Staying Hydrated During Your Runs

When summertime is in full swing so is the hot weather. I love running in the heat but mind you, I live in Vancouver where it rarely gets really hot. Here are some solid guidelines on what and how much to drink to stay hydrated in the heat.

Don't make the mistake of thinking you need to replace all the fluids you're losing as you sweat. By it's very nature, endurance running is a losing proposition. You cannot physically replace all the water, electrolytes and calories you're losing when distance running.

During your run you can expect to be able to replenish:

• 20 - 33% of the fluids
• 20 - 35% of the sodium
• 30 - 40% of the calories

But that's okay. Your body's mechanisms are equipped to deal with these shortfalls until after you're finished and can fully restore your reserves. The trick is not to interfere by consuming too many fluids, calories or excessive sodium.

One of the best things you can do to avoid getting dehydrated is to maintain good hydration levels even before you head out the door. Drink 2 - 3 litres of water every day. That's 64 - 95 ounces for my U.S. readers.

In the couple of hours before your run drink 500 ml (16 ounces) of water. If you're thirsty drink more but don't force yourself to drink more than your body is willing to take in.

What to drink during your run depends on how long you'll be running. For runs of an hour or less you can drink plain water. Aim for 500 to 750 ml (16 - 24 ounces).

But if you're running for longer than an hour you need to be taking in electrolytes as well. Electrolytes are minerals which perform important physiological functions. Specifically you need to be taking in calcium, magnesium, potassium, sodium and chloride. (Often sodium chloride or salt, is the form these last two electrolytes come in.)

The reason you need to take in electrolytes is to avoid a condition called hyponatremia, also known as water intoxification. Profuse sweating combined with excess water intake combine to dilute sodium levels in your blood to extremely low levels.

This can impair your function and in extreme cases lead to death. There have been a few reported cases of marathon deaths attributed to hyponatremia.

At the other end of the scale, you can drink too few fluids and end up dehydrated. This can cause a host of problems as well so you need to find a balance between drinking too much and too little.

In long distance events (particularly ultramarathons) the leading runners will usually dehydrate while back of the pack runners tend to overhydrate.

As a rule of thumb, drink 500 ml to 750 ml (16 - 24 ounces) of the electrolyte drink every hour. Look for drinks that contain a full spectrum of electrolytes: calcium, sodium, magnesium, potassium and chloride.

In terms quantity of electrolytes to consume, use the following guidelines:

• Calcium 150 - 300 mg/hour
• Magnesium 75 - 150 mg/hour
• Potassium 74 - 150 mg/hour
• Sodium 120 - 240 mg/hour
• Chloride 180 - 360 mg/hour
• (Often salt, which is sodium chloride, is the form these last two electrolytes are found in drinks. In this case, use 300 - 600 mg/ hour of sodium chloride)

The range is given to account for different body sizes and sweat rates. Use near the upper end of the spectrum if you're a bigger runner and/or are sweating a lot. You can buy powders to mix with water or if you prefer to drink plain water but still need electrolytes you can buy capsules.

Two of my favourite electrolyte products are Eload and Hammer nutrition powders and capsules.

Some signs of caution to watch for include gaining any weight during your run and weight loss of greater than 2%. The weight gain is often a symptom of hyponatremia while excessive water weight loss is a sign of dehydration. Performance begins to decline at 2% weight loss, while at 7% collapse is highly likely unless you stop running. In either case of weight gain or excessive weight loss, get medical attention.

So be careful not to drink too much nor too little during your runs. While severe consequences are extremely rare, a poor performance due to either scenario is fairly common in runners.