It seems very simple. Drink water... Or is it?
Signs and SymptomsIn mild to moderate cases dizziness, headache, confusion and cramping are some signs and symptoms. In severe cases the athlete stops sweating and blood pressure decreases.
The condition that is less heard of is hyponatremia. It translates to too little sodium. This occurs when there is too much fluid and not enough electrolytes. The first time I heard this was my senior year in high school when a former California State Champion (competing at Stanford) couldn't finish her race because she drank too much water and her electrolytes were imbalanced. She drank 1 gallon of water before her race.
Runners who run longer then 4 hours are more susceptible to hyponatramia. Since they are on the course longer they tend to take in more water not realizing that sodium is important too. To avoid dehydration runners will drink water at every aide station. However, ingesting more water compared to how much you are sweating will increase the chances of becoming hyponatremic. This will increase the amount of water in the body but the sodium level decreases from sweating causing hyponatremia. An improper balance of water to electrolytes can cause a number of different symptoms and can lead to coma. This is why it's important to have sports drinks along with water.
Signs and SymptomsHeadache, nausea and vomiting, lethargy, and confusion, seizure are symptoms of hyponatremia.
The excess fluid moves from between cells to inside the cells causing the above symptoms. When it is severe it can move fluid into the lungs and brain.
Dehydration vs Hyponatremia
The symptoms of dehydration and hyponatremia are very similar. In the past, the best way to monitor is to weight your self before and after running. If you weight less, there is less water. You're dehydrated. If you weight more, this means have you're over hydrated possibly leading to hyponatremia. However, this way of checking is unreliable. The latest research supports moving away from using weight as the sole monitor.
You can be dehydrated AND hyponatramic (weighing less). In the past, the athlete would have been given more water. However, drinking more water can further put you in hyponatremia. Being more aware of your hydration strategies is the best option. Make sure you drink a adequate balance of water and sports drinks/gels.
Sports Drinks, Gels and Energy Chews
If your gel pack states to drink 6 oz of water. Drink 6 oz. of water. This ensures the proper percentage of carbohydrates. That is 3-6 gulps of water per pack. If you ingest multiple gel packs, let's say 3 over an hour, that would be 18 oz of water which can be a lot if you're not use to it. Or, if you drink a performance drink with the gel, it will increase the concentration of carbohydrates to an undesirable amount. If you're not use to drinking water with your gels or chews and/or use more then you would typically, you can be causing GI stress on race day.
For example- A GU pack typically has 22 grams of carbohydrates, you should have approximately 10 oz of water with the GU for proper percentage carbohydrates. If you ingest 2 packs, you should have 20 oz of water.
Of course, everyone is different. Some athletes feel fine with more or less then the recommended amount. Know your body. If you end up with GI problems you can rebalance your body by drinking more water if you have had a lot of sports performance drinks/gels or taking more sodium if you haven't had electrolytes with your water.
***These are the basic of hydration and performance aides. There is a lot more detail such as protein ratio, caffeine, etc, but would make this post into a book. Please contact me if you have further questions.
Leiper JB, Prentice AS, Wrightson C, et al. Gastric emptying of a carbohydrate-electrolyte drink during a soccer match. Med Sci Sports Exerc 2001;33:1932-1938.
Murray R, Bartoli W, Stofan J, et al. A comparison of the gastric emptying characteristics of selected sports drinks. Int J Sports Nutr 1999;9:263-274.