The past 3 runs or so the back of my legs have been cramping up something horrible. Sometimes if I stop I can stretch it out but others they just keep cramping up no mater how much I stretch. I haven't changed anything and I don't think I'm dehydrated, I drink quite a bit of water. I've been following a training plan and increasing my mileage slowly. The odd thing is it seems to help when I run faster but I can't keep that up for very long.
I don't usually have problems with leg cramping unless I've really overdone it with my training for a few days... also if I'm going really low carb then I try to supplement with Mg, Ca, sometimes K+ and make sure I'm getting plenty of salt... along with making sure I'm well hydrated...
Yep...multi-vitamin. Lack of potassium was my first guess. I'm not a great pill taker either, but I figure remembering to take it several times a week is better than not taking it at all.
Are you on a low sodium diet? Salt is excreted through your sweat during physical activity and if your levels drop too low it will cause your muscles to seize. You may want to try sipping on an electrolyte drink when you run. Even something like Pedialyte should do the trick.