Low back pain leads to greater spine compression
Study highlights pain cycle and suggests solutions
A new study suggests that people who have chronic lower back pain put more loading pressure on their spines during lifting tasks than do people who have no back pain.
While the study did not specifically address rehab treatment of lower back pain, it does suggest that successful treatment programs need to include weight reduction, keeping injured workers out of the workplace long enough to completely heal after a back injury, and providing therapy that teaches patients body motion exercises.
"This study explains why people who’ve had back injuries and are sent back to work before they’re ready will contract their muscles in ways that cause more wear and tear on their spine as they’re doing tasks," says W.S. Marras, PhD, CPE, Honda professor and director of a biodynamics laboratory in the Institute for Ergonomics at The Ohio State University in Columbus.
Marras and other researchers received funding from the Ohio Bureau of Workers Compensation to study the dynamics of low back pain and recurring injury.
A look at the database of Ohio’s state-insured workers’ compensation program showed that 16% of the people who had back injuries accounted for 80% of the costs. These high-cost workers were those who typically had repeated back injuries. It was to answer the question of why certain people had recurring injuries that Marras and colleagues conducted the study.
"So basically what we did was a study where we had a group of people who were not experiencing back injuries, and we matched them for age and size to people who did have back injuries," Marras says.
Each group was studied performing certain tasks, including lifting objects high, lifting low, lifting at medium height, and lifting close to the body. While participants conducted the lifts, their trunk muscle activity, trunk kinematics, and trunk kinetics were used to evaluate three-dimensional spine loading using an electromyography-assisted model.1
"When we did this, we basically found that people with back injuries had a much higher load on their spine than people who didn’t have back injuries, even when we accounted for different weights," Marras says. "We found that people who had back injuries were employing the muscles in the torso to a much greater degree."
This resulted in 26% greater spine compression and 75% greater lateral shear (all resulting from muscle coactivation) than in participants who did not experience back pain.
Weight adds to whammy
Then add the fact that people with back injuries typically are overweight, and it’s a double whammy, Marras says.
"They have more body weight to contend with, and a lot of that weight is forward, in the abdomen, which means it’s like holding something in front of them all the time," Marras explains. "Basically, what was happening was that people with back injuries were constantly contracting those torso muscles, which we’ve known for a long time, and is called guarding.’"
The guarding mechanism creates more wear and tear on the spine, making it more susceptible to recurring injuries, Marras says.
Marras and colleagues will conduct a follow-up study examining what happens during symmetrical lifts, twisting, and turning, and a study that follows people in industry to observe their characteristics and what happens when they return to work after a back injury.
Although the findings are new and will require future research, including studies of who various rehab therapies help or hinder back pain patients, they already suggest several strategies for preventing recurring back pain, Marras says:
1. Workers should fully recover before returning to work after a back injury.
The research suggests that people who have suffered a back injury will place more stress on their spine muscles if they are encouraged to do lifting before they have fully recovered, and this is why they should not return to work early, Marras says.
"Some of our clinical work has found that even when people are beyond their back injuries and whatever was wrong with them mechanically is gone, they still recruit’ muscles in that same guarding type of way," Marras says. "And we think that is the problem."
The study found that increases in spine loading among people with lower back pain may accelerate degeneration of the spine. That’s why it’s important to prevent back injury patients from using the muscles incorrectly in the first place. Another solution is having a patient temporarily stay away from work or other situations that might involve lifting.
2. Workplace ergonomics is important.
Not only should workplaces be designed with ergonomics in mind, but workers who lift on the job should be taught safe and proper lifting methods.
The study found that people who had back injuries were affected much more dramatically by lifting in a poor posture than were people who had not experienced back injuries, Marras says.
"If they lifted from a not-so-extreme posture, maybe at waist level, the cost on the spine was a little bit higher, but not anywhere near what it was with one of the extreme postures," Marras explains.
"So the set-up of the workplace seems to be extremely important, especially for people who’ve had back injuries," Marras says. "That’s one implication of the study."
3. Patients suffering from back injuries should be encouraged to lose weight.
This research confirms the importance of maintaining normal weight to prevent back injuries, Marras says.
Body weight played a major role in spine loading among the lower-back-injury participants of the study; it imposed much greater spine loading than what was expected among uninjured participants of the same size.
It would greatly benefit back pain patients to lose weight during their recovery period, Marras says.
4. Rehab therapists might try teaching back injury patients t’ai chi and similar exercises that improve body kinematics.
The research has some interesting implications for rehab therapists, who typically have approached back injuries with the strategy of improving patients’ torso muscle strength, Marras says.
"We’re hypothesizing that it’s not that the patients don’t have the strength," Marras says. "We think what we could do is educate them how to recruit those torso muscles in a more natural way, and we think that is the root of the problem."
For example, a physical therapist might teach lower-back-injury patients how to do motion kinetic sports, such as t’ai chi, which is a martial art that focuses on kinematics rather than combat training.
"T’ai chi is a very fluid way of moving, and we’re thinking that it might educate the muscles better than traditional back pain therapy," Marras says.
Reference
- Marras W, Davis K, Ferguson S, et al. Spine loading characteristics of patients with low back pain compared with asymptomatic individuals. Spine 2001; 26:2566-2574.
Need More Information?
- W.S. Marras, PhD, CPE, Honda Professor and Director, Biodynamics Laboratory, Institute for Ergonomics, The Ohio State University, 1971 Neil Ave., Columbus, OH 43210. Telephone: (614) 292-6670 or (614) 292-2016. Fax: (614) 292-7852. E-mail: [email protected].
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