During the heatwave I've read lots about people saying that they are hydrating properly before their runs so they can cope during the run. I tend to get up early, go to the loo, get my kit on and walk out the door. I never drink first or carry a drink because I hate to hear that sloshing sound of liquid in my empty tummy but I'm also paranoid that I'll need to go to the toilet during my run! I'm on W9 so it isn't as if I'm running a marathon and not drinking. Should I drink first?
Quick question about hydration : During the... - Couch to 5K
You should do what is right for you. If you don't feel dehydrated when running first thing in the morning, then run without a drink beforehand.
The consensus on this forum is that it is what you drank yesterday that hydrates you for your run today. After all, the water that you drink needs to get from your stomach and into your body to make you hydrated: a quick glug of water before you run just sits in the stomach. So if you are drinking 2-4 litres of water a day, every day (and you'll know what is right for you) then you'll be hydrated sufficiently for C25K running.
Water is absorbed between a few minutes and a couple of hours after drinking it, and in the main doesn’t sit it the stomach as it’s absorbed in the small intestine, so only sits in the stomach if mixed with food to be digested. Lots of middle distance runners take on fluids about 30 minutes before run time. These guys tend not to carry water and so next take on fluids within a few minutes of finishing. Some, maybe most, of us carry and take on fluids during the exercise, so a pre run drink wouldn’t make much difference to us. If you feel thirsty then drink a little.