Your thoughts can hurt your neck and back while lifting

The mental stress of cognitive dissonance — encountering information that conflicts with how we act or what we believe — can lead to extra strain on the neck and lower back while lifting and lowering, new research suggests.

When study participants were told they performed poorly in a precision lowering experiment in the lab, after initially being told they were doing well, their movements were linked to increased strain on the vertebrae in their necks and low back.

The results showed that the higher the cognitive dissonance score, the greater the strain on the upper and lower parts of the spine.

The finding suggests that cognitive dissonance may be a previously unidentified risk factor for neck and low back pain, which researchers say may have implications for workplace risk prevention.

“This increased load on the spine occurred under only one condition with a fairly light load — you can imagine what it would be like with more complex tasks or higher loads,” said senior author William Marras, executive director of the Spine Research Institute in the state of Ohio. University. “Basically, the study scratched the surface to show that something is going on here.”

The research was recently published in the journal Ergonomics.

Marras’ lab has been studying everyday life and occupational forces on the spine for decades. About 20 years ago, he discovered that psychological stress could affect spinal biomechanics, using a study design where he had a fake argument with a graduate student in front of research participants.

“We found that certain personality types increased load in the spine by as much as 35 percent,” Marras said. “We eventually found that when you’re under that kind of psychosocial stress, you tend to co-activate the muscles in your trunk. It causes this tug-of-war in the muscles because you’re always tense.

“To get that mind-body connection, in this study we decided to look at the way people think and, with cognitive dissonance, when people are disturbed by their thoughts.”

Seventeen study participants – nine men and eight women, ages 19-44 – completed three phases of an experiment in which they placed a lightweight box in a square on a surface that was moved left and right, up and down. After a short practice run, the researchers gave almost exclusively positive feedback during the first of two 45-minute test blocks. During the second, feedback increasingly suggested that the participants were performing in an unsatisfactory manner.

To arrive at a cognitive dissonance score for each participant, changes in blood pressure and heart rate variability were combined during the experiment with responses to two questionnaires that assessed both degree of discomfort and positive and negative affect: feeling strong and inspired versus upset and embarrassed .

Wearable sensors and motion-capture technology were used to detect peak loads on the spine in the neck and low back: both vertebral compression and vertebral movement, or shear, from side to side (lateral) and forward and backward (A/ P).

Statistical modeling showed that the maximum spinal load on the cervical vertebrae was, on average, 11.1% higher with compression, 9.4% higher with A/P shear, and 19.3% higher with lateral shear during the negative feedback trial block compared to the baseline measures from the practice run. Peak load in the lumbar region of the low back – an area most affected by spinal loading – increased by 1.7% in compression and 2.2% in shear during the last test block.

“Part of the motivation here was to see if cognitive dissonance can’t just manifest in the low back – we thought we’d find it there, but we didn’t know what we’d find in the neck. We found a pretty strong response in the neck,” said Marras, a professor of integrated systems engineering with academic appointments in the College of Medicine in neurosurgery, orthopedics and physical medicine and rehabilitation.

“Our tolerance for shear is much, much lower than for compression, so that’s why that’s important,” he said. “A small percentage of the load isn’t a big deal for once. But think about when you work day in and day out and you have a job where you do this 40 hours a week – that can be significant, and be the difference between a disorder and have no disorder.”

Marras is also the principal investigator of a federally funded, multi-agency clinical trial evaluating different treatments for low back pain, ranging from medication to exercise to cognitive behavioral therapy.

“We’re trying to unravel this onion and understand all the different things that affect spinal disorders because it’s really complex,” he said. “Just like the whole system has to be right for a car to run correctly, we learn that that’s how it is with the backbone. You could be in great shape physically, but if you don’t think correctly or appropriately, or you have all these mental anomalies, like cognitive dissonance, affecting the system, and until you get that right, you’re wrong.

“We look for causal pathways. And now we can say that cognitive dissonance plays a role and that’s how it works.”