Tingling and Cramps Are Not Only About Muscle

Behind the word "tingling" sit several different sensations. Some people describe it as feeling like someone else's flesh. Some say it is a sharp, prickling feeling. Some say it burns.

The word "cramping" is the same way.

Yet these several different sensations all arise from the same place. Inside the body, cold, heat, and pain travel close, shared pathways. The same is true of why holding something very cold for a long time can go past feeling chilled and start to burn as if you had been scalded.

Temperature and pain are handled by the same endings

The skin has small organs of its own that measure pressure and vibration. Each has its own name, and each measures only what it is assigned to measure.

But temperature and pain do not pass through those organs. The nerve ending itself senses it directly and sends it up, with no separate receptor in between. These endings are called free nerve endings. Itch and the sense of tickling are handled by the same endings.

Because one kind of ending is handling several different things at once, they can get confused with one another. Pain can be felt as heat or as cold, and pain and itch can trade places. What people describe as "tingling" often has some of this mixed in.

The mix-up can happen at the ending, or it can happen further in

This kind of error does not always occur at the nerve ending.

A sensory nerve passes through the place where its own cell body is gathered before it enters the spinal cord. This is called the dorsal root ganglion. But this is only a place where cell bodies gather — it is not a place where signals connect to one another.

The place where signals actually meet is further along, inside the spinal cord itself. Branches coming up from different places converge onto the same neuron. So something that started in one branch can come up as a sensation in a different branch. Pain that starts in the neck and spreads to be felt in the head is the same story.

And when the surroundings of a nerve ending have been altered for a long time, a tingling signal can fire without anyone touching anything. Since there is no stimulus coming in from outside, no matter how closely you examine that spot, the cause does not show itself easily.

Rubbing only the tingling spot brings only momentary relief

A nerve does not stay put in one place — it runs on as a long line. If one point along that line is compressed, it is not the compressed point but the entire stretch running downstream from it that tingles.

So rubbing only the hand because the hand tingles, or only the calf because the calf tingles, often does not settle it down. The spot where the tingling is felt may be where the signal arrived, not where it started.

This is also why points strung along a single line can tingle together. Some people describe not just a tingling fingertip but a tingling that runs continuously along the inside of the arm.

The condition of the receiving end adds to this as well. Even a signal of the same strength comes through larger if the threshold has dropped. Then the degree of compression stays the same, but the degree of tingling changes on its own.

There are sensations you are not even aware of

You know how bent your arm is right now even with your eyes closed. Position, vibration, touch, pressure — these are sensations you can feel if you pay attention to them. They are called deep sensation.

But within that category there is also something that rarely rises to consciousness. This is proprioception, which measures the length of a muscle and the force on a tendon. The muscle spindle inside the muscle and the Golgi tendon organ in the tendon handle this. Instead of rising to consciousness, this signal goes straight through reflexes at the spinal cord and brainstem to adjust movement directly.

Cramping sits in this territory. A muscle contracts without your having applied any force, and it will not release even when you try to pull out of it. Some of this is, of course, the muscle's own failure to release its contraction. But there is also a separate signal that tells that muscle when to tighten and when to let go.

Of these, the Golgi tendon organ works to release force. When a tendon stretches past a certain point, a danger signal is sent, and the force in the muscle attached to that tendon drops. This pathway is thought to be involved in why slowly stretching a cramping muscle brings it down.

Nerves also follow the conditions of where they sit

Not all sensory nerves pass through the same place. Some branches spread in a web-like pattern through the fascia. Fascia is made of loose connective tissue and fat, so a nerve sitting inside it is affected by the condition of that fat. And fat is connected to hormones and metabolism.

When the condition of the whole body changes, the place where that nerve sits changes along with it. This is part of why tingling is not always something that begins and ends in one spot, whether the hand or the calf.

When to get checked first

If sudden tingling appears in only one arm or leg, or comes together with slurred speech and weakness, move quickly. The same is true if sensation disappears entirely from the tingling spot, or if one leg swells and changes color.

---

When people say something tingles, or that they get cramps, they usually think of muscle first. They assume it is knotted and rub the spot.

Muscle does carry a real share of this. But the ending that sends the signal, the pathway the signal travels, and the condition of the receiving end are all present together. This is why it is hard to explain with the muscle layer alone.

And the tingling spot and the compressed spot can be apart from each other. If your hand tingles but nothing seems wrong with the hand itself, I also look at the pathway leading to that hand. When hands and feet tingle and cramp often but tests come back normal covered a different branch of this — electrolytes and breathing.

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