Moving loads on a trolley : Loads on a trolley, are normally moved through pulling or pushing process. During the pulling process, the whole strain is to be taken by the back muscles. Care should be taken to move the trolley with a steady speed that it does not run on and injure the feet. During pushing process, an optimum height of push (about mid-chest height) helps in minimising the strain. The push load is taken by the back bone. Pushing at too high a level puts excess strain on stomach muscles and can cause strain of shoulder muscles and hernia. Also pushing at too low a level is ineffective.