What causes muscle cramps?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Muscle cramps can occur because of a lack of activity, dehydration or too much activity. Low levels of potassium, magnesium or calcium in the body may contribute to cramping. Overuse of the same muscle for long periods as in painting, gardening or sports activities can cause cramping, too.

The causes of muscle cramps (sudden and involuntary contraction of one or more of our muscles and are unable to fully relax) range from:

  1. Longer period of exercise, a long run or physical labor, particularly in hot and humid weather, can lead to cramps. It can occur during the activity or several hours later. That's why its very essential to stretch the muscles after the activity to prevent muscle cramps and increase optimal muscle functions.
  2. Dehydration/loss or lack of essential electrolytes (potassium, magnesium and calcium) and water, which can lead to muscle cramps and increased muscle fatigue. That's why its very essential to drink water before, during and after activity.
  3. Burning of protein for fuel in the absence of carbohydrate can also lead to cramps. Increased level of ammonia indicates that protein is being used for the muscles during exercise. A need for greater carbohydrates (hold more water) stores before and better replacement of those stores during intense and long-lasting activity (marathon running, playing football, etc).
Jay Morgan, NASM Elite Trainer
Fitness Specialist

Cramps that happen in the presence of a higher heat/humidity index and during physical activity are most commonly associated with hydration and electrolyte imbalances (salt, potassium, magnesium and calcium). When these nutrients fall to certain levels, the incidence of muscle spasms increases.

Athletes are usually the group associated with the above causes. Athletes are more prone to cramping during the pre-season of their sport. The lack of conditioning and improper nutrient uptake can act as catalysts for cramping.

There are many incidences of muscle cramping that are not associated with heat, humidity or exercise. These incidences are usually caused by overexertion, muscular fatigue and over-repetitive movement patterns (prolonged sitting, computer work, driving). Overexertion, fatigue and repetitive movements create an imbalance within the body. The imbalance leads to an increased demand on oxygen and nutrient uptake, which can lead to an increased buildup of waste products in the muscle. The waste products can cause the muscle to spasm.

Age also seems to play a factor as it relates to declines in muscle, resulting in the muscles not being able to function optimally. Therefore, actions that you performed in your earlier years may not be as well handled by the skeletal muscle system due to biological aging. Completing repetitive tasks during the day either during work or physical activity could cause eventual fatigue in the muscles being activated, which can lead to cramping as discussed previously.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.