If you’ve been watching the Tour De France this week, you will have seen Frenchman Lilian Calmejane in his first TDF participation win stage 8 to Station De Rousses in the Jura mountains. But not before he almost lost the stage through cramps. Almost everyone can relate to Lilians anguish, especially if you have experienced the familiar sensation of a muscle cramp on a long hot ride or at the pointy end of a race! So why do we get cramps during exercise and what can we do about them?
The short answer is that we don’t have all the answers yet. As always at Cycle Physio we will take the scientific approach to try and help. What we DO know about exercise induced muscle cramps is:
1. Cramp is common in endurance sports (23% of iron man triathlon competitors and 14-41% of ultramarathon runners).
2. Cramp usually affects the major muscle groups doing all the work (calves, quads, hamstrings in cyclists and runners).
3. Cramp is a strong involuntary muscle contraction that causes pain and can leave your muscle feeling sore for days afterwards.
4. Cramps occur more frequently in hot weather, esp. at the start of the season.
5. Cramps are more likely to occur in athletes who have had them before or whose blood tests show signs of greater muscle damage (elevated serum CK levels) suggesting higher intensity efforts (Hoffman & Steumpfle 2015).
Scientists are still debating and investigating what causes cramps, more properly known as “exercise associated muscle cramps”. There are currently two main theories:
1. Altered neuromuscular control: exercising for longer and/or at higher intensities than you are accustomed to causes muscle damage and in some way triggers cramps.
2. Metabolic / electrolyte imbalance: excess loss of electrolytes in sweat along with dehydration causes cramps.
Dehydration and sweating have long been thought of as key causes of cramps, but the science behind this has conflicting results. Aside from the higher prevalence of cramps in hot weather, where did these ideas come from?
When you sweat, electrolytes are lost and the main electrolyte lost is sodium (ie regular table salt). The normal amount of salt loss in sweat varies between individuals (0.5 to 2.3g/l). This can equate to 2.5g -30g loss per day depending on duration, intensity of training / racing, the temperature and individual differences in the sodium content in sweat (Cage et al 1965). In America this has led to some recommendations regarding electrolyte replacement for athletes. The National Athletic Trainers Association recommends 0.3 – 0.7g/l sodium for your sports drink, and the American College Sports Medicine recommends a higher concentration of between 1.2 – 2.5g/l. Other high sodium supplements have been tried widely, most notably pickle juice (yep, that stuff pickles are stored in which happens to be high in sodium and fairly acidic).
Somewhat surprisingly, when sodium supplementation (via sports drinks, salt tablets or pickle juice) has been tested, there usually isn’t a change in blood sodium concentration. Despite this, pickle juice in relatively low doses has been shown to rapidly reduce cramps in one study and do so faster than water alone (Miller et al 2010). This same research group demonstrated that the relief from cramping occurs so fast (in about a minute) that there hasn’t been enough time for the salt in the stomach to be absorbed. The thought here is that the pickle juice stimulates a cardiovascular reflex when it hits the stomach that causes plasma (fluid) in the blood to shift out of the vessels to the gut to aid digestion, thus raising the relative sodium content which might alleviate cramp (ie supports the neuromuscular theory of cramp). This along with the finding that dehydration and sodium levels don’t appear to be different between ultramarathon runners who do and do not get cramps (Hoffman & Steumpfle 2015) suggests that the neuromuscular theory of cramp is the more likely cause of exercise induced cramps at the present time. Stay tuned, as this may change!
SO WHAT DOES THIS MEAN FOR ME?
1. Preventing cramp is the best treatment.
2. If you do cramp you can either try a shot of pickle juice (about 80-100ml) or a salt tablet, and stretch the muscle.
3. How do I prevent cramp:
Train for the distance and intensity of your event to minimize the “shock” to your system. A good coach can help you design an appropriate program. This should reduce the risk of neuromuscular causes of cramp.
Determine if you tend to lose lots of salt when you sweat (does your jersey show salt stains in summer?). If so you may need more sodium than average and will need to check that your dietary intake of salt is adequate.
Hydration: even if dehydration is not a completely proven cause of cramps, your performance will be loads better if you stay hydrated. What does this mean for a cyclist? It’s hard to offer precise instructions as temperature, humidity, wind, intensity of riding and so forth all affect fluid loss, but in winter one 750ml water bottle per hour, and two in summer, is a reasonable estimate when cycling. For juniors substitute “500ml” for “750ml”. One water and one electrolyte sports drink is a good combination to use. Focus on sports drinks where the main electrolyte is sodium (excessively high potassium can cause cardiac problems!).
Nutrition: anecdotally some athletes find magnesium supplementation helps, as can adequate dietary sodium content (e.g. using salt on your meals). Those who have seen “The Feed Zone Portables” cookbook by Thomas & Lim will notice that the homemade foods for eating on the bike all have some added salt for this reason. Again, even if the science is not foolproof for salt preventing cramp, being adequately “fuelled” for your ride certainly is proven to enhance performance.
Consider a professional bike fit. If your position excessively overloads your quads, for example, then you have a greater chance of developing muscle cramps.
If these tips don't work, consult a sports dietician or sports medicine doctor.