How does dehydration affect muscles?

Find out what happens to the muscles when you don’t drink enough water

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S.A.C. Dip (Diet, Exercise & Fitness), Advanced Human Anatomy & Physiology Level 3
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05 July 2021

How does dehydration affect muscles?

There are several ways that dehydration can affect your muscles. Firstly, poor hydration can worsen delayed onset muscle soreness (DOMs) after exercise. Dehydration and muscle cramps are also known to be closely linked. Two other muscle problems which can be made worse or caused by dehydration include muscle fatigue and muscle weakness.

4 ways dehydration affects muscles

Let's take a closer look at these ways and why dehydration can worsen or cause these problems:

1. Dehydration can worsen DOMS

Fluids can be lost through exercise, making it especially important that we drink extra water whilst doing any kind of movement. However, did you know that failing to keep your water intake up whilst exercising could also make DOMs (delayed onset muscle soreness) worse?

In research, people who exercised in hot and humid conditions without receiving proper hydration experienced more skeletal muscle damage (DOMs) than those who exercised in a cooler environment, yet still had their fluid levels restricted. So, this indicates that, when exercising in warm environments, rest and rehydration breaks are particularly important for the muscles. (1)

2. Dehydration and muscle cramps are closely linked

Dehydration can also affect the muscles by contributing to muscle cramps – painful contractions of the muscles. This problem is particularly apparent during or after exercise when we lose lots of fluids. Also, a build-up of lactic acid in the muscles during lots of exercise can cause cramp, which may worsen with the addition of dehydration.

However, that's not to say we should focus solely on drinking massive amounts of water at this time. In fact, research shows that muscle cramps could be made worse by drinking a lot of water around exercise as it dilutes levels of electrolytes in the body. This is significant, as electrolytes like magnesium and potassium are essential for normal muscle function. (2)

On top of this, cramps can be caused by a nutrient deficiency which is then worsened due to dehydration. So, whilst drinking water will rehydrate the body, it will not replace electrolytes lost through sweat. Instead, it is recommended that we drink plain water infused with electrolytes.

Balance Mineral Drink is one way to do this. It is a strawberry-flavoured powder containing magnesium, potassium, zinc, vitamin D and calcium which can be added to water to help you rehydrated, whilst also supporting the muscles.

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3. Dehydration may contribute to muscle weakness

When the body becomes dehydrated, it also loses lots of electrolytes such as sodium, potassium and chloride through sweat. One of the more surprising effects that this can have on the body is muscle weakness. This is because, as was mentioned previously, the muscles need these electrolytes to function efficiently. Magnesium, for one, is essential for the likes of muscle strength and function; plus, it can influence pain levels.

You may be prone to muscle weakness as a result of dehydration and electrolyte loss during times of illness (perhaps whilst experiencing a vomiting bug, for example), or if you regularly experience bouts of digestive distress, including diarrhoea.

4. Dehydration can lead to muscle fatigue

Staying properly hydrated is helpful for our energy levels. In fact, when you are feeling fatigued but aren't quite sure of the cause, it could be linked to dehydration, as this impedes healthy blood flow and affects the supply of oxygen and nutrients to the brain, leading to feelings of fatigue.

When this muscles themselves feel fatigued this is, once again, linked to the reduction in electrolyte levels that occurs with dehydration. Potassium and sodium, for example, help to support muscle contractions. When the body has low levels of these nutrients, these processes are hindered.

How can dehydration be prevented?

To keep your water intake up and prevent dehydration from affecting your muscles, here are a few tips you can try:

  • Put a 'water bladder' in your backpack when heading out for long walks or hikes.
  • Always have water to hand after exercise.
  • Try Balance Mineral Drink in some water to top up the body's electrolyte stores.
  • Eat fruit after exercise – this can top up your water intake, as well as providing some essential nutrients.
  • Avoid exercising in very hot or humid conditions.

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