Everything You Know About Muscle Cramps Might Be Wrong
It’s an athlete’s worst moment: A hammy seizes like an old engine down the homestretch to Olympic glory or in the middle of your rec hoops game. Suddenly, instead of chasing gold or bragging rights, you’re crumpled on the ground praying for deliverance. And it’s not uncommon: Research reveals exercise-associated muscle cramps affect up to 70 percent of endurance runners and cyclists. Who hasn’t experienced a cramp at some point while exercising hard?
You’d think science would have discovered a cure. After all, researchers have been studying cramps in industrial laborers ever since the early 1900s. In 1932, researchers from Harvard’s “fatigue laboratory” traveled to the construction site of the Hoover Dam to take samples from workers who developed cramps in the heat. They noticed that cramp sufferers had lower concentrations of salt in the blood and little to no salt in the urine. The scientists concluded, reasonably, that cramps were related to the loss of water and salt via sweat.
This idea, that cramps are caused by dehydration and an imbalance in electrolytes, persisted. Athletes were encouraged to down sports drinks, salt tablets, and/or bananas (a source of the electrolyte potassium) to relieve or prevent cramps. Trainers also began giving cramping athletes pickle juice—a brine of salt, vinegar, and water. It worked so quickly that scientists found it biologically confusing. “In our 2010 study, we had this weird phenomenon where cramps seemed go away faster when you drink pickle juice,” says Kevin C. Miller, Ph.D., ATC, a cramp researcher at Central Michigan University, “but there’s no change to the major electrolytes or blood.”
In 1997, a South African exercise researcher had put forth a theory about muscle cramps that explained the pickle-juice phenomenon: Two categories of neuroreceptors act as a kind of teeter-totter for your muscles—and they can get out of whack when you exercise too hard. “One side tells your nervous system, Relax, chill out. The other side, Hey, get excited,” Miller says. “When you become fatigued, there’s an imbalance in that teeter-totter towards the excitatory side.”
Miller now thought that something in the pickle juice—vinegar, maybe?—was initiating a neural reflex in the mouth that zipped down the spinal cord and calmed the overexcited teeter-totter. But people who had dedicated their careers to studying dehydration didn’t switch over easily.
It’s difficult to model muscle cramping in a lab, and people questioned the method Miller used, which involved shocking the big toe until it cramped. That’s not comparable to the cramps that occur after an athlete runs or cycles for hours, says exercise researcher Michael Bergeron, Ph.D. “For you to tell me that there’s no sodium issue because your blood sodium is normal tells me you have no idea what you’re talking about,” he says.
Nothing lights up academics like a pissing contest over a new theory. Experts quibbled over official sports-organization opinions, sent negative reviews of each other’s talks, and took potshots at each other in journals. On one side, you had people who believed Miller: It was a haywire neural process. Think of them as the neurological camp. On the other side, the dehydration camp, who felt that eliminating electrolyte imbalances from the cramp equation was a mistake. Further muddying the controversy was that a substantial portion of sports-nutrition research is funded by electrolyte-hydration brands. No one knew whom to believe.
Marketing to the anti-cramp rescue!
In 2016, the makers of a product called HotShot launched a 1.7–ounce beverage that tastes like getting punched in the face by a pack of Big Red gum. It’s only the latest in a long line of over-the-counter cramp remedies, including CrampX, Sportlegs, and various formulations of pickle juice. But HotShot inspired a scathing editorial in an academic journal and ignited the cramp blogosphere.
HotShot’s inventors were a pair of nerve and muscle scientists—Rod MacKinnon, M.D., who shared the Nobel Prize in chemistry in 2003, and Bruce Bean, Ph.D., a Harvard professor of neurobiology. The two scientists had been kayaking together for years, and after a fateful trip off Cape Cod when they both fell victim to forearm cramps, they came upon the neurological-function theory and Miller’s take on pickle juice and applied their own research to them.
Both Bean and Dr. MacKinnon are experts on ion channels, the chemical pores that make nerves and muscles work. They thought that if pickle juice was causing a calming reflex in the mouth and digestive system, it might act through a set of pores called TRP channels. Activating these would cause neural interference to run down the spinal cord to stop cramping in, say, your calf.
In their own kitchens, Bean and Dr. MacKinnon experimented with ingredients that would target TRP receptors—including extracts from ginger, cinnamon, and capsaicin (from hot peppers). They tested the resulting formulation on themselves and their families and then performed case studies using experimental models to induce cramps similar to the big-toe shocks Miller invented.
Before long, Dr. MacKinnon, Bean, and biotech entrepreneur Christoph Westphal, M.D., Ph.D., founded a company, Flex Pharma, that began marketing HotShot. In bold type, its website said that the theory tying cramps to dehydration and electrolyte imbalances was all wrong. The truth, according to HotShot, was that misfiring nerves caused cramping—and its treatment was proven to help.
Cramp experts prickled. “There’s a couple of conflicting theories; nobody knows which one is accurate,” says Shawn Kane, M.D., a neutral observer in the cramp wars and the editor-in-chief of Current Sports Medicine Reports. “For a company to say if you drink this, you won’t get a cramp—it’s not accurate. It’s based on a little glimmer of scientific knowledge, but then this company has taken it to the extreme.”
This hasn’t deterred the HotShot team. “We believe in our science and our claim of being scientifically proven,” says Matthew Wohl, HotShot’s current CEO. (Dr. Westphal and Dr. MacKinnon have left the company.) “We’ve done our own clinical studies proving efficacy, and [there was also] work that was done by Penn State, which was independent of us…We are firmly in the neurological camp.”
Finding smart solutions to muscle cramps
Corrine Malcolm, an ultrarunner with a degree in environmental physiology, says the dispute around HotShot represents a pervasive problem with sports supplements. She and some former colleagues at Simon Fraser University coined the term bioplausible to explain how ideas that “might work” get quickly promoted to “do work.”
In the case of HotShot, the theory was solid, but scientists on both sides of the debate worried about the distance between the claims and the data. While HotShot was raving about being “scientifically proven,” the studies the company used to market its product showed that cramps were reduced in strength and duration, says Miller. “Everybody still cramped. If HotShot works, shouldn’t nobody cramp? I mean, it’s silly.”
Strangely enough, scientists on opposing sides of the cramp debate have been coming together, just not toward a miracle cure. Many researchers now recognize that multiple factors can cause cramping, including over- or undertraining, sleep quality, nutrition or fluid imbalances, hot or cold weather, and even limited range of motion.
Bergeron (dehydration camp) says cramps generally fall into different categories, each with different causes and prevention. Miller (neurological camp) likes to think of it as a threshold. “Your recipe for cramping might be very different than my recipe,” he says. “Maybe I cramp when I don’t get a good night’s sleep or I don’t eat enough carbs. And I pushed myself a little bit harder. If I get all three of those things happening to me, I get a cramp. If I get two out of those three things, I don’t cramp.”
HotShot is an official supplier of the USA Cycling team, and they now hope Olympic riders will use it before an event to prevent cramps and mentally pump themselves up. If that reduces pre-race anxiety, it might even help prevent cramps, too. Win, win.
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