July 8, 2015
Assessing the Effects of MMH on the Low Back
In an effort to minimize the astounding number of back injuries each year resulting from lifting in manual material handling (MMH), many lifting duties have been replaced with pushing or pulling. While this does take much of the pressure off the back, experts are surprised to discover that pushing and pulling also places the low back at risk in other ways. In fact, low back injuries from pushing and pulling account for about 20% of reported work injuries. How is the low back still so vulnerable when pushing and pulling, and what is the next step to resolve these injuries?
What’s The Problem?
When the back muscles are used in lifting, they’re recruited for stabilization, movement, and force. The actual movement taking place is extension of the spine – as in straightening the back after bending forward. When weight is carried through extension of the spine, the low back bears the weight of the object as do the arms. Pushing and pulling don’t require extension of the spine. However, it does usually force flexion of the spine – bending forward as in touching your toes. When the spine is in flexion, the low back muscles are still needed for stabilization and force. As it turns out, spinal compression is actually greater during flexion than it is during extension. So the back is vulnerable to injury in a new, albeit unexpected, way during pushing and pulling tasks.
How Do We Fix It?
As successful as it was to reduce the number of back injuries by replacing lifting, these muscle traumas can be very debilitating. Creating a new means to injure the back really doesn’t solve the problem. Some companies have already invested in pushing and pulling solutions and can’t completely change everything again. There are important measures one can take to make his current pushing/pulling task safer.
- Assess grip to the floor: this goes for both the employee moving the object and the cart itself. Are the worker’s shoes gripping to the floor or slipping around? How easily do the wheels turn? Is the handle loose? Does the cart turn easily? Ensuring that the employee has solid contact points and isn’t moving something too heavy to maneuver will create better posture to push or pull.
- Assess the height of the handle: the handle on the cart (or pallet jack, etc.) should allow the employee to push/pull without bending forward. This will be different for everyone.
- Assess the angle in which the employee’s body needs to be to move the cart: this seems like a no-brainer based on the previous two points, but weight, size of the object, and a variety of other factors determine whether a person can remain standing straight when pushing or pulling an object. Pay attention to the demands placed on the body.
- Implement motorized carts: removing the need to both lift and push or pull is ideal. The entire process of lifting and transporting can be automated or motorized. This is safest for employees as far as musculoskeletal disorders (MSDs) go. If making the change to automation isn’t feasible right now, taking action to make pushing and pulling as safe as possible will be a great start.
As with any ergonomic concern, there are a variety of steps to take in order to make a workstation it’s very safest. Consult the expert that is right for you to evaluate your options to minimize MSDs in manual material handling.