Aching, Stinging, Cold — These Are All Different Words

"It throbs." "It stings." "It feels cold." "It feels like something crawling."

The words people use for what hurts, in the consulting room, are remarkably various. I do not write these down in words of my own. I write them down as they are said. There is a reason.

There is no sensor dedicated to "throbbing"

There are not as many sensors fitted to the body as there are kinds of feeling. What the body actually notices comes down to a few strands — being pressed and stretched, temperature, the surroundings tilting toward acid, and damage signals.

Yet dozens of words come out. Where that difference arises is the centre of this story.

It resembles the way we see colour

The devices in the eye that notice colour are of only three kinds. Yet we see millions of colours.

It is because the proportion in which those three are switched on is what makes the colour. There is no device dedicated to orange.

Sensation is the same. Which sensors have switched on together, and in what proportion — the feeling comes out of that. So a few strands of sensor give dozens of words.

Arrangement plays a part as well. Lay warm and cool side by side, alternating, against the skin, and a burning pain arises. Nothing hot has touched at all. The same stimulus becomes a different feeling depending on how it is arranged.

Throbbing is not the feeling of your pulse

When someone says "it throbs," we generally take it they are feeling the pulse beat. I thought so too.

There is a study that actually measured this, and it is not so. The rate of the throbbing was about forty-four a minute, while the pulse at the same moment was about seventy-three a minute. The two rhythms ran separately.

So throbbing is a rhythm made inside the body, not one that came in from outside. What sets that rhythm has not yet been worked out.

Sleeping sensors can wake up

There are a good many sensors that do not respond to movement in ordinary times. They lie quietly asleep.

But when inflammatory substances pool at that place, these sensors wake. Then they begin sending signals even at ordinary movement that would have been nothing before. In joints this was recorded directly in animal experiments, and in people the same kind has been confirmed in the skin.

That a movement which was fine yesterday hurts from today may be not because the joint has suddenly broken down but because a sleeping sensor has woken.

The ache of an overworked place is one of these too

Earlier I mentioned the sensor that knows the surroundings tilting toward acid.

When a muscle works for a long time, the environment around it tilts a little toward acid. The body reads that tilt and notices that this place is straining now.

The feeling that comes when this sensor switches on is not a piercing pain but a heavy, dull ache. The way the calves ache the day after a long climb of stairs is close to this.

So I listen to the words as they are

"It aches dully" and "it feels like an electric jab" are words made by different combinations.

To me, "it aches dully" reads as this place has worked long and the clearing-up is not finished yet, while "it jabs" makes me look somewhere else entirely. "It feels cold" and "it feels like something crawling" each point somewhere different again.

So I write down what is said without tidying it up. Write both down as "pain" and that clue is erased.

Where this story continues

That pain is not a ruler measuring the size of the damage but a device switched on separately I have written down in The Swelling Has Gone Down, but It Still Feels Stiff.

That the place that hurts is not necessarily the place of the trouble is in When Treating the Painful Place Does Not Heal It.

When to see a doctor first

If there is a distinct patch where sensation has dulled, if strength drops away, if it comes suddenly on one side only, or if it has continued since an injury — before a story like this, examination and testing come first.

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Sources

• A study measuring and confirming that the rate of throbbing and the actual arterial pulse do not match — The Journal of Neuroscience, 2012
• A review setting out, by comparison with colour vision, that sensation comes not from single sensors but from the combination and proportion of several — Journal of Clinical Investigation, 2010
• A review setting out that pain sensors ordinarily lying asleep wake up in inflammation — Frontiers in Molecular Neuroscience, 2017

Written by Dr. Heo Ji-young (Ph.D. in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)