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WaterI wrote this for some friends who are running Tough Mudder. Here is a simple guide to staying hydrated during exercise.

First, the goal is to achieve a well hydrated state and stay there for as long as possible. The easiest way to measure this is by looking at your urine. It should be the colour of pale straw. You can also measure the change in your body weight. Try not to lose more than 2% to fluid loss (1).


1. Make a plan and test it

The American College of Sports Medicine sets recommendations. This is a good place to start. Based on your body size (weight in kg), ACSM recommends the following (1):

4 hours before exercise: 5-7 mL of fluid per kg of body weight

2 hours before exercise: 3-5 ml of fluid per kg of body weight

During: .4-.8 L of fluid per hour

After exercise: 1.5 Liters per Kilogram of weight lost


For example, a 70kg (154lbs) person would drink 350ml-490ml of water 4 hours before exercise.

Please note, it is better to drink slowly. Take frequent sips and avoid drinking a lot at one time. Also, you can drink less once your are in a well hydrated state. You can drink too much, so don’t over do it.


2. Adapt the plan to your needsTim Running

Ask yourself the following questions and either increase the amount of fluid in your plan or decrease it.

How much do you normally sweat, buckets or a light sheen? Obviously, people who sweat more will need to drink more fluids to maintain an optimal level of hydration.

Are you a salty sweater? Do you notice salt lines on your body or clothing after exercise? If so, you should consider electrolyte drinks for any activity longer than 1 hour in duration.

What will the temperature be like? You will lose more fluid when it is hot and dry. Even if you don’t sweat much, plan to drink more.

3. Record your results. Experiment and tweak

Every person and every activity is different. The best way to come up with a plan that is best for you is through trial and error. Let me know how it goes. I would love to hear from you


Yours in fitness,

Tim Begley



1. Medicine & Science in Sports & Exercise:
doi: 10.1249/mss.0b013e31802ca597
Accessed via:


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