Aching Like the Flu, the Morning After Drinking or a Bad Night's Sleep

There are days when the whole body feels stiff and sore like the flu, with no hint of a cold. The shoulders are tight, the calves cramp, the body feels heavy. There is no fever. Nothing strenuous happened.

Trace it back and the pattern is similar. There was drinking the night before, or a meal skipped for a long stretch, or a restless night's sleep.

I do not treat the muscle pain on days like this as a matter of muscle alone. On a day the metabolism has been shaken, muscle sometimes carries the cost.

When the Body Senses Danger, Muscle Tenses First

The body has a place that regulates its overall level of arousal: the reticular formation in the brainstem. Like a volume knob, it turns the body's wakefulness up or down. When it judges the situation to be dangerous, this is the place that raises arousal by a notch.

When arousal rises, muscle tension rises with it.

Inside muscle there is a sensor that measures its own length: the muscle spindle. When arousal rises, this sensor tightens first. Muscle then reads this as "I am being stretched," and it contracts reflexively. You did not consciously tense it. This is why trying hard to relax your shoulders often does not work.

So what makes the body sense danger? Blood pressure, body temperature, the concentration of body fluids, and blood sugar. Alongside these, stress, fatigue and overwork, and meals thrown off schedule belong on the same list. These are the conditions the body reads as "the current state is unstable."

This happens even when nothing has troubled your mind. A body whose blood sugar has dropped sharply, or a body short on water, is itself an emergency.

The Day After Drinking, Several of These at Once Are Shaken

A night with drinking touches several items on this list all at once.

Sleep grows shallow. Even if it feels like you fell asleep, the later stages of sleep are disrupted, so the recovery that should happen overnight falls short.

Water is lost. More water leaves as urine, and the concentration of body fluids shifts.

Blood sugar drops. During a fast, the liver makes new glucose to keep up supply, but with alcohol to clear first, that job gets pushed back. This is especially true on days you drank without food, or skipped dinner after drinking.

So the body the next morning is one where the mind rested but the body was on emergency footing all night. It is not strange for muscle to be stiff and sore. A restless night, or a day of working long hours while hungry, follows the same path — only the number of items shaken differs.

Stiff, Without Ever Consciously Tensing

Tension like this hurts to the touch. Pressing on the muscles around the skull in people with headaches hurts them clearly more than it does healthy people. Yet when you measure electrically (EMG) whether the muscle is actually contracting hard, it is often, surprisingly, quiet. One study measured this in the neck and head muscles of headache patients. Tenderness on pressure was clear, but electrical activity showed no difference from normal.

Rather than being knotted, what is present alongside it is a state of heightened sensitivity. The same amount of pressure feels more painful.

So there are days when simply kneading the sore muscle only helps for the moment. The condition that made the muscle tighten is still there.

I Look at That Day's Metabolism Together with the Muscle

When this kind of muscle pain recurs, I look at those recent days before I look at where it hurts. Meal intervals, drinking, sleep, water. I check whether the sore days cluster around days of going hungry and the days after drinking.

Once the condition is visible, what to work on becomes visible too. I release the muscle, but I also reduce the condition that made it tighten.

This touches on something Korean medicine has long attended to: not looking at the painful spot alone, but reading it together with how the person eats, sleeps, and drinks.

When Testing Comes First

If the whole body aches along with fever, check for infection first. If muscle pain is severe after intense exercise or heavy drinking and urine turns the color of cola, that needs checking the same day. Swelling and pain in only one calf is also not something to wait out.

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Flu-like aching without fever is, more often than not, a record the past few days left in the muscle.

So after asking where it hurts, I ask about those recent days. This follows the same path as asking about the time of day when the heart races and cold sweat breaks out.

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