Exercise Associated Muscle Cramps

It is fair to say that anyone who has experienced muscle cramps after prolonged and hard riding will agree that they are painful and best avoided. However the theory as to how this is achieved is not so clear. This blog will hopefully make matters somewhat clearer.


The first thing to say is that there are many reasons why a person can experience cramps. This document only covers cramps felt purely during exercise. If you are experiencing cramps at other time it may be best to explore other avenues than those stated below.


Exercise Associated Muscle Cramps (EAMC) commonly affect the muscles used during exercise. In cycling obviously these being the muscles of the legs. They are also more likely to affect muscles that cross over two joints. In the legs these are the Hamstrings, Calf and Quadriceps muscles. EAMC are usually felt in spasms that last between 1-3 minutes. It would also appear that some people are more prone to EAMC than others.


There are a number of theories as to why EAMC occur. I suspect that the truth is that there is not one single reason and that each of us may have slightly differing reasons. Scientific study has been undertaken into this subject. As ever, lots of study doesn’t necessarily lead to clarity but this is a summary of what is thought at present:


Dehydration and Electrolyte depletion


·      Dehydration

·      Low blood calcium

·      Low blood sodium (salt)

·      Low blood magnesium

·      High blood potassium


Although there is some evidence that dehydration and low blood sodium causes whole body cramps in some medically unwell people this has not been shown to be the case in athletes. EAMCs are not seen to be related to any of the above issues, specifically when people are studied and the amount of fatigue and the exercise intensity are taken into account. If you are fatigued and are exercising hard you may cramp irrespective of electrolyte changes or dehydration. This on the face of it would appear correct as changes in the makeup of the blood should effect the whole body and EAMCs only tend to effect the muscles that are being used.


Fatigue and Neuromuscular Control


Stay with me! This bit could be easy to skim over, but may just be the difference between cramping on a ride and not. There is a growing thought in the scientific community that EAMC may be more related to the mechanism by which your nervous system controls your muscles (neuromuscular control) and the effect that fatigue within the muscle has upon it.


It is thought that when muscles are asked to work repetitively a number of factors affect how fatigued that muscle gets. They are:


·      Increasing intensity

·      Increasing duration

·      Reducing energy stores in the muscles

·      Hot or humid conditions

·      Inadequate training/conditioning

·      Using the muscle in a shortened position


It is also thought that there may be a link with previous muscle injury and potentially a genetic link to the development of EAMCs.


It is then thought that all or some of these issues conspire to alter the way the nervous system can control the muscles, ultimately leading to the development of very painful muscle cramps. It is known that stretching the muscles is the best way of alleviating the cramp when it is present. However wouldn’t it be best to stop the cramps coming on in the first place?!


What can be done?


Some people will never know the pain of exercise associated muscle cramps and will never have to think about this. However here are a few pointers on what to try if you do suffer.


1.    Train to the intensity and duration that you intend to ride. I suspect that this is the single most important point.


2.    Ride to the level at which you’ve trained. If you surpass your training level I suspect points 3, 4 and 5 get more important.


3.    Make sure that you maintain your muscle energy stores. Training will improve your muscle energy storage and will make them more efficient. However consuming carbohydrates to replace the ones you have lost may reduce your chance of EAMCs.


4.    Before your ride make sure your have prepared with appropriate nutrition. Eat and drink plenty if you are going to ride long or hard.  


5.    Use your muscles in their optimum position. Although I would say that bike fit is certainly not on the front line of combatting EAMCs, sometimes an alteration in the position that you are using your muscles in can effects their efficiency and thus their tendency to fatigue. If you consistently get cramps in a particular leg muscle group then this may be something to think about. As you would imagine, Cycloform would be more than happy to help with this, although a good place to start is to change something and see if it changes your cramps. If it does, for better or worse, then your position may be a key component of why you are getting cramps. Raising or lowering your saddle is a simple place to start.


If you have any questions about anything that is written above please ask away. Thanks for reading.




More reading…

  • Braulick et al (2013) Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency. Br J Sports Med; 47:710-714
  • Schwellnus et al (2004) Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners. Br J Sports Med; 38:488-492
  • Scwellnus (2008) Cause of Exercise Associated Muscle Cramps (EAMC) - altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med43:401-408
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