Originally Posted by GFish

Twice now, both legs started cramping at 40 miles. I could't get off the saddle without severe muscle tightness in the quads and medial greats, just above the knees. I didn't have this problem last year on rides between 40 and 80 miles. Had sore legs, but not severe cramping.

Saturday started good, I felt strong for the first 30 miles. Then at apx. 45 miles, I stood up to power over a slight incline and the thigh muscles on both legs cramped up. I could hardly move the pedals, the cramping was extremely painful and debilitating. Once the pain sub-sided slightly, I down shifted to lower gears to try spinning faster and downing a bottle of an electrolyte drink (Nuun). I rode easy for several more miles and the legs started to respond. But I could never fully recover, any hill or incline was still painfully challenging. I rode with 2 buddies and we finished 85 miles in 5 hours and 40 minutes total riding time. We weren't riding for speed, just cruising at a comfortable pace.

So what is the biggest reason why muscles cramp and are there other factors?

My list of things to consider...
1) Hydration
2) Inadequate fuel, carbs
3) Poor conditioning
4) Not enough base riding
5) Bike fit

On #5, I'm not sure if the saddle height or setback is optimum, need to have this checked. I've switched off between saddles and may have this setup slightly off. Sunday, I measured the saddle height and it was low (again), raised it 4mm before a recovery ride and the height felt good. Could a low saddle cause cramps?

Thanks for the help