased proprioceptive awareness, and an increased perception of safety as potentially beneficial reasons for wearing back belts.22 There is a paucity of evidence that might lend further support to these ideas at this time. Further clinical testing will be required to more completely elucidate some of these potential benefits.

Biobehavioral or Psychophysical Studies

There is some evidence that wearing a back belt increases a sense of security that may either be wanted or unwanted. McCoy and colleagues evaluated 12 male students while they repetitively lifted loads of their choice from floor to knuckle height at a rate of three lifts per minute for a duration of 45 minutes. This bout of lifting was repeated three times, once without belt, and once each with two types of belts (air belt and elastic belt). After examining the amount of total weight lifted by each student under the various conditions, the researchers noted that wearing belts increased the loads students were willing to lift by approximately 19%.23 These types of observations lend credence to the idea that lumbar belts do provide persons with a increased sense of security.

In 2004 the author’s group sought to test the hypothesis that there might be a general perception amongst the public that back belts provide some mechanical support to the spine, and in doing so, reduces the overall risk of back injury. The method was to essentially poll the general orthopedic patient population as they came in for their physical therapy session. They were given a page with two pictures and two questions. Picture A showed a man wearing a back support (elastic corset) and picture B a man wearing no support. Only two questions were posed. The first was whether if all other factors being equal, should man A (with belt) be able to lift more than man B (no belt). The second question was whether if all other factors being equal, would man A (belted) be at less risk for low back injury than man B (unbelted).

“In the absence of any good science that supports a positive mechanical effect in lifting by wearing a lumbar belt, workers can be inadvertently putting themselves at greater risk for back injury by wearing a belt.”

A total of 32 patients with various orthopedic problems — not necessarily back pain — were polled. The overwhelming majority of patients responded affirmatively to both questions believing that wearing a lumbar support provided extra lumbar strength that would allow a higher load to be lifted, and also that wearing a brace would confer some degree of immunity against low back injury.24 It would seem logical to think that people will behave in a manner consistent with their belief system.

If people believe that wearing a back belt will reduce their risk of injury by possibly providing them with increased lumbar stability facilitating more lifting power (mechanical effect), then we should expect the use of back belts in the workplace to continue. In the absence of any good science that supports a positive mechanical effect in lifting by wearing a lumbar belt, workers can be inadvertently putting themselves at greater risk for back injury by wearing a belt. It is for this reason that employers are paying special attention to these debates regarding belt wearing, and some employers have proactively formulated work policy rules prohibiting employees from wearing back belts in material handling jobs.

Clinical Trials

The clinical trials completed to date have for the most part been criticized for some glaring methodological problems including small sample sizes, lack of matched control groups, and short trial durations. It is generally acknowledged that a well designed, controlled clinical trial would be very difficult to execute. Walsh and Schwartz studied 81 male wharehouse workers and divided them into three groups, a control group, a group receiving 30 minutes of lifting instruction, and a group receiving 60 minutes instruction and who wore a back orthoses (molded plastic) for six months. The outcomes of interest (dependent variables) were; abdominal strength, accident rate, and lost time from work. The control group and 30 minute instruction group showed no changes in abdominal strength or lost time from work. The third group showed no change in abdominal strength and accident rate, but did show a reduction in lost time. Further analysis showed that this benefit was present primarily to those who had a previous back injury.25 Van Poppel et al reached a similar conclusion in a study of 312 airline baggage handlers.26

In another study that examined 642 baggage handlers and divided their sample into a control group, a belted group, a one hour education group, and a combined one hour education with belt group. Despite the trial lasting about eight months, there was a high degree of non compliance among the belt wearing or experimental group. The researchers found no difference among treatment groups for injury rate, lost work days or workers compensation rates. Those who began wearing belts but discontinued did have a higher lost day case injury incident rate, as well as an increase in the number and severity of lumbar injuries occurred following the trial in those who previously wore belts.27 In 1994, a large retrospective study involving 1316 materials handling workers was undertaken by Mitchell et al. They reviewed data for a six year period prior to the study and found that costs of back injuries that occurred while wearing a belt were considerably higher than costs of injury while not wearing a belt.28

The most influential studies on this topic came in 1996 and 2000, one in response to the other. In 1996 Kraus and colleagues published the then hallmark study of lumbar belts known as the Home Depot study. From 1989 to 1994, the injury rates of 36,000 employees at Home Depot were monitored as the company embarked on a mission to reduce workplace injury and implemented a policy that included mandatory belt wearing. Unfortunately, there were a number of concurrent interventions introduced at the time and no control group was built into the study. The authors of the study credited the belt wearing as the primary reason for a reduction in the incidence of back injury. The uncontrolled nature of this study design does not allow the reader to conclude with any degree of certainty that belt wearing was the most important intervention, since several interventions were implemented simultaneously.29 In response to the enormous promotion of the Kraus et al study by special interest groups, and the study’s methodological shortcomings, Wassell et al in 2000 published a replication study of the Kraus project. These researchers applied stricter controls in a similar retail environment using Walmart employees as subjects. The Walmart study, as it has come to be known, surveyed 13,873 employees at 160 stores. They focused solely on belt use without any other confounding interventions as they compared injury rates among the 89 stores mandating belt wearing versus 71 stores which had implemented a voluntary policy towards belt wearing. The results showed no difference between belt wearing and non belt wearing employee injury incidence rates.30

Conclusions

Given the contradictory findings that exist in our current body of literature, it would be difficult at this time to be able to make a universal statement supporting the use of back belts in industry. At the same time, there appear to be some benefits to belt wearing for some people. A summary of prescription guidelines has been published by McGill et al and incorporate the research findings of the various larger scale studies to date. They recommend that all potential back belt candidates be screened for cardiovascular risk factors by appropriate medical personnel prior to being issued a back belt. This is to protect from the possible increase in blood pressure and heart rate that might occur while wearing a back belt.

Given the widespread perception that back belts will confer a certain degree of immunity from back injury, it is imperative that back education (back school) be provided along with a back belt. Workers need to be instructed in proper lifting technique and injury causation issues, so that musculo-skeletal overload is avoided. The back belt is not recommended as a stand alone intervention, but rather should be part of a larger, more comprehensive ergonomics program emphasizing correcting the cause of musculo-skeletal overload and injury avoidance.

Furthermore, it is not recommended that workers wear back belts for long periods of time, but rather, embark on general fitness programs including core stabilization along with back education and job site assessment for problematic work processes. It would also be prudent to continue to monitor former back belt wearers for potential problems given that the period immediately following the back belt weaning process appears to be one of high risk for injury.31

Given the widespread perception that back belts will confer a certain degree of immunity from back injury, it is imperative that back education (back school) be provided along with a back belt.
Last updated on: November 14, 2012
close X
SHOW MAIN MENU
SHOW SUB MENU