Leg cramps can be excrutiating. And if you are an athlete, a cramp at a crucial time can cramp your performance. Just ask basketball star Lebron James or tennis player Madison Keys whose muscle cramps during her Wimbledon match with Simona Halep of Romania likely contributed to her loss. The prevailing wisdom is that cramps are caused by dehydration or by some sort of electrolyte imbalance brought on by exercise. And often drinking an “energy beverage” or eating a banana brings relief by supplying sodium and potassium.