Proper Hydration Guidelines for the Endurance Runner

The Rules about Fluids When Participating in Long Distance Running

You need to drink. But how much? The International Marathon Medical Directors Association - IMMDA - presents guidelines to help you remain healthy and safe on race day.

How Much Fluid Should I Drink During Endurance Events?
It is IMMDA's desire to educate and ensure that participants consume proper amounts of fluids during endurance events to remain healthy and perform well. Too much or too little may bring about health concerns and/or poor performance.

What Should You Drink?
If your event or workout is longer than 30 minutes you should drink a sports drink instead of water. The added carbohydrates and electrolytes speed absorption of fluids and have the added benefit of energy fuel and electrolytes. There is actually decreased benefit to watering down or diluting sports drinks or alternating sports drinks with water.

How Much Should You Drink?
Drinking too much or too little can be of risk to health and performance. Hyponatremia - low blood salt level due to abnormal fluid retention from over-drinking - and dehydration - due to net fluid losses from under-drinking - are conditions easily averted by understanding your individual body needs. Just as you have a unique face and fingerprint, your body's need for fluid is individual as well. Body weight, gender, climate and sweat rate are just a few variables that individualize your needs. It is normal to lose a small amount of bodyweight during a half or full marathon: bodyweight will re-equilibrate over the next 24 hours through the consumption of sodium and fluids with meals. A weight loss of more than 2% or any weight gain are warning signs that justify immediate medical consultation and indicate that you are drinking properly.

Try to Drink for Thirst:
This advice seems way too simple to be true; however, physiologically, the new scientific evidence says that thirst, will actually protect athletes from the hazards of both over and under-drinking. Do not feel compelled to drink at every fluid station and do not follow the cues of other runners - their fluid needs are probably very different from your own. If you are "over-thinking" and feel you cannot rely on this new way of thinking, experiment in your training with one of these other ways, realizing each has its own cautions as well.

Fluid Hydration Tips Prior to Race Day:

1. Check your urine. If yellow - like light lemonade - you are well prehydrated
   
2. If dark and concentrated - like iced tea - drink more fluids
3. If clear, you are drinking too much; back down on fluids