Pushing and pulling tasks are among the most common industrial activities. Pallets of goods need to be moved from one point to another and equipment needs to be moved to a usage point. Workers at factories, hospitals, distribution centers, grocery stores and many other businesses engage in pushing and pulling activities numerous times a day. The Ergonomics of Manual Material Handling – Pushing and Pulling Tasks provides a useful overview of the costs and consequences of neglecting ergonomics in common industrial tasks that involve pushing and pulling. Click here to read the white paper published by Darcor, an industry leader in the design and manufacture of ergonomic casters and wheels, and Ergoweb, an ergonomic web resource.
While often taken for granted, wheeled carts and equipment are integral to the operation of nearly all manufacturing and distribution facilities as well as many businesses. Musculoskeletal disorders from pushing and pulling injuries cost American businesses billions of dollars each day in medical, insurance, disability and downtime costs. Ergonomically-designed carts, wheels and casters can significantly decrease the incidence of musculoskeletal disorders.
To be effective, ergonomic design for push/pull tasks must consider:
- Human factors such as height, weight, age, gender, strength, posture and physiological capacity.
- Task factors including distance moved, forces required to initiate and sustain movement, direction and nature of movement and task duration.
- Cart/equipment factors such as size, weight, stability, caster/wheel specification and handhold type, height and orientation.
- Floor/ground factors including surface characteristics, slope and contaminants.
Contrary to popular belief, horizontal push force is more significant than load weight in pushing and pulling tasks. Proper wheel or caster selection and equipment design can enable workers to move thousands of pounds safely and efficiently. Caster/wheel choice alone can reduce push force significantly. Rolling resistance refers to forces that resist movement and defines the amount of force a person must generate and apply to move wheeled equipment.
This force — called the starting or initial force by ergonomists — is always greatest at the start, just before movement begins. Fortunately, starting force must only be exerted briefly. Once acceleration is achieved, less force — called the sustained or rolling force — is required to maintain movement. The final major force that affects cart movement is turning force which can occur while the cart is in motion or during positioning.
Next time: How ergonomics mitigates force.