Add sodium and Calcium to your intake. When I first ran triathlons I would cramp badly each race. There are 2 levels of hydration, plasma (blood), and muscles. A person cramps because that specific muscle was not hydrated. Once I started supplimenting those 4 minerals the cramping stopped completely. The key is upping the intake a few weeks before a race. Muscles will only hydrate when there is enough water mixed with the 4 minerals in a persons system.