Why do Muscles Spasm? – Information from Rowlands Castle Physiotherapy Clinic

Jan 17, 2023

What is it?

Muscle spasms occur when a skeletal muscle involuntarily contracts and does not relax, which is forceful and can be painful. They can involve part or all of a muscle, or several muscles in a group. The condition normally resolves without intervention, however its beneficial to work out what caused the muscle to spasm. They are especially in older adults and athletes.

Why does it happen?

The exact cause is idiopathic, meaning that it is unknown. Spasms can be brought on during functional tasks that require increased effort that the muscle is prepared for; this can range from going from a sit to stand position to completing an endurance exercise.

There are two main theories, Dehydration:Electrolyte (water:salt) imbalance and Altered Neuromuscular Control. Both can lead to premature fatigue, metabolic and heat accumulation, as a result muscle function and threshold will be compromised, it can tighten to tolerate demands and protect to form injury.

Dehydration/Electrolyte Imbalance

Water and electrolytes are vital in maintaining body function for example fluid balance in cells, nerve conduction, and muscle contraction. In the UK, guidance is to drink 6-8 glasses of fluid per day (1.2 litres). Physical activity can increase these requirements to maintain hydration, because fluid and electrolytes are the main components in sweat.

Altered Neuromuscular Control

When we are tired we don’t function as well. When there’s a muscle fatigued, its ability to regulate length (Stretch) and tone (Contraction) is compromised, the level of fatigue is unique to each individual.

Receptors in muscles are stimulated by stretching or contracting movements, this is regulated by the central nervous system. Muscle contraction receptors can be ‘over firing’ compared to the stretch receptors which can lead to spasm. This is why you will often see people trying to stretch the muscle to help counter-act the contraction. Spasms are also common after a neurological injury, such as a stroke or head injury.

Risk Factors

  • High intensity exercise
  • Long duration exercise
  • Dehydration
  • Older age population
  • High BMI
  • Irregular stretching habit
  • Poor muscle strength
  • Hot weather
  • Underlying chronic issue
  • Stress
  • Restricted blood supply


  • Hydrate – avoid coffee and alcohol
  • Contrast therapy – apply hot or cold to the muscle
  • Gentle massage to encourage the tissue to calm down
  • Gentle mobility – keep moving and walking as much as can be tolerated
  • Gentle Stretching to counteract the contraction
  • Vitamin B12 complex is believed to help relieve symptoms

When to seek treatment

If muscle spasms are happening frequently, last for a long time and are intense it is important to see advice and treatment to understand the underlying cause. A soft tissue massage will provide pain relief helping to mobilise the tissue, increased muscle blood flow and removal of toxins.

Immediately seek treatment if you are experiencing:


  • Significant pain
  • Swelling or numbness
  • Changes to the skin
  • If they are disturbing sleep
  • Fluid abnormalities

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