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Originally Posted by Ben E Lou
Bumping this line of discussion as my Sunday runs are planned to be roughly 1.5 to 2 hours for the next three months. Yesterday's was 1:54:37. I took some Gu Energy Gel along with me but didn't consume it, and didn't do anything about hydration. Four of my last five miles were faster than my average pace for the overall run, so I wasn't exactly hurting at the end, but I'm wondering a few things here...
1. Since race pace is going to be significantly faster than long run pace, might that make me need to hydrate/fuel on race day even if I don't during training?
2. What would be the signs that I needed to hydrate/fuel? I felt ok and my pace didn't slow down, but are there other things I should be looking at here?
3. I am a long-time heavy water drinker. I make sure I take a whizz right before my long runs, and typically need to do so again shortly afterward, if not immediately. Might I just have a generally high level of hydration and not really need to worry about it in the 10-15 mile range?
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My understanding is that hydration is not an at the moment thing, but instead is something you need to handle all week long. Since you say that you are a heavy water drinker, your hydration is probably in a fine shape. You are not going to suddenly de-hydrate in 60 minutes and pass out in most cases.
The times that hydration is important is probably more to do with handling the heat or more severe environment than you are used to. As you sweat more, there is a higher amount of sodium that leaves your body which will effect your performance if you have enough loss. Here is a little science on the subject:
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Everyone knows that dehydration is bad. But how bad? Current research indicates that some level of dehydration (up to 3%) does not impact performance, or impacts performance much less than expected[1]. (Dehydration of 5% does impact performance[2].) This may be due to the fact that carbohydrate (Glycogen) is stored with water, in the ratio of about 1g Glycogen to 2.5g water[3]. This means that 2000 calories of Glycogen depletion that are likely to occur in marathon distance runs would result in about 4lb Weight Loss with no reduction in hydration (2000Kcal/4=500g Glycogen + 1250g water = 1750g).
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You can read a whole bunch of information on Hydration here that might be helpful:
The Science Of Hydration - Running tips for everyone from beginners to racing marathons and ultramarathons
For me personally, I can run 10k fine without any drink. I have run further without needing anything on cooler days, but if it is hot out, or I am running closer to 2 hours, I'll bring gatorade with me just in case I feel that I need it.
Here is Fellrnr's Practical Hydration guidelines:
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Fellrnr's Hydration Guidelines
- When you are thirsty, drink. If you are not thirsty, don't drink. Over-hydration kills!
- If salty things (potato chips, etc) appeal, eat salty things or drink with electrolytes. If salty things (or the thought of salty things) are nauseating, drink water.
- Don't drink to make the suffering of a race less - if you're not thirsty, drinking won't help your misery.
- Don't drink a fixed amount; let your thirst guide you.
- If you're thirsty, don't skip drinking to make up time; unless you are very close to the finish, you'll end up slower.
- Don't start your run thirsty - it is better to hydrate before you start than to try to 'catch up' on the run. However, drinking lots of water before a run without plenty of electrolytes is a bad thing. This practice can flush out electrolytes, creating a problem ahead of time.
- Try a little extra salt in your drink. A 1/4 teaspoon of table salt per quart of sports drink can make a lot of difference and is easy to try in training.
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You can see more here:
Practical Hydration - Running tips for everyone from beginners to racing marathons and ultramarathons
As for gels or other glycogen supplement during a race, those are generally used to help replace some of the glycogen that is used up as you run. With proper runner's diet you generally can store 2000 calories of carbohydrates to burn up during the run. For many marathoners, that is depleted somewhere around mile 20, which is why you often hear about the mile 20 wall that they have to push through. For us, running a half-marathon, it is unlikely that you should burn through all of your glycogen store in 13.1 miles, and that makes the need for gels to be less likely. That said, some people still use them for runs even as short as 10k, but most common belief that i have read is that gels aren't really necessary for a half-marathon.
Since mid-run fueling is very individualistic on what works for different people, you can read through some more of fellrnr's suggestions on that here:
Mid Run Fueling - Running tips for everyone from beginners to racing marathons and ultramarathons