Is Hip Extensor Weakness Causing Your Back Pain?
Back pain. One of the injuries that can be the most damaging to a runner.
Not only do you feel it while you are running, but almost every movement you make triggers that pain that reminds you something is wrong.
Low back pain is something no one wants to ever have to deal with, and if you do have it, you would do almost anything to make it feel better.
If you stay up to date with the latest information on injury prevention for runners, you have probably have already read our post on the 2 Hip Strength Tests That can Determine Your Risk of Knee Injuries.
In this post, we’re going to look at how the hips (specifically the hip abductors) can impact your lower back health.
Hip abductor and extensor muscles role in low back pain
Two of the most common injuries that affect runners—patellofemoral pain syndrome and IT band syndrome—are directly linked to weakness of the hip abductor and external rotator muscles. But did you know that poor hip strength has been linked to low back pain as well?
Isometric back extension as an indicator of back pain susceptibility?
The first set of evidence that hip muscle weakness might be associated with back pain came from a small study published in 1998 by Markku Kankaanpää and coworkers at Kuopio University in Finland.1
Twenty women with long-standing low back pain had their muscular strength and endurance tested in their back extensor and hip extensor muscles (the glutes). These values were compared to the same measurements from fifteen control subjects with no back pain.
The researchers found that the control subjects were able to hold an isometric back extension significantly longer than the subjects with low back pain. The researchers did however, note a big confounding factor in the design of their study; was it the muscular weakness that caused the back pain, or does chronic back pain lead to muscle atrophy from disuse and pain avoidance?
Female differences in hip extensor strength
This issue became evident in another paper on low back pain in Division I athletes. In a study published in 2000, Scott Nadler and other researchers tested hip abductor and hip extensor strength in 210 athletes. They then inquired about any low back pain in the previous year.2
While no differences in absolute hip strength appeared when comparing the previously injured athletes to the healthy ones, a distinct side-to-side difference in hip extension (but not abduction) strength did emerge, but only in women.
Like the previous study, Nadler’s paper was a retrospective study: it took measurements after an injury had occurred, which is easier to do, but makes separating cause and effect very difficult. A prospective study takes a measurement on a large group of healthy subjects, then waits to see who gets injured later. This is always preferable to retrospective studies.
Hip extensor strength imbalances
Nadler and colleagues followed up their previous work with a prospective study the next year3 They tested hip abductor and extensor strength of 163 DI athletes before participating in various sports.
The researchers then tracked the study’s participants for a year, recording any athlete who suffered from low back pain not related to an acute injury (like being tackled in football).
Only five women and eight men suffered from low back pain during the following year, making it difficult to draw any strong statistical evidence, but the same pattern emerged: women with an imbalance in hip extensor strength had a increased risk of low back pain.
What is interesting is that the absolute strength of the hip abductor or extensor muscles did not seem to have an impact. However, the percentage difference between the extensor strength on the left side versus the right side did.
This study also highlights one of the drawbacks of prospective studies: although they are significantly better at prediction, researchers need to conduct a very large study for a very long time to get enough results to provide statistically significant evidence.
Further studies required to generalize
Why does hip extensor weakness and imbalance appear to be linked to low back pain, and why does this only seem to be the case in women?
This is a tough question to answer, because the biomechanics of the issue are not obvious.
In studies looking at hip strength and knee injuries in runners, there was a clear connection between the biomechanical problem (inward rotation at the knee) and the muscular cause (weakness and poor coordination in the external rotators and abductors at the hip).
This is not the case when it comes to low back pain.
There is a lot more work to be done on this area: larger, longer-term prospective studies are needed to sort out the specifics on hip extensor weakness or imbalance in low back pain in athletes. Careful biomechanical analysis is also needed to determine why hip muscle imbalance could result in a back injury.
Even though it is likely to take some time until that research comes in, female runners with low back pain should assess to see if hip extensor imbalance is contributing to injury susceptibility. If you are at the point where you have exhausted other options, this may be something that you chose to look into.
If hip muscle imbalance and back pain follow the same pattern as hip muscle weakness and knee injuries, it should be possible to improve or eliminate the problem with a well-designed hip strength program.
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