Understanding Cramp

Over the past 6 years I’ve competed in the Mighty Deerstalker with some family member. The Deerstalker, for those of you that aren’t aware, is a 10 mile night time cross-country race. Every year towards the end of the race, as I’m pushing to beat my rivals, cramp sets in. The calves and the hamstrings are the prime candidates to go – the pain is intense but with a little bit of stretching and walking it passes. However, the final mile tends to be a real struggle as the cramp affects my movement, ability to maintain a good running pace and the harder I push the more the cramp returns.

So what should I do to try and prevent cramp? Eat a banana? Try to maintain hydration levels? Stretch more regularly?

Well firstly, we need to understand the mechanism and causation of muscular cramps. The problem is that scientists actually don’t know for definite what causes cramps but some theories do exist. With that being said it’s important to remember that these are theories not facts which may explain the causes of cramp.

What is cramp?

Cramp is a muscular spasm which can be onset through exercise – these cramps are termed as Exercise-Associated Muscular Cramps or EAMC. The muscle contracts and then fails to relax which leaves the muscle in a contracted state. The cramp will often causes intense pain and leaves the muscle extremely tight.  In order to relax the muscle, the muscle often needs to be “manually” relaxed which is often done through stretching out the cramping muscle – a sight which can be often seen on the football pitch towards the end of the game. Cramps can also continue to occur even after exercise has ceased.



The Two Main Theories on Cramp Causation

1) Sweating / Electrolyte Depletion

Probably the most commonly stated theory when it comes to EAMC’s. The theory is that during strenuous exercise the body loses many electrolytes through sweat and this deficiency in electrolyte imbalance is what can onset EAMC’s.

What are electrolytes?

A substance which carries the ability to conduct electricity. Chemicals such as calcium, phosphate, potassium and sodium are examples of electrolytes in the human body.

What do electrolytes do?

Electrolytes are required for production of energy and maintenance of function of cells within the human body. Therefore, scientist theorise that a deficiency of electrolytes can negatively impact function and energy production from the cells and could potentially be the driving force behind EAMC’s.

The advice to eat a banana to stave off or reduce muscular cramp is based on this theory as a banana is packed full of potassium, magnesium and phosphorus (all essential electrolytes). Similarly, performance drinks such as Lucozade Sport market replenishing electrolytes in order to maintain or boost performance, once again this is based on this theory.

What has Science found?

There have been numerous studies that have supported this theories. For example, one such study found that the majority of cramping incidents in football occurred within the hottest months of the year (where sweating will be at it’s most profuse). However there are a couple of examples where cramp occurs and yet the individual may not be sweating profusely or in hot conditions. Exercise within a cold environment, where sweating is at a minimum, has been found to still bring on cramp in individuals.

Therefore, many researchers believe that exercise in a hot environment may indeed increase the likelihood of experiencing EAMC’s but may not be the causation of cramp.

Others have hypothesised that perhaps it is fluid imbalance (dehydration) rather than electrolyte imbalance that can onset EAMC’s however this theory lacks strength as if this were the case EAMC’s could be simply dealt with through rehydration. It has been found that keeping hydrated throughout strenuous does not cease muscular cramps from occurring.

It’s clear to see that this theory has certain limitations and lacks solid scientific evidence.


2) Neuromuscular Causes / Muscular Overload and Fatigue

This theory is based on changes in neuromuscular activity that occurs when muscular overload and fatigue begin to become a factor during exercise.

What is Neuromuscular Activity?

Neuromuscular Activity refers to the relationship between the body’s nervous system and the control of muscles.

How does Neuromuscular Activity alter during exercise?

The belief is that an imbalance occurs between impulses to contract (from muscle spindles) and impulses to resist relax (from the Golgi Tendon Organs (GTO’s).

Muscle spindles are sensory receptors found in the muscle that detect change in muscle length. GTO’s are found in the tendons (connective tissue connecting muscle to bone) which detect changes in muscle tension.

EAMC’s often occur in a muscles which are in a contracted state. Keeping this in mind, the theory suggests that a reduced tension in the tendon may reduce inhibitory feedback from GTO’s and cause an imbalance between inhibitory and excitatory drives (muscular relaxation and contraction) and therefore may leave a muscle in a contracted state when it should relax. In simpler terms, there is a “confusion” with the control of muscular contractions as result of muscular fatigue which can leave the muscle in a contracted state when it needs to relax.

What does Science found?

However, studies on Neuromuscular control and muscular cramp tends to have some inconsistencies and it is clear that not enough studies have been completed on human subjects. Many studies have used electrical impulses in order to onset muscular cramp which is incomparable to cramp that has been onset by muscular fatigue. One further issue is that fatigue is different for every individual and it is not apparent to how far an extent a muscle needs to fatigue before cramp occurs. This can make reliable and consistent testing on this theory difficult. However, evidence for this hypothesis seems to carry a little more weight than the electrolyte / deyhdration theory when it comes to explaining the causation of an EAMC.

It is clear that the underlying cause of cramp is not yet known for definite and more research needs to be done to attempt to establish the true cause of EAMC’s.


Reducing the risk and relieving cramp

If cramp hits, stretch the muscle as best you can. As mentioned previously, the muscle is in a contracted state and therefore must be “manually” relaxed. Massage has also been found to help relieve the cramp.

In terms of avoiding cramp, it is difficult to avoid without knowing the causation. However, avoiding extreme heat conditions will lessen the risk of experiencing cramp. In situations where this is not possible, stretching, maintaining hydration and electrolyte levels may not have a huge impact on the development of cramp but it certainly will not harm your chances.

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