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Distance Running and Hydration

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In any length running race, as short as 5k, there will be multiple water stops for the participants. Research in exercise physiology has shown that when a person is running more blood is sent to the working muscles and as a result less blood is sent to the organs, so typically anything eaten or drank while running will not be digested in time to be useful for the run and that is why it is so important to be properly hydrated before the race starts.. Knowing this, I tend to think that water stops in short races are silly, but now that I am training for a marathon, which places different demands on the body, I wonder about the role of hydration and distance running.
Before the 1970s, people believed that it was best not to drink at all during exercise (Noakes, 2007). The initial push for lots of water was led by a belief that the more water the better, until there were a few significant cases of hyponatremia, especially in slower marathon runners. Since then, organizations interested in running have been reviewing their hydration guidelines.
On the one hand there is the possibility of dehydration. The physical demands of running a marathon can cause significant water loss through sweat, which in turn can impair performance (Cheuvront, Montain and Sawka, 2007). One way dehydration impairs running performance is through decreased cardiac output. As people sweat and lose water, they also lose blood volume which leaves less for the body to use (Kenefick and Sawka, 2007). On top of impairing performance, dehydration can be dangerous. It can cause fatigue, increased body temperature, cramps, confusion and even unconsciousness (Mayo Clinic, 2009).
The main problem with drinking too much water during physical activity is the potential for hyponatremia, which is basically a low concentration of sodium in the blood caused by all the water diluting the blood. Hyponatremia can be very dangerous and over the past few years the number of occurrences has been increasing in events like the marathon (Hsieh, Roth, Davis, Larrabee and Callaway, 2001). In a study by Hsieh, et al. (2001), in one marathon the researchers found that 5.6% of participants needed medical treatment for hyponatremia.
According to Cheuvront, et al. (2007), water needs vary greatly between individuals based on the distance of the run, the pace at which they run, the weather and the individuals body mass. That being said, it is difficult to create one standard that is good for everyone. The guideline that seems most logical is the one from USA Track and Field. The USA Track and Field guideline suggests that thirst should drive water consumption (Levine and Thomson, 2005). This makes sense because our bodies are pretty good at telling us what we need and this process has been improved and adapted over many years.

References
Cheuvront, S., Montain, S., & Sawka, M. (2007). Fluid replacement and performance during
the marathon. Sports Medicine, 353-357.
Hsieh, M., Roth, R., Davis, D., Larrabee, H., & Callaway, C. (2002). Hyponatremia in
runners requiring on-site medical treatment at a single marathon. Medicine & science
in sports & exercise, 185-189.
Kenefick, R. & Sawka, M. (2007). Heat exhaustion and dehydration as causes of marathon
collapse. Sports Medicine, 378-381.
Levine, B., & Thompson, P. (2005). Marathon Maladies. The new England journal of
medicine, 1516-1518.
Mayo Clinic staff. (2009). Dehydration. Mayo Clinic. Available at http://www.mayo
clinic.com/health/dehydration/DS00561/DSECTION=symptoms.
Noakes, T. (2007). Hydration in the marathon: Using thirst to gauge safe fluid replacement.
Sports Medicine, 463-466.

7 Replies

  • I find this blog very interesting because I am training for a half-marathon but I cannot drink any water while running or before because I get horrible side aches. However, knowing that drinking more water may help me and make me faster and stronger throughout the training process and the race makes me re-think my strategies. I probably won't drink water before I run but drinking water throughout the day and during my runs is not a bad idea.

  • This is such an interesting article! I've definitely wondered the reason for water stops at 5k races. I suppose for the safety of those runners who have not hydrated well enough before the race may need water during the race due to weather, sweat loss, and/or pace. For those individuals training for a half marathon and marathon, should take the event seriously when it comes to hydration. Understanding your body and what it needs will allow you to train and compete optimally. Training runs are opportunities to figure out what your body needs to feel at its best. By the time race day comes, your knowledge and experience will hopefully allow you to excel.

  • This is a very interesting blog entry. We're always so focused on drinking more water, but we never think of whether or not we are actually harming our performance. I think it's interesting that most people don't hydrate during their training, but try to during the race. Running outside, how many people do you see holding a bottle of water? Even at the rec, i very rarely see people with bottles of water on the treadmill.

  • I completely understand water stops at marathon races, but at 5K races? I feel as though most people, especially runners in general, can complete 5K without proper hydration before and during a race. It is all about proper preparation for any exercise. People tend to get side aches when they drink right before a run and during. However, if you hydrate and get proper nutriets well before the run, there should be fewer aches.

  • I agree water stops for a 5K are kinda rediculous. But I do think it is a challenge to properly hydrate throughout a marathon. I find it interesting that there are quite a few people who drink too much and that they are the slower marathoners. This may be also be a result that the slower runners are less experienced and dont understand proper hydration.

  • The problem with water stops is that a lot of people over-drink. As you mentioned, this is just as harmful as not drinking enough. Like anything else, you need to balance what you put into your body with what you're expending. The sodium problem can be solved by drinking anything with electrolytes, rather than plain water. But over-all moderation seems to be key.

  • Well although this is interesting, I find that it is quite easy to control your water intake, if anything at the water stops you can grab on little Dixie cup and does it all in your mouth and slowly drink it. Surely people realize that they need to hydrate the night before a race, not during.

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