 A tremendous increase in the use of back belts by companies attempting to control back injury costs has been seen in recent years. Numerous belt designs are being made available to industry based on the premise that they reduce the risk of low back pain. Many claims have been made regarding the effectiveness of back belts. However, not many of these have been based on sound scientific evidence. In fact, there was contradictory information on the value of back belts. Some studies have supported the use of belts, while others have suggested that workers would be better advised to refrain from their use. This video was written by the U.S. Bureau of Mines to review evidence relating to back belt effectiveness and to provide some suggestions relating to their use in the workplace. It is largely based on a review of back belt literature by the noted spinal biomechanist, Dr. Stuart McGill. There are several potential benefits and drawbacks associated with wearing back belts that should be considered before a responsible policy can be established. Let's begin by examining some of the claims regarding the possible benefits of back belts that are typically made by back belt proponents. One claim made by supporters of back belts is that they may decrease the load experienced by the low back. Some feel that back belts may help to stiffen the spine to make it stronger. Supporters also claim that back belts may restrict spinal mobility and prevent hazardous movements. Others state that back belts may provide a safety margin by increasing an individual's tolerance to heavy loads. And finally, supporters claim that the use of back belts has been proven to significantly decrease the number of back injuries in industrial settings. Let us now examine the scientific evidence in support or in opposition of each of these claims. Do back belts decrease the load experienced by the low back? Every time a muscle contracts, a small electrical charge is generated. The harder the muscles work, the more electricity is generated. These electrical charges can be measured using electrodes and help us to see how hard muscles are working. If back belts decrease the load on the low back, we would expect this to reduce the amount of electrical activity of the powerful back muscles. However, studies have shown convincingly that there is no difference in back muscle activity when one is wearing a belt compared to one is not wearing a belt. Thus, back belts do not appear to lessen the load experienced by the muscles of the low back. Do back belts help to stiffen the spine? There is some evidence to support the claim that back belts help to stiffen the spine, but only to a relatively small extent. The added stiffness results from the increase in pressure within the abdomen that results from wearing a back belt. Years ago, abdominal pressure was thought to provide a large amount of force that helped to support the low back. However, it now appears that the benefits of abdominal pressure were exaggerated. Most experts now feel that the benefit to the back from this increase in abdominal pressure is probably fairly small. Do back belts restrict spine mobility and hazardous movements? This slide shows the ability of the spine to tolerate a load as the trunk is bent forward. As you can see, the spine is fairly strong in an upright position and even gets slightly stronger when it is bent forward slightly. However, as you continue to bend forward, the spine becomes much weaker until when fully bent, it can only take 60% of the load it could when upright. Thus, if back belts prevent workers from bending too far forward, they may help keep the spine in a stronger position. Unfortunately, studies performed thus far indicate that back belts do not prevent this forward bending of the spine. Thus, even with a back belt on, the spine is allowed to bend fully, placing it in a weak and vulnerable position. However, while forward bending does not appear to be reduced by back belts, some studies have indicated that twisting and side-to-side bending of the trunk may be slightly reduced when wearing a belt. This reduction in side bending and twisting is probably somewhat helpful. However, it is important to realize that people wearing back belts may still be putting their spines in very dangerous positions. Do back belts provide a safety margin by allowing workers to withstand heavier loads? Many people believe that use of back belts permits workers to handle heavier loads or more weight. However, data from recent studies do not support this claim. Workers wearing a belt cannot take any more of a load on their backs as workers without belts. Thus, it does not appear that belts provide an additional safety margin for the wearer. Does use of back belts in industry decrease the incidence of back injuries? Several recent studies have been performed attempting to determine whether belts actually do reduce the incidence of injury in the workplace. Unfortunately, the quality of many of these studies has not been very good. However, two studies have been performed which are worth discussing. These studies were performed by Walsh and Schwartz in 1990 and Reddell and others in 1992. The Walsh and Schwartz study is the one pointed to most frequently by back belt proponents as evidence of the effectiveness of back belts. These investigators studied 81 workers in an industrial warehouse setting using a very rigid back belt. Results of this study did in fact demonstrate a reduction in lost time back injuries due to the use of back belts, but only among workers who had experienced previous back injuries. No benefit was observed for previously uninjured employees. The second of these studies examined the effectiveness