For seasoned runners....

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  • waldo56
    waldo56 Posts: 1,861 Member
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    I always carry water. Just a small 12 oz water bottle, I buy bottled water specifically for the water bottles and reuse them a few times.

    I learned to run on a treadmill with water next to me and always carried it outside. Running with a small water bottle in my hand feels totally natural at this point.

    It is a matter of what is more distracting, thirst or carrying a water bottle. For me it is thirst, I can easily ignore the water bottle in my hand, but being thirsty kills my running focus.
  • cowgirlslikeus86
    cowgirlslikeus86 Posts: 597 Member
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    .
  • cowgirlslikeus86
    cowgirlslikeus86 Posts: 597 Member
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    Lately, my runs are in 100+ temps, and since I usually don't go out for less than 5-6 miles, I always have water with me. After a 12 mile, hilly run in 103 temps last week, I drank approx 60 ounces of fluids, and still managed to lose 5 pounds in the 1:45 it took to run. I just don't understand why anyone would want to play around with their lives by running far in hot weather without having fluids on-hand.

    Good point. It doesn't usually get 100+ where I am, and there's usually a cool breeze at the beach, even on a hot day (90+), so it's not that big of a deal for me. If it was 100+, and I was running 10 or 12 miles, I'd probably need to bring some water with me.

    Same here, I would have to adjust. In the summer, I get out before it's gets too hot. My LSD is usually done before 9 AM in the summer time, so at worst, I might see 90 toward the end.

    All you early morning SoCalians. Psh! Think hot,humid, stagnant air and mosquitos. Maybe I need to reconsider where I run. The trees tend to deflect all the "Breeze" around here.

    I'm not from SoCal, I'm just down the road from you in Northern Baltimore County. :)

    Ahh, Thats right. Also, I think Trail-addict is from AZ. Maybe by SoCal comment was incorrect. I just need to suck it up:ohwell:
  • cowgirlslikeus86
    cowgirlslikeus86 Posts: 597 Member
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    I never carry water with me but I also virtually never run outside if it's over 85, I'll wait till the sun sets or run on a treadmill. If I decide I do want water, I will run a 3 or 4 mile loop and stash my bottle under a shrub.

    I should be less judgemental but I usually internally roll my eyes at people doing 5Ks and such while loaded down with water. I did Race for the Cure 5k on Saturday and it was warm, maybe 80, and I saw people wearing those waist bands that hold 5 or 6 little water bottles. The race had 2 stops on the course.

    I don't care what other people do/don't carry on a run. They know their bodies and psyche better than I do. I think the fact they're there and racing is a "high five" on their part. Believe me, it's not that I don't have my judgemental issues, but in sports and exercising, I could not care less. The whole "suck it up" attitude has no place in good sportsmanship, in my opinion.

    I feel bad when I judge those people too. If water on a 5k course makes them run better, who am I to think anything. Maybe they had too much booze the night before?:laugh:
  • jonnyb62
    jonnyb62 Posts: 426
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    I just need to suck it up :ohwell:

    Or not.

    You have to do what's right for you. Like many others have said, I just don't want to drink anything when I'm running, so why carry the extra weight? If a drink now and then helps you, then stay with it. :flowerforyou:

    BTW, thanks for the add!
  • JoolieW68
    JoolieW68 Posts: 1,879 Member
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    I am not a long distance runner, but don't usually carry water. Just the sight of water makes me have to go to the bathroom and I don't feel like squatting at the side of the road/trail :laugh:
  • thebiggreenmachine
    thebiggreenmachine Posts: 66 Member
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    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.
  • brandyk77
    brandyk77 Posts: 605 Member
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    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.


    - No one here has ever been dehydrated enough that it hurt their performance, ever.


    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.


    re: weighing yourself - Disagree - it is a valid manner to estimate water lost via sweat. I just recently had this suggestion from person, former olympian and current nutritionist to NCAA athletes and she is a PHD. I'll trust her on that. In addition, that is basically what race officials are doing in events such as Badwater or other ultra races. I think they have a bit of experience with dehydration.

    Re: dehydration being related to speed. I would think that the higher % of weight lost has more to do with the elite athletes overall lower body weight and better ability to preload glycogen stores for the event vs. speed.

    Also you say "The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined" and then "No one here has ever been dehydrated enough that it hurt their performance, ever". - those statements are contrary to each other. In addition, it is pretty simple logic to understand that a decrease in hydration = a decrease in blood volume (since it is made up of a lot of water). Decreased blood volume means that getting oxygen to your muscles is harder. Here is a link to some information for that. http://www.humankinetics.com/excerpts/excerpts/dehydration-and-its-effects-on-performance

    Good summary below of it:
    Fatigue toward the end of a prolonged sporting event may result as much from dehydration as from fuel substrate depletion. Exercise performance is impaired when an individual is dehydrated by as little as 2% of body weight. Losses in excess of 5% of body weight can decrease the capacity for work by about 30% (Armstrong et al. 1985; Craig and Cummings 1966; Maughan 1991; Sawka and Pandolf 1990).
  • willismack2
    willismack2 Posts: 84
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    Interesting info from Noakes. I carry water when it is hot and I run longer than about 45 minutes, because I get thirsty.
  • CarsonRuns
    CarsonRuns Posts: 3,039 Member
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    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.


