"How much weight can a worker safely lift?" Every type of workplace involves manual material handling (MMH) tasks that are the direct cause of a large number of injuries to workers, the most common being back injuries. MMH involves workers physically moving materials or objects by lifting, lowering, carrying, pushing, pulling, shoveling or stacking. This course explores how size, shape, repetitiveness, bending, twisting, the environment and distance all play a role in the re-design, elimination, or reduction of workplace injuries.