Low Back Pain & Reverse Ergonomics: Fit the Person to the Job?

Evolving ergonomics? McGill SM. Ergonomics. 2009 Jan;52(1):80-6.

Abstract

The theme developed in this position paper follows the current evolution of injury prevention in the backs of workers. Job change or ‘fitting the task to the person’ has come far, but will probably not result in zero injury rates. This is because the cause of injury is heavily influenced by the way that a worker moves. A review of injury mechanisms reveals the need for the biomechanist/ergonomist to incorporate features in biomechanical models that recognise these injury mechanisms. The implication of one such model is that the next leap toward a zero injury rate may be approached with ‘fitting the person to the task’ or at least retraining the way that workers move. A few examples of movement-based back injury prevention strategies are provided. Finally, some thoughts on implementing such an approach are expressed. This is a review and position paper written in honour of Professor Don Chaffin’s career.

My comments:

The entire paper is great, concise, poignant, and full of useful advice for avoiding lumbar injuries in the work place. While prevention is ideal, as a physical therapist I rarely see people pre-injury, however the same techniques described in this paper make up a full third or more of my rehab programs for low back pain, as it is really difficult, or rather impossible, to get the patient’s pain to go away and stay away, if they are continuing to injure it on the job. So retraining movement patterns is every bit, if not more important, than restoring strength and endurance. The good news is that if you choose your exercises properly you can do both at the same time. Exercises that do such are things like standing cable rows & presses, squats, lunges and RDLs, all performed with a neutral spine. What’s great about these exercises is that they build a lot of strength and a lot of core stability that you just don’t get with yoga, bridges, pelvic tilts, trunk twists and knee to the chest stretches, much don’t build much fitness and are bad for your back and will likely cause you to go back to your doctor saying physical therapy didn’t work. As which point you are on to “pain management” meaning narcotics and spine surgery, which often doesn’t work either and does nothing to prevent the worsening of spine degeneration, and frequent recurrence of pain.

Comments from the paper that I both like and endorse are:

“Job change or ‘fitting the task to the person’ has come far but will probably not result in zero injury rates. This is because the cause of injury is heavily influenced by the way that a worker moves…”

“…the next leap toward zero injury may be approached with reversing the axiom ‘fitting the task to the person’ to ‘fit the person to the task’. More specifically, this means training the way that workers move.”

“…reasonably robust measures of both psychosocial and biomechanical factors have shown that both are important but that mechanical loading, at least for low back injury, dominates…”

“…there simply is not a safe or justifiable way for workers to repeatedly pick heavy objects from the floor. So starting height is governed by job design. But if the weight is raised to the height such that a worker can move about the hips without flexing the spine, substantial loads can be lifted.

“Those with healthy backs tend to utilise very low spine power – in other words, if they have high spine loads they have virtually no spine motion…”

Olympic lifters provide a wonderful example of maximising hip power and minimising spine power to lift without back troubles. They violate popular ergonomic guidelines for load limits, yet rarely experience back injury.

“Specifically, maintaining the spine in a neutral posture ensures the most resilient spine possible…”

“Surprisingly, the chronic backs had higher strength measures. While this was initially puzzling, analysis of the mechanisms revealed they used their backs more than their healthy colleagues! They chose to move with more spine motion and activate muscle in a way that caused higher back loads.

“This evidence suggests that an approach to address the cause rather than the symptoms must include ergonomics, but also to look farther and consider changing the individual.

“In the case of disc herniation, repeated joint flexion appears to be a necessary condition (McGill 2007). If the motion is transferred to the hip, the mechanism is eliminated.”

“This is an essential component in removing the cause of the painful condition so that any subsequent therapy has a chance for success.”

“Specifically, a fully flexed disc will sustain damage at a 23–43% lower load than when in a neutral posture (Gunning et al. 2001).”

Use skill to transfer momentum and reduce loading – even though it is popular in various work manuals, instructing workers to ‘lift slowly and smoothly’ reduces their joint-sparing skill.

“In many cases, ergonomic approaches involving job design are impractical or do not address the injury mechanisms that form the root cause of disabled backs. Entire sectors of the workforce cannot use job design (in jobs such as in law enforcement, forestry, farming, fishing, to name a few). The argument made here is that optimisation of the ergonomic effort for successful reduction of back injury rates in the future will have to consider ‘changing the person to fit the task’ or training the way an individual moves.

I don’t have a lot to add. It’s all right. A lot of my recent blogs on low back pain have been about avoiding treatments that don’t appear to work (traction, vertebral manipulation/manual therapy, Kinesiotape, William’s flexion stretches or McKenzie method) but it’s definitely good to have something positive to talk about. Improving the way a person with back pain moves is definitely a good thing. For more good things; lumbar supports work, strength training works, electric muscle stimulation works.

As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.

Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.

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