    - No one here has ever been dehydrated enough that it hurt their performance, ever.


    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.


    re: weighing yourself - Disagree - it is a valid manner to estimate water lost via sweat. I just recently had this suggestion from person, former olympian and current nutritionist to NCAA athletes and she is a PHD. I'll trust her on that. In addition, that is basically what race officials are doing in events such as Badwater or other ultra races. I think they have a bit of experience with dehydration.

    Re: dehydration being related to speed. I would think that the higher % of weight lost has more to do with the elite athletes overall lower body weight and better ability to preload glycogen stores for the event vs. speed.

    Also you say "The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined" and then "No one here has ever been dehydrated enough that it hurt their performance, ever". - those statements are contrary to each other. In addition, it is pretty simple logic to understand that a decrease in hydration = a decrease in blood volume (since it is made up of a lot of water). Decreased blood volume means that getting oxygen to your muscles is harder. Here is a link to some information for that. http://www.humankinetics.com/excerpts/excerpts/dehydration-and-its-effects-on-performance

    Good summary below of it:
    Fatigue toward the end of a prolonged sporting event may result as much from dehydration as from fuel substrate depletion. Exercise performance is impaired when an individual is dehydrated by as little as 2% of body weight. Losses in excess of 5% of body weight can decrease the capacity for work by about 30% (Armstrong et al. 1985; Craig and Cummings 1966; Maughan 1991; Sawka and Pandolf 1990).

    Thanks for taking the time to put my thoughts down. :)

    I got my information on weight loss to measure sweat rate from Jack Daniels' book. He's considered a lot less kooky than Noakes is.
  • katapple
    katapple Posts: 1,108 Member
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    I wear my camelbak for even 3 milers. I like being able to take a sip whenever I want, and I hate having to wait for a water station especially when I could use a drink10 minutes ago ;-P
  • grinch031
    grinch031 Posts: 1,679
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    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.

    Wow some bold claims. If being dehydrated doesn't hurt performance, why does a race need to have water stops at all?
  • grinch031
    grinch031 Posts: 1,679
    Options
    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.

    Wow some bold claims. If being dehydrated doesn't hurt performance, why does a race need to have water stops at all?

    So I read more on this on The Science of Sport blog and it seems maybe there is some truth in all this.

    http://www.sportsscientists.com/search?q=dehydration

    Anyways today I conducted a little n=1 experiment. It was sunny, upper 70s, and 75% humidty and I ran 10 miles. I drank 2 8oz cups of coffee in the hours beforehand, no other fluids, and ate nothing and ran completely fasted. I brought one 16.9oz bottle of water with the intention of drinking only when I feel thirsty.

    I ran at marathon pace (8:20/mile), which is about 20 secs/mile slower than my normal comfortable training pace for this distance. It definitely slowed to about 8:30s in the last mile or two, but I never felt awful. I sweat profusely on days like this and today was no different. Both my shirt and shorts were completely drenched.

    Typically I might occasionally slow down to a crawl after mile 8 on a day like this when I am pre-emptively hydrating myself in anticipation that it will catch me off guard (Based on the notion that if you wait til you are thirsty, its too late).

    Anyways by the end of the run I only drank about 1/3 of the water ~5.6oz because I just never got very thirsty. I'd say there's definitely a good chance that the body really is capable of managing fluids and electrolytes appropriately and that over-hydrating may very well be a reason for hindered performance during hotter temperatures.
  • Trail_Addict
    Trail_Addict Posts: 1,350 Member
    Options
    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.

    Wow some bold claims. If being dehydrated doesn't hurt performance, why does a race need to have water stops at all?

    So I read more on this on The Science of Sport blog and it seems maybe there is some truth in all this.

    http://www.sportsscientists.com/search?q=dehydration

    Anyways today I conducted a little n=1 experiment. It was sunny, upper 70s, and 75% humidty and I ran 10 miles. I drank 2 8oz cups of coffee in the hours beforehand, no other fluids, and ate nothing and ran completely fasted. I brought one 16.9oz bottle of water with the intention of drinking only when I feel thirsty.

    I ran at marathon pace (8:20/mile), which is about 20 secs/mile slower than my normal comfortable training pace for this distance. It definitely slowed to about 8:30s in the last mile or two, but I never felt awful. I sweat profusely on days like this and today was no different. Both my shirt and shorts were completely drenched.

