Mechanical load on the low back and shoulders during pushing and pulling of two-wheeled waste containers compared with lifting and carrying of bags and bins

Objective. Compare the mechanical load on the low back and shoulders during pushing and pulling a two-wheeled container with the load during lifting a nd carrying the same amount of waste. Background. Only little is known about risk factors and mechanical loads du ring push/pull operations. Design. A complete 2(3) factor push/pull experiment. A two-wheeled containe r with 25 or 50 kg was pushed in front of and pulled behind the body by sev en waste collectors. Further, the same subjects lifted and carried a paper bag and a dustbin both loaded with 7 and 25 kg. Method. All operations were video recorded and the push/pull force was meas ured by means of a three-dimensional force transducer. Peak Motus and Watba k software were used for digitising and calculation of torque at L4/L5 and the shoulder joints and compression and shear forces at L4/L5. Results. During pushing and pulling the compression at L4/L5 is from 605 to 1445 N. The extension torque at L4/L5 produced by the push/pull force is c ounteracted by the for-ward leaning of the upper body. The shear force is b elow 202 N in all situations. The torque at the shoulders is between 1 and 38 Nm. Conclusion. In the present experiments the torques at the low back and the shoulders are low during pushing and pulling. No relation exists between th e size of the external force and the torque at the low back and the shoulde r.