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Athletic development specialists dedicated to the art and science of excellence in movement

Pain and Movement Compensation

It’s fairly common sense to most people that pain affects movement.  Without getting into specific mechanisms, pain represents a threat and the brain is naturally programmed to alter its movement in the presence of pain.  Additionally, because pain often correlates poorly with actual structural damage, decoding the body’s messages can be tricky.   

If someone is in severe pain, its fairly obvious when they alter movement…limping, favoring one limb compared to the other side, restricted breathing patterns, r tortured facial expressions (yes, facial expressions are a movement…the face connects to the neck, which connects the shoulders…)  Because most overuse injuries are not life-threatening, we can often ignore pain signals or suppress them.  Well practiced athletes can also alter the visual presentation of their movements while in pain so they look normal even if they don’t feel normal.  Unfortunately, continuing to plow onward with pain or artificially suppressing pain can have consequences (I’m not saying that artificial pain relief is always bad, but most would agree it is overused to avoid confronting the actual cause of the pain….)

To this end, it helps when possible to quantify the links between pain and movement.  Most literature in this area deals with back pain, in part because back pain is so common and in part because back pain correlates poorly with actual damage to structure.  There would be serious ethical issues to experimental exercise on subjects with broken bones…and you probably wouldn’t find many volunteers to run on a broken leg in the name of science!

Many observe protective mechanisms triggered when someone’s in pain.  Intuitively this makes sense as stiffening is a natural protective mechanism for many types of threats.  However, the consequence of excessive stiffness is the body loses movement “options.”  Van den Hoorn (2012) studied pain-free subjects compared to low back pain subjects in gait analysis.  They measured relative rotations of the pelvis, thorax, and trunk and found reduced trunk movements relative to pelvic and thoracic movements in the low back pain group.   “People with low back pain (LBP) had lower variability of trunk rotations, as a result of the coupling of deviations of residual rotations in one segment to deviations of a similar shape (correlation) and amplitude (regression coefficient) in the other segment. These results support the argument that people with LBP adopt a protective movement strategy, possibly by increased trunk stiffness.” 

In other words, with the same pelvic and thoracic movements, the low back pain group was working harder to achieve the same results.  The consequence is that if you must stiffen the trunk just to walk, you don’t have much in reserve for tasks more demanding than walking.  Though you might question whether pain caused poor motor control or did poor motor control cause pain, in this instance with a simple task of walking, there should not be a statistically significant difference in motor.  As such, we’d suspect that pain, not underlying weakness, was the cause of greater stiffening while walking.   

Lamoth (2006) also compared gaits for healthy controls versus back pain subjects and had similar findings: “In the LBP participants, the pattern of ES activity was affected in terms of increased (residual) variability, timing deficits, amplitude modifications and frequency changes. The gait of the LBP participants was characterized by a more rigid and less variable kinematic coordination in the transverse plane, and a less tight and more variable coordination in the frontal plane, accompanied by poorly coordinated activity of the lumbar ES. Pain intensity, fear of movement and disability were all unrelated to the observed changes in coordination, suggesting that the observed changes in trunk coordination and ES activity were a direct consequence of LBP per se.”

What about referred pain?  Simmonds (2012) not only studied a back pain group and a control (pain free) group, they also included a third group of subjects with back pain referred into the leg.  They found that each group differed in gait velocity, ranking the pain free group the fastest and the referred pain group the slowest.  Interestingly, there was no significant difference in ground forces between the control group and the low back pain group, but there was a significant difference to the referred pain group, which delivered significantly less horizontal and posterior ground force at both the fastest and slowest paces tested. 

Conclusion

The idea that pain affects movement is hardly novel, but it is worthy for us to examine its veracity in part to test its truth, and in part to explore the exact mechanisms of how the body responds to pain.  In general, the evidence supports the ideas that the body takes protective measures by stiffening and that stiffening one body segment/region relative to others will alter timing.  Unwritten in these studies, but clearly relevant to us in the field is that altered timing will affect our capacity for learning.  When pain is present and we “succeed” with altered programming, the brain will adopt altered movement as normal.  Keep this consideration in mind when deciding whether to plow through the pain next time, particularly if it’s a movement where high skill is involved.

References

van den Hoorn W, Bruijn SM, Meijer OG, Hodges PW, van Dieën JH.  Mechanical coupling between transverse plane pelvis and thorax rotations during gait is higher in people with low back pain. J Biomech. 2012 Jan 10;45(2):342-7. Epub 2011 Nov 10.

Lamoth CJ, Meijer OG, Daffertshofer A, Wuisman PI, Beek PJ.  Effects of chronic low back pain on trunk coordination and back muscle activity during walking: changes in motor control.  Eur Spine J. 2006 Jan;15(1):23-40. Epub 2005 Apr 29.

Simmonds MJ, Lee CE, Etnyre BR, Morris GS.  The influence of pain distribution on walking velocity and horizontal ground reaction forces in patients with low back pain.  Pain Res Treat. 2012;2012:214980. Epub 2012 Apr 4.

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