Wednesday, May 29, 2013

Beat the heat: hydration for performance

Lots of "army places" are hot and dry and austere and as part of my training, I was lucky enough to participate in a course aimed at physical performance maintenance in hot and unsavory environments.  I would even lump El Paso summers into this category!  This overview is based on what I learned and I've cited the Human Performance Resource Center at the end of the article.  I love this stuff and I hope it gives you a new perspective on adequately meeting your body's hydration needs.

Basically, human thermoregulation is impaired when you lose 2% of your body weight (in water).  When you have lost 3-6%, you experience reduced muscular endurance and strength.  At more than 6%?  That's the heat cramps, exhaustion, stroke, coma threshold.Before any race or long run, I struggle with hydration (fantastic) vs. empty bladder (also quite nice).  My professor advised that we drink copious fluids for the 24H preceding an event and then an additional 14-20 oz 2-3H before exercise, leaving enough time for urine production and micturation and thus adequate hydration without having to tote a full bladder around town (or at least to the next aid station).
Dan is so thirsty he could not keep his eyes open
    During exercise, the key is to maintain this balance- and she suggested 6-12 oz every 15-20 minutes which is best adjusted by the individual sweat rate, a pretty common sense equation...try it on a training run and see how well you are maintaining your fluid balance!
  1. Weigh yourself before and after exercise
  2. Convert to ounces (by multiplying by 16)
  3. Add this to the number of fluid ounces consumed
  4. And divide by minutes exercised
  5. This gives you the volume per minute you need to drink to maintain hydration during exercise
As it turns out, after exercise, we recover best when we replace MORE than the amount of sweat lost- it's not 1:1, more like 3:2 or 2:1, let's just call it 24-32 oz for every pound of water lost.  In truth, the amount depends on the sodium content of the fluid with which you rehydrate after exercise.  Plain water?  You will find yourself hyponatremic and hypo-hydrated within 2H post-exercise.  Better beverages are tomato juice, sports drinks, milk, coconut water.  Or, if water's your thing, drink up but have a food snack with it.  I don't like most sports drinks but I do have Spicy V8, chocolate almond milk, coconut water in the fridge.  I guess it doesn't do me much good unless I drink it...something to work on this summer.

I wish everyone a safe summer running season!
 
More information: the Human Performance Resource Center
Source: My memory and MAJ R. Rogers, MHA, RD, CSSD, LD, CSCS "Fueling for Optimal Performance" lecture