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🏥 Gotokuji Orthopedic Clinic / Patient Guide

Calf Muscle Cramp

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Why your calf cramps at night and how to prevent it

A calf cramp is when the calf muscle suddenly tightens and spasms, causing intense pain.
It often happens during sleep at night, waking you up with sharp pain.
Muscle fatigue, shifts in mineral and fluid balance, and sleeping posture are all thought to play a part, but the exact mechanism is still not fully understood.

1
Muscle fatigue builds up

Long hours of standing or exercise leave the calf muscles tired

2
Mineral and fluid balance is disrupted

Low magnesium or potassium and dehydration have been suggested as contributors, but no clear link with night-time cramps has been proven

3
Sleeping posture and reduced blood flow

During sleep the toes tend to point downward, keeping the calf in a shortened position, and this is thought to act as a trigger

4
The muscle suddenly spasms

These factors combine and the calf muscle contracts unexpectedly

🧍 Standing for long hours 💧 Dehydration 🏃 After intense exercise 🍺 Alcohol (age 60+)
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Gently pull your toes toward you to stretch the calf
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Do an Achilles tendon stretch
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Apply a warm towel to the muscle
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Take Shakuyaku-kanzo-to (herbal medicine) if it has been prescribed to you (response varies from person to person)
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Stay Hydrated
Drink water regularly throughout the day
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Get Your Minerals
Get magnesium, potassium, and calcium from your diet
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Stretch Before Bed
Make calf stretching and massage a nightly habit
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Warm Bath
Soak in a bath to improve blood circulation
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Shakuyaku-kanzo-to (As Needed)
The package insert directs it to be taken before or between meals (on an empty stomach). Response varies from person to person. It must not be used by anyone with aldosteronism, myopathy, or low blood potassium
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Moderate Exercise
Walking and calf raises help maintain muscle strength
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Preventive habits can be expected to reduce how often cramps occur

By making hydration, mineral intake, and bedtime stretching a routine, you can expect the frequency of cramps to go down. If cramps happen often, there may be an underlying condition, so consult a doctor.

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Frequent cramps may be a sign of another condition.
If cramps happen several times a week, conditions such as diabetes, lumbar spinal stenosis, thyroid disorders, or peripheral vascular disease may be the cause. Also, the licorice (kanzo) in Shakuyaku-kanzo-to can cause pseudoaldosteronism (low potassium, raised blood pressure, swelling, and heaviness or weakness in the arms and legs). It becomes more likely with long-term use, but it can also occur with small doses taken for a short period, so use only the minimum needed and tell your doctor or pharmacist if you notice swelling, rising blood pressure, or weakness.

💡 Things to Remember

  • Alcohol has been linked to more frequent night-time cramps in people aged 60 and over, so be careful not to drink too much
  • Use Shakuyaku-kanzo-to only as needed; avoid long-term daily use
  • Maintain muscle strength with regular exercise
  • If cramps happen frequently, see an orthopedic doctor to find the cause