Muscle cramps during exercise are an annoying issue for cyclists that are often treated by taking supplements like magnesium or changing hydration practices. However, the evidence over the last 15 years shows that hydration and electrolyte imbalance are not associated with cramping. This article will explore the evidence behind this controversial topic.
What are exercise associated muscle cramps? (EAMC) They are best defined as painful, spasmodic, involuntary contractions of skeletal muscle that occur during, immediately after, or within 24 hours after muscular exercise. Most are localised to a single limb or muscle group and stop when exercise ceases. Up to 60% of cyclists and up to 78% of tri-athletes suffer from EAMC in their lifetime. Be aware that severe cramps that occur in many muscle groups, ie in both arms and both legs, or cramps that are associated with confusion, dizziness, collapse, nausea, vomiting or dark urine are of concern and require urgent medical attention.
When people ask what causes cramps, it is important to look at the evidence. Repeated studies in the British Journal of Sports Medicine by South African Professor Martin Schwellnus identify that there is no evidence that athletes suffering EAMC are more dehydrated than controls or there is any association between serum electrolyte disturbance and EAMC http://bjsm.bmj.com/content/43/6/401. While there is no one absolute cause of EAMC, it is now thought that neuromuscular fatigue is the driving factor in the onset of cramps.
In simple terms, if you push yourself beyond your body’s neuromuscular capacity, cramping can occur. Neuromuscular fatigue sets in when your body is unaccustomed to the load you are pushing yourself through, for example when your body is used to cycling 50kms in training and then you increase that to 100kms without gradually increase your load over time. Rapid increases in intensity carry a similar risk of cramping.
Training and preparing for events helps decrease the risk of cramping in a big event. As a rule, increasing your load gradually, ie by a max of 10% a week, decreases your risks of injury. Adjuncts such as pickle juice and hot shots can take away cramps but don’t treat the cause. Other medications such as quinine and magnesium have been shown to not only be ineffective but also have side effects that are undesirable in competitive athletes.
In summary, EAMC are most likely a sign that the exercise you are doing is exceeding your body’s neuromuscular capacity. They can be prevented for by being well trained but they are not associated with serum electrolyte imbalance or dehydration as previously thought. However, if the cramps are severe, occurring outside of exercise or are affecting more than one limb, it is important to seek medical advice because they may be caused by something other than exercise!