I woke up in the night with a killer calf cramp. I stretched and it went away but all day today it felt like it was going to cramp - stretching staved it off so far. The other leg felt a little crampy too. I had some vitamin water with calcium and a banana which helped, and I've been stretching every chance I get.

However, I can still feel the muscle twitching right now

I have been training - about 4-5 days a week - some hill repeats (6 X on a .20 mile medium grade) nothing crazy, since March. I did my first century at the end of May. I am starting to work on hills, which hasn't bothered my calves at all.

Now yesterday it was raining, so I went to a spinning class which was an endurance ride where we tried to keep a 90 RPM cadence for 30 min. I kept up at about 80 RPM. I then did a light weight workout (nothing I haven't done hundreds of times). Maybe this caused it somehow? I haven't done spinning in a few months but was a regular during the winter.

So my question is -- what did I do to myself, and how do I fix it?