A material handler working for the warehouse operation is expected to lift several boxes of canned motor oil from a pallet on the floor to a conveyor that operates at a height of 40 inches from the floor. The bottom of each box rests on the top surface of the pallet, which is 5 inches from the floor. Each box weighs 25 lbs. and must be gripped under the bottom of each box and since there are no handles on the boxes, one could consider the coupling to be “fair”. The worker has to lift 60 boxes per hour for the first four hours of the eight hour shift. She is well trained in proper lifting and is able to keep the box the same distance from her body (close) throughout the lift (she can even advance towards the conveyor to place the front of the box on the leading edge (static lip of the conveyor) without reaching the box forward to place it on the belt. During the lift, she must engage in a slight turn while first facing the pallet and then the belt - the angle of this slight twist is 18 degrees. She then can slide each box forward onto the belt after the actual lift phase of the task is complete. The distance between the vertical centerline of the bag and the point between the worker’s ankles is 12 inches. a.) What is the Recommended Weight Limit (RWL) for this particular lift? b.) What is the resulting lift index (LI)?

How would your answer change, if this same task (above) became part of a larger task that contains a second and third type of lift from a pallet on the floor to a shelf at a height of 48 inches from the floor? For the next two hours, bags of sand are moved. The bottom of each bag of sand rests on the top surface of the pallet, which is 3 inches from the floor. Each bag weighs 40 lbs. and must be gripped under the bottom of the bag and since there are no handles on the bags, one could consider the coupling to be “fair”. The worker has to lift 50 bags per hour for the 2 hours after the first lifting task has been completed (described above). The distance between the vertical centerline of the bags and the point between the workers ankles is 10 inches. For the last two hours of the day, the material handler then has to move boxes of paint cans (four containers of paint per box) from a low shelf 12” above the floor to a shelf that is 52” above the floor at a rate of 60 boxes per hour. The boxes are 15”x18”x18”, weigh 36 pounds and have no handles (must be grasped by slipping fingers underneath the box – fair coupling). Again, the worker is well trained in proper lifting and is able to keep the boxes and bags the same distance from her body (close) throughout the lift (she can advance towards the shelf to place the front of the bag or box on the leading edge (static lip) without reaching the bag or box forward to place it on the shelves. During the both additional lifts, she must also engage in a slight turn while first facing the pallet and then the shelf - the angle of this slight twist in the case of the bags is 10 degrees and the boxes require a twist of 20 degrees. She then can slide each bag and box forward onto the shelf after the actual lift phase of the task is complete. The distance between the vertical centerline of the boxes and the point between the workers ankles is now 17 inches.