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What Are the True Causes of Cramps While Running?


  • Cramps do not occur as a result of the body lacking minerals or hydration. They occur because of over-contraction of muscles, overuse of muscles or lack of muscle strength.
  • Runners who experience cramp while competing tend to have over-trained in the three days prior to the event, whereas the correct way to prepare for competition is actually to reduce the training load and get plenty of rest before the day of competition.
  • When a cramp does occur, the fastest and most effective way you can relieve it is to stretch the affected muscle. This is because stretching the muscle will stimulate the muscle into preventing contractions, meaning the cramp will go away.


Many runners will have, at some point, thought about the causes of cramps, wondering whether or not cramps really do happen as a result of a lack of minerals or dehydration. Furthermore, this may let the same people question why, if a lack of minerals or water does cause cramp, do we not get cramp all over our body?

Before anything else, we must understand that so-called exercise-associated muscle cramp, or EAMC, relates to cramps that occur due to exercise. They differ from cramps associated with mineral deficiencies or dehydration, which can happen due to a number of factors, such as diarrhea, severe vomiting, pregnancy or the use of diuretic medication. Therefore, the dehydration experienced by athletes is dissimilar to EAMC in this regard.

To provide more clarity, please allow me to use examples from research into dehydration. Such research shows that dehydration is not associated with cramps occurring during exercise. For example, one study asked participants to cycle using only one leg until they were 3% dehydrated, at which point researchers used an electric current to stimulate cramp in the leg not being exercised (both before and after they had cycled to ensure that muscle fatigue was not at play). Another research assessed the effects of 5% dehydration – which is considered extremely severe – and both studies produced the same results, namely that severe dehydration is not a cause of cramping.

A simple way to observe this is to watch world-class long distance runners who hardly drink at all which competing. These athletes can actually suffer from over 5% dehydration by the time they have completed a marathon. Yet you don’t see them cramping up, do you?

As for the issue of mineral deficiencies, research has found that it does not have an effect on running cramps. Such research looked at information taken from ultra marathon runners who had their blood taken and their weight measured both before and after competition.

It was found that there were no changes in the various blood mineral levels, including sodium, potassium, calcium and magnesium. Moreover, this study also analyzed dehydration levels – before and after competition – in those who suffered from cramp and those who did not. Even when assessing information gathered from triathletes, the results did not differ at all.

If that’s the case, what are the actual causes of cramps that occur when running or exercising?

Researcher Dr. Martin Schwellnus presented a theory in his work titled “Altered Neuromuscular Control”, which came out in 1997 and is still viewed as the best explanation for the occurrence of exercise-associated cramps to this day. Additionally, this is the most highly rated theory among researchers and running enthusiasts who work in the field of research.

Altered neuromuscular control

The theory explains that contracting or flexing of muscles happens as a result of neurological signals which must maintain a balance. Cramps occur when there are too many signals sent to the muscles, causing them to tighten up completely. Thus, it can be said that cramp occurs due to the overuse of muscles or a lack of muscular strength.

Although altered neuromuscular control is just a theory which is awaiting supplementary data to provide additional proof, it can offer clear explanations for various types of cramps that occur.

Another interesting research piece asked participants to undergo stimulation of muscle cramping before drinking extremely sour pickle juice. It was found that the cramp subsided just a minute or so subsequent to them drinking the juice, meaning the body would definitely not have had enough time to absorb the minerals into the bloodstream.

This research helped to confirm that cramping is in no way associated with mineral deficiencies or dehydration, and that the sour taste of the pickle juice instead stimulated the body’s neurological system – stemming from the upper digestive system – into automatically stopping any muscle contractions.

So, what can be done to stop cramps occurring while running?

Let’s first take a look at the risk factors which can lead to cramp while running.


Research has found that groups who suffer from cramp tend to go out too quickly in the first half of their race, despite their training times being closer to those who do not suffer cramp. Hence, runners should be careful to pace themselves whether training or racing, while also being sure not to go out too quickly when racing.


Research has also found that runners who experience cramp while competing tend to have over-trained in the three days prior to the event. Truth is that the correct way to prepare for competition is to reduce the training load, avoid intense training sessions on the days leading up to the race, and get plenty of rest.

Muscle damage

From comparisons of creatine kinase levels (which is an effective measure of how much muscle damage has occurred) in the blood across two groups of runners, it was found that those in the group which had existing muscle injuries were more susceptible to cramp than those in the group without any existing muscle injuries.

At this point, please allow me to summarize the key factors at play when considering how to prevent exercise-associated cramp: Training is crucial because if sufficient running is not undertaken, and you still try to achieve a quick time on race day, this will mean that your muscles will be overworked to a point greater than for which your body is prepared. Therefore, regular training is the best form of cramp prevention as no matter how much water or minerals you take on, if you haven’t trained enough, the risks of cramp are significantly increased (except in cases where runners walk, sip water and take on mineral solutions continuously because this will mean that the legs are not overworked as they would be when running for the whole duration of a race).

Nevertheless, if a cramp does occur, the fastest and most effective way you can relieve it is to stretch the affected muscle. This is because stretching the muscle will stimulate those muscles into preventing contractions, meaning that the cramp will go away. That being said, if a medical team is close by, massaging the affected muscles with ice or a cooling spray is also a highly effective form of treatment.

Cramp prevention

The following techniques are a summary of the ways how we can prevent cramps while competing in running races:

  1. Train a sufficient amount for the distance you will be racing
  2. Build leg muscle strength, focusing on the calf muscles, quadriceps and hamstrings
  3. Pace your race carefully, making sure not to go out too quickly
  4. Taper your training in the days leading up to your race and don’t forget to get enough rest
  5. If you do experience cramp, stretch the affected muscles or massage them with ice to relieve the symptoms

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