You’re running along your favorite path and then it happens: You get a cramp in your hamstring. While theories abound, there is limited consensus on why exercise-associated muscle cramps (EAMC) develop and how to get rid of them. A research review from the Brooks College of Health at the University of North Florida may clear up the confusion.
The review, published in Muscle & Nerve (2016; 54, 177–85), featured a series of studies analyzing the etiology and treatment of EAMC. Here’s what they learned:
Etiology. The most widely held beliefs for why people develop cramps are (a) dehydration and electrolyte imbalance and (b) altered neuromuscular control. According to the review, the science favors the latter.
Lead researcher Nicole Nelson, MSH, LMT, explains why this might be the case: “In a non-cramped state, there is a balance [between the] activity of muscle spindles (which are excitatory mechanoreceptors) [and the activity of] golgi tendon organs (GTOs) (which are inhibitory mechanoreceptors). Muscular overload or fatigue, and likely other factors, causes an imbalance in the activity of these local receptors, where there is an increase in the excitatory spindles and a suppression of the inhibitory GTOs. The result is an overall increase in alpha motor neuron activity, which ultimately produces a cramp.”
Risk factors. There are a variety of hypotheses as to why people might experience EAMC. Possibilities include age, body size, exercise intensity and duration, previous or current injury, gender, family history, genetics, and history of EAMC. The researchers determined that the strongest risk factors are history of EAMC, male gender, and prolonged and relatively vigorous endurance exercise.
Nelson suggests that cramps may affect men more than women because men possess more fast-twitch muscle fibers, which fatigue more quickly than slow-twitch fibers. Also, women oxidize more fat and less carbohydrate than men, which may make them less prone to overload compared with men. These are merely theories, as gender-related EAMC mechanisms are not fully understood, she adds.
Treatment. Finally, the researchers scoured reports on common treatment practices, including electrical cramp induction, kinesiotaping and compression garments, massage therapy, electrolyte supplementation and hydration, corrective exercise, stretching, quinine, pickle juice and hyperventilation strategies. Of the remedies, stretching seemed to offer the greatest relief.
“Though the cause of EAMC is still a bit elusive, recent evidence does suggest that muscular overload is a factor,” Nelson concludes. “As such, prevention of EAMC should attempt to offset muscular overload and fatigue. Empirical evidence is still scant, but promising and plausible strategies might include managing soft tissue quality (e.g., foam rolling or massage), scheduling adequate rest, and placing a special emphasis on muscular balance in resistance training. Stretching still appears to be the best treatment for an acute bout of EAMC.”