You're having a great race, feel phenomenal and like all the training has paid off. All of sudden, your legs start cramping. First it's just a tingle, something you can ignore, but then it escalates and feels as if a bulldog has clamped its jowls down on your quadriceps. There's no denying it now: You're either dehydrated, electrolyte depleted or both. And so the game of catch-up ensues. First you slug water, then a sports drink, then you eat the two remaining gels in your pocket. Your run slows to walk, then a limp, and next you're slumped over, massaging your screaming muscles. Your competition flies by you, saying, "Hey, are you doing OK? Need anything?"
Later that night, after you've congratulated your friend (who took your spot on the podium) you review your pre-race and race nutrition. It all seemed go as planned: You hydrated that morning before the start, consumed your usual pre-race meal at the prescribed time, set your heart rate monitor to beep every 20 minutes to drink a pre-determined amount of your favorite sports drink and slurp down a gel.
More: Runners and Electrolytes: When to Replace Them
So what happened, what's missing? It might just be magnesium.
Magnesium 101: The Undervalued Electrolyte
Magnesium? Isn't that something mined from the ground? It's also a mineral found in the human body that regulates so many biochemical reactions it causes the head to spin. More than 300 enzyme systems in your body are dependent on an adequate level of magnesium; the most important of these govern athletic performance and include the function of muscles and nerves, blood sugar control via glycolysis and all-important cardiac function.
In other words, without magnesium, your muscles won't contract, your heart might not beat properly, and your blood sugar level will drop into the basement. The chemical that tells your hemoglobin to release oxygen to your working muscles, heart and brain is dependent on magnesium. It doesn't matter how high your hemoglobin is if you can't effectively access the oxygen that it's designed to deliver.