    Typically I might occasionally slow down to a crawl after mile 8 on a day like this when I am pre-emptively hydrating myself in anticipation that it will catch me off guard (Based on the notion that if you wait til you are thirsty, its too late).

    Anyways by the end of the run I only drank about 1/3 of the water ~5.6oz because I just never got very thirsty. I'd say there's definitely a good chance that the body really is capable of managing fluids and electrolytes appropriately and that over-hydrating may very well be a reason for hindered performance during hotter temperatures.

    Great test. Do you consider "70 degrees" hot weather? Personally, I know I wouldn't need but a few sips of water on a 10mile run (just to wet my throat) in 70 degrees. Conduct that test in 90+ degree weather, and see if your results vary. I'm guessing the added heat will demand more fluid replacement.
  • Trail_Addict
    Trail_Addict Posts: 1,350 Member
    Options
    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.

    So you're contending that all of these facts pertain to "hot weather" running, as per the OPs original topic?
  • grinch031
    grinch031 Posts: 1,679
    Options
    Thank you for everyones replies. There is alot of good information in your comments. I don't think I drink as much water as I should, in general. If I did, maybe I would have better luck like some people. I don't really "Want" to run 10 miles without water, however, it would be nice to know that I could. Maybe it would be good to build up my tolerance. I suppose you never know when you'll have to run for your life without your favorite pair of running shoes and 80 oz. of water on your back.:laugh:

    So much misinformation, so little time.

    - First off, heatstroke/heat illness, whatever you call it, is not caused by dehydration. It’s caused by the environment you’re exercising in and the intensity of your exercise. Hydration DOES NOT play a part.

    - Less than half the weight you lose during exercise is due to water loss. Weighing yourself before and after exercise is pointless unless you're just curious.

    - The only correlation between how fast runners are and dehydration, is that the faster the runner the more dehydrated they will be. Studies have shown that the more dehydrated runners are the winners while the least dehydrated are those in the back of the pack. Haile G. dropped 10% of his weight when ran his 2:03:59 marathon. The percent of weight loss that will ‘cause a decrease in performance has yet to be reliably determined.

    - You drink to thirst. That’s the best way, period.

    - No one here has ever been dehydrated enough that it hurt their performance, ever.

    - The last long run I did, I ran 20 miles, four 5 mile loops, with each loop faster than the previous. It was around 70 and sunny. Was able to get the last loop in under 7 min/mile pace. I never drink or eat during a run, my body doesn’t ask for it, therefore, I don’t force my body to take it.

    - No one ever needs to ever carry any fluid during a race as long as the race has water stops.

    - 7 signs of drinking too much fluid:
    1. Impaired performance
    2. Nausea and vomiting
    3. Headache
    4. Altered level of consciousness
    5. Seizure
    6. Bloating/Swelling of hands, legs and feet
    7. Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

    Symptoms NOT caused by dehydration:
    1. Dizziness and fainting
    2. Cramps
    3. Wheezy breathing
    http://www.humankinetics.com/excerpts/excerpts/seven-clear-symptoms-of-exercise-associated-hyponatremia

    Google ‘Tim Noakes dehydration’ if you disagree with any of these facts I’ve presented.

    Wow some bold claims. If being dehydrated doesn't hurt performance, why does a race need to have water stops at all?

    So I read more on this on The Science of Sport blog and it seems maybe there is some truth in all this.

    http://www.sportsscientists.com/search?q=dehydration

    Anyways today I conducted a little n=1 experiment. It was sunny, upper 70s, and 75% humidty and I ran 10 miles. I drank 2 8oz cups of coffee in the hours beforehand, no other fluids, and ate nothing and ran completely fasted. I brought one 16.9oz bottle of water with the intention of drinking only when I feel thirsty.

    I ran at marathon pace (8:20/mile), which is about 20 secs/mile slower than my normal comfortable training pace for this distance. It definitely slowed to about 8:30s in the last mile or two, but I never felt awful. I sweat profusely on days like this and today was no different. Both my shirt and shorts were completely drenched.

    Typically I might occasionally slow down to a crawl after mile 8 on a day like this when I am pre-emptively hydrating myself in anticipation that it will catch me off guard (Based on the notion that if you wait til you are thirsty, its too late).

    Anyways by the end of the run I only drank about 1/3 of the water ~5.6oz because I just never got very thirsty. I'd say there's definitely a good chance that the body really is capable of managing fluids and electrolytes appropriately and that over-hydrating may very well be a reason for hindered performance during hotter temperatures.

    Great test. Do you consider "70 degrees" hot weather? Personally, I know I wouldn't need but a few sips of water on a 10mile run (just to wet my throat) in 70 degrees. Conduct that test in 90+ degree weather, and see if your results vary. I'm guessing the added heat will demand more fluid replacement.

    Did you intentionally omit the word 'upper' that I put next to 70 degrees? It was closer to 80 degrees...and it felt hot enough to me to hinder my performance.