Two days ago, before embarking on a fairly hard 90 minute run, I weighed myself just before leaving the house - and immediately after I returned . There was exactly 1Kg difference between the 2 weighings -- obviously water used during the run. However, I can't say that I was gaspingly thirsty when I got home - or hungry come to that.
Lost 1Kg in 90 minutes: Two days ago, before... - Couch to 5K
Lost 1Kg in 90 minutes
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You will find that immediately after the run but it evens out after a bit so weigh yourself again the morning after and compare
It does show though how much dehydration goes on. I don't take water with me but as runs get longer I will have to. I hate carting stuff about with me do you
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Oh yes -- I know that this was just a temporary loss of water -- I was just surprised at the amount!!! As I said, I did not feel that I desperately needed any water when I got home - although I did have some plus a coffee plus breakfast
I have read that Jeff Galloway says that we only need to drink around 100 mls of water every 2 miles - but of course this depends on weather and he doesn't say when this should start.
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If you're planning long runs, you need to stay hydrated. Drink at least 2 to 3 litres of water a day in the run up to your long runs and then about 500 ml before you set off.
If it's hot, you're probably best using a sports drink with electrolytes to rehydrate whilst you're out or taking electrolyte gels for energy and drinking water - hyponatremia is apparently becoming more common (drinking too much plain water and so not replacing the salts lost through sweating) and can be fatal.
As far as amounts are concerned, the "experts" seem to be moving away from specific amounts to advising people to drink when they need it. I tend to find I only want a mouthful or so at a time anyway, and when I did my half marathon last weekend I probably poured more over my head than into my mouth