STUDY: Exercise eases inflammatory back pain—but why?

We already know for sure that exercise is good medicine for systemic inflammation over the long term. For instance, Klasson 2022 is a good trial that linked long-term daily physical activity to reductions in major biomarkers for inflammation.

We do not know for sure that faster and more specific benefits are possible … but they might be. Last week I made the case that exercise is a short term treatment for the much more localized inflammation of musculoskeletal injuries like tendinitis.

What about for pathological inflammation? Like autoimmune disease? Is exercise anti-inflammatory enough for that challenge? We have new evidence that it is.

Cheezy stock photography I wouldn’t buy today, but I did once upon a time… might as well get some use out of it!

Today’s featured study, by Zhang et al, a Chinese team, is an encouraging scientific review of exercise for axial spondyloarthritis — inflammatory pathology of the spine. This is a whole category of related rheumatic diseases, but it’s mostly about inflammatory back pain and ankylosing spondylitis.

Nasty inflammatory conditions indeed. Although they usually develop slowly and don’t always get serious, this is one of your scarier causes of back pain. No explanation for back pain is definitely preferable to this explanation. I’ve mostly only ever written about them in the context of red flags for more serious back pain.

Zhang et al. reviewed twenty randomized controlled trials of exercise therapy for spondyloarthritis, including 1700 patients, looking at many different outcomes: four different scoring systems, oxygen consumption, and chest expansion (because spondyloarthritis often affects the ribcage), two major biomarkers (C-reactive protein and erythrocyte sedimentation rate), and, last but not least, the two most consistent symptoms of inflammation: pain and fatigue.

That’s ten outcomes, and seven of them improved, most of them quite a bit. That’s a fantastic result! Leading to this unstintingly positive conclusion:

“Exercise therapy is an effective strategy for improving disease control and symptom relief in axial spondyloarthritis.”

So what didn’t improve? Uh, this is awkward…

The two biomarkers for inflammation did not improve — unfortunately. (The other dud was “chest expansion,” likely because it’s a function of irreversible damage to the spine.)

These patients somehow seem to have gotten much better without a measurable anti-inflammatory effect. So what was going on here? How do you get substantial improvements in a disease that is really all about the inflammation … without, apparently, changing the inflammation?

I think the most likely explanation is that the inflammation actually did change — just not in a measurable way.

Justifying the result as “anti-inflammatory” despite unchanged biomarkers

All inflammation is a function of the immune system, but with mind-boggling variety. Immunity isn’t just “complex,” it’s “where intuition goes to die.” It makes rocket science look easy. Inflammation can be thoroughly weird and sneaky. So let’s not even pretend we can guess what “makes sense” here.

And CRP and ESR are rather blunt instruments, notoriously unreliable for diagnosis. Some spondyloarthritis patients never get high CRP/ESR in the first place! And yet no one really doubts that inflammation is still the wrecking ball of their disease. It’s probably possible to get an anti-inflammatory effect rolling without a clear effect on these biomarkers, especially in the short term. And most of these studies were relatively short term. CRP and ESR might well come down in time.

Of course, it is possible that exercise could work its magic on spondyloarthritis without an anti-inflammatory effect, and the lack of a change in CRP/ESR even in the aggregate does point that way. Exercise might protect us from inflammation rather than actually nuking it, for instance.

But we also already have many other evidence-based reasons to suspect that exercise is anti-inflammatory … and here we have a study showing robust benefits for truly serious inflammatory disease! So I don’t think the static CRP/ESR scores are any kind of a deal-breaker.

UPDATE: And then there's this! A fresh systematic review, showing that inflammatory biomarkers are in fact fact reduced by regular moderate exercise.