There is already some great advice about hydration here on the RaceTri site, but I wanted to give a little more information for those who are looking for an advantage as they move forward with their training and competition goals.
When we talk about hydration we should really divide it into two categories. First, is simply good old H20. You need water to function. Failure to consume enough water can elevate blood pressure, contribute to increased risk of heat illness (including both heat exhaustion and heat stroke), and decrease muscle function. If you break down the biochemistry you’ll see that water is a key component to basically every process in your body. So make sure you drink enough water. A good rule of thumb is one half cup per 20 minutes of exercise.
The second category of hydration is electrolyte replacement. For this I recommend becoming aware of what I call the Big 3: sodium, potassium, and calcium. These three are heavily involved in the normal function of muscles and nerves in the body. This includes skeletal muscle as well as heart muscle. Unfortunately, normal electrolyte levels can require a delicate balance to function well. In all three cases the electrolyte in question can have negative effects when the levels are too high or too low.
For sodium, not getting enough is not usually the problem. Even if you consciously eat a low sodium diet you probably still get plenty of it. However, there is a condition called hyponatremia that most commonly affects endurance athletes. Despite having adequate sodium in the diet, consuming large quantities of water without any electrolytes can dilute the concentration of sodium in the blood. This is a serious medical emergency and the consequences may be severe. The purpose here is not to scare you, but to make you more aware of the need to replace those electrolytes as you go. This is why I recommend using a sports drink (or sports gel and water) containing electrolytes while you are doing any vigorous endurance exercise, especially if the conditions are hot and humid.
Potassium is almost an opposite of sodium. Where most diets have more than adequate sodium, they often lack potassium. There are two ways to combat this. You can take a supplement or you can improve your diet. The concern with taking a supplement is that it may not be absorbed as well and it may be too much. Unlike sodium where too little is dangerous, having too much potassium can lead to a condition called hyperkalemia, which can also have severe consequences. So I recommend getting your potassium from food sources. Many people think of bananas as a great source for potassium, but better still are sweet potatoes and dark, leafy greens. Here’s a link to other great food sources of potassium http://www.health.gov/dietaryguidelines/dga2005/document/html/appendixb.htm.
Calcium is probably the least severe of the group since the body is very effective at regulating the concentration in the blood. However, one of the ways this is done is by pulling calcium from bones when it becomes scarce. This is one of the reasons female endurance athletes are more susceptible to conditions such as osteoporosis. Dairy remains one the best sources for calcium, but can be accompanied by less healthy nutrients, especially if you think ice cream is the best way to get calcium. In addition, many people choose to eliminate dairy due to personal choice or food allergies. You can eat foods fortified with calcium (soy milk, some juices) or spinach and some other leafy greens. The above link has tables for both typical dairy sources of calcium as well as non-dairy sources.
So what’s the bottom line for all this? First, when hydrating during long exercise bouts, choose a sport drink (or gel and water) that contains sodium and potassium to reduce the risk of severe side effects. Second, get enough calcium as part of your daily diet to prevent bone loss. If you eat right and keep exercising you’ve put yourself in the best possible position to have a long healthy life.
Dr. Eagar is a dual credentialed provider with degrees in sports medicine, chiropractic medicine, and exercise science. Dr. Eagar owns Active Advantage, a private sports medicine practice with an emphasis on rehabilitation and chronic injury management. He enjoys answering questions and can be reached at email@example.com. For more general information you can visit his website http://www.activeadvantagechiro.com.