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Managing Hydration Requirements While Running

As the temperatures rise during the summer months, I was reminded of the need to manage fluid consumption. The short of it, I lost 4% of my pre-run weight after a 2 hour long run that included 21 oz of water mixed with HEED and Endurolytes. A 4% loss is not good!

From what I could remember, the little white line you don’t want to cross was a loss of 3% pre-activity weight. So I decided to take another look at Hammer Nutrition’s Fueling Handbook to re-edumacate myself on proper hydration.

First, per the guide, here are some of the symptoms encountered by percent body weight water loss:

  • 0% – none, optimal performance, normal heat regulation
  • 1% – thirst stimulated, heat regulation during exercise altered, performance declines
  • 2% – further decrease in heat regulation, hinders performance, increase thirst
  • 3% – more of the same (worsening performance)
  • 4% – exercise performance cut by 20-30%
  • 5% – headache, irritability, “spaced-out” feeling, fatigued
  • 6% – weakness, severe loss of thermo-regulation
  • 7% – collapse likely unless exercise stops
  • 10% – comatose
  • 11% – death likely

Even though I had no cramping issues, I was doing myself no favors by not consuming enough fluids. This may be why I had to walk a couple times during the last 2 miles. I am sure this dehydrated state doesn’t help with recovery either.

So what does Hammer Nutrition recommend as a general guide?

  • 21-24 oz per hour (must remember to take care of electrolyte needs as well)
  • Up to 2% weight loss after a long race or training session is OK.
  • Over-hydration (weight gain) can be just as dangerous.

I basically only took in 50% of the recommended amount. I am not sure if I can drink 21 oz per hour during a run but I definitely will have to increasing the consumption and observe the weight loss percentage. I really don’t want to be beyond a 2% loss so I will be doing a bit of experimenting during the next few weeks to see what works for me.

What have you found to be your idea amount of fluid per hour during the summer months of training?

Happy Hydrated Training!

About the author

David Hanenburg David Hanenburg is the passionate dirt-lovin' creator of Endurance Buzz and has been playing in the endurance sports world since 2000 after knockin' the dust off of his Trek 950 hardtail thanks to a friend asking to go ride some local dirt. In 2007 he ran his first ultra on the trails and fell in love with the sport and its people. For more information on David's endurance sports journey, check out the About page.

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