See, when it starts to fall apart,
man it really falls apart
Like boots or hearts oh when they start,
they really fall apart.
~ “Boots Or Hearts,” The Tragically Hip
If you’re recovering from a injury, I have some good news and some bad news. The bad news is that there’s probably nothing you can do to rush it. There are whole industries devoted to selling the hope of accelerated recovery, but few examples of it actually working.
So what’s the good news? Healing works amazingly well without much help. The prognosis for most painful problems is good. In fact, as things get better, you can usually count on getting better faster. You can’t rush it, but healing speeds up on its own.
In fact, this is exactly why many products and therapies promising to accelerate healing seem to work: because they are often applied right around the time that healing is picking up speed anyway.1
Positive feedback: the good, the bad, and the ugly
“Positive feedback” is usually negative. It’s what causes public address systems to squeal. It powers public hysterias and riots. It’s how droughts get worse. Positive feedback is a vicious cycle:
The worse something gets, the faster it gets worse.2
But there are several positive feedback loops in biology that are actually positive.
- Blood clotting uses positive feedback: platelets attract more platelets which attract more platelets, and so on.
- And two more of the best examples concern the reproductive system: both childbirth and orgasm involve runaway positive feedback cycles. These cycles aren’t so much vicious as they are necessary and happy cycles!
And there’s another kind of happy positive feedback cycle: the positive feedback loop that usually occurs in the later stages of healing from injury and pain problems.
Positive feedback in healing and recovery
Poor health is often defined by a downward spiral, like the way a broken hip late in life often leads to rapidly declining vitality. But if it’s not a downward spiral, it’s an upward spiral: if healing progresses, it tends to produce positive feedback. Its progress improves conditions for more progress. Healing accelerates. Examples:
- As swelling goes down, it becomes faster for oxygen and nutrients to diffuse through tissue fluids from capillaries to the cells they feed.
- As more movement becomes possible, the stimulation facilitates recovery, which makes more movement possible … and so on.
- As scar tissue forms and tissue stabilizes, more stress on the tissue becomes possible, which results in quicker formation of more organized scar tissue.
There are many such examples, and they really add up. Here’s a trickier one …
Pain and sensitization (when it’s working properly)
Pain tends to cause more pain: that is, the experience of pain often sensitizes us, so that we experience more pain too easily. That’s a positive feedback cycle that’s particularly vicious. Sensitization can be an awful trap.
Fortunately, most positive feedback cycles fizzle out. The sensitization process, when it does occur, usually reverses itself in normal healing.
Pain is often weirdly out of proportion to injury at first — think about stubbed toes — but as we recover the nervous system reduces the alarm and stops “warning” us about injured tissue long before it’s actually done healing. The alarm stops because the brain is confident that there’s no danger. And so pain reduction usually speeds ahead of tissue recovery.
And what if the delicious cycle doesn’t happen?
Where’s my upward spiral?! Obviously, healing doesn’t always go well and accelerate! This website is mostly devoted to problems to injuries that don’t heal, to pain that keeps going on (and on and on). If most healing accelerates, then what’s going on when an eight-month old injury is still driving you nuts?
Strictly speaking, it’s probably not an “injury” — maybe never was, or it changed.
We can assume that a garden variety injury should heal steadily and then quickly, if given half a chance. If that does not happen, it’s valuable diagnostic information — something is not what it seems. You’re probably not just dealing with simple damaged tissue any more. So what are the other possibilities? In broad strokes:
- It may be an injury that cannot heal because, like picking at a scab, it is constantly reinjured. This is basically what’s going on with stubborn cases of repetitive strain injury.
- It may never have been an “injury” in the first place. For instance, there may be a progressive or self-sustaining medical problem, like a benign cyst growing in an uncomfortable place. There are countless possibilities.
- It may have started as an injury, but it has been replaced by a new problem, such as muscle pain or persistent sensitization.
When “injuries” don’t involve traumatized tissue, per se
People often think they are “injured” when they aren’t. The classic example is back pain: its bark is worse than its bite. People are often convinced that they have damaged their back when there’s no detectable tissue trauma or lesion of any kind.3 It’s one of the most studied phenomena in all of chronic pain science.
Another example: the condition of frozen shoulder often begins with painful limitation of shoulder movement, and patients often assume that they have wounded themselves somehow. But this condition is more like a passing wave of disease than an injury: a strange seizing up of the shoulder joint that is biological in character, not traumatic.
Muscle pain can develop with ferocious speed. The victim assumes that they’ve damaged something, but the most meticulous investigation would never reveal anything but soft tissue that’s extremely sensitive to pressure: the phenomenon known as “trigger points.”
Out of the frying pan, into the fire
Tissue heals, but pain is another matter. Pain is weird. In theory, pain should fade as injuries heal. In practice, pain often carries on long after tissue has healed.
The mechanism for this is probably the formation of trigger points and/or sensitization in the aftermath of injury. (It’s not clear that trigger points are distinct from sensitization. So-called muscle pain may just be a common manifestation of sensitization.4)
Trigger points again: The persistence may be due to subtle lesions in muscle tissue. These can also form in reaction to more obvious tissue trauma — and then they just take over, like very rude house guests that simply will not leave. It is surprising the degree to which trigger points can essentially replace the pain of injury, taking over the job of making you miserable even as the tissue otherwise recovers.
But the pain itself can go on the fritz, like a car alarm set off by the slightest vibration.
Sensitization: I mentioned it above as a normal part of healing. How it goes chronic is largely a mystery, but even surprisingly minor traumas can set it in motion, and of course stress and anxiety are likely factors, but perhaps many other medical factors as well. Sensitization is one of the main reasons that pain is not only weird, but sometimes a disease process in its own right: that is, you don’t have pain because of a problem, but rather your problem is that you have pain, full stop. See Pain is Weird: Pain science reveals a volatile, misleading sensation that is often more than just a symptom, and sometimes worse than whatever started it.
About Paul Ingraham
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
- Most problems eventually resolve on their own, often right around the same time we’re getting desperate and trying long-shot cures — the Darkest Before Dawn Effect. The snake oil gets the credit instead of natural healing. The natural acceleration of normal healing can exaggerate this effect quite a bit, if the timing is right. BACK TO TEXT
- More technically defined, from Wikipedia: “Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A.” BACK TO TEXT
- Brinjikji W, Luetmer PH, Comstock B, et al. Systematic Literature Review of Imaging Features of Spinal Degeneration in Asymptomatic Populations. AJNR Am J Neuroradiol. 2015 Apr;36(4):811–6. PubMed #25430861. ❐ PainSci #53872. ❐ “Imaging findings of spine degeneration are present in high proportions of asymptomatic individuals, increasing with age. Many imaging-based degenerative features are likely part of normal aging and unassociated with pain.” This is just one good sample of the science available on this theme. BACK TO TEXT
- People experience muscle pain and acutely sensitive spots in muscle tissue that we call “muscle knots.” What’s going on? The dominant theory is that a trigger point is basically an isolated spasm of a small patch of muscle tissue. Unfortunately, trigger point science is half-baked and controversial, and it’s not even clear that it’s a “muscle” problem. Meanwhile, people keep hurting, and massage — especially self-massage — is a safe, cheap, reasonable way to try to help. That’s why I have a large tutorial devoted to how to self-treat “trigger points” — whatever they really are. See Trigger Point Doubts: Do muscle knots exist? Exploring controversies about the existence and nature of so-called “trigger points” and myofascial pain syndrome. BACK TO TEXT