An H-block, or double open-end unit, is a substitution material that can help reduce musculoskeletal disorder from lifting. The H-block is open on both ends which increases the space available for rebar and grout.
Lifting and laying concrete masonry units can strain the muscles or sprain the ligaments surrounding the spinal joints in the lower back causing low back pain. H-blocks are designed to reduce the need to lift by allowing them to be placed around the vertical rebar.
Musculoskeletal disorders and worker fatigue due to manual materials handling. Manual materials handling may include heavy lifting, reaching above shoulder level and awkward postures.
H-block is open on both ends which allows masons to place the blocks around vertical rebar. This innovative design eliminates the need to lift the CMU above shoulder level reducing the risk for musculoskeletal disorder of the back and shoulder.
Contractors indicate the design of H-block allows masons to work around a vertical rebar making the job easier, safer, more efficient, and with less stress for the body. Instead of lifting the CMU over the top of the rebar, masons can maneuver the block around the side of the rebar at a height that is comfortable for them.
Safety and health experts believe that masons will be less likely to develop musculoskeletal disorders of the back and shoulder if they are able to substitute regular CMU for H-block.
Lifting H-blocks around the rebar instead of above the rebar is less fatiguing and should increase productivity.
Health and safety experts believe reducing the risk of developing musculoskeletal disorders may lead to increased productivity because: 1) workers can lay block for longer periods with fewer breaks and less fatigue, and 2) there may be a reduction in lost time injuries.
Contractors indicate that one of the drawbacks is that H-blocks break frequently due to improper shipping, storing or handling. Other contractors have mentioned that they are difficult to handle. Additionally, efficient workplace layout is important as this may help limit damage and promote load balance with could limit heavy loads.
Dan Anton, PT, PhD, ATC – Eastern Washington University, and Carlos Sanchez-Marin, DDS, MS – University of Iowa