Anyone cramp up out on the road during El Tour? Rattlesnake Pass – 20 miles out from the finish – tends to be my nemesis. As soon as I get up out of the saddle to get over the top, my legs revolt with intense muscle spasms. I fueled early and frequently, electrolyte tabs, shot blocks… so what’s going on?
Well, let’s consider the intensity and duration factors –
Cramps are most common when you use your muscles beyond their accustomed limit (either for a longer than normal duration or at a higher than normal level of intensity) – which explains why cramps are more common at the end of a long or particularly strenuous ride. In fact cramps are among the most frequent complaint in marathon participants (18% in one study), and of cyclists competing in a 100-mile event (70% of male and 30% of female participants experienced cramps).

Early research suggests that muscle cramps are brought on by disturbances in electrolyte and fluid imbalance, associated with heavy sweating. Although this may be the entire story as individuals involved in activities requiring sustained contraction of muscle without sweating (musicians for example) will also experience cramping. The pain appears to be brought on by continuous, intense, active contraction of the muscle cells and study of the neurophysiology of muscle cramping gives us the best insight into why we cramp during strenuous bouts of long duration exercise.

Disturbances at various levels of the central and peripheral nervous system and skeletal muscle that involve sustained motor neuron activity appears to cause a lack of control of the muscle spindles and golgi tendon organs. Muscle fatigue causes an abnormal neuromuscular response by disrupting the balance between neural input and feedback causing too much excitation of the muscle and not enough inhibition. Without this balance, a single contraction can become hyper-excited (loose it’s ability to relax and veer out of control) leading to cramping.

Here are the four factors to consider in the prevention of muscle cramps:

training – training to the level (durations and intensity) of the anticipated activity will decrease the possibility of cramps

dehydration – the second most common cause of muscle cramps after exerting beyond your training is hydration

electrolyte replacement -A sports drink, with adequate ratios of electrolytes and glucose might help, but it is likely that maintaining adequate hydration is more important than the small amount of electrolytes they contain. The role of other micronutrients and vitamins are still inconclusive. In a recent review, it was suggested that magnesium might be the most important of the electrolytes (after hydration was attended to).

muscle glycogen reserves – replenishment of ATP is important for proper muscle cell functioning with adequate caloric intake needed to achieve optimal physical performance. However the role of adequate glycogen reserves in preventing muscle cramps is speculative.