Hydration

HYDRATION

A challenging topic needless to say. The amount of water, electrolytes and carbohydrates you need during training and a race has to do with temperatures, sweat rates, exertion levels, heart rate, VO2 Max, Lactate Threshold, distance, type of drink you are consuming, etc. etc. To complicate matters, there is conflicting advice everywhere and new studies showing up that contradict earlier hydration rules and “laws”. To further complicate matters, electrolyte replacement is challenged by every athlete's needs being different, every athlete losing electrolytes to sweat at different rates per hour, and every product having different levels of sodium, potassium, chloride, and other minerals like magnesium. This whole electrolyte replacement issue will be tackled in another forthcoming article / blog.

With respect to pure hydration, I was told years ago, drink, drink, drink leading up to a race and during training to get your body properly hydrated. Always have a bottle of water in your hands and drink 5 liters of water minimum a day. I read similar stories and studies to confirm what experienced triathletes had told me.

Now however, that is not the case. Below, I have copied and pasted several facts, articles and studies that speak to varying methods and beliefs about hydrating, including replacing all those electrolytes you lose in sweat. What we absolutely want to avoid is hyponatremia, which is a dilution of the blood caused by the over consumption of fluids (most of the time water), and it can cause you to fall into a coma and die. Dehydration is the opposite, where there is a thickening of the blood through the lack of fluids and this can cause dizziness, nausea, cramps, and other more serious ailments. I've been dehydrated before, as have many of you reading this, and it sucks. But thankfully, dehydration is less serious than hyponatremia.

So is it all a balancing act of not too much, not too little combined with effective electrolyte replacement for those lost in sweat? Remember that I wrote in a previous piece that the stomach can only absorb 8 ounces of water in a 20 min period. Carbohydrate drinks can help increase this absorption rate, but the question is, do we need this extra absorption of liquids into our blood stream. Here are some bullet points to remember and some interesting articles written by others about this topic. (this picture is of me having lost an estimated 8 lbs through sweat on the IM course - notice the white stains on my shorts from dry sweat)

IM finish

±New research suggests that drinking too much water – especially in the hours or days leading up to a race – can reduce your body’s ability to conserve water during a race and cause a drop in performance, not to mention serious health issues.
±To achieve optimal training and racing results, you need to condition your kidneys to conserve water with periods of moderate dehydration, just as you train your muscles with periodic bouts of anaerobic training.
±Thirst is NOT a good measure of hydration needs during a race. Your body usually needs water and electrolytes well before thirst sets in.
±Thirst is a good indicator of hydration needs during regular rest days and when not training.
±The color of your urine can be a good indicator of how well you are hydrated (see page 14 and 15 of Runners magazine December 2007 for a full explanation) The lighter the color, the more hydrated you are. The darker, the less hydrated you are. This can’t help much on a course as you likely will not be urinating if you are dehydrated.
±The most effective prevention from dehydration and hyponatremia is full body conditioning.
±Water intake should be guided by thirst and by experience.
±Condition your kidneys to conserve water with brief periods of moderate dehydration which will reduce water intake requirements during a race and will allow for better control of your water balance.
±Because hyponatremia is characterized by low salt concentration in the blood, some experts advocate consuming extra salt during exercise as a way to prevent it. However, the primary cause of hyponatremia is not consuming too little salt, but is rather drinking too much fluid. Therefore the best way to avoid hyponatremia is not to consume more salt, but to drink less fluid instead.
±In a New Zealand study of Ironman participants, salt tablets were found to be unnecessary to maintain normal blood sodium levels.

Dehydration:

Runners need 400 to 800 milligrams of sodium per hour during warm and hot weather conditions.

The average pretzel or saltine has only 30 milligrams of sodium. Most sports drinks have more sodium, but still may not have enough sodium because they would taste like sea water if they had sodium levels equivalent to 800 milligrams per hour.

Cola drinks typically contain little or no sodium. A steady diet of half water, half cola could lead to inadequate sodium after only a few hours of running.
Don't be fooled by running in dry weather. Sweat may evaporate so fast in dry weather you may think you're not sweating much when you're actually sweating a great deal and losing water through your lungs as you exhale.
Don't assume you're hydrated if you urinate late in a run. If you're low on sodium, your body will be forced to dump water to keep you from going into a state of hyponatremia (low sodium). Thus, it is possible to be dehydrated, but still be urinating.
If you do get dehydrated, take salt and water together. Your body will not properly rehydrate in you don't take in sodium. Therefore, avoid soda and sparkling water unless you also take sodium.
Don't trust your sense of thirst in a long run. Most people are actually dehydrated by the time they acknowledge their thirst. Use the standard refrain, "eat before you're hungry, drink before you're thirsty" as a guideline.
If you do get dehydrated, your blood pressure will be low. If you take hot shower after the run, the blood vessels near the skin will dilate and your blood pressure will drop so low that your heart will not be able to push blood to the brain for a few seconds and you will faint in the shower.
If you feel dizzy or have a queasy stomach during a run, slow down or sit for a while. If it is really hot, you weren't going to have a record time anyway, so why kill yourself to finish a few minutes sooner?
The runners most in danger of dehydration are not the speedsters at the front of the race, but those at the back of the pack who spend more hours out in the heat.
If there is ice at the aid stations, consider wearing a white mesh cap in which you can put ice cubes. It may look silly but it can reduce your body core temperature and help prevent a good training effort from becoming disastrous.

James Raia is a syndicated journalist and long-distance runner in Sacramento.

How much salt do you need while running?

By Matt Fitzgerald For Active.com

September 19, 2005

Avoiding hyponatremia

The major salt-related risk to the health of runners is hyponatremia, a potentially fatal condition that has received a lot of attention lately. Also known as water intoxication, hyponatremia results when the sodium concentration of the blood falls too low due to prolonged sweating combined with excessive fluid consumption. Symptoms include dizziness, muscle cramping, confusion, and stomach bloating. Severe cases can lead to seizure, coma and even death.

Because hyponatremia is characterized by low salt concentration in the blood, some experts advocate consuming extra salt during exercise as a way to prevent it. However, the primary cause of hyponatremia is not consuming too little salt, but is rather drinking too much fluid. Therefore the best way to avoid hyponatremia is not to consume more salt, but to drink less fluid instead.

A recent Swiss study compared the effects of three different fluids -- water, a low-sodium drink and a high-sodium drink -- consumed at a high rate of one liter per hour -- on the blood sodium levels and performance of runners in a four-hour run.

Despite the fact that the high-sodium drink contained almost as much salt as sweat, 46 percent of the study subjects developed mild hyponatremia when using it. While this percentage was slightly lower than the percentage of subjects who developed mild hyponatremia when using the low-sodium sports drink, these results clearly show that it's hard to avoid diluting your blood, now matter how much salt you consume, if you overdrink. (The current recommended drinking rate for runners is 400-800 ml/hr.) It's also worth noting that none of the three drinks tested in this study had any effect on performance as compared to the others.

Studies involving salt tablets -- which are popular among ultra-runners and long-distance triathletes -- have produced similar results. In a New Zealand study of Ironman participants, salt tablets were found to be unnecessary to maintain normal blood sodium levels.

The underlying conclusion we can draw from all of the research on salt intake in endurance events is that the typical sports drink provides plenty. Salt tablets and extra-salty sports drinks provide no additional benefits for performance or health protection.