Whenever I really exert myself on my bike my calves seem to prematurely cramp. I rarely ever have any other indication of cramping in any other muscles besides the calves (both right and left). I understand the importance of hydration and I don't feel that hydration is the sole reason for the tendency to cramp. I think that if it were driven by hydration or dehydration that cramps would appear in other muscles as well. My calves and thighs are very well developed. I run a minimum of 20 mi/week on mountains. So I don't think it's a matter of building the muscles to alleviate the problem. I have been thinking that I may need to get re-fitted on the bike or change some things on my bike in order to alter my position on the bike. Maybe my pedal stroke is somehow influencing the cramps? Any advice appreciated.