I'm a 46 year old guy, 5' 8", 145 lbs.
Historically I was a low volume runner who focused on the 5k. Started running as a freshman on college, didn't run as much after first year of grad school, then came back to running very consistently as a masters runner. Went from being an on and off again 40 mile per week 5k guy to a martathon focus, usually running (during marathon training) at least 70 miles per week and peaking at 90 mpw. I live in Florida.
My issue is that starting with my second marathon, I have been experiencing serious muscle cramping. In that race, my calves locked up at 21 miles. As I trained for my third marathon, I repeatedly had heavy full body muscle cramps including pecs, lats and triceps. I even had cramping the night before my marathon. The following day, my calves locked up right before Heartbreak Hill and I had to stop more than a half a dozen times to stretch my calves. I'm training for Boston again and feel like I'm in PR shape, but my calves locked up on me again about two weeks ago and feel like they are constantly on the verge of cramping up again.
I would attribute it to muscle fatigue but for the fact that it happened in my upper body muscles at the end of my taper and before race day.
I know that I sweat a ridiculous amount, even by Florida standards. I dropped 3 lbs of water weight on a 6 mile run tonight (81 degrees) and dropped over 8 pounds of fluids on the 20 miler that I cramped after (72 degrees).
So I'm leaning toward chronic electrolyte depletion as the cause of the cramps. I've used salt tablets in the past, and they definitely helped me feel recovered more quickly, but I still locked up on race day. I've been going with a ton of Pedialyte in an effort to replace electrolytes and it might be helping a little, but I'm still concerned that I will lock up again in Boston.
So my questions are, does anyone else sweat as much as I do (over 5% of my body weight at times)? Does anyone have any ideas as to what else I can do beyond salt tablets and Pedialyte and cutting back my alcohol consumption to minimize the risk of dehydration and electrolyte depletion?