I've only been cycling now for about 3 weeks and yesterday was the 1st time I started to Cramp up. My normal circuit is 7.5 miles out (30-45 min break) and 7.5 miles back home. I started to get cramps about 2 miles from home... I was not looking forward to walking the bike back for that distance. I stopped, raised my saddle a bit... just trying to change something. This appeared to prevent things from getting worse but I could tell they were ready to freeze up at a moments notice. The main difference was I switch shoes for this ride... I had a pair of tennis shoes with a flat and relatively stiff sole. I thought the harder sole would help me avoid some rare foot cramps I had experienced with the other softs-soled shoes.
It may have just been random that the different shoes and calf cramps happened... just curious, since I'm currently looking for shoes to use (none of the real bike type shoes... too expensive) and I just ordered a set of PoewrGrip straps.