Half-weight cement bags are packed with less cement material and reduce the weight that has to be lifted and carried during cement-laying tasks.
Using half-weight cement bags is an administrative control that can reduce musculoskeletal disorders (MSD) from manual material handling and stooped postures. A regular cement bag weighs approximately 94 pounds, which exceeds the NIOSH recommended lifting weight of 51 pounds. Half-weight cement bags fall withing NIOSH recommendations.
Mason tenders work in support of bricklayers and blocklayers. A regular part of their work involves carrying or lifting heavy cement bags (94 lbs) and manually emptying them into mortar mixers. The weight of these bags (94 lbs and up) exceeds the NIOSH recommended lifting weight of 51 lbs. Decreasing the weight, by using half-weight cement bags, significantly reduces the risk of low back pain and back injury.
Heavy lifting and carrying and stooped postures can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg. The half-weight cement bag can help reduce heavy lifting and carring by reducing the amount of material that has to be lifted and carried at one time.
Half-weight cement bags (less than 51 pounds) reduce the amount lifted by mason tenders in each lift.
There have not been independent published studies measuring the effect of half-weight cement bags on reducing musculoskeletal disorders. Regardless, safety and health experts believe that masons will be less likely to develop musculoskeletal disorders if the weight of the bags is reduced from 94 lbs to below 50 lbs by using half-weight cement bags on the jobsite. While handling half-weight cement bags, spinal compression would be less compared to handling standard-weight bags. Thus, the risk of low back pain or back injury would be decreased.
With the use of half-weight cement bags, mason tenders would probably have to lift twice as many bags. However, lifting half-weight cement bags is less fatiguing and should not slow down productivity.
Research in exercise physiology has shown that lifting a weight near a person's maximum lift capability is much more exhausting then lifting even a slightly reduced weight. Exercisers can be expected to perform 12 lift repetitions with a weight that is about 70% of their maximum lift weight. Maximum productivity is likely to be achieved at even lower percentages of maximum lift weight. Productivity gains begin at the point where increase in repetion rate plus reduction in recovery time (both immediate and long term) exceeds time lost to multiple repetitions.
Dan Anton, PT, PhD, ATC – Eastern Washington University, and Carlos Sanchez-Marin, DDS, MS – University of Iowa