I was afraid this might happen someday: an experiment shows that both ice and heat are equally and minimally effective for low back pain

For many years I’ve held a complex position about ice and heat: see The Great Ice vs. Heat Confusion Debacle (soon to be revised). My position has been that heat is better than ice for most acute back and neck pain.

(The only clear exception is when the muscles are clearly inflamed after an obvious trauma. There’s still a fairly clear need for ice when tissue has been damaged. It’s just rarer than people think. This is one of the reasons this is such a surprisingly complicated subject.)

But a recent experiment at a busy emergency department has clearly shown that it probably doesn’t matter much which one you use: their effects are positive, but minor and equal.

This study was not powerful enough to rock my world and change everything, but the evidence is definitely compelling. If I follow my own rules, there’s no way I can avoid taking this seriously: a therapy has to have enough of an effect to impress me when it is tested.

But both ice and heat clearly failed the impress me test here, and so obviously I have to change my mind about something.

I kind of saw this coming

The benefits of ice have always been dubious and minimal because they almost certainly boil down to a reflex effect — because ice can’t really “reach” deep into the tissues to cool any inflammation (even if there’s any inflammation in need of cooling, which is probably much less common than generally supposed). Over the years, I’ve started to wonder if the benefits of heat were dubious and minimal for very similar reasons — also limited to reflex effects, which are probably real but probably trivial.

This experiment seems to confirm exactly that.

The test was simple: give some patients ice packs, and give other patients some heating pads, and see how they do. Just to level the playing field a little bit, everyone also got 400mg of ibuprofen (anti-inflammatory).

The researchers concluded that adding heat or cold to ibuprofen therapy did not change the result. Both heat and cold resulted in “mild yet similar improvement in the pain severity.” They recommend that the “choice of heat or cold therapy should be based on patient and practitioner preferences and availability.”

What gives?

I suspect that what’s going on here is yet another piece of evidence that it’s all about the nerves. The non-neurological effects of both heat and ice are probably barely there, because the body is just incredibly good at maintaining a nice comfortable internal temperature, no matter what you put on the skin. The only effect that either ice or heat can have is on the nervous system — alarming or relaxing, soothing or irritating — and that in turn is strongly determined by context and how we feel about it. And that’s the common denominator, the equalizer, the thing that makes both treatments mildly positive.

It can be said of either heat or ice: sometimes we like the idea, and sometimes we don’t. A person may think that a ice pack sounds just lovely — or they may think, “Ack, yuck, cold!” And the same with heat. It depends.

How we feel about heat or ice is affected by many rapidly changing variables. For example, if we’ve been waiting for an hour, inadequately dressed, in a chilly examination room at the emergency department, cold is much less likely to seem soothing. But, on the other hand, if a charismatic doctor warmly gives us an ice pack … et voila, now the cold pack seems a bit more like needful medicine, and we accept the discomfort as a necessary evil in service of a greater good for our screaming back.

In fact, I’ll bet you 100 bucks that cold packs magically “work” better when given to patients by doctors in hospitals than if they were prescribed by, say, belly dancers.

And so on.

This would explain why the ice/heat confusion is so great, and why the benefits of either treatment will average out to “modest.”

The risks of ice

There is one thing I’m not changing my mind about here: I still think that ice has the potential to do harm.

Despite the fact that this evidence strongly suggests that both ice and heat are routinely mildly helpful, over the years I have seen many nasty-ish reactions to icing, particularly in the back, particularly when the patient is feeling anxious and vulnerable, particularly when the patient would rather be heated but is given ice for their own good.

Giving ice to patients in hospital emergency rooms is probably quite safe, and I suspect you could study icing in that context in hundreds of patients before seeing a single case go badly, and even then it wouldn’t be very bad. But when a nervous patient who prefers heat is told by a manual therapist that they must go home and ice … things are lot more likely to go sideways. I cannot tell you how many times I have had conversations like this:

PATIENT: My physiotherapist told me to ice, and it’s horrible. My back just seizes up every time!

ME: Why are you still doing it?

PATIENT: He told me I had to.

ME: Would you prefer heat?

PATIENT: Yes!

ME: You have my permission to use heat, if that’s what sounds nicer to you.

PATIENT: Oh thank you thank you thank you!

You could almost turn that conversation inside and out, and make it about a patient who was told to heat but wishes that she could have used ice, but there is one key difference: unwanted ice tends to cause a nastier reactions than unwanted heat. Unwanted heat is irritating but doesn’t tend to cause muscle contraction and pain. Ice does. And that’s directly relevant to neck and back pain. Ice is somewhat riskier simply because it tends to have a stronger negative effect on patients who don’t want to be iced.

And that’s why I will continue to tell people to err on the side of heat.