Hi Chris! Please spill your guts in a very detailed manner on how you hydrated the day before, morning of, and during your marathon. I've ran 4 marathons and I still don't think I hydrate right the morning of the marathons. Thanks!
"Spill your guts" implies I have some kind of secret! I’ll lay out some tips here that I try to follow, but I highly doubt this is scientifically proven:
Cut out the caffeine about a week ahead of time. I’m not a coffee drinker, but I have to stop drinking soda. There’s differing opinion on whether caffeine is truly a diuretic, but I figure better safe than sorry.
Carb-load 2-3 days before the race. Those carbs will help retain extra water. It’s like bonus points before you even run a step.
Drink plenty of water the day before the race. Carry a large bottle with you everywhere you go and keep refilling it. You want to pee clear by the time you go to bed.
Drink electrolytes pre-race. I’ll usually nurse a large Gatorade from the time I get up to the starting gun. I do this because I’d rather drink water during the race and avoid getting sticky fluids all over my face.
Drink two big sips of water every two miles. This largely depends on the availability of aid stations in your marathon (or fluids you carry with you), but I’ve found this to be adequate for me. I also do my long training runs with a similar pattern. Don’t skip the early stations! If you’re feeling thirsty later in the race, it’s often too late to recover those lost fluids.
Supplement with salt tablets if you’re a heavy sweater. I’ve only recently started experimenting with this, but it makes sense if your fluids and gels don’t already provide enough sodium and/or potassium to prevent dehydration and cramping.
Everyone’s going to be different, but so far this seems to be working for me. While it was relatively warm at the Boston Marathon, I don’t think I suffered from any dehydration symptoms out there. Just sunburn. Ouch.