Not sure if this should go under injuries or not.

But on long runs I struggle with cramp.

At Borrowdale at the weekend I drank plenty of liquid before the race (over 2 litres of SIS Electrolyte) and the cramp kicked in climbing bessyboot, on route I drank 2 litres of liquid. At the finishing after crossing the river the cramp was that bad I was struggling to walk to the finish!

Any suggestions on how to stop cramp?