Avoiding muscle cramps

Muscle cramps can affect some athletes quite badly, leading to poor race performances and often preventing training sessions being completed to their full potential. They often occur during exercise sessions, but can also occur as nocturnal cramps. Nocturnal cramps are known to affect the elderly more often than the young, however many athletes get more than their fair share of them and this is because of the extra demands they place on their muscular system. I often get asked how it is possible to reduce the incidence of these cramps. It seems that a full understanding of muscle cramps has not yet been reached, however there are a number of possible explanations. 

Cramp caused by muscle fatigue

Cramps in the legs are common and in particular cramps of the calf and toes seem to beset endurance athletes. A very common scenario in my experience has been the athlete who has previously cycled or run quite hard, and who then attempts a swim session the same day, or even immediately afterwards. This athlete will often experience lower leg cramps. While a change in hydration or electrolyte status is possible what this type of cramp points to is a physiological change in the muscle due to muscle fatigue.

These types of cramps are caused by faulty neuronal signalling. Your central nervous system is being misled about the state of your lower leg by the sensory receptors in the muscle. The detection of how contracted your muscles are is determined by two types of sensory receptors. One type in the tendon and another type in the muscle.

  1. The golgi tendon organ (GTO) is situated at the insertion point of muscles into tendons. It is a receptor that signals to your brain how much force your muscles are generating. To correct over contraction they initiate muscle relaxation.
  2. The muscle spindle is a muscle based stretch receptor that tells your brain how well stretched your muscles are. To prevent over stretching they initiate contraction.

When your muscles become fatigued the tendon receptors are inhibited while the stretch receptors are activated. An inhibited tendon receptor fails to tell the muscle to relax, while and activated stretch receptor will initiate a contraction. This can lead to over correction and excessive contraction, or cramp1. Gentle stretching of the affected area is one way to overcome this. For a while at least you will need to avoid doing any of the movements that seem to trigger the cramp. For instance a swimmer may need to avoid tumble turning, pushing hard off the wall or may even need to use a pull bouy to prevent the calf cramping. Equally during cycling it may be necessary to avoid too much effort on certain gradients as this will trigger a cramp. Experiment with standing and seated climbing if cycling uphill. You may find that one position eases off the cramp more than another.

Cramp caused by lack of nutrients and minerals

Often listed as causes of cramp are dehydration, lack of circulation and lack of salts such as sodium, magnesium, calcium and potassium. What these all have in common is that they are involved either directly or indirectly in the contraction and relaxation cycle of the muscle fibres. Lets look at each in turn.

  • Lack of circulation and dehydration may be related as when blood volume is reduced, as is the case with dehydration, then oxygen transport to the muscle is decreased. This leads to a reduction in the production of the energy molecule ATP. ATP is needed by the muscle during its contraction cycle. The energy derived from ATP allows the muscle to either relax or to contract further. 
  • Sodium is required to allow the message to contract to pass from your central nervous system to your muscles. As sodium runs short it is possible that some fibres will not get the message to contract this could lead to confused messages being sent by the sensory receptors in the muscle, leading to cramp.
  • A lack of magnesium can cause problems as magnesium in combination with ATP is needed by the thick muscle filaments in order to release their grip on thin filaments2. In other words it allows the muscle to either relax or to contract further.
  • Calcium is the mineral that moves about in the muscle fibre in response to stimulation from the motor neurons that tell the muscle fibres to contract. By moving from the sarcoplasmic reticulum (think sac like container), into the vicinity of the myofibrils (filaments that contract), calcium primes the filaments to contract. 
  • A lack of potassium could cause problems as it is required to repolarise the outside of the muscle fibre so that it can continue to receive messages to contract. 

Possible solutions


In cases of cramp after extensive sweating, that involve more than one muscle group,  lack of salt in the bloodstream is a likely cause. Drinking a salt containing drink, formulated to match your salt losses should help in these cases. A lot of research in this area has been done by a UK based company Precision Hydration(3).


Magnesium is worth considering as there is good evidence that it can relieve muscle cramps. Magnesium works not just on skeletal muscle, but also the smooth muscle in your airways and intestines. As a result it can sometimes help with cases asthma and irritable bowel. Magnesium can be taken as a supplement of about 400mg per day or by eating more of the key food sources of magnesium. Nuts are one of the best sources.


Quinine is used to treat malaria and has also been found to reduce muscle cramps. It is clearly effective in this role. However it can have side effects in excess. Indian tonic water contains quinine as does bitter lemon. However the normal dose used medicinally for malaria is about 100 times greater than that in a large glass of tonic water. As such the use of indian tonic water, which contains quinine, should be safe enough. I have come across a number of people who think that tonic water has helped them reduce their incidence of cramps. If cramps are really severe, and don't respond to tonic water then there are pills that contain a lot more quinine. If you take these you need to discuss it with your doctor as quinine can cause serious side effects in a small number of people, especially those with pre-existing heart conditions(4).

Regular conditioning & stretching

To reduce the likelihood of cramping, strengthening the affected muscle is a good idea. So for a swimmer who regularly gets calf cramp try some calf raises to strengthen the calf. You could also try a PNF stretch.

PNF stretching involves repeatedly getting to the fully stretched position and then tensing the muscle for 10-20 seconds. Again the swimmer with cramp in the calf would sit and pull on their foot with a bent knee until it is at maximum stretch. Then push the hand away with the soles of the feet for 10-20 seconds and repeat the stretch. The stretch should then go further. Repeat this cycle, hopefully stretching a tiny bit more each time.

If you have just had a cramp, then static stretching is definitely worth a try. Stretch the affected muscle slowly to avoid possible muscle damage. Don't try to force it if it is hurting. 

Adequate hydration

Hydration is important if you want to avoid cramp. Including salts such as sodium, calcium and potassium in this mix should help also by reducing the risk of inadequate energy being available to the muscle and dodgy messages being sent from sensory receptors in the muscles. Sports drinks should help.


1) http://www.ncbi.nlm.nih.gov/pubmed/9232553

2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC427330/

3) http://www.myh2pro.com/index.htm

4. http://www.mhra.gov.uk/Safetyinformation/DrugSafetyUpdate/CON085085