The past two rides I've been getting some severe cramps in the calves 1/2 hour into my ride. I'd like to do a century this year and it will take that much longer if I have to get off the bike to stretch every 30 minutes.
What can I do during or before the ride to avoid this? As a backgrounder, I'm clipped in on the balls of the feet and my seat seems to be at the correct height with my knee very slightly bent at the bottom of the pedal stroke. Could I be sitting too far (5mm ?) forwards? I can play with the seat position and not much else. Maybe I'm deficient in some vitamin - HELP!