of back belts using 642 airline baggage handlers. These authors used a more flexible belt than the Walsh and Schwartz study. Results of this study showed no differences in back injury incidence rates between groups wearing back belts and those not using belts. However, these authors did discover a disturbing trend. Workers who started the study wearing back belts and who discontinued the use of the belts had a higher rate of back injury. The authors of this study concluded that back belt use may cause some physical dependency, leaving the back at increased risk when the device is withdrawn. This study also found that workers often quit using the belt, with less than half using them for the full eight months of the study. It is important to note that neither of the studies cited above demonstrated that belt use had any benefits for uninjured workers. However, it is noteworthy that belts did seem to help workers who had experienced prior back injuries. This indicates that the belts may have had some usefulness in the workplace under certain specific conditions. On the other hand, when workers quit using back supports, they appear to be more prone to back injury. We've now examined the claims made by back belt supporters. Now let's examine some of the claims made by critics of back belts. One of the main arguments of back belt opponents is that the use of belts may lead to weaker back muscles, or muscle atrophy. Others are concerned that back belts may lead to a false sense of security, making the wearer think that he or she can lift more than they really should be lifting. Finally, some critics are concerned that back belts may result in some changes in blood flow or blood pressure because they are cinched so tight around the waist. Let us examine the evidence with regard to these issues. Do back belts cause back muscles to become weaker or atrophy? Several studies have examined this issue, and all of these seem to agree that back belts do not lead to a decrease in muscle strength, at least over the short term. However, one recent study suggested that while back belt use does not result in loss of strength, muscles may tire more quickly with prolonged back belt use. Do back belts create a false sense of security? There is some evidence that back belts may lead to a false sense of security in workers. Studies have indicated that workers are willing to lift up to 20% more weight when wearing a belt. Thus, it appears that workers who use belts may be willing to place a higher strain on the back. If workers who wear belts do lift more weight, they may actually be working with a decreased safety margin for the low back. Do back belts result in adverse physiological changes? Back belts do seem to create certain physiological problems. The most important of these is that the blood pressure has been shown to be increased almost 15 millimeters of mercury when lifting with a belt. An increase in blood pressure by 15 millimeters of mercury may lead to serious health problems such as heart attack or stroke, especially in individuals already having high blood pressure. This presentation has demonstrated a somewhat mixed bag of evidence, some in support of back belts and some in opposition. Evidence supporting use of back belts includes some restriction in end range of motion in twisting and side bending, a clinical evidence of a decrease in lost time back injuries among those with prior back injuries, and a suggestion of increased trunk stiffness, which may be of some benefit. Evidence in opposition of back belt use includes an increased risk of injury upon discontinuing belt use, increased blood pressure, and a false sense of security that may lead workers to over strain their backs. This review of the literature indicates that the following approach to the use of back belts be followed, following Stuart McGill's advice in 1993. If you have a job where you think workers need a back belt, consider redesigning the job instead. Job designed to minimize lifting is bound to be much more effective at reducing back injuries than providing a back belt. If back belts are to be used, they should be treated as a prescription item and should be provided only to individuals having had a previous back injury. These workers should be weaned from the belts as soon as it is appropriate. Back belts should not be universally distributed to all workers at a work site, given the lack of demonstrated effectiveness among uninjured workers and a potential increased risk of back injury after discontinuation of use. Individuals considered for back belt prescription should be screened for cardiovascular risk factors due to the increased blood pressure associated with back belt use. Individuals using back belt should be required to participate in a mandatory exercise program and should continue in the program after being weaned from the belt during the period of increased back injury risk. Workers using back belt should be exposed to a mandatory education program to ensure that the back belts are used properly. The evidence presented in this paper suggests that back belts have a rather limited role to play in controlling the costs and incidents of back injuries. Reliance on back belts as a sole method of combating the problem clearly is not an effective solution. Effective back injury control programs tend to emphasize job redesign, where the worker's job is changed to reduce the amount of manual lifting that has to be done. Employers who are interested in keeping the cost of back injuries down are encouraged to focus on job design as a primary method of injury control, and if back belts are to be used, careful consideration should be given to the limitations discussed above.